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Earth not too sensitive?

by Nomad Tue Feb 5th, 2013 at 07:50:59 AM EST

At the New York Times, journalist Andrew Revkin provides a comprehensive run-down of current scientific thinking on a crucial aspect of a warming climate – the sensitivity of the planet to increasing greenhouse gasses.

A Closer Look at Moderating Views of Climate Sensitivity - NYTimes.com

There’s still plenty of global warming and centuries of coastal retreats in the pipeline, so this is hardly a “benign” situation, as some have cast it.

But while plenty of other climate scientists hold firm to the idea that the full range of possible outcomes, including a disruptively dangerous warming of more than 4.5 degrees C. (8 degrees F.), remain in play, it’s getting harder to see why the high-end projections are given much weight.

This is also not a “single-study syndrome” situation, where one outlier research paper is used to cast doubt on a bigger body of work — as Skeptical Science asserted over the weekend. That post focused on the as-yet-unpublished paper finding lower sensitivity that was inadvisedly promoted recently by the Research Council of Norway.

In fact, there is an accumulating body of reviewed, published research shaving away the high end of the range of possible warming estimates from doubled carbon dioxide levels.

After years of reports in the media that doubling the amount of greenhouse gasses in the earth's atmosphere could see temperatures creeping up to more than a worrying three (IPCC, here), a frightening six (2007, here) or even an apocalyptic eight degrees Celsius (2013, here), now a stack of science findings that show lesser extremes is beginning to find its way.

Previously, media presentation on climate sensitivity have predictably focussed on the high and sensational end of the computed ranges – but plenty of scientists have actively played the part to toot around scary numbers. Just see the last example.

Findings listed by Revkin are not even particular new; some have been around for years. But the topic is controversial and will likely remain that for a while. Before media start writing on a revision of what they've been writing for years, it needs a bit of weight behind it. It now seems we've reached a first turning point.

Of course, even when the implications of earth's lower sensitivity are huge, it doesn't mean we're out of the woods. It doesn't mean either that the earth is practically insensitive to increasing carbon, which is how the sceptical crowds frame the discussion. It does mean that the earth destroying scare scenarios have lost ground – yet again.


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Well, 2 degrees (especially coupled with the other overconsumptions) does sound to me like an earth destroying scare scenario.

Plus, we are way ahead in terms of losing the Arctic cap. So even if the higher scenarios don't happen (good) in terms of temperature, some of the effects of higher temperature may have been underestimated.
And again, the lower scenarios are scary enough. Let alone the median.

Earth provides enough to satisfy every man's need, but not every man's greed. Gandhi

by Cyrille (cyrillev domain yahoo.fr) on Tue Feb 5th, 2013 at 08:31:03 AM EST
I agree that even a 2 degrees increase doesn't look to be a fun ride - but not as unpractical for the future of humanity as, say, six degrees per doubling of CO2 concentrations. The current median looks to be 3 degrees C - but is definitely not carved in stone.

Still, an implication of a lower sensitivity also means it will take a lot longer before the earth reaches a 2 degrees C - and it implies that with 40% more CO2 in the atmosphere since 1850 there won't be a lot more warming in the pipeline, something that was commonly feared.

by Nomad on Tue Feb 5th, 2013 at 08:59:00 AM EST
[ Parent ]
Earth and nature can take whatever we throw at them. But our civilization can't.
by epochepoque on Tue Feb 5th, 2013 at 08:18:35 PM EST
[ Parent ]
Welcome to Jurassic Park.


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sapere aude
by Number 6 on Wed Feb 6th, 2013 at 05:07:11 AM EST
[ Parent ]
I remain intrigued by the huge spike in global warming, roughly 1980-2000 (since then, it looks like we're on a bumpy plateau), which induced the higher-range climate sensitivity numbers.

I haven't yet seen (or assimilated) any explanation for this : it doesn't seem to be in step with any well-understood cyclical phenomena.

It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II

by eurogreen on Tue Feb 5th, 2013 at 10:27:42 AM EST
I would say that the faster than expected melting of ice in the poles may well be part of the story. Temperature in the atmosphere is only one of the places where the extra energy can be stored. The phase change of colossal quantities of ice would be able to absorb a lot of heat.

How much? Well, I'd need to know exactly how much melting we've had and, obviously, I don't have that ready at hand. But you'd expect any extra melting relative to what was expected to be accompanied by a slowing down of the air temperature increase.

