Posts Tagged ‘richard lindzen’

Rick Santorum misrepresents our climate survey results on Bill Maher show

September 2, 2015

In our survey of more than 1800 scientists we found that the large majority agree that recent climate change is predominantly human induced. The article where we discuss our results is publicly available and a brief rundown of the main conclusions is provided in this blogpost.

We were quite surprised to hear a US Presidential candidate, Rick Santorum, make the opposite claim based on our survey. On the Bill Maher show he said:

The most recent survey of climate scientists said about 57 percent don’t agree with the idea that 95 percent of the change in the climate is caused by CO2. (…) There was a survey done of 1,800 scientists, and 57 percent said they don’t buy off on the idea that CO2 is the knob that’s turning the climate. There’s hundreds of reasons the climate’s changed.

What did we actually find in our survey?

In our survey of 1868 scientists studying various aspects of climate change, we asked two questions about the causes of recent global warming. Of all scientists who provided an estimate ~85% think that the influence of human greenhouse gases is dominant, i.e. responsible for more than half of the observed warming. ~15% think greenhouse gases are responsible for less than half of the observed warming. If you zoom in to those respondents with arguably more expertise, the percentage agreeing with human dominated warming becomes 90% or larger.

The existence of a strong scientific consensus about climate change is also clear from previous surveys of scientists and of the scientific literature and from statements of scientific societies. A scientific consensus is a logical consequence of the evidence for a certain position becoming stronger over time.

Rick Santorum’s claim is misleading and wrong because:

1) it is based on a wrong interpretation of just one of the two survey questions about the causes of recent climate change.

2) it is based on the argument that respondents who didn’t provide a specific estimate for the contribution of greenhouse gases (22% of the total number) think that this contribution is small. That is a wrong inference.

3) it is based on the argument that respondents who think it is “very likely” or “likely” or “more likely than not” that greenhouse gases are the dominant cause of recent warming disagree with this dominant influence. That is a wrong inference.

Politifact also did a fact-check of Santorum’s claim and found it to be false. It gives a very good overview of what’s wrong with Santorum’s claim. Several people are quoted in their article, myself included as well as the blogger Fabius Maximus who came up with the 43% consensus figure used by Santorum to claim a 57% dissensus:

(more…)

Radiative forcing by aerosol used as a wild card: NIPCC vs Lindzen

February 22, 2011

(This is also featured as a guest post on Skeptical Science)

The greatest source of uncertainty in understanding climate change is arguably due to the role of aerosols and clouds. This uncertainty offers fertile ground for contrarians to imply that future global warming will be much less than commonly thought. However, some (e.g. Lindzen) do so by claiming that aerosol forcing is overestimated, while others (e.g. the NIPCC) by claiming that aerosol forcing is underestimated. Even so, they still arrive at the same conclusion…

Let’s have a look at their respective arguments. Below is a figure showing the radiative forcing from greenhouse gases and from aerosols, as compared to pre-industrial times. The solid red curve gives the net forcing from these two factors. The wide range of possible values is primarily due to the uncertainty in aerosol forcing (blue dotted line).

The greenhouse gas forcing (dashed red curve) is relatively well known, but the aerosol forcing (dashed blue curve) is not. The resulting net anthropogenic forcing (red solid curve) is not well constrained. The height of the curve gives the relative probability of the associated value, i.e. the net climate forcing is probably between 1 and 2 W/m2, but could be anywhere between 0 and 3 W/m2. (From IPCC, 2007, Fig 2.20)

NIPCC’s argument

The NIPCC report (a skeptical document, edited by Craig Idso and Fred Singer, made to resemble the IPCC report) says:

“The IPCC dramatically underestimates the total cooling effect of aerosols.”

They hypothesize that natural emissions of aerosol precursors will increase in a warming climate, causing a negative feedback so as to dampen the warming. Examples of such gaseous aerosol precursors are dimethyl sulfide (DMS) emitted by plankton or iodocompounds created by marine algae. They use these putative negative feedbacks to claim that

“model-derived sensitivity is too large and feedbacks in the climate system reduce it to values that are an order of magnitude smaller.”

