Talk:Climate change/Archive 68

In the lead, we use IPCC's word "likely" regarding projected ranges of warming for different emissions scenarios. Just like the prior paragraph, which says they are "more than 90% certain" based on their use of "very likely" and their explicit definition of that term, use of the word "likely" for temp projections is also explicitly defined in our RSs. (same one that defined the 90% bit)

In short, IPCC would only say they are more than 66% sure temps will rise somewhere in the stated range for each emissions scenario. That means they are only "more than 66% certain" it won't be less (I can hear all the pro-fossil fuel people ready to pounce on this) but it also means IPCC is only "more than 66% certain" it won't be even more.

One more point. In a recent thread Enescot and I were discussing uncertainty, and I pointed out that AR4 WG1 came up with a best guess for each SRES, and then IPCC added the lower and upper bounds to create the ranges. They added more to the upper boundary, for more uncertainty on the higher end of the spectrum.

But the main thing I want to discuss is whether, and how, the article could be improved by explaining that "likely" in the sentence with temp ranges means IPCC only said they are "more than 66% certain" it won't be lower (which has been all over the media to a greater or lesser degree at different times), or or higher (which is essentially absent from mainstream media) than the projected ranges we report in the lead. NewsAndEventsGuy (talk) 18:58, 24 February 2013 (UTC)

Personally I wouldn't have a problem with adding "more than 66% certain" to the "likely" statement. My own preference would be to drop "likely" in favour of "could". I don't think that the existing revision of the lede is clear enough in explaining why the word "likely" is used.

I think that the issue you raise has to set against other sources of uncertainty. As I've said before, I think that abrupt/large-scale/climate "surprises" should be briefly mentioned in the lede. I agree that uncertainty in the tails of the distributions is important, but there are many important impacts in the centre of the distribution as well.

I think that because of the limited space available, it is difficult to explain these uncertainties in the lede. I would prefer it if these uncertainties are described in the main part of the article, rather than the lede. If "high-end" risks are to be mentioned, then I think it would only be fair to mention the probability of small changes in climate. For example, the IPCC say that a climate sensitivity less than 1.5 degrees C is "very unlikely", i.e., less than a 10% chance. Enescot (talk) 06:07, 28 February 2013 (UTC)

As others have noted, the problem with the phrasing "more than 66% certain" is that it applies to a range of temperatures, not to climate change itself. It is likely to be understood by some casual readers as meaning there is a 44% chance of no climate change at all, which isn't the case. I agree with Enescot that if this belongs in the article at all, it should not be in the lead. Rick Norwood (talk) 13:17, 28 February 2013 (UTC)

44%+66%=110% - so there must be a -10% chance of something else somewhere ;-) --Stephan Schulz (talk) 13:49, 28 February 2013 (UTC)

Thank you for the correction. Rick Norwood (talk) 13:57, 28 February 2013 (UTC)

I've had an idea over how this issue might be partially addressed. MIT (p51 of PDF) and the Hadley Centre (Excel spreadsheet) have produced probabilistic temperature projections for mitigation and baseline emissions scenarios. These data could be plotted as a graph and added to the article.

I'd also repeat my previous suggestion of moving the quantitative temperature projections from the lead to a later section of the article. In the lead, they could be replaced with a more qualitative statement, e.g., "Projections suggest that the future rate/rapidity of global warming might be unprecedented in the last 10,000 years ." Enescot (talk) 06:39, 19 March 2013 (UTC)

I still plan to return to this.NewsAndEventsGuy (talk) 23:25, 1 April 2013 (UTC)

Not sure if this has been mentioned before but I believe that the Farenheit measurements are incorrect.
The formula for Farenheit is:
(Celcius * 1.8) + 32 = Farenheit

1. 0.8°C should be 33.44°F
   
2. 1.1°C should be 33.99°F
   
3. 2.9°C should be 37.22°F
   
4. 2.4°C should be 36.32°F
   
5. 6.4°C should be 43.52°F
   

and so on...
— Preceding unsigned comment added by TheGameGits (talk • contribs) 09:32, 6 March 2013 (UTC)

The temperature values are temperature increase values: mean surface temperature has increased by about 0.8 °C (1.4 °F) (note the {{convert|0.8|C-change|F-change|1}} template used to convert) rather than actual temperature values. Vsmith (talk) 11:36, 6 March 2013 (UTC)

Santamoly recently added this to the article:

"In a paper published by Columbia University on January 15 2013, NASA's James Hansen acknowledged that global warming has reached a standstill that has lasted for more than a decade^[1]."

I believe that this statement is misleading. Other reliable sources explain how internal climate variability can affect global warming trends. Indeed, the cited source states (p1):

"The 5-year mean global temperature has been flat for a decade, which we interpret as a combination of natural variability and a slowdown in the growth rate of the net climate forcing (...)

The long-term warming trend, including continual warming since the mid-1970s, has been conclusively associated with the predominant global climate forcing, human-made greenhouse gases2, which began to grow substantially early in the 20th century"

In the section on "Observed temperature changes", the article already mentions this issue:

"Global temperature is subject to short-term fluctuations that overlay long term trends and can temporarily mask them. The relative stability in temperature from 2002 to 2009 is consistent with such an episode"

I've previously reverted Santamoly's edit, as has KimDabelsteinPetersen. Both Kim and I have explained why we reverted Santamoly's edit.

In my opinion, Santamoly's edit does not accurately reflect the views of Hansen or of the wider scientific community. In my opinion, the edit should be removed. Enescot (talk) 06:52, 26 March 2013 (UTC)

I've appended Santamoly's edit with this:

Hansen and others state: "The 5-year mean global temperature has been flat for a decade, which we interpret as a combination of natural variability and a slowdown in the growth rate of the net climate forcing (...) The long-term warming trend, including continual warming since the mid-1970s, has been conclusively associated with the predominant global climate forcing, human-made greenhouse gases (...), which began to grow substantially early in the 20th century."

Taken together, I believe that Santamoly's and my edit are unnecessary additions to the article. However, I think that my edit provides an accurate context for the Hansen et al source. Enescot (talk) 07:09, 26 March 2013 (UTC)

Should be removed completely per FAQ question 3. --Kim D. Petersen (talk) 07:47, 26 March 2013 (UTC)

Looking at the paper, the excerpts stopped short of the conclusions. To add some quotes:
In a paper published by Columbia University on January 15 2013, NASA's James Hansen acknowledged that global warming has reached a standstill that has lasted for more than a decade^[1]. Hansen and others state: "Global surface temperature in 2012 was +0.56°C (1°F) warmer than the 1951-1980 base period average, despite much of the year being affected by a strong La Nina. Global temperature thus continues at a high level that is sufficient to cause a substantial increase in the frequency of extreme warm anomalies. The 5-year mean global temperature has been flat for a decade, which we interpret as a combination of natural variability and a slowdown in the growth rate of the net climate forcing (...) The long-term warming trend, including continual warming since the mid-1970s, has been conclusively associated with the predominant global climate forcing, human-made greenhouse gases (...), which began to grow substantially early in the 20th century. (...) The annual increment in the greenhouse gas forcing (Fig. 5) has declined (...) primarily a consequence of successful phase- out of ozone-depleting gases and reduction of the growth rate of methane. (...) A slower growth rate of the net climate forcing may have contributed to the standstill of global temperature in the past decade, but it cannot explain the standstill, because it is known that the planet has been out of energy balance, more energy coming in from the sun than energy being radiated to space. The planetary energy imbalance is due largely to the increase of climate forcings in prior decades and the great thermal inertia of the ocean. The more important factor in the standstill is probably unforced dynamical variability, essentially climatic 'noise'. (...) Indeed, the current stand-still of the 5-year running mean global temperature may be largely a consequence of the fact that the first half of the past 10 years had predominately El Nino conditions, while the second half had predominately La Nina conditions (...) We conclude that background global warming is continuing, consistent with the known planetary energy imbalance, even though it is likely that the slowdown in climate forcing growth rate contributed to the recent apparent standstill in global temperature."
Too long for a quote, and as noted above it's not an "other view", it confirms what we cover elsewhere. The main points are climate variability associated with La Nina–El Nino, phase- out of ozone-depleting gases and reduction of the growth rate of methane, and uncertain changes in aerosols. A brief paraphrase would be useful in these sections. . dave souza, talk 08:17, 26 March 2013 (UTC)

On the issue of understanding the paper (per NAEG's comment below at 09:44, 26 March) Hansen et al.'s section intro clarifies their intent, "Global Warming Standstill. The 5-year running mean of global temperature has been flat for the past decade. It should be noted that the "standstill" temperature is at a much higher level than existed at any year in the prior decade except for the single year 1998, which had the strongest El Nino of the century. However, the standstill has led to a widespread assertion that "global warming has stopped". Examination of this matter requires consideration of the principal climate forcing mechanisms that can drive climate change and the effects of stochastic (unforced) climate variability." His attempt to clarify has unsurprisingly been met with widespread quote-mining. The "paper" seems to be an opinion piece published on his university website, not a peer reviewed paper, and as such is due less weight. . dave souza, talk 10:46, 26 March 2013 (UTC)

If I understood Hansen's paper, he was (foolishly?) only talking about surface temps, even as he acknowledged "the great thermal inertia of the ocean" where most of the BTUs of global warming end up. A just-published analysis that includes temp measurements from various ocean depths paints a very different picture... global warming has accelerated NewsAndEventsGuy (talk) 09:44, 26 March 2013 (UTC)