Then, if I recall correctly, the first decade of the millennium had a solar minimum in it, so that you'd expect it to be a low period of the temperature cycle.

Finally, I don't think it looks that we've been on a bumpy plateau since. 1998 may do that to you, but it's something like 7 of the 8 hottest years ever in the last decade. Clearly the last decade was hotter than the one before that.

Earth provides enough to satisfy every man's need, but not every man's greed. Gandhi

by Cyrille (cyrillev domain yahoo.fr) on Tue Feb 5th, 2013 at 11:19:59 AM EST
[ Parent ]
There are one trillion tons less Arctic ice than there was a year ago. How much phase change energy is that?

Phase change requires 334 Joules per gramme = MegaJoules per tonne of ice.

So, this year's polar melt  accounts for 334 trillion megajoules of energy.
How much would that have warmed the atmosphere?.....

Dunno.

(Also, heat absorption by the ocean is poorly understood. A change in deep currents could be sucking heat out of the atmosphere and warming the depths.)

 

It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II

by eurogreen on Tue Feb 5th, 2013 at 11:34:49 AM EST
[ Parent ]
Too few data points, too much variation, your fit may vary, but I say bumpy plateau. HadCRUT :



It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II

by eurogreen on Tue Feb 5th, 2013 at 11:48:31 AM EST
[ Parent ]
Three El Niños with similar peaks (including 1998) but three La Niñas of increasing bottoms. This could be consistent with both a plateau and a warming trend. I say wait for the next El Niño before settling for a plateau.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Fri Feb 8th, 2013 at 06:07:16 PM EST
[ Parent ]
While I'm personally a very big fan of Ocular Econometrics (i.e. "just look at the fucking data"), it is not a good tool for determining break points at the outermost edge of an autocorrelated time series.

(Arguably there is no good tool for determining break points at the outermost edge of an autocorrelated time series, other than waiting for more data to roll around.)

- Jake

Austerity can only be implemented in the shadow of a concentration camp.

by JakeS (JangoSierra 'at' gmail 'dot' com) on Sat Feb 9th, 2013 at 04:38:39 AM EST
[ Parent ]
A comment on Real Climate addresses the question of an inflection point around the year 2000 :

RealClimate: 2012 Updates to model-observation comparisons

While not closed, given that there are depths below 2000 m, one might notice that the energy gain in the depth range 0-2000 m is steady so the rate of gain in the range 700 to 2000 m must have grown in the period you point to. Thus, disregarding the lowest depths, a change in the rate of mixing between the 0 to 700 m layer and the 700 to 2000 m layer during that period might explain what you noticed in fig. 3. It might also contribute to what you noticed in fig. 1. Look at the third figure (Comparison of Global Heat Content 0-700 meters layer vs. 0-2000 meters layer) here: http://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/

There are measurements indicating that wind strength and thus wave action are increasing globally http://www.sciencemag.org/content/332/6028/451 which might influence mixing as might increased evaporation which can change the vertical density profile in salt water. http://journals.ametsoc.org/doi/abs/10.1175/2010JCLI3377.1

This is not an explanation, just a few guesses at what might be occurring. That the 0-2000 m level of the oceans continues to gain thermal energy at a steady rate does indicate that warming continues at a steady rate though.

This led me to look up Tsonis and Swanson (loved but misunderstood by "climate sceptics") :

It's a climate regime shift

Conventional understanding for the switch to warming in the 1970s is that warming from CO2 overcame cooling from forcings such as sulfate aerosols. Tsonis and Swanson suggest an 'alternative hypothesis, namely that the climate shifted after the 1970s event to a different state of a warmer climate, which may be superimposed on an anthropogenic warming trend'. It's this final phrase, 'superimposed on an anthropogenic warming trend', that Swanson and Tsonis explore further in a subsequent research.

In 2009, they continue to examine the coupling of ocean cycles, stressing 'caution that the shifts described here are presumably superimposed upon a long term warming trend due to anthropogenic forcing' (Swanson & Tsonis 2009). They extend their analysis further in a paper that uses climate modelling to separate man-made and natural variability (Swanson et al 2009). When internal variability is filtered from the smoothed observed temperature (solid black line), the cleaned signal (dashed line) shows nearly monotonic warming throughout the 20th Century. In fact, the cleaned signal fits a quadratic shape which indicates the warming is accelerating.




