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May 16, 2008

The Politicization of Climate Science

Posted to Author: Pielke Jr., R. | Climate Change | Prediction and Forecasting | Science + Politics | Scientific Assessments

[Update: The ever helpful David Roberts of Grist Magazine points out that an op-ed in the Washington Times yesterday makes the same logical error that I point out in this post below made by Patrick Michaels -- namely that short-term predictive failures obviate the need for action. The op-ed quotes me and says that I am "not previously a global warming skeptic," which is correct, but implies that somehow I am now . . . sorry, wrong. It also quotes my conclusion that climate models are "useless" without the important qualifiers **for decision making in the short term when specific decisions must be made**. Such models are great exploratory scientific tools, and were helpful in bringing the issue of greenhouse gases to the attention of decision makers. I've emailed the author making these points, asking him to correct his piece.]

Here I'd like to explain why one group of people, which we might call politically active climate scientists and their allies, seek to shut down a useful discussion with intimidation, bluster, and name-calling. It is, as you might expect, a function of the destructive politics of science in the global warming debate.

We've had a lot of interest of late in our efforts to explore what would seem to be a simple question:

What observations of the global climate system (over what time scale, with what certainty, etc.) would be inconsistent with predictions of the IPCC AR4?

The motivation for asking this question is of course the repeated claims by climate scientists that this or that observation is "consistent with" such predictions. For claims of consistency between observations and predictions to have any practical meaning whatsoever, they must be accompanied by knowledge of what observations would be inconsistent with predictions. This is a straightforward logical claim, and should be uncontroversial.

Yet efforts to explore this question have been met with accusations of "denialism," of believing that human-caused global warming is "not a problem," of being a "conspiracy theorist." More constructive responses have claimed that questions of inconsistency cannot really be addressed for 20-30 years (which again raises the question why claims of consistency are appropriate on shorter timescales), have focused attention on the various ways to present uncertainty in predictions from a suite of models and also on uncertainties in observations systems, and have focused attention on the proper statistical tests to apply in such situations. In short, there is a lot of interesting subjects to discuss. Some people think that they have all of the answers, which is not at all problematic, as it makes this issue no different than most any other discussion you'll find on blogs (or in academia for that matter).

But why is it that some practicing climate scientists and their allies in the blogosphere appear to be trying to shut down this discussion? After all, isn't asking and debating interesting questions one of the reasons most of us decided to pursue research as a career in the first place? And in the messy and complicated science/politics of climate change wouldn't more understanding be better than less?

The answer to why some people react so strongly to this subject can be gleaned from an op-ed in today's Washington Times by one Patrick Michaels, a well-known activist skeptical of much of the claims made about the science and politics of climate change. Here is what Pat writes:

On May Day, Noah Keenlyside of Germany's Leipzig Institute of Marine Science, published a paper in Nature forecasting no additional global warming "over the next decade."

Al Gore and his minions continue to chant that "the science is settled" on global warming, but the only thing settled is that there has not been any since 1998. Critics of this view (rightfully) argue that 1998 was the warmest year in modern record, due to a huge El Nino event in the Pacific Ocean, and that it is unfair to start any analysis at a high (or a low) point in a longer history. But starting in 2001 or 1998 yields the same result: no warming.

Michaels is correct in his assertion of no warming starting in these dates, but one would reach a different conclusion starting in 1999 or 2000. He continues,

The Keenlyside team found that natural variability in the Earth's oceans will "temporarily offset" global warming from carbon dioxide. Seventy percent of the Earth's surface is oceanic; hence, what happens there greatly influences global temperature. It is now known that both Atlantic and Pacific temperatures can get "stuck," for a decade or longer, in relatively warm or cool patterns. The North Atlantic is now forecast to be in a cold stage for a decade, which will help put the damper on global warming. Another Pacific temperature pattern is forecast not to push warming, either.

Science no longer provides justification for any rush to pass drastic global warming legislation. The Climate Security Act, sponsored by Joe Lieberman and John Warner, would cut emissions of carbon dioxide — the main "global warming" gas — by 66 percent over the next 42 years. With expected population growth, this means about a 90 percent drop in emissions per capita, to 19th-century levels.