Here is the Paper and a plain English blog about paper NewsAndEventsGuy (talk) 09:47, 26 March 2013 (UTC)

The cold snaps that can last into spring like right now in Europe and the US are thought to be caused by climate change. However, I haven't read about the effect this in turn has on global warming. If the cold air that is normally confined to Northern lattitudes moves much further South, then the energy balance at those Southern lattitudes changes. The flux of solar energy stays the same, but less is radiated into space. Count Iblis (talk) 12:40, 26 March 2013 (UTC)

On the other hand, we have significant snow cover in Germany at the end of March. This has been very rare in the last few years, and changes albedo. So it's not obvious either way. I'm not aware of any paper that discusses the effect so far. --Stephan Schulz (talk) 13:35, 31 March 2013 (UTC)

Which cold snaps? For all that the northeastern U.S. has had some unusually cold spells, it was warmer than usual in the Pacific Northwest. For all that some particular weather catches the public's attention, there is a lot of weather that does not, so there is a sampling problem. That's why we measure. ~ J. Johnson (JJ) (talk) 16:54, 31 March 2013 (UTC)

The Easter Bunny translates..... dave souza, talk 17:37, 31 March 2013 (UTC)

That's a helpful article for the patterns, but doesn't really address the effect on GW: in that, its seen purely as an effect of GW. And I haven't seen anyone else discuss it either William M. Connolley (talk) 09:05, 1 April 2013 (UTC)

The point that jumped out at me was that when the patterns were "Averaged over the northern hemisphere the anomaly disappears - the average is close to the long-term average." The implication being no obvious effect on GW. However, Neven helpfully highlights an explanation by R. Gates that weird is the new norm, and sudden stratospheric warming (SSW) events are behind much of the fun. The Beeb relates this to lots of spaghetti, bringing FSM theory to mind as well as von S's noodly commentary on hockey sticks. In other words, it looks complicated. . dave souza, talk 10:06, 1 April 2013 (UTC)

The arctic oscillation is a major contributor of month to month variability in the global temperature, during the negative phase warm oceanic air advection over NH landmasses is reduced and thus global temperature, however over longer time period the effect is quite small because it is seasonal(larger during boreal winter) and the index isn't locked for long time into the negative or positive phase.

Thompson et al. estimated that the dynamical induced changes in global temperature ranges from ~-0.2 to ~+0.2 but the long term trend and variability is quite small compared to global warming(~0.04°C).(although the pattern that maximize the land-ocean temperature contrast isn't exactly the same of the arctic oscillation but it's very similar): http://www.atmos.colostate.edu/ao/ThompsonPapers/ThompsonWallaceJonesKennedy_JClimate2009.pdf

Attribution to climate change maybe is a little premature, internal variability is large and the remote response to arctic sea ice loss quite uncertain in models. http://www.cgd.ucar.edu/cas/cdeser/Docs/submitted.screen.seaice_atm_impacts.pdf --Giorgiogp2 (talk) 20:36, 2 April 2013 (UTC)

I'm interested in discussing improvements to the section of the article on "natural systems." In my opinion, the section presents a good summary of the subject, but I have some criticisms.

The section states that the Arctic will be largely ice-free by 2037. There are, however, other estimates. In IPCC AR4, some models using the SRES A2 emissions scenario projected ice-free summers by the end of the 21st century . According the UK Met Office, recent models project an early "plausible" date of 2025-2030 .

I do not agree with how the section covers attribution of climate change. In my view, there is an undue focus on the study by Hansen et al. The section should provide a summary of the literature on attribution, rather than focussing on individual studies. AR4 contains a number of attributions which aren't mentioned, including the contribution of anthropogenic forcing to sea level rise and loss of Arctic sea ice .

Hansen et al's work on this issue does not appear to reflect a consensus view (Seneviratne et al., 2012:127). Kevin Trenberth has stated that "James Hansen and I are pushing to get scientists to think about and do statistics on this rather differently, and now we are not part of mainstream in this regard" .

The section's summary of extreme events is not consistent with the recent IPCC SREX report. The section states that in the future, there will be more intense droughts and floods. No caveats are given. By contrast, the SREX report is far more cautious in its projections of changes in droughts and floods (IPCC, 2012:11). A number of projected changes in extremes described in the SREX are not mentioned, e.g., increased intensity, duration and frequency of heat waves. Enescot (talk) 06:25, 11 February 2013 (UTC)

I've prepared a draft revision of the "natural systems" section that I would like to discuss. New or revised sentences are italicized:

"Global warming has been detected in a number of natural systems. Some of these changes are described in the section on observed temperature changes, e.g., sea level rise and widespread decreases in snow and ice extent. Anthropogenic forcing has likely contributed to some of the observed changes, including sea level rise, changes in climate extremes (such as the number of warm and cold days), declines in Arctic sea ice extent, and to glacier retreat (Hegerl et al 2007).

(as current revision) In the IPCC Fourth Assessment Report, across a range of future emission scenarios, (as current revision...) contribute 4–6 metres (13 to 20 ft) or more to sea level rise.[125]

Changes in regional climate are expected to include greater warming over land, with most warming at high northern latitudes, and least warming over the Southern Ocean and parts of the North Atlantic Ocean.[123] During the 21st century, glaciers and snow cover are projected to continue their retreat (Meehl et al 2007). Projections of declines in Arctic sea ice vary (Meehl et al 2007). Recent models suggest that Arctic summers could be ice-free (defined as ice extent less than 1 million square km) as early as 2025-2030 (UK Met Office 2012).

Future changes in precipitation are expected to follow existing trends, with reduced precipitation over subtropical land areas, and increased precipitation at subpolar latitudes and some equatorial regions (NOAA GFDL, 2007, p.1). Projections suggest a probable increase in the frequency and severity of some extreme weather events, such as heat waves (IPCC 2012, pp9-13).

Enescot (talk) 09:57, 20 February 2013 (UTC)

In view of the discussion below ("IPCC projection underestimations"), I was thinking of revising the "natural systems" section to include a summary of more recent global sea level rise projections. At present, the section only mentions the 2007 projections from the IPCC 4th Assessment (AR4). A recent (2012) literature assessment was conducted by the US National Research Council. The NRC study includes their own projections of sea level rise and cites projections by Vermeer and Rahmstorf (2009) . I was thinking that these two projections could be cited in the section alongside those from AR4. It would probably only require one or two sentences. Alternatively, a graph of the projections could be added. Enescot (talk) 05:54, 6 March 2013 (UTC)

I've prepared a draft image of sea level rise projections, shown above. Enescot (talk) 06:49, 16 March 2013 (UTC)

The image for sea level rise mis-states the IPCC AR4 (2007) because it suggests IPCC stated an upper bound for their projection. That's false. The SPM says "Because understanding of some important effects driving sea level rise is too limited, this report does not assess the likelihood, nor provide a best estimate or an upper bound for sea level rise". Also, trying to put all the info in one table instead of breaking the tables into three with a header for the year makes it confusing. I was familiar with the numbers but took several seconds to orient myself. A newbie could easily miss the years on the right hand border. NewsAndEventsGuy (talk) 14:32, 29 March 2013 (UTC)

Thanks for the feedback. If you want to draw a new graph, then the current graph could be replaced. Alternatively, I'd be pleased to redraw the graph in view of your comments. However, I'm not entirely clear on what you have in mind. If the graph is to be broken up into three graphs, then I presume that each graph would have its own set of axes. In my view, it might be more straightforward to omit the 2030 and 2050 projections.

The image description does mention the limitations of the IPCC projections:

"The IPCC (2007) estimates do not include all of the possible contributions from ice sheets (US NRC, 2012, pp.84-85). According to US NRC (2012, p.88), "the IPCC (2007) projections are likely underestimates because they do not account fully for cryospheric processes"."

I've added the SPM text you've quoted to the image description. The comment could also be added to the graph itself. I should note that the other projections shown in the graph are much higher than the IPCC's. Therefore, I think it should be fairly obvious that the high-end IPCC projection is not an upper-bound estimate.