Figure 2: Observed GISS 21-year running mean global mean surface temperature (heavy solid) along with that temperature cleaned of the internal signal (dashed). The cleaned global mean temperature warms monotonically, and closely resembles a quadratic fit to the observed 20th century global mean temperature (thin solid) (Swanson 2009).

The takeaway is that we would be in a "flattening" phase similar to the mid-20th century, due to changes in ocean mixing which swamp the anthropogenic signal.

Takeaway from the takeaway : if it is alleged that the climate forcing was overestimated in the late 20th century due to oceanic phenomena which were not taken into account augmenting the apparent anthropogenic signal, then there is a danger that it will be underestimated in the current phase, if indeed oceanic changes are lowering temperatures and are not accounted for by those estimating the climate forcing.

It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II

by eurogreen on Wed Feb 13th, 2013 at 08:55:05 AM EST
[ Parent ]
Well, the atmosphere weighs 5.3 million billion tons (quadrillion tons?).
And it takes 1.005J to heat up a gram of air by one degree.

So if your figures are correct, that absorbed .063°C of heating last year. That would mean quite a bit over a few years. Of course, some melting (glaciers certainly -however initially Antarctic ice was growing, not shrinking) may well have occurred in the previous period and you'd want to only account for the extra melting to see the impact on the trend if that was the case.

Earth provides enough to satisfy every man's need, but not every man's greed. Gandhi

by Cyrille (cyrillev domain yahoo.fr) on Tue Feb 5th, 2013 at 12:43:52 PM EST
[ Parent ]
The heat to melt Arctic ice has to come from somewhere and that somewhere appears to be a combination of solar warming, atmospheric convection and ocean currents. We have become aware of dramatically increased rates of ice melt not only of sea ice in the Arctic Ocean but also of glacial shelves and glacial ice itself in Greenland and Antarctica. The phase transition undergone by this ice absorbs massive amounts of heat and the increased area of open ocean in summer allows additional solar warming, thus providing a positive feedback loop to the process.

Since 2008 I have noticed changes to summer temperature patterns in northern Arkansas that are unlike anything from my childhood in adjacent north central Oklahoma or in the memory of longtime local Arkansas natives. For two years we had brief heat waves in June and early July followed by very mild temps in late July through September, which traditionally was the hottest period of the summer. I recall posting concerns at that time that we were 'benefiting' from the melting of Arctic ice.

Of course the process is chaotic and we have had somewhat different patterns since, but the most noticeable change seems to have been a strengthening and lengthening of the early summer heat wave which led to my installing a sun shade and misting over my garden last summer, as the heat was stopping tomatoes and cucumbers from setting fruit. The other change seems to have been a lessening of the cooler periods after the middle of July. So, in my own microcosm, I see little about which to be more optimistic. The effects of such warming as has been documented are quite sufficiently worrying and the trends are all in the wrong direction.  

As the Dutch said while fighting the Spanish: "It is not necessary to have hope in order to persevere."

by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Tue Feb 5th, 2013 at 01:02:50 PM EST
[ Parent ]
Interesting.
Trying to thing where I saw the opposite point of view: that the really scary predictions held by more than half of researchers are just not reported on because they conflict with conventional wisdom. Krugman? Had a graph with outcomes from Benign on the left to End of world at the right.

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sapere aude
by Number 6 on Tue Feb 5th, 2013 at 11:11:39 AM EST
The basic science here is still that we don't understand this system very well, that pumping more energy into it is a really, really, really bad idea and we should stop as soon as possible.

But we won't, because we're systematically incapable of it.

by Colman (colman at eurotrib.com) on Tue Feb 5th, 2013 at 12:02:16 PM EST
Systemically?

I distribute. You re-distribute. He gives your hard-earned money to lazy scroungers. -- JakeS
by Migeru (migeru at eurotrib dot com) on Tue Feb 5th, 2013 at 12:37:36 PM EST
[ Parent ]
I think you underestimate the power of the All-Knowing Infallible and Invisible Guiding Hand of the Free Market.

For example, consider the CO2 emissions of the U.S. for the past few years. There are a couple of reasons for this, first off the economy has been in the tank, reducing the demand for energy and therefore reducing CO2, and secondly, cheap natural gas has replaced a lot of coal-fired energy production. (Although the leaking of methane from the fracking systems seems to be a lot higher than normally accounted for.)

http://grist.org/news/co2-emissions-from-energy-production-drop-to-1994-levels-in-the-u-s/

So what happens when you get a 2 or 3 or 4 or 6 or 8 degree C rise in temperature? Crop failures, for one thing. Increased disease. Disruption of the restaurant economy because nobody wants to eat veggie pizza when the cattle business has gone under. Etc. Result: economic collapse. Side effect: Significant reduction in CO2 emissions.

