Lewis and Curry

9/26/2014

This is interesting. Lewis and Curry estimate equilibrium climate sensitivity (ECS) at 1.64°C. That's remarkably low. If it turns out to be true – and it seems like we won't know the true value for ECS for another decade or longer – then AGW would have been largely overstated. The estimates constantly change, which is frustrating.

I can't evaluate their methods. I'm curious to read any critiques by other climate scientists.

ECS is the long-term change in temperature from a doubling of atmospheric CO2. It's arguably the most important fact or estimate in the AGW issue. Ultimately, this is what anthropogenic warming is about. I think the baseline is the pre-industrial level, for which I've seen different estimates. I think it was 280 ppm. Now we're around 400 ppm. A doubling of the baseline would be 560 ppm. I have no idea when we're supposed to hit that.

One of the things that surprises me about AGW skeptics and lukewarmers is that they don't seem to worry about the future consequences to themselves if they're wrong. Most of them aren't elderly, so they'll likely be around for decades. If AGW turns out to be a serious problem, I expect skeptics to be pilloried. So it's ballsy to be a skeptic – I won't be surprised by violence against them in 2050 if warming becomes a problem.

It's also ballsy to be a climate scientist who offers low estimates of ECS. We haven't yet built a rational civilization when it comes to science and politics. An honest scientist who offers low estimate of ECS which turn out to be wrong will be savagely attacked. They'll be savagely attacked even before we discover whether they're right or wrong. So I think it's remarkably brave of them – being wrong on this issue is so risky, not just to themselves, but to the world. It would weigh heavily on me if I were a climate scientist. I'd have to quadruple-check the data, the analyses, and think very deeply about the validity of the methods and framework. I'd be terrified to offer estimates of ECS. It would feel like so much responsibility. At the high end, AGW could do serious harm to lots of people (well, they'd be able to see it coming decades in advance, so that might reduce the harm)

The fact that the estimates always change would give me pause, because it would imply that my estimates would change, or at least be replaced by others' future estimates using new and better methods, where the "future" could be next year. The epistemology or meta-epistemology of ECS looks very tough from the outside looking in – if the estimates are always changing, what does this mean about the methods used to generate them? Or the nature of our knowledge of climate circa 1990 - 2014? Thankfully, they've tended to go down, like from IPCC4 to IPCC5, or at least the low end of the range has gone down. It's odd. We don't keep revising Planck's Constant or our estimate of the acceleration of gravity on earth, though admittedly these aren't the best analogies. It's just tough to know what to do with ECS estimates, because we know they always change. That's the one thing we know about them. This implies that we should expect them to change in the future, until we know something that tells us to stop expecting that.

24 Comments

Fernando Leanme link

9/25/2014 09:55:46 pm

José, a "skeptic´s" bravery depends on the degree of "skepticism". Saying that TCR is 0.5 degrees C to doubling is a lot ballsier than setting it a 1.5.

On the other hand those who back a high sensitivity and then insist we must make very fast moves and stop burning fossil fuels are irresponsible.

Do you know what I noticed? Most of the individuals proposing fast action tend to be social scientists and politicians. A large portion is made up of joiners who get a lot of satisfaction being part of the "good crowd". However, most of them lack training in engineering and economics, and this makes them think the transition from fossil fuels is easy.

Other (the "de-developers") seem to be socialists who prefer to reduce our standard of living to a uniform low level. This is easy to understand because they know socialism tends to lower living standards. Thus the global warming problem is used as a spear head (or a Trojan Horse?) to advocate profound changes to the economic system they can´t achieve in an open fashion.

I spend time reading their articles, their blogs, and their posts, and these common threads are emerging with increasing frequency. I´m also noting some are advocating "civil resistance", some advocate violence, and quite a few are advocating repression and jail for those who happen to oppose their beliefs.

Thus, what I observe is a wide spectrum of positions, with large groups of radicals at either end. The "scientific community" represented by the likes of Mann, Hansen, et al can be considered to be on the radical fringe. These guys are scientists, but when it comes to the politics and to implementing actions to solve the global warming problem they might as well be chimps waving red flags.

Gerard Wroe

9/25/2014 11:22:37 pm

I've been using Feynman's explanation for the gradual change in the measurement of the charge of an electron starting with Millikan's oil drop experiment. Millikan got it slightly wrong, but subsequent experimenters only adjusted slowly to the correct result.