Another point is that graphs often do not include the full range of possible outcomes. An example is the IPCC's graph of temperature projections . Enescot (talk) 09:56, 31 March 2013 (UTC)

I don't do graphics. If you've got the knowhow is that something you could do? I like the layout used in the graphic in this article, which would work well here, I think. NewsAndEventsGuy (talk) 23:32, 1 April 2013 (UTC)

I've found a sea level rise graph by NOAA which could be used to replace the existing graph . The graph's on p.3 of the report. Enescot (talk) 09:26, 16 April 2013 (UTC)

I've prepared a new graph of projected sea level rise, shown above. It is based on several studies. Enescot (talk) 07:49, 5 May 2013 (UTC)

I've had a look at the section of the article on "ecological systems". In my opinion, the section should be revised. I don't agree with how ocean acidification is described. I find the existing text alarmist. I'm comparing it to an assessment by the US National Research Council (US NRC, 2010), and a 2009 joint-statement made by 105 science academies (the Interacademy Panel). I recognize that the impacts of ocean acidification could be highly significant, but scientific understanding of these impacts is limited. US NRC (2010, p.5) state:

"Unless anthropogenic CO2 emissions are substantially curbed, or atmospheric CO2 is controlled by some other means, the average pH of the ocean will continue to fall. Ocean acidification has demonstrated impacts on many marine organisms. While the ultimate consequences are still unknown, there is a risk of ecosystem changes that threaten coral reefs, fisheries, protected species, and other natural resources of value to society"

Enescot (talk) 08:20, 11 May 2013 (UTC)

See here https://www2.ucar.edu/atmosnews/news/2904/climate-change-drought-may-threaten-much-globe-within-decades Hammerfrog (talk) 16:22, 13 May 2013 (UTC)

?? I don't follow. The link you point to is from 2010, but the current image is from 2012? And they both show broadly the same patterns (although the 2012 one seems to show slightly worse drought conditions). Could you please elaborate on how our current maps are out of date? Sailsbystars (talk) 19:17, 13 May 2013 (UTC)

Oh, wait, I see! The original maps contained a serious error and overprediction, as indicated by the update in the post. We should probably replace the map then.... Sailsbystars (talk) 19:30, 13 May 2013 (UTC)

While there are graphs here for overall warming (from NOAA and other sources), there seems to be nothing for the U.S.-- as shown in Climate change in the United States. My understanding is that Wikipedia users here have made graphs showing U.S. temperature changes. But where are they? CoffeeWithMarkets (talk) 06:07, 13 May 2013 (UTC)

There's a nice graph on page three of this U.S.government-related publication that would show U.S. Historical Climatology Network data from 1950 to 2009. Though a bit out of date (but not my much, really), it looks pretty cleanly made and interesting. I'm not sure if this is public domain, though. Help? CoffeeWithMarkets (talk) 07:00, 13 May 2013 (UTC)

Keeping on my lovely pattern of talking to myself (which I must admit, I do far too often for my own good, alas), I'd like to link to this and that, which I pulled from / made with help from the NOAA publication (respectively). Maybe something could be made out of those. CoffeeWithMarkets (talk) 07:07, 13 May 2013 (UTC)

Why would we give special emphasis on any one region in the article on global warming? We do have Climate change in the United States, though I've never (AFAIK, at least not recently) checked it out in detail. --Stephan Schulz (talk) 07:38, 13 May 2013 (UTC)

What's missing for me is more emphasis on the implications of having broken through the milestone of 400 PPM.

There should also be more emphasis on the implications of rising sea levels for East Coast cities in the US increasing at an increasing rate or accelerating. There are more than 100 coastal cities with populations over 100,000 people for whom the 2010 interim report of the 1st group of the IPCC on rising sea levels strongly indicates the possibility of a rise sufficient to make sea walls and levels impractical to safeguard the BosWash corridor, a rise measured in multiple meters rather than multiple feet, possibly occurring sooner than 2100 but definitely occurring. The cost of relocating coastal cities can be estimated by the cost of repairing New Orleans and the Gulf Coast after Katrina and Staten Island after Sandy as somewhere in the range of $150 Billion dollars a year for the next twenty five years per each city involved. That's aside from all the other problems such as would occur with abandoning in place Nuclear power plants, hazardous waste encapsulations, water treatment plants and sewer treatment plants; harbor facilities and urban high rises which would collapse to clog shipping lanes once their foundations were undermined. 12.187.95.227 (talk) 12:20, 13 May 2013 (UTC)

{update} Alright, well I went ahead and transferred over the image, edited it, and here we are. I don't really know for sure if it should be included in this article per se, but it's great for the U.S.' own article.

Anonymous' comment about the affect of sea level changes is interesting. I don't really know how to respond because I don't know that much about the issue. I do know that the IPCC said in its 2007 report that global sea levels would increase by 39cm by 2100 (using their "most likely" emissions scenario). That's about a foot, which is approximately the same as the increase in sea level from 1860 to 2000. That's global data, though, which is different than what could happen in the U.S. CoffeeWithMarkets (talk) 01:24, 14 May 2013 (UTC)

IPCC 2007 AR4 explicitly says they were not putting an upper boundary on sea level rise due in large part to uncertainties with the ice sheets. Their projections are minimum numbers only. NewsAndEventsGuy (talk) 01:40, 14 May 2013 (UTC)

Of course, there are uncertainties either way. We do see for the past years data being on the least warming, least climate sensitive side, which might seem to indicate that the IPCC values are too high, but they're still well worth looking at. CoffeeWithMarkets (talk) 01:51, 14 May 2013 (UTC)

Jury is still out on climate sensitivity. See e.g., "Future Warming Likely to Be On High Side of Climate Projections, Analysis Finds" NewsAndEventsGuy (talk) 12:56, 16 May 2013 (UTC)

It's useful that our editors are collapsing any discussions that run contrary to our in-house expert opinions. Should we not delete those discussions so that readers don't get the idea that there is some significant disagreement on the Global Warming issue? Providing a forum for disagreement surely must weaken our cause. Santamoly (talk) 01:16, 22 May 2013 (UTC)

Where there is discussion about how to improve the article based on RSs given appropriate WEIGHT, then such threads should be preserved not collapsed. That includes coverage of disagreements found in RSs of appropriate weight. On the other hand, threads which advance a POV (either way) and which lack article improvement suggestions based on RSs are most likely WP:SOAP and/or WP:FORUM lying outside the scope of our talk page guidelines. Threads such as this one which rely primarily on sarcasm instead of RSs usually belong in the latter group. NewsAndEventsGuy (talk) 05:42, 22 May 2013 (UTC)

Fully agree. The WP:SOAP and WP:FORUM guidelines are pretty clear that the talk page isn't a forum, and if people want to right great wrongs (or write great wrongs in this case), then they should do that elsewhere, IRWolfie- (talk) 20:15, 22 May 2013 (UTC)

Indeed, the right place for people to put forward their arguments is here. Count Iblis (talk) 21:56, 22 May 2013 (UTC)

It is not my expertise nor is this area of the encyclopedia my focus as an editor, but I'm curious...where is the discussion regarding the measurement of CO2 exceeding 400 ppm? My nderstanding is that "achievement" is "game over" in terms of our ability, let alone willingness, to reverse damage/warming attributed to human causes. Furthermore, my understanding is that now all "we" can do is "mitigate" the damage we now (at present) have no technological capacity to "fix" going forward even if we now try to reverse the staggering levels of CO2going into the atmosphere, which are still steeply increasing. I understand these are fighting worlds for some, but am curious where the discussion of this phenomenon is, despite my own understanding (or bias), in the Wiki. Regards, Norcalal (talk) 02:27, 18 May 2013 (UTC)

400 ppm is only a symbolic level, not some hard physical boundary substantially different from 399.8 ppm or 401.2 ppm. In general, the higher the CO2 level rises, the higher the environmental impact will be. As a result, we will be forced to to do more mitigation in the future. But each further increment in CO2 will further exacerbate the problem, so it's not "only" mitigation from now on. --Stephan Schulz (talk) 12:59, 19 May 2013 (UTC)

Congratulations for all the good science here and NPOV treatment of this very important topic. There is room for improvement though, in that some of the info lacks context to help the layman understand its significance. And a great many of the sources seem to be over 5 or even 10 years old. I dont usually like to advocate overwriting previous editors work, but it seems warranted in this case. I'll make an update to the article along these lines, hope it's acceptable. FeydHuxtable (talk) 12:57, 27 May 2013 (UTC)

We don't just randomly require sources written in the last X years. If you can find something which you think has been invalidated by more recent work, then bring that issue up but otherwise change for the sake of change is pointless. For example, in Quantum mechanics articles there is a reason we can use a source that is 30 years old; the pertinent information is not time sensitive like medical claims. Likewise, the general thrust and historical coverage of global warming is the same in older sources as it would be in later ones. Global warming is about long term trends, and so we should not engage in excessive recentism, IRWolfie- (talk) 13:32, 27 May 2013 (UTC)

Wolfie, there's never anything random about an edit from an ARS squad member.

Global warming isn't all that comparable to QM. QM is a pure science topic about trying to find static laws, and for those articles you'd be right there's no need to update unless there were substantial changes in consensus or new experiments invalidating older work. GW on the other hand is an ongoing process. It falls into the domain of applied science with huge political and social dimension. It seems rather unhelpful to our readers to prefer older estimates and findings. Its not a question of the older claims being invalidated, but outdated. Anyway, would you be happy with the new material being added without removing any of the older work? I do agree it's generally not good to delete other folk's work. FeydHuxtable (talk) 13:52, 27 May 2013 (UTC)

Climatology is science in the same way that quantum mechanics is science. Much of the material is fairly static and does not need "updating" for no reason. I am just saying your initial assumption is wrong. You added "Without the warming caused by natural level of greenhouse gasses, the temperature across almost the entire surface of the earth would be below freezing", where is the source? IRWolfie- (talk) 14:04, 27 May 2013 (UTC)

You may be saying that Wolfie, but you've not in anyway convinced me that updating wouldn't be an improvement. This article is about global warming, surely no one denies GW is much better charaterised as a dynamic process rather than a static state of affairs? No one's saying we should update for no reason. It was implicit in my update that the reasons include new estimates on quantities like CO2 levels supercedeing old ones, and new meta studies better quantifying the level of support for the AGW concensus.

