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February 05, 2007

Intergovernmental Panel on Climate Change – Summary for Policymakers

If you want to get a leg up on most policymakers, a good way is to actually read the “Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change”.  The good news is that it’s pretty much written in English and that it’s only 21 pages long.  The bad news (besides the dire forecasts) is that none of the factual backup to this summary is included.  It’s referred to in footnotes but hasn’t been published yet.

Although you shouldn’t trust any summary of a summary (even if you read it on Fractals of Change), let me give you a few highlights which may be a little different than what you heard on CNN.  When you get time to read the report, you can see whether I got it right.

What the report doesn’t say is “man is the cause of global warming.”  What it does say on that subject is “Most of the observed increase in globally average temperatures since the mid-20th century is very likely [they define ‘very likely’ as meaning more than 90% probable] due to the observed increase in anthropogenic [our fault] greenhouse gas concentrations.”  Also: “It is likely [greater than 66% probability] that there has been significant anthropogenic warming over the past 50 years averaged over each continent except Antarctica.”

In other words, odds are very strong that we are the major (not the only but the major) cause of the warming OVER THE LAST 50 YEARS.  Warming has clearly been happening since the time 12,000 years ago when there was a mile thick sheet of ice over the place where I’m writing in Vermont; most of that we weren’t responsible for.  Warming would presumably be continuing, albeit at a slower pace, if we were not driving around in our SUVs.

I’m not arguing against reducing greenhouse emissions; I think we should.  But it’s important that we understand that global warming is likely to continue even if we do.  According to the summary, even if were to stabilize emissions almost immediately, climate change is likely to keep rolling along at its anthropogenic-heightened rate for the next two centuries; then possibly settle down to its previous slower pace.

One reason this understanding is important is that we may have to prepare to deal with the effects of climate change no matter what we do about emissions.  The oceans may continue to rise; the tropics may get drier; the high latitudes may get wetter; more permafrost may melt.  Some of the beneficial effects like a longer growing season in high latitudes may have to be used to offset less rain nearer the equator.

It’s even possible that we will need to take more extreme actions to reverse what we probably helped set in motion.  We could start to remove MORE greenhouse gasses from the atmosphere than we put in to stop a reinforcing cycle of warming and counter the momentum in the change that’s underway.  The summary asserts that much climate change (cooling) has been caused by dust from volcanoes.  Will we get bailed out by a couple of giant eruptions?  Do we need to put dust in the atmosphere? That sounds pretty bad but so do some of the consequences of rapid climate change.

Some politicians would like us to believe that we’re at a magic tipping point: action now and no great consequences from warming; elect me now or the world is doomed.  There’s nothing in the summary even taken at face value to support that.  There may be no tipping point; we may already be past the tipping point; we may have caused the problem and not be able to fix it; we may have not caused it but still can fix it; all of these are possibilities.

If there’s a “greater than 90% probability” that we caused the warming of the last 50 years, there’s a possibility of up to 10% that we didn’t.  Is this possibility sufficient reason for inaction?  No! But, if there’s any significant chance that we’ve missed something big about how the climate works – and obviously there is – we can’t be blinded by what seems most likely today; we have to keep in mind that something we don’t know about may be driving climate change so we don’t get surprised by whatever that is or pursue a cure which is worse than the disease because we stopped looking for evidence to disprove the theory du jour.

Here’s a wild scenario: suppose we overshoot and the world goes into a cooling cycle because we removed too much greenhouse gas after natural ecosystems had already begun to adjust to elevated levels.  Then we have a couple of volcanoes; really big ones.  Now we have global cooling which can also be a self-reinforcing cycle.  Don’t forget, we’re still technically in an ice age.  Sounds absurd when I write it but, when I was in college, the climate scare at the time was a nuclear winter brought on by dust in the atmosphere from nuclear testing or perhaps a war plus industrialization.

It’s a tribute to those who wrote the report that it IS readable.  We have huge decisions to make and we’ll have to make them on more than a sound bite.  We will have to act on incomplete information; that’s the way of the world.  But we don’t have to pretend that incomplete information is conclusive.  We must remain skeptical while acting.  We should act on 90% probabilities; we shouldn’t pretend that they’re certainties.

Note:  this post is written assuming the science in the summary is impeccable.  Once the detail is available, we should try to read that and judge the science as well.

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