I suspect it will be years / decades before there is enough data with the required accuracy to pin this down. Assuming that TCR/ECS are in fact constants in the climate response to increasing CO2.

I suspect that since climate is a non-linear chaotic system and we are dealing with small disturbances around a local attractor. We don't know what it will take to move to a different meta-stable state such as an ice-age or polar cap free warm period.

Russ R.

9/26/2014 04:01:27 am

Jose,

There are a couple of points I'd make about Lewis & Curry's estimate of ECS (which is derived from recent temperature observations).

First, and most importantly, climate sensitivity is not really "a thing", in that it's not some fundamental, unchanging constant of the planet (like g= 9.8m/s^2). Climate sensitivity is the sum total of a whole array of forcing and feedback mechanisms, which are themselves not constants. So, ECS isn't always equal to 3.0, or 1.64 or some other fixed value. It can (and very likely will) vary under differing climactic conditions as those underlying forcing and feedback mechanisms vary. Treating ECS like a constant is a useful shorthand for back-of-the-envelope estimates, but it's nowhere close to a law of physics.

As a simple example, consider Ice Albedo feedback. It only applies at the transition zone of polar ice extent, and as that ice extent retreats to higher latitudes with less surface area and insolation, the magnitude of IA feedback weakens. So, you'd expect feedback (and ultimately ECS) to be higher at the peak of an ice age vs. during an interglacial period. As such, different methods of estimation (paleo proxy measures vs current observations) might yield markedly different findings, and both can be entirely correct about the conditions they measured.

Second, model estimates of ECS range from 2.0 to 4.5 with a "best estimate" of 3.0. Models all assume ice albedo feedback is positive (i.e. warming causes polar ice to retreat, which causes more sunlight to be absorbed, which causes more warming.)
Surprisingly, for the last couple of decades, the southern hemisphere has experienced the exact oppposite... ice extent has increased in the face of warming, acting as a damper rather than amplifier (i.e. negative feedback). Nobody can say for certain why this has occurred, or if it will continue to do so, but in the long term, the anomaly should correct and warming should lead to less ice and positive feedback. Looking at the recent temperature record, this anomaly will "contaminate" observations, and likely lead to discrepancies between observation based estimates of ECS and model based estimates.

Joe Duarte

10/6/2014 09:49:35 am

Thanks Russ. That's very helpful.

What does ice extent in the Antarctic tell us about ice mass? Has mass changed?

vieras

9/26/2014 04:04:55 am

"What if climate change appears to be just mainly a multidecadal natural fluctuation? They'll kill us probably..." Tommy Wils in the climategate mails

Let me tell you, even if the doomsday predictions were right and ECS would be high, these people have wasted hundreds of billions on renewables which have no chance whatsoever of solving the problem. And at the same time any working solutions have been badly neglected to the point where European countries have a huge risk of running out of electricity this winter. And all that in the middle of a recession.

People will be after the warmists with a pitchfork, carrying a torch. And this is their best case scenario. Imagine what will happen if the temperatures refuse to raise.

Canman link

12/9/2014 04:13:50 am

The futility of renewable energy can't be emphasized enough. Studies are finding unsustainably low EROEI (energy return on energy invested) values:

http://bravenewclimate.com/2014/08/22/catch-22-of-energy-storage/

Google has given up on a renewables project:

http://www.greentechmedia.com/articles/read/google-engineers-explain-why-they-stopped-rd-in-renewable-energy

If anyone is looking for someone to blame for climate change, they might want to consider anti-nuclear activists.

John M

9/26/2014 10:59:11 am

"One of the things that surprises me about AGW skeptics and lukewarmers is that they don't seem to worry about the future consequences to themselves if they're wrong."

I can only speak for myself, but I'm not really worried about being wrong for a variety of reasons.

