Pure Pedantry

The Intergovernmental Panel on Climate Change report is out today, and I was shocked to discover that it is already being misreported. It was being mis-reported before, but that was just leaks. You can lie with leaks. They are easily selective.

Now the mis-reportage is being done with the actually report out, so I have a piece of advice for everyone. Just read the thing. It isn’t that complicated. Read it for yourself because every time I read a news article about it I notice some new crock of hooey.

Take this for instance:

The panel predicted temperature rises of 2-11.5 degrees Fahrenheit by the year 2100. That was a wider range than in the 2001 report.

However, the panel also said its best estimate was for temperature rises of 3.2-7.1 degrees Fahrenheit. In 2001, all the panel gave was a range of 2.5-10.4 degrees Fahrenheit.

How do you resolve the first and the second sentence? This report said it could be as high as 11.5 degrees, but it also said that the best range was less than 7.1 degrees?

Here is the actual chart of the temperature projections the IPCC made, below that is a description of what each scenario entails (what changes are made to emissions for instance):


A1. The A1 storyline and scenario family describes a future world of very rapid economic growth, global population
that peaks in mid-century and declines thereafter, and the rapid introduction of new and more efficient technologies.
Major underlying themes are convergence among regions, capacity building and increased cultural and social
interactions, with a substantial reduction in regional differences in per capita income. The A1 scenario family
develops into three groups that describe alternative directions of technological change in the energy system. The
three A1 groups are distinguished by their technological emphasis: fossil intensive (A1FI), non-fossil energy sources(A1T), or a balance across all sources (A1B) (where balanced is defined as not relying too heavily on one particularenergy source, on the assumption that similar improvement rates apply to all energy supply and end use

A2. The A2 storyline and scenario family describes a very heterogeneous world. The underlying theme is self reliance and preservation of local identities. Fertility patterns across regions converge very slowly, which results in continuously increasing population. Economic development is primarily regionally oriented and per capita economic growth and technological change more fragmented and slower than other storylines.

B1. The B1 storyline and scenario family describes a convergent world with the same global population, that peaks
in mid-century and declines thereafter, as in the A1 storyline, but with rapid change in economic structures toward a service and information economy, with reductions in material intensity and the introduction of clean and resource
efficient technologies. The emphasis is on global solutions to economic, social and environmental sustainability,
including improved equity, but without additional climate initiatives.

B2. The B2 storyline and scenario family describes a world in which the emphasis is on local solutions to economic,
social and environmental sustainability. It is a world with continuously increasing global population, at a rate lower
than A2, intermediate levels of economic development, and less rapid and more diverse technological change than in
the B1 and A1 storylines. While the scenario is also oriented towards environmental protection and social equity, it
focuses on local and regional levels.

An illustrative scenario was chosen for each of the six scenario groups A1B, A1FI, A1T, A2, B1 and B2. All should
be considered equally sound.

The SRES scenarios do not include additional climate initiatives, which means that no scenarios are included that
explicitly assume implementation of the United Nations Framework Convention on Climate Change or the emissions
targets of the Kyoto Protocol.

So where did the AP get their numbers? Who knows… (Ed: Dave Munger has clarified that I neglected that one is in Fahrenheit and one is in Celsius. That clears up that problem. Also, they are doing a lowest projection highest projection deal which I agree with but I think I would rather they put the best estimate as a single number not as the range.) This is why I read things for myself.

Then there is the bit in the report about the Greenland ice sheet which I knew was going to be trouble. Here is what the report said about Greenland:

Contraction of the Greenland ice sheet is projected to continue to contribute to sea level rise after 2100. Current models suggest ice mass losses increase with temperature more rapidly than gains due to precipitation and that the surface mass balance becomes negative at a global average warming (relative to pre-industrial values) in excess of 1.9 to 4.6°C. If a negative surface mass balance were sustained for millennia, that would lead to virtually complete elimination of the Greenland ice sheet and a resulting contribution to sea level rise of about 7 m. The corresponding future temperatures in Greenland are comparable to those inferred for the last interglacial period 125,000 years ago, when paleoclimatic information suggests reductions of polar land ice extent and 4 to 6 m of sea level rise.

