Sunday, November 18, 2007

Reading the IPCC Report

The reports are now in part out and webbed, and I started by looking over "Summary for Policymakers" from the Working Group II report. It makes an interesting contrast with the news stories. For instance:

"Globally, the potential for food production is expect to increase with increases in average temperature over a range of 1-3 degrees centigrade, but above this it is projected to decrease."

Or in other words, given the predicted temperature increase of .2 degrees/decade, global warming will tend to increase food production for at least the next fifty years, and perhaps as much as the next hundred and fifty. Has anyone noticed that prediction in news stories about the report?

"Globally, commercial timber productivity rises modestly with climate change in the short- to medium-term, ... "

I also like "Nearly all European regions are anticipated to be negatively affected by some future impacts of climate change, ... ." Note the "some." It's hard to imagine any substantial change in the world, good or bad, for which which the statement would not be true.

Also note, from Chapter 2, that the projections of sea level rise "are smaller than given in the TAR due mainly to improved estimates of ... " TAR appears to be the 2001 estimate, if I understand it correctly. Perhaps I missed it--did any news story report that fact?

As Tim points out, the IPCC is now hedging its sea level predictions--in part by pointing out the uncertainty, in part by saying what might happen over thousands of years and adding that they can't be certain it won't happen over mere centuries. But the six scenarios they provide numbers for give predictions ranging from a low of .18 meters to a high of .59 meters--about two feet. The bulk of that is from thermal expansion, so actual melting of continental ice would have to be several times as high as their estimate in order to substantially increase it.

I am, of course, selecting bits from the post that support my point--that the news stories are hype, selecting out negative predictions, often very uncertain ones, and ignoring positive predictions and ambiguity. There are other bits of the report that do indeed support a negative view of the consequences.

Another point that struck me was how much of the report depended not on climate science, however good or bad that may be, but on social science, especially economics. My guess, from a quick look over it, is that those results are very uncertain and might easily get the sign of the effects wrong.

People adjust to change--they vary the crops they grow, the areas under cultivation, where they live and the like in response to changing climate. If you assume no such adjustment--not, I think, what the IPCC is doing--then the net result is almost certainly negative. With enough adjustment, taking advantage of opportunities produced by, for example, longer growing seasons, the net result can be positive. It's not clear how they know, or how they can know, how much adjustment will actually take place. I am reminded, perhaps unfairly, of just how bad the predictions in _Limits to Growth_ turned out to be.


At 1:53 AM, November 19, 2007, Blogger Tim Lambert said...

DF: "Also note, from Chapter 2, that the projections of sea level rise "are smaller than given in the TAR due mainly to improved estimates of ... " TAR appears to be the 2001 estimate, if I understand it correctly. Perhaps I missed it--did any news story report that fact?"

Yes, most of them did and they usually did not report that the 59cm was not an upper bound. Here is a Real Climate post attempting to set things straight.

Because reporters like to "balance" their articles by including contrary views, news reports tend to exaggerate the uncertainties. Readers find out what the IPCC says and also what the one scientist who thinks that the IPCC is wrong says. And perhaps gives up in confusion.

At 7:49 AM, November 19, 2007, Blogger jimbino said...

One great adjustment the human population could make is to stay right where they are and stop all the breeding, thus lowering demand for food and timber, freeing up land for planting, easing the load on the fish stocks and making the rest of the world's biomass very happy. This is an "adjustment" that could have enormous impact in just one generation!

At 10:13 AM, November 19, 2007, Anonymous tobbic said...

Maybe more efforts should be directed towards estimating the probability of catastrophic climate change (positive feedback loops). If we stay near the current climate equilibrium (slowly drift away), damages are likely to be very small (only adaptation is required, no mitigation, at least in the near term).

At 12:32 PM, November 19, 2007, Anonymous Anonymous said...

Jimbino: "One great adjustment the human population could make is to stay right where they are and stop all the breeding, thus lowering demand for food and timber, freeing up land for planting, easing the load on the fish stocks and making the rest of the world's biomass very happy. This is an "adjustment" that could have enormous impact in just one generation!"

I don't see how the adjustment you mention falls into the "could make" class at all. In fact, it seem to me to be quite impossible for the human population to "stop all the breeding".

Asking people, world-wide, to stop breeding will be about as successful as asking them to stop eating and breathing. And any attempt to force people, world-wide, to stop breeding would result in far worse consequences than the worst global-warming scenerios I've heard of.

In other words, that's just not a realistic option at all.

At 1:13 PM, November 19, 2007, Blogger jimbino said...


All we need is for someone to come up with a contraceptive or abortifacient that could be broadcast in the world's air or water. That seems more practical than getting the non-breeders to pay carbon taxes, forgo fish, endure pollution, drive tiny cars and then subsidize breeding by SCHIP and school taxes and otherwise pay for all the misery the breeders are causing.

Think about it: there is almost no world problem that couldn't be solved by such a contraceptive.

At 2:22 PM, November 19, 2007, Blogger Augustin Moga said...

jimbino: "Think about it: there is almost no world problem that couldn't be solved by such a contraceptive."

It looks to me like the contraceptive you are talking about is the one that the Iranians are (supposedly) trying to build. If they succeed then there's a tiny chance that the "Stop Breeding" program will be implemented in such remote areas as Tel Aviv.

I can only hope that we'll never reach that point.

At 2:45 PM, November 19, 2007, Blogger David Friedman said...

Tim points out that my implied claim is wrong--the reduction in sea level estimates did get reported.

I note that the post he links to focuses largely on effects past 2100, however, while pointing out various uncertainties in the figures for that date coming out of the models.

At 4:58 PM, November 19, 2007, Anonymous RKN said...