Rebuttal

These are intriguing processes (the “CLAW hypothesis” first got me interested in aerosols, when I assisted with DMS measurements on some remote Scottish islands), but their significance on a global scale is ambiguous and highly uncertain. As a review article about the DMS-climate link says:

“Determining the strength and even the direction, positive or negative, of the feedbacks in the CLAW hypothesis has proved one of the most challenging aspects of research into the role of the sulfur cycle on climate modification.”

The NIPCC report exaggerates the uncertainty in climate science, but seems to put a lot of faith in elusive and hardly quantified processes such as natural aerosol feedbacks coming to our rescue.

Lindzen’s argument

On to Lindzen:

“The greenhouse forcing from man made greenhouse gases is already about 86% of what one expects from a doubling of CO2 (…) which implies that we should already have seen much more warming than we have seen thus far (…).”

Lindzen again (E&E 2007):

“How then, can it be claimed that models are replicating the observed warming? Two matters are invoked.”

The “two matters” he refers to are aerosol cooling and thermal inertia from the oceans (a.k.a. “warming in the pipeline”). He then proceeds to argue that both of these factors are much smaller than generally thought, perhaps even zero. E.g. on aerosols, Lindzen writes:

“a recent paper by Ramanathan et al (2007) suggests that the warming effect of aerosols may dominate – implying that the sign of the aerosol effect is in question.”

By downplaying the importance of these two factors, Lindzen argues that the observed warming implies a small climate sensitivity. The same line of argument is also used by Dutch journalist Marcel Crok, who writes in his recent book (in Dutch, my translation):

aerosols probably cool much less than commonly thought

Rebuttal

While it is true that aerosols can warm and cool the climate (by absorption and reflection of solar radiation, respectively, besides influencing cloud properties), most evidence suggests that globally, cooling is dominant. Whereas Ramanthan et al (2007) don’t quantify the net aerosol effect (in contrast to Lindzen’s implicit claim), Ramanathan and Carmichael (2008) (quoted by Crok) do. They estimate both the warming ánd cooling effects to be stronger than most other estimates, but the net forcing (-1.4 W/m2) is right in line with (even a little stronger than) the IPCC estimate (see the above figure). Taking into account realistic estimates of aerosol forcing and ocean thermal inertia, the earth has warmed as much as expected, within the admittedly rather large uncertainties. Ironically, it is exactly because aerosol forcing is so uncertain and because the climate hasn’t equilibrated yet that the observed warming since pre-industrial times is only a very weak constraint on climate sensitivity. Lindzen seems very certain of something that most scientists would readily admit is very uncertain.

Conclusion

So we have the peculiar situation that both of these approaches try to claim that climate sensitivity is small, but the NIPCC approach is to claim that aerosol forcing is very large (thus providing a negative feedback to warming), whereas the Lindzen approach is to claim that aerosol forcing is very small (thus necessitating a small sensitivity to explain the observed warming so far). Of course they can’t both be right, and probably neither of them are. Looking back at the figure above, both approaches are based on assuming that aerosol forcing is at the edge of the probability spectrum (as if it were some fudge factor), whereas the most likely value is somewhere in the mid range. Both approaches also ignore the other lines of evidence that point to climate sensitivity likely being in the range of 2 to 4.5 degrees. E.g. a value as small as suggested by the NIPCC (0.3 degrees) is entirely inconsistent with the paleo-climate record of substantial climate changes in the earth’ history. And finally, both approaches implicitly assign high confidence to some of the most uncertain aspects of climate science, even though they routinely mock climate science as if nothing is known at all.

Of course it is not mandatory for all those who dismiss mainstream climate science to agree, but to see two important “spokespeople” for climate contrarians take such mutually inconsistent approaches is peculiar. Even more so when you realize that Lindzen signed the recent “prudent path” letter to US Congress, in which the NIPCC report was approvingly cited… Most people can’t have it both ways, but apparently climate contrarians can.