What that means is that contraction of the Greenland ice sheet will continue after 2100. If it were to continue to its logical conclusion this would result in a sea level rise of 7m, but that doesn’t mean that the sea level rise of 7m will occur by 2100 — because it takes a long time for these things to happen. It might, but they aren’t certain about that subject yet, in spite of the claims of scientists arguing that ice melting will be highly non-linear.

My problem with the coverage of this part is that the articles mention that we don’t know the rate of sea level rise, and then imply that it will be very rapid — ignoring the body of opinion that it will be gradual. Here is the NYTimes:

Should greenhouse gases continue to build in the atmosphere at even a moderate pace, temperatures by the end of the century could match those last seen 125,000 years ago, in the previous warm spell between ice ages, the report said.

At that time, the panel said, sea levels were 12 to 20 feet higher than they are now due to the melting of great amounts of ice now stored, but eroding,on Greenland and in parts of Antarctica.

The panel said there was no solid scientific understanding of how rapidly the vast stores of ice in polar regions will begin to erode, so their estimates on new sea levels were based mainly on how much the warmed oceans will expand, and not on contributions from melting of ice on land.

Other scientists have recently reported evidence that the glaciers and ice sheets in the Arctic and Antarctic could flow seaward far more quickly than estimated in the past and have proposed risks to coasts could be much more imminent. But the I.P.C.C. is proscribed by its charter from entering into speculation and so could not include such possible instabilities in its assessment.

Michel Jarraud, the secretary general of the United Nations World Meteorological Organization, said the lack of clarity should offer no one comfort. “The speed with which melting ice sheets are raising sea levels is uncertain, but the report makes clear that sea levels will rise inexorably over the coming centuries,” he said. “It is a question of when and how much, and not if,” he said, adding: “While the conclusions are disturbing, decision makers are now armed with the latest facts and will be better able to respond to these realities.”

Here is an even worse statement in the NYTimes article:

The report released here represented the fourth assessment since 1990 by the group, the Intergovernmental Panel on Climate Change of the United Nations, of the causes and consequences of climate change. But for the first time the group asserted with near certainty — more than 90 percent confidence — that carbon dioxide and other heat-trapping greenhouse gases from human activities were the main drivers of warming since 1950.

In its last report, in 2001, the panel, consisting of hundreds of scientists and reviewers, put the confidence level at between 66 and 90 percent. Both reports are online at www.ipcc.ch.

If carbon dioxide concentrations reach twice their pre-industrial levels, the report said, the climate will likely warm some 3.5 to 8 degrees. But there would be more than a one in 10 chance of much greater warming, a situation many earth scientists say poses an unacceptable risk. (Emphasis mine.)

That is not what 90% confidence means. It means that you are 90% certain the true value lies within that interval, but there is a 10% chance it lies outside it — and it could be above or below that interval. There could be greater warming, but there also could be significantly lesser warming. Both scenarios are unlikely but are equally unlikely under the confidence interval. The NYTimes is throwing all of the uncertainty into the much greater warming basket.

I am not a climate change skeptic. (Although — particularly in light of this report — I have my doubts that changes in emissions can stop global warming from going forward. Adaptation to climate change has yet to have its fair hearing in the debate, but it will eventually when we realize we don’t really have a choice.) However, what makes me so mad about this debate is the tendency of both sides to use rhetoric and engage in wild speculation. Speculation justifying what we think is the higher good is not good science, is not good reporting, and is not going to save us. There is a good reason why the IPCC doesn’t engage in speculation: speculation is dangerous.

Policy-makers should read this report directly, and you should too. If there is one thing I have learned from this, don’t trust anyone to explain the data for you because they could be shamelessly full of it. Go out and find it yourself.

I haven’t had time to digest the whole thing, but I will be certain to post more on it later on.