I'd be interested to know if people here are convinced of the scientific consensus supposedly underlying the conclusions of this latest report? I'm arguing with friends in e-mail over this issue, and they're convinced the deniers are merely outliers.

At 5:07 PM, November 19, 2007, Blogger Tim Lambert said...

The deniers are outliers -- the media give them undue weight because it makes a better story.

At 7:11 PM, November 19, 2007, Blogger David Friedman said...

rkn wants to know if the deniers are outliers, Tim says they are.

The first question is "deniers of what?" As I read it, the fact that global warming has been happening of late is the most solidly established claim. That it is due to human action seems likely but less certain. How it will progress over the next century is less certain still--it isn't as if the climate models that are being used have been successfully predicting outcomes over periods of decades.

The human consequences of global warming are the least certain part of all. I don't think you have to be an outlier to be skeptical of the claim that, if we don't do something drastic now, global warming is going to make humans much worse off by the end of the century, for instance--on the contrary, I regard that claim as highly speculative.

And, as I pointed out, while the report contains language that can be taken to imply that, there are also a lot of qualifications in it.

At 8:02 PM, November 19, 2007, Blogger Jeff said...

I give IPCC all the credit in the world for at least making fence sitters take notice. Every environmental cause should have such a mechanism for churning out science to overcome and overwhelm the skeptics. I noticed that this past weekend the biodiversity camp is getting closer to its own version of IPCC, only they call it IMoSEB. I've summarized the report in my frog blog, and the link to the report is in there, too:

At 1:09 AM, November 20, 2007, Anonymous Paulo said...

a sad example of how the "scientific community" was used for cheap partisan politics.

Or, as Spiked's Rob Lyons put it:

"This product may look like a set of scientific statements, but is in many ways the exact opposite of science. ‘The Science’ is ‘unequivocal’ rather than sceptical and cautious in its conclusions; ‘The Science’ is built on an artificial consensus rather than on a real battle of competing ideas that admits the possibility that current thinking could be completely wrong; ‘The Science’ very strongly implies a particular direction for policy (greenhouse gas emission reductions) which is apparently above politics, rather than merely informing a political debate about how we take society forward on the basis of human need and desire."


I wonder if the more recent report will get the same headlines as the first one ("for policy-makers") back in February...

At 1:19 AM, November 20, 2007, Anonymous Simon Andersson said...

"Every environmental cause should have such a mechanism [as the IPCC] for churning out science to overcome and overwhelm the skeptics."

Oh. I thought the idea with science was to find new truth, possibly overthrowing your present views. Now I see that the task of science is to campaign for already established beliefs.

At 2:11 AM, November 20, 2007, Blogger Tim Lambert said...

Thanks paulo for linking to Rob Lyons' piece. Notice how Lyon misrepresents the IPCC findings:

So, for example, while the headlines would suggest that the Greenland ice sheet is about to melt, catastrophically resulting in sea level rises of seven metres, the report makes clear that this process would take millennia. The report actually suggests that sea level will rise over the next century by 18-59 centimetres.

What the report actually says:
Because understanding of some important effects driving sea level rise is too limited, this report does not assess the likelihood, nor provide a best estimate or an upper bound for sea level rise. Table SPM.1 shows model-based projections of global average sea level rise for 2090-2099. The projections do not include uncertainties in climate-carbon cycle feedbacks nor the full effects of changes in ice sheet flow, therefore the upper values of the ranges are not to be considered upper bounds for sea level rise. They include a contribution from increased Greenland and Antarctic ice flow at the rates observed for 1993-2003, but this could increase or decrease in the future.


Partial loss of ice sheets on polar land could imply metres of sea level rise, major changes in coastlines and inundation of low-lying areas, with greatest effects in river deltas and low-lying islands. Such changes are projected to occur over millennial time scales, but more rapid sea level rise on century time scales cannot be excluded.

Lyons even has a link to the report, so there is no excuse for his conduct.

At 5:26 AM, November 20, 2007, Anonymous RKN said...

The first question is "deniers of what?"

Right, good question. I specifically meant deniers (skeptical scientists if you will) of the conclusion that warming is caused by human activity.

I too think the conclusion that the earth has been warming since ca. 1850 is correct, to the extent the data and reports I've read are fairly representative of all the evidence, which I haven't personally evaluated.

I can also believe that atmospheric [CO2] is up since the industrial revolution. I'm merely skeptical that this high frequency change is primarily responsible for warming, as opposed to the natural, long period contributors to temperature change which, presumably, have been extant since the earth has had an atmosphere.

Whether or not there is in fact a scientific consensus underlying the conclusion of anthropogenic warming turns out to be a question all its own. Without being intimately involved with evaluating the evidence for anthropogenic warming, I find it difficult as an onlooker to know if the consensus is real or not.

At 12:26 PM, November 20, 2007, Blogger Book Calendar said...

I too read the complete NEA report this morning. There seem to be some interesting ideas. However, I take exception to what they are defining as reading. I think teenagers are spending much more time online reading things like 98 million users and -- over 17 million users. If you really consider reading properly, they probably are also reading emails, so their functional reading skills may be better than thought.

However, I think their literary reading skills are probably on the extreme decline. I see it everyday, kids are more interested in "graphical research" looking for images, videos, cartoons, blogs and other free flowing content with very little editing. This applies to middle aged people as well.

Older adults still seem to be doing fine with reading.

It really is a concern that is important. Schools and libraries really need to address this issue.

At 9:03 AM, November 23, 2007, Anonymous Al Fin said...

The term "deniers" is used by idiots. The proper term is "debaters." Those who believe the debate continues wherever there is scientific evidence that requires interpretation.


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