He has laid out the bait, complete with reference to Al Gore, claiming that recent trends of no warming plus a forecast of continued lack of warming mean that there is no scientific basis for action on climate change.

There are several ways that one could respond to these claims.

One very common response to these sort of arguments would be to attack Michaels putative scientific basis for his policy arguments. Some would argue that he has cherrypicked his starting dates for asserting no trend. Other would observe that the recent trends in temperature are in fact consistent with predictions made by the IPCC. This latter strategy is exactly the approach used by the bloggers at Real Climate when I first started comparing 2007 IPCC predictions (from 2000) with temperature observations.

The "consistent with" strategy is a potential double-edged sword because it grants Pat Michaels a large chunk of territory in the debate. Once you attack the scientific basis for political arguments that are justified in those terms, you are accepting Michaels claim that the political arguments are in fact a function of the science. So in this case, by attacking Michaels scientific claims, you would be in effect saying

"Yes while it is true that these policies are justified on scientific conclusions, Pat Michaels has his science wrong. Getting the science right would lead to different political conclusions that Michaels arrives at."

Here at Prometheus for a long time we've observed how this dynamic shifts political debates onto scientific debates. Any I discuss this in detail in my book, The Honest Broker (now on sale;-).

Now, the "consistent with" strategy is a double-edged sword because the future is uncertain. It could very well be the case that there is no additional warming over the next decade or longer, or perhaps a cooling. Given such uncertainty, scientists with an eye on the politics of climate change are quick to define pretty much anything that could be observed in the climate system as "consistent with" IPCC predictions in order to maintain their ability to deflect the sort of claims made by Patrick Michaels. For if everything observed is consistent with IPCC predictions, there is no reason to then call into question the scientific basis used to justify policies.

But this strategy runs a real risk of damaging the credibility of the scientific community. It is certainly possible to claim, as some of our commenters have and the folks at RC have, that 20 years of cooling is "consistent with" IPCC predictions, but I can pretty much guarantee that if the world has experienced cooling for 20 years from the late 1990s to the 2000-teens that the political dynamics of climate change and the standing of skeptics will be vastly different than it is today.

Now I am sure that many scientist/activists are just trying to buy some time (e.g., buy offering a wager on cooling, as RC has done), waiting for a strong warming trend to resume. And it very well might, since this is the central prediction of the IPCC. Blogger /activist/scientist Joe Romm gushed with mock enthusiasm when the March temperatures showed a much higher rate of warming than the previous three months. We'll see what sort of announcement he or others put up for the much cooler April temperatures. But all such celebrations, on any side of the debate, do is set the stage for the acceptance of articles like that by Pat Michaels who point out the opposite when it occurs. One way to buy time is to protest, call others names, and muddy the waters. This strategy can work really well when questions of inconsistency take place over a few months and the real world assumes the pattern of behavior found in the central tendency of the IPCC predictions, but if potential inconsistency goes on any longer than this then you start looking like you are protesting too much.

So what is the alternative for those of us who seek action on climate change? I see two options, both predicated on rejecting the linkage between IPCC predictions and current political actions.

1) Recognize that any successful climate policies must be politically robust. This means that they have to make sense to many constituencies for many reasons. Increasing carbon dioxide in the atmosphere will have effects, and these effects are largely judged to be negative over the long term. Whether or not scientists can exactly predict these effects over decades is an open question. But the failure to offer accurate decadal predictions would say nothing about the judgment that continued increasing carbon dioxide is not a good idea. Further, for any climate policies to succeed they must make sense for a lot of reasons -- the economy, trade, development, pork, image, etc. etc. -- science is pretty much lost in the noise. So step one is to reject the premise of claims like that made by Pat Michaels. The tendency among activist climate scientists is instead to accept those claims.

2) The climate community should openly engage the issue of falsification of its predictions. By giving the perception that fallibility is not only acceptable, but expected as part of learning,it would go a long way toward backing off of the overselling of climate science that seems to have taken place. If the IPCC does not have things exactly correct, and the world has been led to believe that they do, then an inevitable loss of credibility might ensue. Those who believe that the IPCC is infallible will of course reject this idea.