The glass-half-full view of the situation is that we will keep on pumping CO2 into the atmosphere for the next few years, while the baby-boomers are still around, and then they will start to die off just when things get really out of hand, then the economy will collapse and the post-boomers will get to deal with a 16th century lifestyle.

Problem solved. By the Fantastic and Practically Magical Guiding Hand.

by asdf on Tue Feb 5th, 2013 at 11:14:53 PM EST
[ Parent ]
With 'systematically incapable' deriving from the fact that, for our societies, the profits of the financial sectors far outweigh all other values we still possess - up to and including the provision of a liveable world for our descendents.

As the Dutch said while fighting the Spanish: "It is not necessary to have hope in order to persevere."
by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Tue Feb 5th, 2013 at 01:08:25 PM EST
[ Parent ]
In order to maintain the normal E.T. standards of Fairness and Balancedness, I look forward eagerly now to 99 front-page posts and articles about how the actual scientific facts of climate change, namely those published in peer-reviewed journals, show the various facets of doom and gloom that are rapidly descending on mankind. Just to keep things "balanced," don't you know...
by asdf on Tue Feb 5th, 2013 at 11:20:21 PM EST
I don't accept your veiled criticism that this post is not based on "actual scientific facts of climate change". That's baseless. Correct me exactly where I'm not relying on peer-reviewed scientific publications.

Factually, this post is more about media presentation of a climate science topic than about the science itself - because that speaks for itself. I've been pointing out at ET for years that climate science brought in most media is exaggerated and does injustice to the realistic picture of the science. Similarly, I've been saying for years that plenty of climate scientists eagerly contribute in highlighting the far end of the scenarios - either for political action or for getting a headline in the press. This aspect of climate science provides examples on both accounts.

For a daily shot of doom and gloom, there's Joe Romm instead - who has by now gone so out of sync with science consensus, he's nothing more than an unreliable source.

by Nomad on Wed Feb 6th, 2013 at 06:58:07 AM EST
[ Parent ]
It's not a veiled criticism, it's an open criticism. All reputable, knowledgeable sources unanimously agree that anthropomorphic global warming is occurring and is a huge problem. The normal scientific debates about the details continue, just as they do in any other academic inquiry. Any suggestion to the contrary is driven by a combination of financial gain, ignorance, or willful contrarianism. The public debate, if there is any, should not be whether or not there is a problem, but whether it will cause a moderate global catastrophe or the complete collapse of civilization.

Perhaps you are aware of this chart.

by asdf on Wed Feb 6th, 2013 at 07:46:46 PM EST
[ Parent ]
Your criticism remains baseless.

asdf:

All reputable, knowledgeable sources unanimously agree that anthropomorphic global warming is occurring and is a huge problem.

I didn't write anything that even remotely contradicts this. And you don't show me that I wrote anything not based on science studies.

I didn't know the graph - but with a little Google I understood why.

OK Getting Serious Again | Only In It For The Gold

Now the image is purely a schematic. It isn't social science, and though I imagine it could be put to the test in a formal study it might be difficult to refine the design enough to really identify the two populations. In short this isn't a formal claim, it is a schematic. Still I think it captures something of how the situation is structured and at least part of why the public's position is so extremely out of tune with that of the expert community.

No wonder I never came across it before. It's from a blog.

So. A claim that I'm not basing my post on actual science publications you defend by relying on a graph, created not as a result of a science study, not peer-reviewed, not published - but doodled by someone with an opinion. He's entitled to it, so are you.

But stop claiming nonsense.

by Nomad on Thu Feb 7th, 2013 at 06:24:51 AM EST
[ Parent ]
Ok, I expressed myself poorly. There are and will continue to be proper scientific arguments about the details of AGW. That is fine, and this question of sensitivity is part of that discussion. If somebody wants to post something in a general interest blog that talks about one of those arguments, that's fine.

The point is, though, that the "balance" between the blog posts needs to reflect the underlying reality of the science. Anything posted that suggests that AGW is less of a problem than some other might think, is immediately grabbed onto as proving or supporting the "sceptic" side of "the argument." In that sort of environment, the realists need to confront situations where that actual balance is tilted.

