Is the new IPCC report conservative? Optimistic? Misleading? Inquiring minds…

ipcc.jpgThe fourth assessment report of Intergovernmental Panel on Climate Change is a remarkable document. It contains the consensus views of thousands of climate experts, and is so thoroughly vetted that it represents the true gold standard of our current understanding of global warming.

It’s also an odd sort of document. I can’t think of any other academic discipline that undertakes a similar process of self-analysis. The sausage-making that goes into the report has been well-documented, and has led to a conventional wisdom in certain circles that the IPCC report is a sort of optimistic baseline, the least-bad scenario that could possible come to pass.

Said one senior UK climate expert:

The really chilling thing about the IPCC report is that it is the work of several thousand climate experts who have widely differing views about how greenhouse gases will have their effect. Some think they will have a major impact, others a lesser role. Each paragraph of this report was therefore argued over and scrutinized intensely. Only points that were considered indisputable survived this process. This is a very conservative document — that’s what makes it so scary.

This logic has an intuitive sort of appeal. And yet, it feels off to me, or at least deeply oversimplified. The term “conservative” — elsewhere the report has been labeled “optimistic” — is one that crops up over and over again in discussions of the report’s conclusions.

The term conservative in this context refers to scientists’ natural reticence to draw conclusions that aren’t supported by solid data. But is that the same thing as suggesting the the report consistently underpredicts the effects of global warming? Common sense suggests that there is nothing particularly conservative about being systematically wrong.

Let’s take a look at the headline conclusions from all four reports:

  • 1990: The unequivocal detection of the enhanced greenhouse gas effect from observations is not likely for a decade or more.
  • 1995: The balance of evidence suggestions a discernible human influence on global climate.
  • 2001: There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.
  • 2007: Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the increase in anthropogenic greenhouse gas concentrations.

Here the so-called conservatism of the report comes into slightly sharper focus. The conclusions of the report are probabilistic in nature, dealing in likelihoods rather than certainties. Every statement has a confidence interval around it, determined by the quality and amount of supporting data.

This doesn’t strike me as “conservatism” so much as “science.” The term “very likely” in the most recent report means “with a greater than 90% chance of being true.” It doesn’t mean “100% true, but we’re hedging our bets (wink wink).”

However, there seem to be at least a few areas in which the report genuinely does understate the risks of climate change. One of these is sea level. The most recent report actually reduces the projections for sea level changes this century, despite the fact that sea level increases have actually been outpacing the predictions of climate models.

The issue here is not that the authors of the IPCC actually think sea level changes have been overstated in past reports. Rather, the science and data around glacier flow have become murkier due to recent observations that glaciers are melting faster than expected. The report summary acknowledges as much:

Dynamical processes related to ice flow not included in current models but suggested by recent observations could increase the vulnerability of the ice sheets to warming, increasing future sea level rise. Understanding of these processes is limited and there is no consensus on their magnitude.

Due to these uncertainties, the ice flow effects have been dropped from the report. Some critics have labeled the change misleading, but this seems off-base to me. If scientists don’t have enough data to model the effects of ice flow, then they don’t have enough data. This isn’t misleading, but it is conservative.

(As an aside, I keep waiting for someone more knowledgeable than myself to chime in on this topic, but so far, no dice.)

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  1. Brad Gash - February 7, 2007

    People tend to panic when scientific reports on climate change do not produce alarming recommendations stemming from 100% certainty because they feel that very often such uncertainty… or less than 100% certainty can, and often is, used as justification for inaction or “conservative” approaches to tackling climate change. How often have we seen governments excuse their inaction based on “uncertainty” in scientific data. Inevitably, however, this is the scientific model at its finest. Good science never proves; rather it supports theory, in that if it states it has proven something, you know it not to be real science. But I can understand people’s frustration in light of the fact that scientific output is so often inappropriately interpreted to affirm ones own ideological stance, and very often this means being able to try and justify an aversion to progessive action on climate change.

  2. Larry Grob - February 7, 2007

    True, the natural skepticism behind the scientific method does play into the hands of those who want to deny or disparage. But at least science, such as that behind the IPCC reports, is built on real, substantive data–sufficient at least to bolster claims of 90%+ ‘likelihood’.

    In contrast, look at the models and ‘predictability’ that seem to be readily accepted in deciding other no less significant issues–like, say, going to war. There is hardly anyone among us who, when pressed, would deny that critical decisions are made day in and day out on the basis of much less outcome certitude than the IPCC report gives us.

    This raises some very intriguing communication challenges for those who can help put things in their proper perspective.

    Larry Grob

  3. Leslie Davis - February 7, 2007

    Global Warming is a long-term matter and should not be taken out of proportion relative to other environmental matters such as sewage treatment, clean water, clean energy, mercury reduction, etc. I suggest we stay cool about warming and work it into our various agendas rather than allowing it to take us over.