Who knows? Maybe warming will resume in May, 2008 at a rapid rate, and continue for years or decades. Then this discussion will be moot. But what if it doesn't?

Posted on May 16, 2008 08:38 AM


I think a lot of the ad hominem attacks are a result of "personal investment" as opposed to politics per se. If your career is to make predictions, you will not take it lying down if people suggest your predictions are false. If you spend years working/researching a particular issue, it is not fun to find out that work was all in vain. I'm not saying this has occurred, but after another 10-20 years of no warming/cooling that would likely be the case. This "personal investment" in anthropogenic global warming is also the reason why so many people appear to be happy when the data shows warming. They are almost gleeful when they report about thinning sea ice or rising temperatures. It seems like vindication is a more satisfying result than the earth not experiencing a climate catastrophe.

Posted by: Captain Obviousness [TypeKey Profile Page] at May 16, 2008 10:55 AM


You've almost got it right, now.

It's important for policy makers and the public to understand:

1) That all prediction entails some uncertainty, and under the best of circumstances, issues of "consistency" will arise – but these needn't necessarily 'upset the boat'.

2) That confidence in even predictions about 'stationary', but noisy processes, build only about in proportion to the square root of the time interval of accumulated data.

3) That non-stationary processes, like the effects of steadily increasing atmospheric concentrations of CO2, take even more time to characterize with some confidence.

4) That random large events, like some volcanic eruptions, 'break' trends in data, making it especially difficult to 'statistically aggregate' longer time intervals that span such events, to gain the confidence associated with longer records.

5) That 'periodic' climate 'events', like 5–10 year ENSO events, and multi-decadal events like NAO, that involve the high inertia of the oceans, and which are still poorly understood, perturb the record. 'Compensating' for these is difficult, and therefore confidence in statistical analysis of global observations is further compromised.

6) That until the public and policy makers understand this as well as expert climatologists, the BEST they can do is put SOME trust in the accumulated judgment of a majority of those experts – who may none-the-less be wrong!

7) That when all of this involves risks of possible severe global economic and ecological disruption – in the future – it's exceedingly prudent to do as much as is 'feasible', NOW, to avoid such risks, even if it looks a bit expensive and discomforting – and just might turn out to be 'unnecessary'!

This is a tall order. But I'm afraid it's what should be the burden of concerned 'experts' at this disturbing juncture in our history.

Len Ornstein

Posted by: Len Ornstein [TypeKey Profile Page] at May 16, 2008 11:22 AM

"Blogger /activist/scientist Joe Romm gushed with enthusiasm when the March temperatures showed a much higher rate of warming than the previous three months."

The "gushing enthusiasm" was a *parody* of the zeal with which the Watts-type spin on January 2008 temperatures was bandied about. It's not exactly subtle.

"We'll see what sort of announcement he puts up for the much cooler April temperatures."

From Romm's very post you referenced: "I’m going to go out on a limb here and predict that the remarkable warming of the last couple of months won’t continue at the same pace over the next two months." He understands the role of natural variability. That's the whole point of his post- that salivating over month-to-month temperature fluctuations is ridiculous because basing any sort of trend on them will lead to very misleading conclusions (e.g. 100 years of warming being wiped out, or in Romm's example, Venusian temperatures on Earth).

I don't understand how it is possible for you to have actually read the post and still make the comments about it that you did.

Posted by: Jon [TypeKey Profile Page] at May 16, 2008 12:16 PM

Roger must have been joking back. Look at the title "Breaking News: The Great Ice Age of 2008 is finally over — next stop Venus!" And "a staggering +0.67°C." Compared to January 2007 of .87!? Ha ha ha funny.

Posted by: Lupo [TypeKey Profile Page] at May 16, 2008 12:25 PM

Jon- Thanks for the editorial advice, dry wit often fails to come across in blogs. Was this your sole reaction to this piece?

If we ever have an opening in the department of BloGotcha for a chief sematicist/editor, you are my guy;-)

Serious, thanks for reading and commenting. As you know, blogs are imperfect, first drafts of ideas, and getting them clear is always helpful.