That's all I'm saying. I want to see 99 postings now about low-level arguments on the models or the observations or the temperature trends or whatever that do not encourage the sceptical viewpoint.

by asdf on Thu Feb 7th, 2013 at 02:52:33 PM EST
[ Parent ]
Thanks for that.

I understand your argumentation - but don't agree with it.

My activity at ET has commonly been to examine aspects of the climate change debate that fly below the radar of major media or to point where media hopelessly derails. Science and media don't mix very well in general, climate science and media doubly so - because it deals with probabilities and math which frighten reporters and because of scientists who crave political action. The signal easily transmutes into noisy garbage.

asdf:

I want to see 99 postings now about low-level arguments on the models or the observations or the temperature trends or whatever that do not encourage the sceptical viewpoint.

Actually a hard request. The factual science has lessened a number of scares associated to global warming that were frequently plied in the media the past 5 years - increasing hurricanes, floods or tornadoes, a decreasing 'Gulf Stream', unstable oceanic clathrates, acceleration of permafrost thaw, the melting of glaciers on Kilimanjaro.  The pause of global temperature rise, as noted by eurogreen, has also people mystified - though there's a decent chance 2013 may break that trend.

But there still are plenty of topics in the pipeline.

by Nomad on Fri Feb 8th, 2013 at 05:28:28 AM EST
[ Parent ]
Thanks. I've been looking for that graph. Source?


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sapere aude
by Number 6 on Thu Feb 7th, 2013 at 12:19:55 PM EST
[ Parent ]
by asdf on Thu Feb 7th, 2013 at 02:58:26 PM EST
[ Parent ]
Source is blogger Micheal Tobis. See here.
by Nomad on Fri Feb 8th, 2013 at 04:43:49 AM EST
[ Parent ]
Re "plenty of climate scientists eagerly contribute in highlighting the far end of the scenarios," please read the response by Gavin Schmidt: "The consensus statements in the IPCC reports have remained within the 1.5 - 4.5 range first set by Charney in 1979."

http://dotearth.blogs.nytimes.com/2013/02/04/a-closer-look-at-moderating-views-of-climate-sensitivit y/

The problem is that we are confronted with a gigantic problem, and there are powerful vested interests that want to maintain their power by, potentially, causing ruination to humanity. Yes, there is some discussion about how big of a problem it is, but it is very big.

Any article, blog post, comment, tweet, TV interview, or scientific report that even suggests that the problem is not huge and not caused by humans is immediately grabbed onto by agents of those vested interests to further press their agenda. It makes it hard to have a sensible discussion. But it is important, in my view, to not get sucked into that agenda by raising the visibility of side arguments about some specific details of the situation. All that does is distract the discussion from the main point which is that we are fucked unless we stop this bickering and actually cut, drastically, and immediately, our carbon emissions.

by asdf on Wed Feb 6th, 2013 at 08:14:45 PM EST
[ Parent ]
Did you actually read the post of James Annan?

James' Empty Blog: A sensitive matter

The list of pollees in the Zickfeld paper are largely the self-same people responsible for the largely bogus analyses that I've criticised over recent years, and which even if they were valid then, are certainly outdated now. Interestingly, one of them stated quite openly in a meeting I attended a few years ago that he deliberately lied in these sort of elicitation exercises (i.e. exaggerating the probability of high sensitivity) in order to help motivate political action.

But the point stands, that the IPCC's sensitivity estimate cannot readily be reconciled with forcing estimates and observational data. All the recent literature that approaches the question from this angle comes up with similar answers, including the papers I mentioned above. By failing to meet this problem head-on, the IPCC authors now find themselves in a bit of a pickle. I expect them to brazen it out, on the grounds that they are the experts and are quite capable of squaring the circle before breakfast if need be. But in doing so, they risk being seen as not so much summarising scientific progress, but obstructing it.

Thus: 1) a climate scientist admitting that a colleague publicly exaggerated in order to gain political action and 2) clear criticism that the IPCC clung to outdated figures and didn't include newer studies - which also renders Schmidt's point moot.

Furthermore, a suggestion that the topic of climate sensitivity covers "some specific details of the situation" underlines a complete underestimation of its significance.