Unlike the rest of my edit, the part about natural levels was unsourced. IMO no competent scientist would find it in the least bit controversial, but it will be helpful to the layman for understanding the topic. If anyone challenges it, finding a source ought to be trivial. Anyway, there's lots of other articles needing improvement, and the conversation to constructive improvement ratio here is a little high for my liking. I stand by my statements about the need for updates, perhaps your or others will eventually agree to allow improvements. FeydHuxtable (talk) 14:41, 27 May 2013 (UTC)

The main reason I stuck with wikipedia after the Missippi Floods that first drew me in was because I thought this article could stand a great deal of improvement. Not much has changed. Feyd, IRWolfie has a lot of respect from me for being a level headed ed. My money says we could try harder to identify areas of agreement, and do some good here. That said, it isn't at all clear to me that earth would freeze without greenhouse gases. The other three inner planets are all mighty toasty on the side that faces the sun. Unless its truly a WP:SKYISBLUE sort of thing, it all needs RSs. NewsAndEventsGuy (talk) 15:43, 27 May 2013 (UTC)

It is a sky is blue sort of thing I'm afraid. See our article on Planetary equilibrium temperature. Equilibrium temperature for venus is 260K, and equilibrium for earth is more like 220-230K. Water freezes at 273..... This is very basic astronomy/planetary science. Sailsbystars (talk) 16:17, 27 May 2013 (UTC)

I don't think it's immediately clear how close to the planetary equilibrium temperature we would be if there were no greenhouse gases but we still had an atmosphere, and our geothermal activity. IRWolfie- (talk) 16:49, 27 May 2013 (UTC)

With a 370K max temp on the moon, it isn't utterly unambiguously obvious in the same way that the sky is blue. Of course even that is questionable.... how do blind or color blind people know what we're talking about? NewsAndEventsGuy (talk) 16:38, 27 May 2013 (UTC)

The atmosphere doesn't matter unless it has GHGs. See for example, Mars which has an atmosphere without substantial GHGs and temps close to equilibrium. The reason the moon is so hot and cold is because it's a slow rotator. If the moon were spinning at asteroid rates, it would be pretty close to equilibrium temperature. This is why asteroid folks use the thrice-damned "beaming factor" when describing the temperature of an asteroid to account for the fact that the temperature has a variable distribution across the surface related to rotation rate and other factors. Sailsbystars (talk) 16:59, 27 May 2013 (UTC)

An excellent explanation, thanks. However, the necessity of this explanation proves my point, namely, that this tidbit is not so blindingly obvious that it doesn't need an RS. NewsAndEventsGuy (talk) 17:04, 27 May 2013 (UTC)

You didn't appear to mention geothermal energy and it's contribution if significant. It may very well be as you say, but I don't think it should be assumed as a given. For example the mid latitudes of Mars are -50 to -60 Celsius (presumably the equator even more, which apparently peaks at 20 Celsius during the summer according to google), which is in the range of what you say the PET for earth is, yet Mars is further away, and has less geothermal energy. Reality is rarely as simple as a spherical cow model might suggest. I'm merely saying this so that we don't take things as a given. IRWolfie- (talk) 22:54, 28 May 2013 (UTC)

Thankyou.

@NewsAndEventsGuy Again it's not all that good a comparison to compare with the other 3 inner planets. Mercury and Venus are much closer, while the surface temp. on Mars is generally well below freezing, including on the side facing the sun. As expected, the claim is trivial to source, I googled "natural level of greenhoue gases" and got this article as the no 1 result , a very good explanation for the layman, phrasing it the same way I did. If you want more scholarly sources or a more quantitative introduction, they're on offer in the lede of our Greenhouse gas article. For more in depth treatment, see the article Sailsbystars linked you to. Ironically, the science relating to the NGHE is one of the few parts of article that are largely static.

GW is a process that according to many sources, is already degrading the lives of millions of people. This article averages over 10K hits a day, and helps shape the media coverage which in turn influences policy responses that could potentially slow the process. I guess we could find common groud, but Im finding it a little too frustrating that editors are having to explain schoolboy science to try and get some simple updates accepted. FeydHuxtable (talk) 16:26, 27 May 2013 (UTC)

Some of those 10,000 daily hits are from schoolboys, I'm afraid. If you won't talk RSs, you won't be able to make improvements here. NewsAndEventsGuy (talk) 16:38, 27 May 2013 (UTC)

Looks like I previously had my wiki-markup wrong, sorry about that. The RS I linked to is from the National Geographic, and there's more scholarly sources supporting the claim in our Greenhouse gas article. FeydHuxtable (talk) 16:53, 27 May 2013 (UTC)

Reset. Are there still any article improvement suggestions on the table for discussion here? NewsAndEventsGuy (talk) 17:06, 27 May 2013 (UTC)

• I've updated the article to reflect what the source says; specifically without the atmosphere rather than without greenhouse gases. You might think that makes no difference, but I don't think it is necessarily clear what the average temperature would be if there where just non-natural causes of greenhouse gases and the rest of the atmosphere; a simple blackbody model does not apply. With a featured article care should be taken to avoid any original research. IRWolfie- (talk) 17:08, 27 May 2013 (UTC)

"care should be taken to avoid any original research" Amen. NewsAndEventsGuy (talk) 17:10, 27 May 2013 (UTC)

That's great. There's still a general need for updated information IMO. Specifically, can I please be allowed to re-add my updates concerning the latest updates for CO2 levels, and the metastudy released this month quantifying the consensus for AGW (this time without removing any of the older work)? FeydHuxtable (talk) 17:17, 27 May 2013 (UTC)

Why not just use use some of Scientific opinion on climate_change, specifically Scientific_opinion_on_climate_change#Scientific_consensus? There is no section in Global_warming#Views_on_global_warming for the scientific consensus (it's mentioned in the other sections, but we should have a section establishing what the consensus is as well. I don't think it's a good idea to just pick the very latest paper; it's very very recent, and we should use some of the other well cited surveys as well, IRWolfie- (talk) 17:48, 27 May 2013 (UTC)

Well because the sources there again seem to be about 5 - 10 years old. This is a fast moving and topical field, though I admit the concensus has been relatively static. Also, the new meta study uses by far the most rigorous methodology for quantifying the consensus.

Just to further justify why updates are needed, the article currently has a claim that CO2 levels have increased by 35% since 1750. That seems to be based on work from 2004. Unless we add qualification, the passage of time has made that claim plain wrong. If there's one thing Im confident we can agree on, it's that care should be taken to avoid this sort of inaccuracy in any article, let alone a featured one of this importance.

Anyway, Im going to re add the updates. If you or others sincerely think the change dosnt help our reader, Im sure you'll revert. I agree having a short dedicated subsection on the scientific consensus is a great idea, with two or three of the older well cited papers.FeydHuxtable (talk) 18:04, 27 May 2013 (UTC)

Well, I like the 2nd "update" though it would have been better to get explicit consensus before reposting to avert appearance of EW.

Peacemaking attempt..... IRWolfie, when you reverted the 1st time you mentioned in the edit summary you werent' sure why stuff was removed. I wonder if there was a miscommunication? Paragraphs were certainly rearranged, somehow appearing on the left with (-) marked, and elsewhere on the right with (+) marked. Beats me why the algorithms depict static text as though it were subtracted AND added in the same edit. Anyway, IRWolfie, I thought something was substracted the first time too, but I was mistaken. Maybe we got off on the wrong foot here?

Comments.... The DIFF for the 2nd attempt is depicted cleaner, and I do think its a small improvement. There is indeed an issue when we say "X is happening" when X is in fact changing. In such cases its better to say "As of Y, X was happening." While this is good fine tuning, it isn't all that radical a change.

Next? NewsAndEventsGuy (talk) 18:23, 27 May 2013 (UTC)

(revised by poster later) PS Oh, and adding the news of 400ppm and the meta review was excellent. Thanks NewsAndEventsGuy (talk) 18:25, 27 May 2013 (UTC)

The material cited to pearson here: disappeared. I think citing the opinion of a single professor sourced to a newspaper is a bad idea since it opens the doors to people using newspapers to push fringe views, IRWolfie- (talk) 18:28, 27 May 2013 (UTC)

Professor Hoskins is a well established and regarded main stream professor. Id say it best to evaluate each source on a case by case bases, you know as well as I do there are abundant "accademic" papers that push fringe views (admittedly not often ones that appear in the L2 journals). The FT is more reliable than many journals and text books, IMO. PS - looks much better now you added a dedicated climatologists section.

@NewsAndEventsGuy Thanks very much for the peacemaking; especially appreciated considering my less than perfectly collegiate remarks! As Wolfie says, I did remove some of the earlier work, including a source over 10 years old. Probably my fault it wasnt clear from the diff, guess I tried to do too much in one edit. IMO improving this article will work best if some of the older and (arguably) outdated info is removed, as otherwise it will get too cluttered to be ideal for the reader. I do agree that sourced content ought not be removed if there's no consensus. FeydHuxtable (talk) 18:41, 27 May 2013 (UTC)

The problem with the Hoskins text is that we appear to be attributing a fact as a mere opinion, contrary to WP:YESPOV. IRWolfie- (talk) 18:46, 27 May 2013 (UTC)

Note that I just changed the text at WP:YESPOV to make it easier to read, IRWolfie- (talk) 18:48, 27 May 2013 (UTC)

Looks like a helpful change. With the Hoskins quote, I attributed the statement to the good professor rather than using the encyclopedia's voice, and used the qualifier "likely." So IMO the edit was WP:YESPOV compliant. And a lot better than many recent RSs, which simply say CO2 is now the higher than its been for millions of years without indicating there's doubt in the matter. I dont think it will be easy to find a more encyclopedic way to make the statement which also gives clear info and context for our readers, but would be happy to be proved wrong. FeydHuxtable (talk)