Posted by: Roger Pielke, Jr. [TypeKey Profile Page] at May 16, 2008 12:36 PM

Len Ornstein has indeed laid out a tall order if for no other reason than that is not how prominent climate scientists (Jim Hansen, for example)and supporters of their expanded funding (IPCC) have sold the narrative of AGW.

We did not get Ornstein-like well-reasoned projections with candid explanations of modeling limitations. We instead got the imminent inundation of New York, malaria in Northern Europe, Hurricane Katrina repeated several times a year indefinitely, every hot day in August anywhere on the planet a sure sign of the apocalypse and every glacial chunk that falls into the sea irrefutable proof of our coming demise.

And the kicker of course is that anyone who dares to question any aspect of The Narrative is stupid, immoral, selfish and/or a lackey of Exxon.

And now that the disaster that The Settled Science foretold is apparently on hold, we are told we would be idiots for thinking that 20 years of rather cool weather is in any way inconsistent with a prediction--oops, excuse me, model scenario set--of rapid warming.

The tone of the AGW issue was set solely by Alarmist proponents. If there is blowback when it turns out the Lukewarmists (if not the Denialists) were right, they have only themselves to blame.

Posted by: George Tobin [TypeKey Profile Page] at May 16, 2008 12:41 PM

"dry wit often fails to come across in blogs."

Consider the failure mine. I confess to having a terrible sense of humor.

Perhaps you can explain it me. If you knew that he was being sarcastic, you knew that he didn't expect a sustained warming into April and May, and you knew the post was written specifically to combat the type of month-moth thermometer watching that goes on, what was the point of rhetorically questioning his response to such month-to-month thermometer watching for April? I'd love to be let in on the humor.


Posted by: Jon [TypeKey Profile Page] at May 16, 2008 12:50 PM

Jon- It was less meant to be humorous than sarcastic, the general point being, once you play the game (via jokes or whatever), you've ceded a big part of the territory, which is the general theme of the post. Romm's joke doesn't work anymore in April, since we get op-eds like that by Michaels.

Posted by: Roger Pielke, Jr. [TypeKey Profile Page] at May 16, 2008 12:57 PM

"once you play the game (via jokes or whatever), you've ceded a big part of the territory"

Is the 'territory' in question the uncertainty of month-to-month variability? If so, how has Romm ceded anything?

I guess I don't "get it". It seems to me that Romm used an excellent rhetorical device to pillory the concept of drawing long term conclusions from short term changes. He closed the door on any April rebuttals himself, not only by illustrating the inherent silliness, but by acknowledging that as it is a matter of uncertain variability he had no expectations (unlike the people that went nuts over Jan 2008) that it would continue.

Are you saying that it is good or bad to acknowledge the large amounts of uncertainty and variability in the short term?

The Romm issue is certainly not my only thought on this post. I have to confess I am also a bit confused by "If the IPCC does not have things exactly correct, and the world has been led to believe that they do, then an inevitable loss of credibility might ensue. Those who believe that the IPCC is infallible will of course reject this idea."

If anyone thought that the IPCC had things "exactly correct" what would have been the point of the SAR, TAR, AR4? Not to mention AR5? The fact that there is constant updating and revision to the Assessment Reports is a pretty big acknowledgment that the IPCC isn't infallible and that it doesn't have things "exactly right". Not to mention the explicit acknowledgments of uncertainty and limits of confidence throughout. People rely on the IPCC reports because they are a synthesis of the science at the time they were written, not because they are inerrant. I've spoken with quite a lot of people with widely different levels of background on climate change, and without exception, the only times I've ever seen the IPCC treated as though it was supposed to be infallible were strawman arguments by those convinced it was all a hoax anyway.

You seem to imply that Michaels is irrelevant and on that I certainly agree. He wrecked his credibility a while back pulling the same stunt over CFC regulation. The debunking of FUD like his isn't even something that anyone devotes a significant amount of time to anymore. Although it is interesting to note that he tries to flog the Keenlyside paper as if that is the consensus view, which emphasizes why RC made their bet.

Speaking of, isn’t that just the kind of falsifiable prediction you ask for? "The climate community should openly engage the issue of falsification of its predictions". Although RC doesn't speak for the community as a whole, they are making a falsifiable short term prediction and trying to make it as visible as possible.