Finally, I fundamentally disagree with your ideas on controlling the message - so much so, that debate on this is pointless. The science is what it is, not what people want it to be.

by Nomad on Thu Feb 7th, 2013 at 06:58:12 AM EST
[ Parent ]
Yep, I agree that debate is pointless, and I look forward to the next 99 articles you will be posting that explain other facets of the actual problem.
by asdf on Thu Feb 7th, 2013 at 11:02:34 AM EST
[ Parent ]
But Nomad, your post is not based on actual scientific facts of climate change.

It's based on highly selective cherry-picking.

That's the antithesis of science.

by LondonAnalytics (Andrew Smith) on Fri Feb 8th, 2013 at 02:42:10 AM EST
[ Parent ]
Nomad's post is not a review of climate science. It's journalistic reporting of a new development.

I distribute. You re-distribute. He gives your hard-earned money to lazy scroungers. -- JakeS
by Migeru (migeru at eurotrib dot com) on Fri Feb 8th, 2013 at 04:04:30 AM EST
[ Parent ]
Also your criticism is baseless and I repeat: Correct me exactly where I'm not basing myself on actual scientific findings, or where I do not rely on the input of climate scientists.

Right now, your response is only ad hominem. I don't waste time on that.

by Nomad on Fri Feb 8th, 2013 at 04:39:33 AM EST
[ Parent ]
Saying someone is cherry-picking is not ad hominem, it's a criticism of the argument. That argument may rely on the input of climate scientists, while being cherry-picking.
by afew (afew(a in a circle)eurotrib_dot_com) on Fri Feb 8th, 2013 at 04:52:18 AM EST
[ Parent ]
your post is not based on actual scientific facts of climate change.

And even when that's not an ad hominem, it remains irrelevant. On what ground is that comment valid? I've sourced my writings.

by Nomad on Fri Feb 8th, 2013 at 05:39:04 AM EST
[ Parent ]
Upon checking (see below), your first paragraph is worse than cherry-picking: it mis-interprets or mis-represents the linked sources.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Fri Feb 8th, 2013 at 05:56:09 PM EST
[ Parent ]
a frightening six (2007, here)

You leave the false impression that this number is a number in the same range of estimates that includes numbers between 2 and 4°C. However, as explained in detail in your source, and here too, sensitivity depends on time allowed for indirect effects to play out. We usually talk about shorter-term effects, 6°C is a long-term number.

or even an apocalyptic eight degrees Celsius (2013, here)

Actually, your source says 8 degrees Fahrenheit (4.4°C), and that until 2100, not 2xCO2.

now a stack of science findings that show lesser extremes is beginning to find its way.

Do you mean to imply that findings in that range haven't found their way before?

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Fri Feb 8th, 2013 at 05:52:52 PM EST
By quoting only the mean number and suggesting that it is one of the high-end estimates that were presented in the "years of reports in the media", I think you are mis-representing the linked IPCC report, too. The IPCC report is of course a meta-study, and the studies covered include low-end estimates.

What about Revkin's quoted blog post?

In fact, there is an accumulating body of reviewed, published research shaving away the high end of the range of possible warming estimates from doubled carbon dioxide levels.

The first link goes to this graph showing some new research:

It's easy to see how Revkin was compelled to conclude a tendency here. However,

  1. six of the results shown are results obtained with different methods and revisions by the same research team;
  2. for another research with several scenarios, Aldrin et al (2012), the diagram shows only the result of a single scenario (the one without aerosols) and ignores others with much higher means;
  3. this diagram doesn't include the high-end result of Fasullo and Trenberth (2012) (the subject of your second link).

In other words, whoever made the comparison diagram was cherry-picking.

The high end shaved away according to Revkin's second link is the change from this in the IPCC 4th Assessment Report:

Values substantially higher than 4.5°C cannot be excluded, but agreement of models with observations is not as good for those values.

...to this in the leaked 5th Assessment Report:

Equilibrium climate sensitivity greater than about 6°C-7°C is very unlikely.

Hardly a significant change, and certainly not something shaving away at estimates with a mean around 4°C.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sat Feb 9th, 2013 at 06:29:07 AM EST
[ Parent ]
For the interested; this article discusses Annan's comments and a number of the studies in the second diagram, finding reasons to suspect that they are under-estimates. This is also interesting: Schmittner et al. acknowledge such an effect (which needs further research). Finally, in the last paragraph of chapter 4 in Ring et al. (2012), the authors echo asdf.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sat Feb 9th, 2013 at 07:55:19 AM EST
[ Parent ]


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