See also a more detailed critique of the NIPCC and of Lindzen’s argument.

Andrew Dessler debating Richard Lindzen

October 20, 2010

Eli Rabett covers the debate between Andrew Dessler and Richard Lindzen (video embedded at the link). Purportedly the former smoked the latter, though I haven’t watched the whole thing yet so can’t vouch for that.

Quoting Eli quoting Andy:

It all fits together (…). The key thing to look at is look for coherence, look for lots of evidence supporting a point and you will clearly see why scientists are convinced that the mainstream view of climate science is right.

The real question I want to address here is this question of how much does carbon dioxide warm the climate [not whether it does at all]. (…) We are going to use a standard measure which is how much warming would occur if we doubled carbon dioxide, so we are going to go through the math and do a very simple calculation that indicates that we might be screwed.

The nature of blogging (“having a beer”) vs the nature of science

April 19, 2010

Robert Grumbine (a scientist-blogger well worth reading) explains how the scientific process works and how scientists communicate, and how it differs from blog debates (which he describes as “having a beer”). The following is lifted from his comment at Chris Colose’s blog a while ago. He sets up his argument in response to another commenter (self-identifying as “a genuine skeptic”):

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As a skeptic, I share your frustration equally, and as a genuine skeptic, and someone who does care about the environment, I am ready any day of the week to have my opinion sway back to believing in / trusting the consensus / IPCC position. Further, I know exactly what would sway me: dialogue, and constructive debate with the skeptics, in particular those skeptics of the ilk of Lindzen, Christy, and, although he refuses the label “skeptic”, Pielke Sr. (…)

(…) I’ve disagreed with Pielke Sr., for instance, but in the scientific norm. Tenderhearted readers, unaccustomed to the scientific norm, might have thought I was awfully hard on Roger. (One did say so.) But his own comment was that he appreciated my constructive discussion. This is a cultural issue that I think the general population does not understand. Normal exchanges, for science, about what’s going on, what’s good, or not, are fairly rough and tumble. It may not be the best thing that science is conducted this way, but it is what it is.

The scientific norm issue is a different matter. The scientific norm is the professional literature, not blog commentary. If you look in to Lindzen and the response in the scientific literature, you’ll find that he’s been met properly (by the standards of science, that is). Namely, he suggested his ‘adaptive iris’ idea. This was based on there being a certain relationship (it had to have a particular sign, and large magnitude) between surface temperatures in the tropics and cloudiness (and, for that matter, particular types of cloud). One paper in the scientific literature doesn’t buy you much. It is the start of the conversation to publish in the literature, not blessing as holy writ. He published, and then got the best possible response — other people used other (better) data sets and observing methods to see if they could get the same answer as he had gotten in his first cut. Unfortunately for his hypothesis, the better data sets erased his effect. Indeed, not only was the magnitude much smaller than he thought, the sign was the opposite of what he thought.

As far as scientific norms go, he got extremely good treatment. a) he did publish his idea (no ‘conspiracy to suppress’) and b) other people took a serious look at it. It is significant work to take a look at somebody else’s new idea. As a scientist, if you can get others to look at your idea, you have done extremely well. As happens in science, perfectly normally, the initial proposition got rejected by more detailed analysis. Since what was at hand was deriving a relationship between observational quantities, and Lindzen is a theoretician, it’s no great surprise or shame that he didn’t get all the niceties on his data sets right. As usual, devils lay in the details, and the responses were from groups familiar with all the devils laying in those details.

Where things went problematic was that contrary to proper scientific practice, Lindzen didn’t drop his disproven idea. A bit of ‘is so’ publishing (sorry, it was painful to read his response article and this is all I can say of it) in response to the objections was it. And then much complaining outside the scientific literature about conspiracy, scam, censorship, … To be honest, even his original Iris publication was an example of lenient reviewing. There were problems in his data management in the original paper that even I saw (correctly) would be a problem for his idea — and I’m not a tropical person (polar regions mostly), nor, then, sea surface temperature, nor then or now satellite sensing of clouds. The later publications — in the scientific literature — about his errors confirmed my suspicions, and, unsurprisingly, added a number of problems to what I suspected. But that’s not what you see out on the blog universe.