Posted by: Jon [TypeKey Profile Page] at May 16, 2008 01:40 PM

Watts did not gush over the large temperature drops. He admitted that there were other causes: "Probable cause- [Una] Nińa muy grande. It looks like we may have a PDO shift as well. But as some say, trying to correlate such things is a “fools errand”. But, judge for yourself." That is not gushing.

In light of the idea that had been sold to the public that CO2 is the main greenhouse gas and the warming would be undeniable, to suddenly get a 6 year levelling off of the warming trend without a large volcanic eruption was startling to me. To be shown that there are some forcings that are strong enough to counteract the AGW darling of CO2, or that the feedback was overestimated, was an eye opener. As Keenlyside points out, multi year ocean cycles may cool us for the next decade. I have yet to see any proof that the warming trend of the 1990s was not boosted by those same multi year ocean cycles while in their warm phase. In light of more recent data, I don't see why we should not wait a few years to see how the models pan out.

John M Reynolds

Posted by: jmrsudbury [TypeKey Profile Page] at May 16, 2008 01:54 PM


I said Watts-type, and perhaps I should have said "Watts-inspired" to be clear. It was his graph that was touted as cooling that overturned a century of warming- though he himself made no claim.

"In light of the idea that had been sold to the public that CO2 is the main greenhouse gas and the warming would be undeniable"

CO2 is the "main" GHG in a certain sense- that it is greatest component of anthropogenic forcing. It is neither the main naturally occurring GHG nor the most potent anthropogenic GHG. This is pretty basic to understanding anthropogenic warming.

"to suddenly get a 6 year levelling off of the warming trend without a large volcanic eruption was startling to me."

Why would six years of a flat trend, eruption or not, startle you?

"To be shown that there are some forcings that are strong enough to counteract the AGW darling of CO2"

Can you please clarify who told you or where you read that anthropogenic forcing would dominate/eliminate internal variability? I have to confess, that's not something I've actually ever seen or heard before.

Posted by: Jon [TypeKey Profile Page] at May 16, 2008 02:11 PM

Thanks for the reply Jon. Since we are now getting into a tangent, if you prefer, I can make an entry on my blog to address your questions. Suffice it to say, I was getting my information back then from the IPCC and the media.

The IPCC reports have progressed over the years to using stronger wording. For example, they moved from likely to very likely with respect to AGW. Taking a strong stance in light of their graphs that show several strong positive forcings and only a few minor negative forcings, the only conclusion was that the world would continue to warm.

Posted by: jmrsudbury [TypeKey Profile Page] at May 16, 2008 02:29 PM

Jon, you assume land use and pollution and others is not a more large anthropogenic forcing component? And then then what they do to sun and water and others?

Posted by: Lupo [TypeKey Profile Page] at May 16, 2008 02:47 PM

"mock enthusiasm" tells the story, yes?

But see how sly this is.
"I’m going to go out on a limb here and predict that the remarkable warming of the last couple of months won’t continue at the same pace over the next two months."
At the time that was .13 and .41 up. Not difficult to say it will not be to 1.21 when May comes in is it?

Posted by: Lupo [TypeKey Profile Page] at May 16, 2008 03:39 PM

In the second post above, Len Ornstein gave a thoughtful response to Roger’s article, but ultimately ends up in the same place as all others who have argued that we must ‘do something’ about climate change. He falls back to invoking the Precautionary Principle.

In point #7 he states:

“That when all of this involves risks of possible severe global economic and ecological disruption – in the future – it's exceedingly prudent to do as much as is 'feasible', NOW, to avoid such risks, even if it looks a bit expensive and discomforting – and just might turn out to be 'unnecessary'!”

Implementing the Precautionary Principle in the past has usually done more harm than good, making the action self-contradictory. It is ultimately based on a linear world view were straight lines are drawn from actions to consequences and from solutions to costs. The given risk is always the worst case scenario, while the cost of the solution is always assumed to be minimal. Invariably, reality never follows those straight lines and decisions based on them turn out to be worse than if no action was taken. The Precautionary Principle is neither precautionary nor a principle, but a noble sounding excuse for engaging in social engineering and generating ‘bad’ policy.

