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James Hansen and the three sigmas at the AAAS conference.

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Jim Hansen (of NASA, not of muppets) was in Vancouver last weekend – and, man, this guy can stir a crowd.

The AAAS conference (that’s the American Association for the Advancement of Science, aka the Big Ass) was in Vancouver – almost unannounced.  I found out by accident, looked up the program (Jim Hansen’s there!); there’s no way I couldn’t go.  Sure enough, I was in for a treat.

Jim Hansen

For the non-science folks, and the non-geek crowd, I need to explain.  Jim is a personal hero of many of us environmentalists.  He was the first one to testify before congress about the dangers of climate change, the first one to call it a catastrophe before a scientific audience (in science, thou shall not use loaded words), and finally the first respected scientist to be arrested at a demonstration (against the Keystone pipeline) – all the while producing ground-breaking, impeccable science.

Hansen’s presence loomed large at the meeting.  Every session I went to, or nearly, presenters kept repeating things like “as Jim said yesterday”, or “as we heard Jim say…”  So what did he say?  He said lots of things, of course, many of them before the conference, but a few were new to me.

In particular, he said that some specific weather events can now be described as being caused by climate change.  The standard line that most climate scientists keep to is that “well, we can’t blame this specific drought on climate change; the weather is too variable to tell, but in the balance of probabilities blablablah…”.  You’ve heard all that before, and it always makes science sound wishy-washy.

Not from Hansen.  He pointed at the amazing heat wave, drought, and forest fires that beset Russia in 2010.  He also fingered the unprecedented drought in Texas last summer.  “These were caused by climate change, no doubt about that”, he said.  His test is what he calls the three sigmas.  Both events were three standard deviations (or “sigmas”) from the norm of the twentieth century.  Hansen could be wrong, of course, and the back-to-back droughts could be just sheer bad luck – random events, not a result of climate change.  But his odds of being wrong are one in one thousand.  That’s what the three sigmas mean.  That’s pretty strong odds, if you ask me.

The other thing that Hansen mentioned is the high probability of the oceans rising by a meter in a mere twenty years.  That got people’s attention.  Mind you, he expects that to happen in the last two decades of the twenty-first century, not overnight.  It was interesting to see some of the other climate scientists clearly rattled.  But the problem (despite what you might read in the popular press) is that Hansen has never had to swallow his words.  He has been right, ahead of his colleagues, every time.  So scientists listen, and so should everybody.

There were many fabulous, stimulating sessions at the Big Ass, and I’ll post about some of them in the future.  But I want to keep this post short, and mostly I want to share a link to the plenary session, Science Is Not Enough, here.  Jim Hansen is one of the featured speakers, and a very human, vulnerable, likeable person he can be seen to be (I must confess I was dreading a hectoring, bitter individual – he is nothing like that).  The whole session is well worth watching.  It is entertaining and, despite the potential for being gloomy, is actually very funny.  A lot of the humour comes from Hans Rosling, a veteran of TED talks.  But all of the presentation, serious as the topic may be, is engaging and wonderful, even at 90 minutes.  Be patient, it’s rewarding, like any good show.

The rest of the program and a summary of the key sessions is found here.


Written by enviropaul

February 20, 2012 at 5:49 pm

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