Thursday, 15 March 2012

Hansen et. al. 2008 - are they all mad?

Every now and then you have one of those "just a minute..." moments. I've just had one, while reading "Climate target is not radical enough - study", in where else but the UK Guardian. They quote from James "75 metres" Hansen and also his co-authored 2008 paper "Target atmospheric CO2: Where should humanity aim?".
One of the world's leading climate scientists warns today that the EU and its international partners must urgently rethink targets for cutting carbon dioxide in the atmosphere because of fears they have grossly underestimated the scale of the problem.
In a startling reappraisal of the threat, James Hansen, head of the Nasa Goddard Institute for Space Studies in New York, calls for a sharp reduction in C02 limits.
Hansen says the EU target of 550 parts per million of C02 - the most stringent in the world - should be slashed to 350ppm. He argues the cut is needed if "humanity wishes to preserve a planet similar to that on which civilisation developed". A final version of the paper Hansen co-authored with eight other climate scientists, is posted today on the arXiv.org website. Instead of using theoretical models to estimate the sensitivity of the climate, his team turned to evidence from the Earth's history, which they say gives a much more accurate picture.
As an aside, I corrected the arXiv.org link in the quote myself. The article didn't give the report title, nor a specific link to it; you'd have to search on the archive site for it. I've never yet found a link to a journal paper in a Guardian article. One might think they don't want you to read the originals. One might be right....
Clearly, this is the origin of the 350.org campaign, the so-called "safe limit". Hold onto that "much more accurate picture" while you read on.....
The team studied core samples taken from the bottom of the ocean, which allow C02 levels to be tracked millions of years ago. They show that when the world began to glaciate at the start of the Ice age about 35m years ago, the concentration of CO2 in the atmosphere stood at about 450ppm.
"If you leave us at 450ppm for long enough it will probably melt all the ice - that's a sea rise of 75 metres. What we have found is that the target we have all been aiming for is a disaster - a guaranteed disaster," Hansen told the Guardian.
So the "much more accurate picture" tells us that the Earth began to glaciate at a CO2 level of 450 ppm, and Hansen et. al. want to ensure levels stay well below that figure, in fact no higher than 78% of it? Surely the Grauniad's got it wrong? Apparently not - this is the abstract to the supporting material for the paper (My bold):
Abstract: Paleoclimate data show that climate sensitivity is ~3°C for doubled CO2,
including only fast feedback processes. Equilibrium sensitivity, including slower surface albedo feedbacks, is ~6°C for doubled CO2 for the range of climate states between glacial conditions and ice-free Antarctica. Decreasing CO2 was the main cause of a cooling trend that began 50 million years ago, large scale glaciation occurring when CO2 fell to 450 ± 100 ppm, a level that will be exceeded within decades, barring prompt policy changes. If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced from its current 385 ppm to at most 350 ppm
The largest uncertainty in the target arises from possible changes of non-CO2 forcings. An initial 350 ppm CO2 target may be achievable by phasing out coal use except where CO2 is captured and adopting agricultural and forestry practices that sequester carbon. If the present overshoot of this target CO2 is not brief, there is a possibility of seeding irreversible catastrophic effects
When I read this stuff, and I regard it as stuff, rather than reasoned analysis, I though "I must be missing something here, surely?". It seems it's Hansen his co-authors, the Guardian journalist, 350,org and all its shrill "born again" followers, especially "Weepy Bill" McKibben who're missing something. Their brains can't be firing on all synapses.

BTW, the journalist Ed Pilkington is the Guardian's New York correspondent, a political correspondent at that, so just the guy to report on a scientific paper about the world's climate. Mind you, it makes a welcome change from failed sports reporters doing the job.

IMHO the "seeding irreversible catastrophic effects" bit is right - onward to the next ice-age. Those wind turbines won't be much good - no convection on an ice-planet to drive the winds. Still, we'll all have a "low-carbon footprint" then - no footprint at all. We'll be dead, gone to meet our maker, (not) pushing up the daisies (no daisies) .

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