In Mr. Ornstein’s statement, the risk is depicted as “…possible severe global economic and ecological disruption...” So far, the only indication of severe global economic and ecological disruption from climate change exists in the computer models. There is no evidence in the real world that points to inevitable disaster, or even serious problems. To the contrary, the lack of warming in the past decade makes the worst case scenarios look ridicules, and calls into question the minimal predictions of warming derived from the models.

Mr. Ornstein’s presents the cost of the solution as “…a bit expensive and discomforting…” The reality is that the cost of mitigating CO2 emissions has already proven to be more than a bit discomforting, with unintended consequences causing some people to go hungry. These initial mitigation efforts would have to be much more severe to have any discernable impact on climate, making any potential ‘solution’ extremely expensive and disruptive (fancy talk for poverty and premature death), all for something that Mr. Ornstein readily admits …”may be unnecessary”.

It is more rational to rewrite point #7 as follows: “When all of this involves speculative and unsubstantiated risks of global economic and environmental disruption of some unknown quantity; and, while the proposed solutions have already demonstrated higher costs, unintended negative consequences and absolutely no indication of effectiveness, it is extremely unwise to pursue this course of action any longer.”

When both the climate system and human history are decidedly non-linear, what wisdom is there in drawing linear trends 100 years into the future, proclaiming predictive skill and implementing punitive laws based on that prediction? The wisest course of action would be to deal with known and well quantified ecological and economical problems that exist today, making future generations much more capable, resilient and adaptive to any ecological problems that we can not foresee, yet may come about in the future. That is what our predecessors did for us. It is what we owe to future generations.

Posted by: Jim Clarke [TypeKey Profile Page] at May 17, 2008 08:41 AM

But Jim, when you say "The reality is that the cost of mitigating CO2 emissions has already proven to be more than a bit discomforting, with unintended consequences causing some people to go hungry." it does not seem the food shortages can be directly attributed to using grain to produce fuel. If that is what you are saying.

Posted by: Lupo [TypeKey Profile Page] at May 19, 2008 04:03 PM

Joe Romm goes absolutely nuts over this post, ironically providing more evidence for its analysis that I ever could have.

Here is how I responded on his blog (my second try):

"Joe are you not letting my response through? This is my second try after seeing the first deleted (by accident?).

Wow Joe, this is a cheap smear even by your standards.

You could have emailed me to ask about the quote or any of the other
allegations that you make about me in this post. But you did not.

My views have remained consistent for many years, and here is how I
summarized them before Congress in 2006:

It is possible to believe that we need to act on climate change
(mitigation and adaptation), while at the same time having little
faith in the ability of climate models to make skillful predictions on
the time scales that that action needs to take place. It is also
possible to support mitigation while realizing that adaptation is also
of critical importance.

And I'm not the only person who thinks a little air needs to be let of
of the climate prediction bubble, compare a leading climate modeler,
Tim Palmer of the UK-based European Centre for Medium-Range Weather
Forecasts who says "Politicians seem to think that the science is a
done deal, I don't want to undermine the IPCC, but the forecasts,
especially for regional climate change, are immensely uncertain."

Will you be slandering Tim Palmer here as well? Other scientists have
expressed similar concerns.

Your intolerance of different points of view is simply stunning. Your
twisting of words and statement to smear speaks loudly for itself."

Posted by: Roger Pielke, Jr. [TypeKey Profile Page] at May 21, 2008 12:11 PM

Joe Romm has let two comments through while sitting on my response. What is proper etiquette for allowing a response to slander?

Posted by: Roger Pielke, Jr. [TypeKey Profile Page] at May 21, 2008 12:58 PM

Roger, the more links you include (if you tried to include any), the longer your posts will hang in the queue. I had a completely factual (i.e. no opinion whatsoever) post linking someone to the basis of GISTEMP's TSI chart that took forever to post because I had three links in it.

That might be the reason.

Posted by: Jon [TypeKey Profile Page] at May 22, 2008 07:47 AM

Thanks Jon, Joe admitted he was screening my responses, but relented.

Posted by: Roger Pielke, Jr. [TypeKey Profile Page] at May 22, 2008 09:45 AM

A comment first on the "politicization" issue, and then on the issue of interannual variability.