I think we are looking at this cross-ways. I am saying that it appears to be a straight forward fact that it's now at the highest in millions of years. Attributing this as an opinion of one man is presenting a fact as an opinion, IRWolfie- (talk) 19:05, 27 May 2013 (UTC)

Ah sorry, that makes more sense. I wouldnt class it as a straightforward fact, due to the guestimates involves in quantifying Co2 levels prior to the 2nd half of the 20th century. But I'd agree it seems very close to certain, and would not object to anyone removing reference to the good professor. If thats done, I guess even the word "likely" could be removed, though then you might want a different source to avoid any risk of OR. FeydHuxtable (talk) 19:29, 27 May 2013 (UTC)

FeydHuxtable, a word of advice. Like you around 2005 I came here with the same good intentions as you to improve the article. Like you I met a wall of denial that anything should change. Like you I tried to argue sensibly and like you will too, I eventually went to look at the real science and realised that this is not a NPOV article but a bunch of baseless propaganda and I became a sceptic. It happens to everyone who tries to change this article ... that is why we don't fuss ourselves over its contents. All the great sceptics have been here, said what you have said and gone onto better things! The big mistake is to believe that anyone outside a few school kids who haven't learnt how to google are ever going to be influenced by this article. So, don't waste your time trying to change their minds, the editors here will not change their mind of global warming even if there were glaciers enveloping their homes. — Preceding unsigned comment added by 82.14.206.26 (talk) 23:13, 27 May 2013 (UTC)

I changed my mind about the addition of Hoskins' opinion. I think we should address how high it is today, but I don't like the way this has been done so far. I'm interested in RSs, and it's not OBVIOUS to me that its higher than it has been in MILLIONS of years. What I found is that the RSs apparently do not all agree, and the range of possible "last time it was this high" spans 800k - 15mil years. There's no debate that the last time was "before us" and that is the tack we should take, in my view. Since we've talked about an amalgam of issues in this thread, and there is already a thread specifically about 400 ppm, I suggest we move the 400ppm part of this discussion to the pre-existing thread. FYI I have already posted my more detailed reply under that pre-existing thread including a link to a ClimateCentral post on this very topic . Please followup there. NewsAndEventsGuy (talk) 00:30, 28 May 2013 (UTC)

@ x.206.26 - thanks for the advice. Very sorry to hear your editing experience here helped set you on the path to becoming a skeptic! You make some good points, especially that this article in its current state is likely to be far less helpful than it could be, except perhaps to those with a purely academic interest in climatology. You're right some AGW proponents use propaganda and other low tactics. As you know, these have backfired, and are part of the reason why you climate skeptics have been winning the political battle. Not that one would know it from the article, but the very promising global collaboration for effective policy responses that was gathering until late 2009 has largely evaporated. I think you're right that it will be a waste of time to attempt further improvements at this point, though perhaps the next editor who attempts it might fare better. FeydHuxtable (talk) 22:27, 28 May 2013 (UTC)

There was a request above for sources to explain why the no-CO2 equilibrium temperature of Earth was far below freezing. A thorough (washing a puppy with a firehose), recent source for this would be Lacis et al. 2010, Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature, which I'm rather surprised we didn't already cite. "To this end, we performed a simple climate experiment with the GISS 2° × 2.5° AR5 version of ModelE, using the Q-flux ocean with a mixed-layer depth of 250 m, zeroing out all the noncondensing GHGs and aerosols. ... The scope of the climate impact becomes apparent in just 10 years. During the first year alone, global mean surface temperature falls by 4.6°C. After 50 years, the global temperature stands at –21°C, a decrease of 34.8°C." Here's the press release. This is rather overkill for the conclusion (which is textbook-level knowledge), but should suffice. There's also a synthesis article at Skeptical Science. - Parejkoj (talk) 13:26, 28 May 2013 (UTC)

Thanks for this. Your Lacis source is much stronger than the SS article IMO, and I think you should add it. FeydHuxtable (talk) 22:27, 28 May 2013 (UTC)

From a quick glance these sources appear to be about what would happen if we reduced CO2 emissions, and the various feedback mechanisms that kick in. What was being discussed above is what would happen if there were no natural greenhouse gases in the first place (i.e not like on earth). Nonetheless an interesting paper. IRWolfie- (talk) 23:03, 28 May 2013 (UTC)

This deserves place. Do you know other source?

Annual greenhouse gas emissions have increased by over one-third from 1992 to 2013.Warming World: It's Time to Give Up the 2 Degree Target Spiegel Online 2013

Watti Renew (talk) 15:53, 18 June 2013 (UTC)

It's an opinion piece (albeit the factual claim is fairly uncontroversial). We already have a paragraph on the increase of emissions in the very section - we could add a half-sentence about the degree there if we find a better source. But see WP:SUMMARY - it should probably go into Carbon dioxide in Earth's atmosphere first (and that article could use some work, anyways). --Stephan Schulz (talk) 17:40, 18 June 2013 (UTC)

"These measurements indicate that the Sun's output has not increased since 1978, so the warming during the past 30 years cannot be attributed to an increase in solar energy reaching the Earth. "

It assumes that the Solar output wasn't in an elevated state in 1978. The graph http://en.wikipedia.org/wiki/File:Sunspot_Numbers.png suggests that it has been in such a state since about 1940... — Preceding unsigned comment added by 95.25.216.37 (talk • contribs) 16:45, 7 July 2013‎

The logic in the article is based upon the high quality scientific literature cited in the references. If you think you have better logic than all these scientists, you either need to get it published in a peer reviewed journal, or find places where it already has been. We don't tend to base article text in a top-level article such as this upon any one paper either, it is based on scientific consensus as summarised in review documents. The reference for the sentence you quote says "During the same period, the Sun’s energy output (as measured by satellites since 1979) has followed its historical 11-year cycle of small ups and downs, but with no net increase", which seems fine to me, and agrees with the graph too. --Nigelj (talk) 17:46, 7 July 2013 (UTC)

Yes, I'm not sure what the IP is looking at from the Sunspots graph to say anything about being in an elevated state, IRWolfie- (talk) 23:24, 7 July 2013 (UTC)

Articles might be correct, the statement as is is false and deceptive, trying to present absence of evidence as evidence of absence by completely ignoring the possibility of alleviated output in 1978 and after. As for sunspot graphs, those same measurements proved that there is some, although minor (~0.1%), correlation between sunspot activity and solar output. If there is some evidence that solar output wasn't in an increased state in 1978, it should be mentioned, otherwise it only proves that there was no increase since 1978 and nothing else, leaving the possibility of increased solar output as the main culprit of global warming. 95.27.58.150 (talk) 21:51, 11 July 2013 (UTC)

Can we just ignore this fringe, forum style nonsense? This isn't an attempt to improve the article. HiLo48 (talk) 23:16, 11 July 2013 (UTC)

Without commenting on whether the underlying point is fringe, flawed or on target, the inference in the article:

Since 1978, output from the Sun has been precisely measured by satellites.[99] These measurements indicate that the Sun's output has not increased since 1978, so the warming during the past 30 years cannot be attributed to an increase in solar energy reaching the Earth.

is incorrect. One cannot draw the conclusion "so the warming .. cannot be attributed" from the premise "the Sun's output has not increased since 1978". A few seconds reflection on how radiation transfer works should suffice to understand the problem.

I suspect the IP's suggestion (that the level in 1978 is elevated beyond earlier years) is flawed, so we ought to either address it, or rethink the sentence construction so it doesn't make the flawed inference. As it currently reads it is not simply OR, it is flawed OR and unsupported by a reference.--SPhilbrick(Talk) 01:13, 21 July 2013 (UTC)

"Warming of the climate system is unequivocal, and scientists are more than 90% certain that it is primarily caused by increasing concentrations of greenhouse gases produced by human activities such as the burning of fossil fuels and deforestation." Footnotes 3, 4 and 5 refer to the IPCC reports. Having Wikipedia use them for support of its Banner Statement in this article is to liken Wikipedia to the IPCC. To have Wikipedia embrace and point to the IPCC. I think we may agree that the IPCC has a mission statement, a track record, and some amount of politics associated with it. I'd expect Wikipedia to know what is Science and what is Science and Politics together. Footnote 6 is the one non-IPCC footnote. The link from the footnote leads to this: "The compelling case for these conclusions is provided in Advancing the Science of Climate Change, part of a 'congressionally requested' suite of studies known as America's Climate Choices." "Advancing the Science of Climate Change 'calls for a single federal entity' or program to coordinate a national, multidisciplinary research effort aimed at improving both understanding and responses to climate change." Is that independence? Perhaps with its Banner Statement on this sometimes contentious issue, Wikipedia can lead us to independent Scientists as the basis for its content. A step in the right direction? A helpful thing maybe? I am not disagreeing with the Statement here. I am questioning the quality of the footnotes? Forgive me if this entry is in the wrong place. It's been quite awhile since I've done this. Nanabozho (talk) 00:05, 14 July 2013 (UTC)

Anyone can kick in the dirt and flab their elbows. We deal here with specific suggestions for ways to improve articles based on the wikipedia meaning of "reliable sources". If you have a suggestion for article improvement based on such sources, then please state it. Vague kicking in the dirt just makes it dusty.NewsAndEventsGuy (talk) 01:12, 14 July 2013 (UTC)

I don't know what you are trying to say or what change you are proposing, IRWolfie- (talk) 08:55, 14 July 2013 (UTC)

I am sorry for bringing up my point. To respond to IRWolfie, I am proposing better footnotes, 3-6 to better support the statement that precedes those footnotes. If the IPCC has as part of its mission, "the implementation of the United Nations Framework Convention on Climate Change." and that framework is a treaty, and if the objective of that treaty is to, "stabilize greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system." I am starting to see a non-independent source. You may not be following me here, but ask yourself is the IPCC independent enough? Can better support for the statement be found? You may conclude that the IPCC is a good enough source for the statement at issue. Thank you NewsAndEventsGuy. I looked at that reliable sources page. I couldn't find the part where governmental organizations were mentioned. I looked here: Wikipedia:Current science and technology sources, and didn't find the IPCC listed. Should it be? — Preceding unsigned comment added by Nanabozho (talk • contribs) 20:38, 14 July 2013 (UTC)

I don't really understand your point. The quote - Warming of the climate system is unequivocal, and scientists are more than 90% certain that it is primarily caused by increasing concentrations of greenhouse gases produced by human activities such as the burning of fossil fuels and deforestation - is either a direct quote, or a close paraphrase, from the IPCC report. So of course it is sourced to the IPCC - how could it not be?