You can make some headway over at scholar.google.com. A fair amount of the non-scientific world shows up there, but a fair amount of the scientific world is present.


always see an ad hominem attack for what it is (I refer to the attacks by commenters at RealClimate, which were not removed by the editors). In most cases, straw men arguments can also be seen for what they are. And then an argument, “we don’t have to answer that ’cause it wasn’t peer-reviewed” always also increases the lay public’s skepticism. No one takes that response seriously, and again, skepticism can only increase.

I agree that outside the scientific community nobody takes seriously that something didn’t appear in the scientific literature.

That is a problem with outside the scientific community.

Doing science is difficult. Over the past 400 years, the modern scientific method has accumulated a lot of knowledge and understanding. Doing science means changing that body of knowledge and understanding. Sometimes that means saying that even though we used to think that something was the case, it really isn’t. Making that argument successfully is hard work. ‘Even’ the easier argument of making an addition is hard work. It’s hard work because other people have to be able to rely very strongly on everything you say in your paper. (…)

There are two parts to the scientific publication process important for your comment here. One is, to publish in the professional literature about your idea, you have to examine and explain your idea thoroughly. ‘thoroughly’ turns out to be a lot of work. Second is, you have to research all the relevant aspects of your problem and honestly discuss them. The up side of this is, once you’ve finished a proper scientific paper, it can stand for some time. You might turn out to be wrong about something — because there were different data than you used, or a better technique than you used, or … several things. Being shown wrong by later and much more labor-intensive examinations is fine. But being shown wrong because you failed to do your homework is disaster.

In contrast is blog posts and comments. The standard there is what I’ll call ‘chatting over a beer’. If you and I sit down and start talking, both of us with something we like to drink, having a relaxed conversation, that’s wildly different than scientific literature. Both of us will say what we think, but there’s no concern about tomorrow you trying to write a paper on which our professional reputations will hang based on what I say. We’re just chatting. I’ll give you my best answer at the time, but if I’ve forgotten something, or the answer is 25.0 instead of 2.50, eh. Just chatting over a beer. Just a blog comment. If someone started writing a scientific paper based on comments in blogs … all kinds of wild things could show up. The earth is flat, hollow, expanding, 6000 years old, and so on. Somebody, somewhere, in the blogosphere has said all such things.

To do science, we need something much more reliable than ‘anything anybody ever says anywhere’. We even need something better than “well, he’s normally pretty good so even tough he’s never worked on this kind of problem before and doesn’t know how the satellites detect what he’s working with, he _must_ be right anyhow.” That something more is the professional scientific literature.

Within the world of science (all 20 or so of us), it is an extremely telling, and negative, thing that much of what the general public thinks is the case about science is actually based on things which are said _only_ outside the scientific literature. If the speaker had confidence in his statement, he’d try to publish it in the literature. And, if they were right about the ‘conspiracy’, they should at least have a rejection letter and comments from the editor and reviewers to show. Instead, they talk about the conspiracy, but have no rejection letters (_I’ve_ got rejection letters — they’re normal to trying to do science.)

But the public perception is quite different. Still, I have to think if someone won’t go in front of his professional peers and stand for what he thinks is scientifically correct, he doesn’t really believe it himself. If his only or major audience is people who don’t know the science thoroughly, I have to figure he thinks that’s the only audience who’ll let him get away with whatever it is he’s saying now. Fine for you and me over a beer. No fine for doing science.

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Just to add a qualifier: Not everything that appeared in the scientific literature is necessarily “good science”. Likewise, not everything that appeared on a blog is necessarily unscientific or wrong. Just as in a bar, the greatest ideas and insights can be heard. But amidst a helluva lot of chatter about the weather. Which is actually pretty nice right now. Enjoy your beer!


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