Roger Pielke Jr at Prometheus had this on the hurricane/warming association. The statement in this report is stronger than before, but he says the science is still unclear.


  1. #1 Dave Munger
    February 2, 2007

    Where did they get their numbers? First off, the temperatures in that chart are in Celsius, while the AP report was in Fahrenheit. It appears that what they did is calculate the value for the low end from the most optimistic model (B1), and the value for the high end from the least optimistic model (A1F1).

    B1 assumes we do our best to solve the problem, while A1F1 assumes we basically keep doing what we’re doing now.

  2. #2 Jake Young
    February 2, 2007

    You’re right about the Fahrenheit/Celsius thing. I should have caught that. Well that clarifies that discrepancy…

    Still I am not optimistic about this reporting.

  3. #3 Dave Munger
    February 2, 2007

    I agree that the reporting is problematic. Without seeing the chart, I would have assumed that the wide span of the estimate was assuming that we continue along as we are now. But only the A1F1 model does that, with the range of options going from 4.4 to 11.5 degrees.

    So to my mind, the reporting is erring on the side of caution. Only through action can we achieve the more optimistic models; most people will look at this report and say “2 degrees doesn’t sound too bad.”

    Similar with removing polar icecap melting from the equation. Icecap melting is what we’re all worried about, so reporting the comparatively trivial rise from temperature increase alone could make some people believe that we shouldn’t be worried about rising sea levels at all.

    But you’re right about the confidence interval thing. That stuff is confusing enough, without reporters messing it up as well.

  4. #4 Gerard Harbison
    February 2, 2007

    http://www.junkscience.com note that what was released yesterday is merely the policy report, and the scientific/technical report will not be released for three months. They claim that the technical document will be edited to conform with the policy report, which seems rather incredible. For this reason, they have leaked the current (second) draft of the technical report. Whether or not you believe their claim, the technical report is lengthy but remarkably interesting reading, at http://www.junkscience.com

  5. #6 Lubos Motl
    February 2, 2007

    Thanks, I’ve linked to you here:


    Sorry for the typo… Please erase the previous comment.

  6. #7 richCares
    February 3, 2007

    here is White House Statement:

    wow, Bush agrees

  7. #8 Mark Bahner
    February 3, 2007

    “I agree that the reporting is problematic. Without seeing the chart, I would have assumed that the wide span of the estimate was assuming that we continue along as we are now. But only the A1F1 model does that,…”

    No, that is completely false. None of the scenarios assume any deliberate reduction in emissions. There is NO “business as usual” scenario reported. The IPCC (ridiculously) claims that all scenarios are equally valid.

    In reality, the B1 scenario is by far the most likely, based on current trends and based on technical analyses of the likely CO2 emissions and atmospheric concentrations, methane atmospheric concentrations, and black carbon emissions (three signficant contributors to global warming) in the 21st century. The A1F1 scenario was thrown in to the IPCC Third Assessment Report *after peer review* in a deliberate attempt to scare the public. There is not even 1 chance in 20 of the A1F1 scenario actually coming to pass.

    See this posting (and others) on my blog:

    Responses to Tom Wigley

    Mark Bahner (environmental engineer)

  8. #9 Thom
    February 4, 2007

    Roger Pielke Jr. is not a climate scientist. And he has the dubious distinction of being the Republican’s invite to a hearing on the politicization of science by the Bush administration.


    If you watch the hearing, which can be found on CSPAN, it did not go well for Pielke.

  9. #10 len
    February 6, 2007

    i wonder why it is that in general people on the political left are apt to believe that climate change is a major problem while people on the political right believe the opposite? Science shouldn’t be based on political opinion. It’s undeniable that ice caps are melting rapidly and sea levels are rising. The point should be WHY(what is the cause) and what can be done to stop it or slow it down or not. It would have to be a global effort and that doesn’t seem likely. China is the world’s number one polluter last time I checked.
    Maybe we’ll go the way of the dinosaurs and something better/smarter will sprout up. Nothing lasts forever…violins

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