As for is the IPCC independent enough? - you may (or you may not, who knows, I'll assume you are for the moment) be saying that in good faith, but you can hardly be unaware that its a common septic talking point. Using that kind of phraseology is going to get people's hackles up. However, I can answer your question, and the answer is Yes William M. Connolley (talk) 20:57, 14 July 2013 (UTC)

William said, "its a common septic talking point"..... I broke a rib there, William. Still laughing NewsAndEventsGuy (talk) 00:29, 15 July 2013 (UTC)

Thank you for your reply and sorry about forgetting to sign my comment. I wasn't able to track down the 90% part using the footnotes or numerous Google keyword searches. The IPCC does talk about various confidence level with 90% being one of them, but that's as close as I got. I think the 90% sight should be easily findable using the included footnotes. If it is a confidence interval and I am not saying that it must be, where's the information behind it? "...scientists are more than 90% certain.." I'd like to know was it a survey? A vote? A study of various peer-review papers and seeing which ones agreed with the statement? I called it a Banner Statement, I've seen it quoted. While we are sensing a bit of disagreement here I am still wondering if there's someway to improve on a Banner Statement on a sometimes contentious page? I recall some of the generalities as to how this is supposed to work, and I am trying to stay within the Wikipedia Guidelines. Nanabozho (talk) 00:49, 20 July 2013 (UTC)

The IPCC quote is "Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations." This is from the third reference after the sentence. The conversion of the phrase very likely into "more than 90% certain" is due to information given in the second reference. I don't know how much clearer that can be, although you do have to click on the references and read what you see. Science does not proceed by surveys and votes, such percentages are estimates of the scientific and mathematical uncertainties in the data and the modelling, but we should not have to explain the whole scientific method in every science article. --Nigelj (talk) 14:15, 20 July 2013 (UTC)

I'm not quite following. Are you challenging the use or the IPCC as a reference, or are you questioning whether the quote in this article is a faithful representation of the IPCC report?--SPhilbrick(Talk) 01:20, 21 July 2013 (UTC)

I'm interested in discussing improvements to the section of the article on "natural systems." In my opinion, the section presents a good summary of the subject, but I have some criticisms.

The section states that the Arctic will be largely ice-free by 2037. There are, however, other estimates. In IPCC AR4, some models using the SRES A2 emissions scenario projected ice-free summers by the end of the 21st century . According the UK Met Office, recent models project an early "plausible" date of 2025-2030 .

I do not agree with how the section covers attribution of climate change. In my view, there is an undue focus on the study by Hansen et al. The section should provide a summary of the literature on attribution, rather than focussing on individual studies. AR4 contains a number of attributions which aren't mentioned, including the contribution of anthropogenic forcing to sea level rise and loss of Arctic sea ice .

Hansen et al's work on this issue does not appear to reflect a consensus view (Seneviratne et al., 2012:127). Kevin Trenberth has stated that "James Hansen and I are pushing to get scientists to think about and do statistics on this rather differently, and now we are not part of mainstream in this regard" .

The section's summary of extreme events is not consistent with the recent IPCC SREX report. The section states that in the future, there will be more intense droughts and floods. No caveats are given. By contrast, the SREX report is far more cautious in its projections of changes in droughts and floods (IPCC, 2012:11). A number of projected changes in extremes described in the SREX are not mentioned, e.g., increased intensity, duration and frequency of heat waves. Enescot (talk) 06:25, 11 February 2013 (UTC)

I've prepared a draft revision of the "natural systems" section that I would like to discuss. New or revised sentences are italicized:

"Global warming has been detected in a number of natural systems. Some of these changes are described in the section on observed temperature changes, e.g., sea level rise and widespread decreases in snow and ice extent. Anthropogenic forcing has likely contributed to some of the observed changes, including sea level rise, changes in climate extremes (such as the number of warm and cold days), declines in Arctic sea ice extent, and to glacier retreat (Hegerl et al 2007).

(as current revision) In the IPCC Fourth Assessment Report, across a range of future emission scenarios, (as current revision...) contribute 4–6 metres (13 to 20 ft) or more to sea level rise.[125]

Changes in regional climate are expected to include greater warming over land, with most warming at high northern latitudes, and least warming over the Southern Ocean and parts of the North Atlantic Ocean.[123] During the 21st century, glaciers and snow cover are projected to continue their retreat (Meehl et al 2007). Projections of declines in Arctic sea ice vary (Meehl et al 2007). Recent models suggest that Arctic summers could be ice-free (defined as ice extent less than 1 million square km) as early as 2025-2030 (UK Met Office 2012).

Future changes in precipitation are expected to follow existing trends, with reduced precipitation over subtropical land areas, and increased precipitation at subpolar latitudes and some equatorial regions (NOAA GFDL, 2007, p.1). Projections suggest a probable increase in the frequency and severity of some extreme weather events, such as heat waves (IPCC 2012, pp9-13).

Enescot (talk) 09:57, 20 February 2013 (UTC)

In view of the discussion below ("IPCC projection underestimations"), I was thinking of revising the "natural systems" section to include a summary of more recent global sea level rise projections. At present, the section only mentions the 2007 projections from the IPCC 4th Assessment (AR4). A recent (2012) literature assessment was conducted by the US National Research Council. The NRC study includes their own projections of sea level rise and cites projections by Vermeer and Rahmstorf (2009) . I was thinking that these two projections could be cited in the section alongside those from AR4. It would probably only require one or two sentences. Alternatively, a graph of the projections could be added. Enescot (talk) 05:54, 6 March 2013 (UTC)

I've prepared a draft image of sea level rise projections, shown above. Enescot (talk) 06:49, 16 March 2013 (UTC)

The image for sea level rise mis-states the IPCC AR4 (2007) because it suggests IPCC stated an upper bound for their projection. That's false. The SPM says "Because understanding of some important effects driving sea level rise is too limited, this report does not assess the likelihood, nor provide a best estimate or an upper bound for sea level rise". Also, trying to put all the info in one table instead of breaking the tables into three with a header for the year makes it confusing. I was familiar with the numbers but took several seconds to orient myself. A newbie could easily miss the years on the right hand border. NewsAndEventsGuy (talk) 14:32, 29 March 2013 (UTC)

Thanks for the feedback. If you want to draw a new graph, then the current graph could be replaced. Alternatively, I'd be pleased to redraw the graph in view of your comments. However, I'm not entirely clear on what you have in mind. If the graph is to be broken up into three graphs, then I presume that each graph would have its own set of axes. In my view, it might be more straightforward to omit the 2030 and 2050 projections.

The image description does mention the limitations of the IPCC projections:

"The IPCC (2007) estimates do not include all of the possible contributions from ice sheets (US NRC, 2012, pp.84-85). According to US NRC (2012, p.88), "the IPCC (2007) projections are likely underestimates because they do not account fully for cryospheric processes"."

I've added the SPM text you've quoted to the image description. The comment could also be added to the graph itself. I should note that the other projections shown in the graph are much higher than the IPCC's. Therefore, I think it should be fairly obvious that the high-end IPCC projection is not an upper-bound estimate.

Another point is that graphs often do not include the full range of possible outcomes. An example is the IPCC's graph of temperature projections . Enescot (talk) 09:56, 31 March 2013 (UTC)

I don't do graphics. If you've got the knowhow is that something you could do? I like the layout used in the graphic in this article, which would work well here, I think. NewsAndEventsGuy (talk) 23:32, 1 April 2013 (UTC)

I've found a sea level rise graph by NOAA which could be used to replace the existing graph . The graph's on p.3 of the report. Enescot (talk) 09:26, 16 April 2013 (UTC)

I've prepared a new graph of projected sea level rise, shown above. It is based on several studies. Enescot (talk) 07:49, 5 May 2013 (UTC)

Reply to comments on User talk:Enescot#Nit police:

SPhilbrick - problem with citations: On the graph's description page, a few of the Harvard citations did not work. I've corrected them.