Chief among them is an understanding of the broader climate picture, which is something that absolutely drives AGW alarmists crazy because they know there is no effective counter-argument to it. In the past thousand years, we've had a Medieval Warm Period that was warmer than today (there is plenty evidence it was global) and the Vikings could subsistence farm on Greenland. We've had a Little Ice Age where the Hudson River frozen solid in the winter. Before that was a Roman Warm Period and a Holocene Warm Period and before that, we had massive glaciers that formed Long Island as a terminal moraine. Before that were inter-glacial periods warmer than today and other glacial periods and, before that, through much of the Earth's history, the climate was so warm that there was no ice at the poles. For details,of the really big picture see http://www.scotese.com/climate.htm .
We are currently in an inter-glacial period, the assumption being that we will see another ice age in the future. One of the most basic types of intelligence tests gives a person three or four figures in a pattern and asks them what comes next in the pattern. Let's play that game with ice age climates. What happens next on this graph? http://www.ncdc.noaa.gov/paleo/abrupt/data2.html

Essentially, the Earth's climate has always changed significantly over time, without any human intervention. Expecting it to remain stable comes from the belief that there is something perfect about our current climate and any deviation from it will produce doom. That's magical thinking, like expecting trees to never lose their leaves. Nature doesn't work like that.
Regardless of the cause, if humanity can't deal with the sorts of temperature changes that AGW alarmists are predicting or can't learn to engineer the climate to change it to be the way we want rather than trying not to disturb it, we are doomed as a species in the next few thousand years because another ice age will come, or the Earth will once again warm and the poles will again be ice free even if we do nothing to make any of it happen. That is how the Earth's climate works. Doing nothings will not produce a magical special moment in amber for eternity so that nothing will evere change. As for other concerns such as ocean acidification, there were periods in the Earth's history where carbon dioxide was thought to exceed 4,000 ppm, about 10 times what it s now.

So if I'm wrong, we'll learn to deal with the changes in climate and weather or learn how to engineer the climate we want. If we can't do that, then it doesn't really matter and it's only a matter of time before climate change that we've had nothing to do with makes current concerns about AGW look irrelevant. How about a mile-high wall of ice bearing down on New York City? How about no ice at the poles and palm trees in Alaska? That's happened in the not too distant past (when the continents were configured pretty much as they currently are) and something like it will happen again, and building windmills and putting up solar panels and going vegan isn't going to stop it because it's happened before human beings existed and it's happened when human beings were living at a subsistence level.

Barry Woods

9/28/2014 09:56:31 pm

Hi Joe
If 'sceptics', 'lukewarmers', dare I say 'members of the public', were preventing policies that would actually achieve anything, you would have a point. if a high amount of warming was to appear.

however most of the policies and solutions, technology or economic are just as dumb, whether there is 1C or 6C of warming this century.

The very climate concerned scientist Prof Myles Allen, at a public debate with Prof Lindzen (last year at Oxford Uni),said that we could all agree that the EU policies are futile symbolic gestures. should he be pilloried to?

MikeR

9/30/2014 03:35:29 am

"One of the things that surprises me about AGW skeptics and lukewarmers is that they don't seem to worry about the future consequences to themselves if they're wrong."
I don't think I agree with the premise behind this point. All political actions have costs. Mitigation kills people too, maybe a lot of people. Mostly these days it's just feel-good theatre, though it looks as though it will probably freeze some people to death in Germany and England in the near future. But if they really got serious with mitigation? It would be necessary to severely delay the growth in development in China and India, and eventually in most of Africa as it develops too. That's the truth, if people are going to deal with what mitigation really requires. You are talking about keeping three billion in grinding poverty for decades, almost all of whom would die younger than they would have. Someone ought to lose some sleep over that as well.
We are talking triage here. Aside from a few "no-regrets" policies that will not have too much effect either way, action has severe consequences, and so does inaction. We desperately need accurate information on what the costs of inaction will be, so that we can compare them with the costs of action.

Judith Curry has said a number of times that she is at least as concerned with "tipping points" as with the gradual temperature rise that TCR or ECS will give you. Most of our economic cost analyses are based on 2 C rise, or 3 C rise, etc. But it's very hard to analyze what-all would happen if (fill in your favorite climate-totally-collapses scenario). Those are the ones that would get a nice libertarian/conservative like me to say, "Large asteroid heading for earth?! Forget what I believe about the free market and liberty; the world has to go all on this one."
But for those kinds of disastrous impacts, the IPCC has little to say about probababilities. I don't think that anyone doubts, though, that the really high temperatures rises (>5C) are much much more likely to have the disastrous impacts. The smaller rises are more likely to have merely very uncomfortable impacts. That's why for me (and I think for Curry as well), establishing the lower limit of ECS is much less important than _restricting the upper limit_. I would think it's very good news for the world if recent papers have been saying, The ECS is somewhere around or below 2 - but it is extremely unlikely to be as high as 4.