Many participants in the scientific debate over AGW have become "advocates" for or against particular policy steps (e.g. Kyoto Protocol). Some of the "politicization" arises from the failure to distinguish between the scientific questions, and the issue of what, if anything, to "do" about them.

In my view (and I think this is what Roger is getting at with many of his posts at this site) the philosophical pitfall comes from the presumption that settling the science questions makes some policy step (or its avoidance) inevitable.

Some people labor under the implicit premise that if only policymakers and society at large could be convinced that global warming is real and due to human action, carbon-limitiations schemes like Kyoto would be implemented (leaving aside the question of the efficacy of Kyoto). Not necessarily – climate science is not the only (and indeed may not be the most important) factor driving energy and carbon-emissions policy. But the premise makes any challenge to the *science* a threat to the policy stance that GHG emissions must be cut.

Similarly, many opponents of limitations on fossil fuel emissions seem intent on discrediting the science of global warming as a way of forestalling action. But there are other, perhaps more immediate reasons to cut our carbon emissions with more certain science behind them. Examples include local and regional pollution which pose a public health risk.

So the "science equals policy" presumption shifts the battleground over this area of policy from politics, economics, sociology, and engineering to climate science.

The 1998 to ~2007 global cooling trend does not, in itself, invalidate the longer-term multi-decadal trends at issue in the AGW discussion. But some advocates for Kyoto-style emissions-limitations set themselves up for an argument over year-to-year trends by citing 1998 as the warmest year of the 1990s decade and citing that warmth as support for the policies they advocated.

Posted by: WHoward [TypeKey Profile Page] at May 22, 2008 08:47 PM

But WHoward, the 1998-2007 trend is .42 to .58

1997-2006 trend is .40 to .58 when you move back 1 year.
1996-2005 trend is .35 to .58 when you move back 2 years.
1997-2007 trend is .40 to .58 when you add 1 year.
1996-2007 trend is .35 to .60 when you add 2 years.

So our minium on the trend line is "getting warmer" going to 1998-2007 when you shift the 10 years or add years. Yes, when you add 2 years the maximum does "get cooler" but not as much as the minimum "go warmer".

How is "cooling trend" defined? What do you compare the anomaly trend of 1998-2007 to and saying it's cooling?

Are you saying because the 10 year period was .16 it is cooling compared to the 12 year period of .25? That seems to make no sense. Or shifting the 10 year period backwards giving a rising minimum making it .16 compared to a shift of 2 years at .23? That seems to make no sense either, when the min is lower and the max the same of course the number is bigger for the range.

I would think the different between the bottom and top of the trend line is not the way to look at it, perhaps the different between the two.

Compared to the 12 years 1996-2007 the 10 years 1998-1997's trend min was .07 higher and max was .02 lower. This gives an overall rise of .05 from the 10 year period compared to the 12, yes?

I am not sure if that is the correct way to see if 1998-2007 is getting cooler or warmer or staying the same. We have to know what to compare it to, don't we?

Oh! 10 years mean min/max is .5 and 12 years .475

Posted by: Lupo [TypeKey Profile Page] at May 23, 2008 01:10 PM

Lupo, I was looking at the RSS TLT data, plotted here on this site by Roger in a post a few months ago.

We could argue for long time about "trends." The data from 1998 to 2007 do not constitute a "trend" in the sense that you could fit a line, but there is a net cooling from 1998 to 2007, driven largely by the 1998 outlier. My point was that this is beside the point.

To make verification of the IPCC projections meaningful we would have to pick a timescale and a variable or set of variables. I would suggest we would need to select at least a decadal time scale (e.g. 10-year averages using an agreed-upon smoothing function). Besides averaging out interannual modes in the climate system (NAO, El Nino, PDO) the other reason for looking at decadal-or-greater timescales is to get a time interval over which we can see significant accumulation in GHGs in the atmosphere. We would need to pick timescale on which the airborne fraction of GHGs increases at something close to the sensitivity of the models to their radiative forcing.

Posted by: WHoward [TypeKey Profile Page] at May 24, 2008 05:23 PM

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