NewsAndEventsGuy - AR4 projections: I've responded to comments on the IPCC projections (see above). The image description explains that the IPCC did not project an upper-bound for sea-level rise. I've tried to make my graph similar to others produced by US NRC (figure 5.6, p.94) and NOAA (figure 9, p.11). As I've already stated, many projections do not include an upper-bound estimate. For example, refer to the studies cited in the graph. To repeat an earlier point, it's hard for me to see how AR4's projections could be misinterpreted. The graph shows several studies that project greater sea-level rise than AR4 does. Enescot (talk) 12:55, 5 June 2013 (UTC)

Where an RS gives no upper boundary, I'm opposed to a picture that looks like it does because I do not trust the reader to read the text that says the picture does not actually say what it appears to say at a simple glance. One way to solve this in pictorial form is to give each projection a solid outline, except for those RSs that do not express an upper boundary make that part of the border a dashed line, topped by an arrow and above the arrow add a question mark. That way, the reader instantly sees what the RS says even if the reader, like the preschoolers I know, "just looks at the pictures". NewsAndEventsGuy (talk) 15:23, 5 June 2013 (UTC)

I don't agree with your interpretation of the graph. I believe that my graph is consistent with graphs produced by reliable sources (see my previous post). As I've stated, all the SLR graphs I've looked at do not show the full range of uncertainty. In my experience, uncertainty is usually discussed in the accompanying text.

I agree that using dotted outlines on the graph instead of solid outlines would be an improvement. As for adding arrows, I disagree. I'm not aware of any graphs in reliable sources that are presented like this. Enescot (talk) 10:30, 12 June 2013 (UTC)

Dotted/pink/polkadotted..... the border is irrelevant unless it communicates information. In this case, any border across the top of a bar for IPCC AR4's sea level rise projections is likely to misrepresent what they said, i.e., they explicitly said the numbers they were giving were for only some factors affecting sea level, and did not include other factors, and their numbers did not express an upper limit. You can wrap the bar in roses, but it still needs something to graphically communicate that the RS explicitly says we should not read the top of the bar as an upper limit. I have suggested an arrow and a question mark to graphically depict the text in this RS. Your rebuttal that you have not seen a graph showing this textual info in this manner doesn't really address the issue we have to meet for graphics here. The top question we have to ask is whether our picture accurately explains the RS text. An up arrow and a question mark would do that, IMO. There are probably other ways but a simple bar that misleads folks into thinking IPCC AR4's numbers were intended as an upper limit will not. NewsAndEventsGuy (talk) 12:23, 12 June 2013 (UTC)

I've already said that I disagree with your interpretation of the graph. However, I have prepared a new graph and draft text for discussion:

revised article text:

"Over the 21st century, the IPCC projects sea level rise of between 18-59 cm. The IPCC do not provide a best estimate of sea level rise, and their upper estimate of 59 cm is not an upper-bound, i.e., by 2100, global mean sea level could rise by more than 59 cm. The IPCC's projections are conservative, and may underestimate future sea level rise (see graph opposite) (US National Research Council, 2010, p.243)."

Enescot (talk) 09:44, 21 June 2013 (UTC)

We appear to be in an infinite loop. Our rules say pics have to show what the RS text shows; your legend has a type of marking for the upper bounds of an estimate; that marking appears in association with AR4; AR4 explicitly says its numbers do not provide an upper boundary. Er go, the pic does not show what the AR4 RS text says. Only a picture that graphically depicts the *lack* of an upper estimate from AR4 will align with that particular RS. I have already suggested various ways to do that. Your only reason for rejecting one of the ideas I proposed is that you have not seen anyone else do that. But our policies do not exclude images for that reason. Rather, our policies say pics should communicate RS text effectively. We seem to be at an impasse. We need a picture that shows no upper limit being expressed in AR4.

X=X+1

RETURN

NewsAndEventsGuy (talk) 15:11, 21 June 2013 (UTC)

As I've said, the graph that I've produced is entirely consistent with two reliable sources: US NRC (2012, figure 5.6, p.94) and NOAA (figure 9, p.11). You may not be satisfied with these graphs, but they still are reliable sources.

Earlier on, I did suggest that the existing graph could be replaced with one by NOAA (Figure ES 1, p.3). This graph does not include the IPCC projections. It is, however, representative of the literature, with projections ranging from 0.2-2.0 m by 2100, relative to 1992. NOAA state: "We have very high confidence (greater than 9 in 10 chances) that global mean sea level (based on mean sea level in 1992) will rise at least 8 inches (0.2 meters) and no more than 6.6 feet (2 meters) by 2100".

Enescot (talk) 12:45, 29 June 2013 (UTC)

PROPOSAL; just omit IPCC AR4 from the image and inclusion of all this more recent work you wish to include will make a great improvement to the article.

DETAILED RESPONSE; Our images have to accurately reflect the source. With respect to our point of disagreement (how to graphically depict IPCC AR 2007 WG1 sea level rise projections), the source to be "reflected" is IPCC AR 2007 WG1. The trouble we're having is that IPCC explicitly said that they were not projecting an upper boundary due in part to what was, at the time, poorly constrained ice sheet behavior.

Your first reference in your last comment appears to deal with the "AR4 no-upper boundary" problem by retroactively calculating an upper boundary. They showed IPCC's numbers, which omitted "rapid dynamical changes in ice flow" and then added what I think is their own number for such rapid changes (17cm). In effect, this image supports my point that we should not just draw out a bar that appears to say IPCC projected an upper boundary at 59cm, because the RSs all agree that is untrue. The way your first reference tried to graphically depict the lack of an upper boundary is not an RS for us to use no approach at all.

Your second link does indeed graphically show IPCC's numbers as though they included an upper boundary for their projection. But the text of that full reference admits "IPCC AR4 estimates did not include, however, potential rapid dynamic response of Greenland and Antarctic Ice Sheets as reflected in our Highest Scenario." So what is this second source an RS for? For one thing, it is an RS for how they dealt with this very problem. But so what? Our rules still say our images have to reasonably represent what is stated in the source. IPCC explicitly refrained from stating an upper boundary on their projection. Even if NOAA did not choose to graphically depict the lack of an upper boundary, if we make a picture of IPCC numbers, we still have to follow our rules, not just blindly endorse NOAA's technical editing decisions.

An up arrow and a question mark is one of the few alternative methods I have suggested. A new idea is to simply omit IPCC from the graphic, and instead deal with IPCC's numbers in text only.

Thanks for caring about adding the more recent research. On the need to do that, I definitely agree!

NewsAndEventsGuy (talk) 12:12, 7 July 2013 (UTC)

I still disagree with your idea of adding arrows to the graph. I also do not agree with your suggestion of omitting the IPCC estimates. The IPCC's estimates are included in both the US NRC and NOAA graphs (figure 9, p.11).

In my opinion, you are placing too much emphasis on the higher end projections of sea level rise. My understanding is that all SLR projections are highly uncertain, including those that project SLR greater than that in AR4. This is discussed in the US NRC and NOAA reports, as well as a literature review by Good et al. For instance, Good et al (p.12) state: "Although there are predictions of sea level rise in excess of IPCC AR4 values, these typically use semi-empirical methods that suffer from limited physical validity".

In my opinion, the NOAA graph (Figure ES 1, p.3) that I suggested previously would be a suitable replacement for the existing graph. It broadly reflects the literature, with each projection assuming a different contribution to SLR from ice sheets. This is discussed in pp.10-14 of the report.

Enescot (talk) 10:04, 9 July 2013 (UTC)

And I am happy to use a modified version of that image, one which includes some manner of graphically depicting IPCC's explicit statement that the largest number in their range did not represent an upper boundary. I am not a graphics guy or I would modify it and post to the article myself. I appreciate your desire to add more recent research to the graph, but not at the expense of an image that casts a false representation of the text in the IPCC RS. Since we've come full circle several times, I would appreciate your taking the next step of DR instead of rehashing the argument for an 7th or 8th time. Even better, maybe others would express an opinion, please? NewsAndEventsGuy (talk) 12:59, 9 July 2013 (UTC)

I haven't read all the above, sorry. My understanding from memory is that the AR4 numbers given in the figure aren't really SLR projections, because they exclude some unknown components . Perhaps they should just be omitted William M. Connolley (talk) 13:20, 9 July 2013 (UTC)

Thanks for joining in and your memory is correct. In my first post in this thread I quoted from where IPCC says they were not projecting an upper boundary. Simply omitting AR4 from the image is also OK with me, but Enescot has (so far) rejected that option. NewsAndEventsGuy (talk) 14:00, 9 July 2013 (UTC)

Omitting AR4 isn't something I'd do lightly, normally its the wrong thing to do. In the case of SLR, though, I think they came in for a certain amount of (justified) stick for omitting important elements. There's also the problem that their estimates are entirely model based - models are fine, of course, but there's a literature on empirical scaling (which some of the other estimates of the figure use, so I'm not complaining that we're ignoring that) which the AR4 ignores. And (although I wouldn't suggest we say this) its clear that the AR4 lower bound is ridiculous - there's no way that anything less than, say, 3mm/yr is believable William M. Connolley (talk) 22:09, 9 July 2013 (UTC)

I think we have our wires crossed. The graph that I've suggested as a replacement (figure 10 on p.12 of the NOAA report) does not include AR4's projections. The projections are by Paris et al, and are based on a literature assessment that includes AR4 projections. The projections by Paris et al range from 0.2-2.0 m by 2100, relative to mean sea level in 1992.