10/6/2014 10:03:28 am

Hi Mike -- Thanks. My point was poorly written. I don't doubt that mitigation policies will carry harms. I wasn't expressing support for mitigation, or any strong views on the issue at all.

There's definitely an asymmetry in the future narrative and consequences for either side being wrong. If environmentalists are wrong, or largely wrong, about future warming, the harms will have been all the economic and mitigation policies that were implemented to try to prevent it. Making energy expensive is very consequential, especially for lower income people. Taxes are consequential. Regulations are consequential. The harms of such policies tend to be diffuse, and to some extent invisible or abstract. It's the classic problem of the seen vs. the unseen.

Our rate of GDP growth will be reduced by such policies. Shaving our rate of growth from something like 2.8% to 2.4%, over a span of 30 or more years, will translate into lots of lost or never-existing jobs. It will lead to lower standards of living in all sorts of ways. And we'll be less wealthy and prosperous at the end, reducing our ability to respond to climate change in some ways. But most of this would be unseen, because it pertains to what would've happened had we not implemented these policies -- it compares the status quo, which can be seen, to an alternative universe which cannot be seen and which never existed. That's the chronic issue with economic policy, though the CBO has done a good job lately in laying out some of the harms of ObamaCare, the huge debt runup, etc.

If the skeptics are wrong, it will be plain. Rising sea levels. More storms. Loss of farming areas (while other regions gain them.) It's very hard to get people to consider a drop in the GDP growth rate and visualize the homeless people, the jobless people, that it would lead to over time. It's not hard to get them to attend to storms and climate change.

So skeptics are in a bind from the outset. Their risk looms more vividly than their reward, which is why they're so interesting to me. Generally, people don't like to be wrong, don't like to admit they were wrong about something. I think some people reject the skeptic view on AGW because they don't want to risk being wrong, and being wrong as a skeptic on AGW is likely to be more costly than being wrong from the other side.

Sheri

10/7/2014 04:08:29 am

That is a very interesting point about comparing the status quo which can be seen to an alternative universe that never existed when one is a skeptic. Not many people recognize the bind.

Simon Marsden

10/13/2014 01:58:58 am

I think you're underestimating the effects if the theory of AGW turns out to be wrong. The public has been repeatedly assured that the science is settled (when it clearly isn't). People are going to stop trusting all scientists.

You also need to think about the effect of spending all that money on trying to combat a minor or non-existent problem. I'm not worried about the developed world, but elsewhere people are dying every day from easily treatable diseases and poor sanitation - problems that we could easily fix if we weren't distracted by the green scare.

9/30/2014 03:42:00 am

It's probably worth mentioning that Curry doesn't claim that this result is "right". She perhaps doesn't even really believe in ECS, for some of the reasons that commenters noted above - she's kind of into natural variability and "Stadium Waves" being the dominant effect in climate. In various comments on the linked post, she basically said, Our goal was to produce an ECS and TCR using the IPCC methods, but analyzed properly.

10/6/2014 10:14:17 am

I think the question of whether ECS is valid is interesting. I love it when people think deeply about validity, and don't take for granted that a concept or construct is valid or should be used. But I don't know enough about this issue -- I have no idea whether ECS is valid, or why.

10/19/2014 10:00:08 am

I guess the issue would be, can you give a number (ECS) that tells you the forcing for a doubling of CO2, that works for a wide range of temperatures and other conditions. Aside from noise, is it more-or-less linear in log CO2.

Or, is the effect of doubling CO2 totally dependent on everything else.

Paul Matthews link

9/30/2014 04:13:48 am

"If AGW turns out to be a serious problem, I expect skeptics to be pilloried."

We are pilloried already. There's a constant stream of attacks and abusive name-calling, and all sorts of completely bogus claims are made about funding and beliefs, along with spurious false analogies (smoking & cancer etc). This comes from climate activists, some climate scientists, and some of your colleagues in the social sciences. Therefore, anyone who 'comes out' in public as a sceptic must already be ballsy enough to face up to such attacks.