  4. Aaron A. - February 8, 2007

    True, Leslie, but climate change is the major topic because it directly affects us all. Too often, when told about mercury levels in fish, or unsafe drinking water in Peru, peoples’ responses range from “Glad I don’t live there” to “Somebody (else) should do something.”

    Climate change has the potential to change middle-class American lives, so it’s one of the few goals toward which we can hope for real action now.

  5. Chad - February 9, 2007

    Aaron, you are exactly right. When people see a problem, far too many of them respond that somebody ELSE should do something. Usually that “somebody else” is the government, and almost always with someone elses’ tax dollars. It is rare to find anyone on either side of the political aisle who says there OWN taxes should be raised so that the government can spend more money on their pet war, environmental project, social program, etc. The few who actually do this are usually so super-rich that money means nothing to them anyway.
    Actually, I think the political left looses much of any moral high ground it might have with its “Don’t worry, I won’t tax YOU – just the rich!” policies.
    Of course, “rich” is generally defined as “anyone who makes more money than you are likely to anytime soon”.

  6. Chris - February 10, 2007

    I think one positive thing about the greenhouse gas issue is that each of us has the power to do something about it. My ability to reduce agricultural fertilizer run-off, and decrease the mercury content in fish is pretty limited, but by making same basic changes in my life, and encouraging family in friends to do the same, I am able to decrease to amount of carbon dioxide emmitted by several tonnes every year. Certainly governments need to step up to the plate and do their part, but there is no other environmental issue which lies so heavily in the hands of the general population.

  7. Anonymous - February 10, 2007

    What is sausage-making?
    I bought a TerraPass to put my money where my mouth is. I found out about it at Syriana is a wonderful movie!
    Lora Bruncke

  8. Anonymous - February 10, 2007

    What is sausage-making?
    I bought a TerraPass to put my money where my mouth is. I found out about it at Syriana is a wonderful movie!
    Lora Bruncke

  9. Edward Mangold - February 10, 2007

    You are right in that GW is a long term matter but this is a reason why it must be given a substantial priority. GW involves all of the people of the planet, rich and poor, affluent and marginal, educated and illiterate, first world countries and third world. We have spent two centuries building up an economy, technology and culture that is based upon cheap, available energy. Except for the die-hards, most reasonable people believe that anthropogenic causes are to a large extent responsible. The solutions will not occur on a small local level, but involve massive sweeping changes in not only our personal lifestyles, but will rise up to the governments of the world and the dominant industries. Saying that we will remain cool and not radically adjust our methods of living will not measure up to the magnitude of the problem.

  10. Aaron A. - February 11, 2007

    I believe the term “sausage-making,” as it is being used here, is a nod to a quote often credited to Otto von Bismarck, “Those who love sausage and respect the law should never watch either being made.” The quote itself has been warped and re-attributed many times over the years (thank you, Internet), but the point is that behind the scenes of this report, there were many hours of arguing, hair-pulling, and name-calling, perhaps even a back-room deal or two.

    You may notice that the term “sausage-making” is a link (haw haw). The linked article talks about last-minute negotiations before the final report was drafted, noting, “With the clock ticking down and translators juggling six official languages, and government representatives trying to insure that findings do not clash with national interests, tussles have intensified between climate experts and political appointees from participating governments.” So even on a report like this, which is supposed to be objective and scientific, we have political and industrial interests jumping in.

  11. Juci - February 25, 2007

    Mmmm barbecuing on top of a rock. Delicious. Though not good for my pale skin which is sensitive. Stupid global warming. What will it take to get people to wake up and do something?
    I maybe on the poverty line but that shouldn’t excuse me from not being environmentally friendly. Most people give out excuses like its too expensive to save the world when in fact its the totally opposite. I only pay about $80 for the electric bill. BTW I have two houses and five to six people live in it, which is amazing. Though I could go for solar power, due to living in south Florida, I don’t have the money to get solar panels, but I do waste less electricity than the average Floridian, beyond the below average, by putting the AC in safer mode and turning everything off when leaving as well as doing other things that Captain Planet have been preaching through out the 90s. It has not only help me find a new hobby like remaking stuff and reusing stuff that would normally be seen in junk yards, it has also saved me hundreds if not thousands of dollars in art supplies (why throw away pill bottles they make get paint storage for future use of the new invented color) and decorations (after the candle is used up use the candle holder for storage or to use as a nursery for planted seeds).
    Not only has being environmentally friendly given bonus points for nature it has also has been soft on the pocketbook. The way I see it if a poor person like myself can make a change so can anyone else, especially those in first world nations. The real problem isn’t about the cost but mostly about people being too lazy and uncreative.