"Our Intermediate-Low [0.5 m] and Lowest Scenarios [0.2 m] are optimistic scenarios of future environmental change assuming rates of ice sheet loss and ocean warming slightly higher or similar to recent observations" – p.13 of report

An alternative would be to have no graph and simply describe projections in text. For example:

"Over the 21st century, the IPCC projects that global mean sea level could rise by 18-59 cm. The IPCC do not provide a best estimate of global mean sea level rise, and their upper estimate of 59 cm is not an upper-bound, i.e., global mean sea level could rise by more than 59 cm by 2100. The IPCC's projections are conservative, and may underestimate future sea level rise . Projections by Paris and others suggest that global mean sea level could rise by 0.2 to 2.0 m by 2100, relative to mean sea level in 1992"

Enescot (talk) 13:25, 16 July 2013 (UTC)

Summary

Thanks for the the back and forth. If I understand correctly, the proposal in this thread has zeroed in on the suggestion to use this image (figure 10 on p.12 of the NOAA report) in place of something. If we do that we will be displaying someone else's graphically misleading IPCC number, but as no one else appears to object, I will at least say this graphic mis-statement softens the misleading impact compared to others we have discussed, so I will probably go along to get along. Before I commit to that, please help me distill the discussion to its essentials. Q1 Remind me please what image you want to take out when this one is put in? Q2 Besides image replacement, are there other open items in this thread? NewsAndEventsGuy (talk) 12:27, 22 July 2013 (UTC)

As I've said, the graph by Paris et al does not include the IPCC's projections. Their low-end projections are their own:

"Our Intermediate-Low [0.5 m] and Lowest Scenarios [0.2 m] are optimistic scenarios of future environmental change assuming rates of ice sheet loss and ocean warming slightly higher or similar to recent observations" – p.13 of report

I do not agree that the graph by Paris et al is misleading. There is nothing unusual about producing projections that span the range in the literature. The IPCC did the same thing when they produced the SRES scenarios.

Q1: The following image would be replaced:

I've also suggested an alternative where the graph above would be removed and replaced with the following text:

"Over the 21st century, the IPCC projects that global mean sea level could rise by 18-59 cm. The IPCC do not provide a best estimate of global mean sea level rise, and their upper estimate of 59 cm is not an upper-bound, i.e., global mean sea level could rise by more than 59 cm by 2100. The IPCC's projections are conservative, and may underestimate future sea level rise [22]. Over the 21st century, Paris and others suggest that global mean sea level could rise by 0.2 to 2.0 m, relative to mean sea level in 1992"

Since my last post, I've altered the text above slightly.

Q2: I don't think so.

Enescot (talk) 12:51, 24 July 2013 (UTC)

I can live with the NOAA graph, though I note that the intermediate range NOAA used was simply imported from IPCC ("Our Intermediate-Low Scenario is based on the upper end of IPCC Fourth Assessment Report (AR4) global SLR projections resulting from climate models using the B1 emissions scenarios." NOAA report, p 12). In so doing NOAA blatantly ignored IPCC's explicit statement that it was not to be used as an upper bound, nor a best estimate. While I agree that it is common to summarize the range of the literature, I remain steadfast in my belief that it is uncommon and improper to summarize it falsely, which is what people do when they say or imply IPCC projected only around 59cm +/-, as though that were an IPCC AR4 best estimate or IPCC AR4 upper boundary, because that is misrepresentation of what IPCC AR4 said. NOAA made that error. Using this graph we import that error, but in a blunted way with which I can live if it is only you and me trying to resolve this. NewsAndEventsGuy (talk) 18:44, 24 July 2013 (UTC)

I don't agree with your criticism of the NOAA report. Their scenarios are intended for the purposes of risk assessment. The authors of the report state that "specific probabilities or likelihoods are not assigned to individual scenarios in this report, and none of these scenarios should be used in isolation" (p.1).

My suggested revision is below. New text is in italics. I haven't uploaded the NOAA graph yet:

"... declines in Arctic sea ice extent, and to glacier retreat.[132]

[NOAA graph. Caption: Projections of global mean sea level rise by Paris and others. None of these scenarios is a best estimate of future sea level rise.]

[new text] Over the 21st century, the IPCC projects that global mean sea level could rise by 18-59 cm. The IPCC do not provide a best estimate of global mean sea level rise, and their upper estimate of 59 cm is not an upper-bound, i.e., global mean sea level could rise by more than 59 cm by 2100. The IPCC's projections are conservative, and may underestimate future sea level rise [22]. Over the 21st century, Paris and others suggest that global mean sea level could rise by 0.2 to 2.0 m, relative to mean sea level in 1992 (refer to graph opposite)

On the timescale of centuries to millennia, the melting of..."

Enescot (talk) 13:47, 31 July 2013 (UTC)

Reconsidering.... If I understand right, your proposed RS (a 2012 NOAA report, see link under the subsection heading above) includes a "low" value for sea level rise based on ice sheet behavior holding steady and past SLR rates holding steady, to yield what even the authors called an "optimistic" low-end projection 20cm above 1992 levels. Besides Enescot does anyone think 20cm on top of 1992 levels reflects the bulk of the literature for low estimates? For one thing, see this press coverage of a new PNAS paper. To be fair, I haven't seen the original PNAS paper, and I don't know if they discuss low estimates. I'd just like to know what those more knowledgeable than myself have seen in other current RSs for low projections? NewsAndEventsGuy (talk) 16:40, 31 July 2013 (UTC)

Since no one else has climbed on board, I defer to the silence and change my "object" to "no contest". Go ahead and make your desired change Enescot (talk · contribs), and I will renew my objection, maybe, if the edit inspires other resistance. Thanks for your patience during an extended yet constructive back and forth. NewsAndEventsGuy (talk) 22:58, 4 August 2013 (UTC)

Thanks for the feedback. I'd just like to further respond to some of your comments. I have never suggested that slr of 20 cm is reflective of recent low estimates. I have said that the range of 0.2-2.0 m is comparable to the range in the literature. This is explained in the NOAA report. The IPCC's estimates were subject to a very rigorous process of review, so they are robust estimates. My suggested revision includes the IPCC's own caveats, as well as the more recent comment by the US NRC: "The IPCC's projections are conservative, and may underestimate future sea level rise ".

I've previously referred to a review by Good et al (p.12), which states that: "Although there are predictions of sea level rise in excess of IPCC AR4 values, these typically use semi-empirical methods that suffer from limited physical validity"

I believe that this is the relevant PNAS paper , which I obtained from . I haven't fully read the paper, but it seems to focus on long-term, multi-century estimates of slr.

The existing revision of the article does mention long-term slr, but it could be improved. At present, it does not mention the commitment to slr from thermal expansion alone. I've put together a draft revision based on US NRC (2011):

"Widespread coastal flooding would be expected if several degrees of warming is sustained for millennia. 2 C of warming (relative to pre-industrial levels) could lead to eventual sea level rise of around 1 to 4 m due to thermal expansion of sea water and the melting of glaciers and small ice caps. Melting of the Greenland ice sheet could contribute an additional 4 to 7.5 m over many thousands of years."

Enescot (talk) 12:05, 6 August 2013 (UTC)

In this well-written and good faith series of edits, Watti Renew (talk · contribs) added a paragraph on GHG emissions related to travel. It is well sourced, but travel is just one slice of the emissions pie. I propose this paragraph be relocated to a sub article focused on GHGs or emission sources or mitigation (or a combination). We should talk about the biggest slices of the pie in a few sentences and have an overview paragraph that briefly reviews the colleciton of smaller slices for navigation purposes.

Anyone else have an opinion? NewsAndEventsGuy (talk) 17:13, 23 July 2013 (UTC)

I agree with you. I've moved the information to greenhouse gas#Sectors. Enescot (talk) 12:24, 24 July 2013 (UTC)

Posting at this top level GW article to call the attention to all users, of whatever persuasion on this issue....

Since we all sometimes want to add, or remove, POV tags from this tree of articles, please take a moment to visit this important discussion about whether we can remove the POV tag when any discussion has long been dormant. NewsAndEventsGuy (talk) 19:01, 25 July 2013 (UTC)

The links get a 500 server error, and have been doing so since March. Should the links to them in the FAQ be removed? Sorry if this has already been discussed. 74.128.43.180 (talk) 18:44, 13 August 2013 (UTC)

144.160.226.53 posted this comment on 28 May 2013 (view all feedback).

Charts Outdated==

Some charts are really old with data only up to 2004, so almost 10 years old - for this topic there should be newer, current data available. It's especially interesting to see the current development over the past few years; this is really crucial and I'm sure the data is available...

Any thoughts?

We should Update charts

Austin56713 12:40, 26 July 2013 (UTC) — Preceding unsigned comment added by Austin56713 (talk • contribs)

Is this a good chart blue line represents average:

http://www.globalsherpa.org/wp-content/uploads/2012/12/noaa-global-warming-mean-temperature-graph-jan-dec.gif — Preceding unsigned comment added by Austin56713 (talk • contribs) 12:49, 26 July 2013 (UTC)

I agree that some of the charts could be updated. The lead section of the article already contains an up-to-date graph of global mean temperature. I have some more recent data on Earth's energy imbalance . I also know of some other sources of more recent data (e.g., of greenhouse gas emissions by sector and cumulative CO2 emissions by region) but I'll have to dig around for these. Enescot (talk) 12:42, 13 August 2013 (UTC)

I've found two possible replacements for the bubble chart showing "where global warming is going" (global warming#Observed temperature changes):

The first is a pie chart (figure 1, public-domain) that shows more recent data in %. Alternatively there is a bar chart in Hansen et al (2011: p.13,433, figure 10b) that shows changes measured in watts per square metre. The bar chart is available under a Creative Commons Attribution 3.0 Unported license. My own preference is for the pie chart.

Enescot (talk) 12:32, 2 September 2013 (UTC)