Also, there is an asymmetry in your comments. What about scientists who make alarmist projections that turn out to be wrong? Might they be pilloried too, if we've spent $trillions on bogus
science and useless wind turbines, forced people into energy poverty, terrified people with climate hysteria so that other more genuine environmental concerns are forgotten? How damaging could it be if science itself ends up a laughing stock?
This is already starting to happen - Peter Wadhams, a Cambridge scientist on record as saying the Arctic ice will be all gone by 2015, was ridiculed by other climate scientists at the recent #RSArctic14 meeting.

10/6/2014 10:11:42 am

That's true. They are pilloried already. Some people fantasize about throwing them in jail. An extremely bad philosopher advocated criminalizing AGW skepticism. To even approach that idea, to even have any kind of argument that had a chance of standing up, you'd need some serious work in epistemology and certainty, something that would allow you to bring the hammer down on people who don't adopt a new scientific hypothesis from a relatively new and dynamic field whose estimates keep changing. You'd have to deal with all sorts of issues, and I was surprised that he did none of the work needed. (Then you'd need a political philosophy that reduced freedom of speech to a very limited and minor status. He didn't do that work either.)

As I noted in another comment, there's an asymmetry in the consequence of being wrong as a skeptic on this issue vs. someone sounding the alarm being wrong. It will be costlier for skeptics.

Well, maybe not. If AGW turns out to be mostly wrong -- which is hard to imagine -- that will be a catastrophe for science, the public's trust in science, and the public's trust in the government involvement and use of science. It would be the worst failure of science in history. It would suck for everyone, in all fields. So maybe climate scientists would be pilloried too. (But I was being descriptive -- I don't think anyone should be pilloried.)

10/7/2014 03:35:50 am

Dr Robert G. Brown from Duke University wrote a really great post about climate modeling and the way CC is used by scientists just to get funding. It's worth a read: http://wattsupwiththat.com/2014/10/06/real-science-debates-are-not-rare/

10/3/2014 12:17:05 am

http://nymag.com/scienceofus/2014/09/how-to-convince-conservatives-on-climate-change.html
Jose? Help - I'm under attack!

10/3/2014 09:41:45 am

That should lead to some amusing attempts to psychologically manipulate conservatives.

10/7/2014 04:17:41 am

It's very sad that science is now reduced to a marketing war. Rather than explain the science as simply as possible and help people understand it, marketing research and techniques are employed to "sell" the "truth" in science. It's not really about science at all and I suspect this will badly damage the reputation of science, if it already hasn't accomplished that. Science should be about educating people, not bullying or playing head games in order to get people to believe. That clearly calls into question the objectivity of science.

10/13/2014 03:57:09 am

"After you have convinced people that you fervently believe your cause to be more important than telling the truth, you've lost the power to convince them of anything else." One of my favorite quotes.

"But the other side does it too - even more!" Of course. They are political hacks. You are political hacks. Please both of you leave me alone; I don't trust you.
Now is that what you wanted?

11/24/2014 06:36:32 am

A more realistic assessment about what needs to be done to reverse climate change from IEEE's Spectrum magazine, if climate change is carbon dioxide driven. Another reason for skepticism is that most of the strategies put forth by those concerned about AGW won't do much if what they are saying is true. This article talks about why it isn't enough and you might find it interesting. I liken most green initiatives to Victory Gardens - more about morale than anything else.

http://spectrum.ieee.org/energy/renewables/what-it-would-really-take-to-reverse-climate-change

Geir Aaslid

12/12/2014 09:19:14 am

There are a few questions we should ask ourselves here. First of all, where are the observations confirming that adding more CO2 to our atmosphere is leading to a higher temperature? The answer is that 30 years of climate research has shown us we don't have such observations.
Next question: Does the assumption that the sun has no significant influence on out climate belong in the real world? That's right, the IPCC folks are all assuming the sun is only a 7% climate driver, whereas CO2 is a 90% climate driver. Ask almost any astrophysicist, the answer is that IPCC are lying to us. A cooling sun will lead to falling temperatures for the next 30 years, this cooling has already stated in quit a few mountainous areas and as soon as the population takes notice of this it is not the sceptics who should worry about their own safety.

Lewis and Curry

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José L. Duarte

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