Posted by: ericgrimsrud | July 23, 2015

James Hansen speaks again

Anyone who has followed the science of climate change is by now well aware of Dr. James Hansen and the central role he has played in climate science over the last three decades.  Therefore, his most recent paper coauthored by 16 others, to appear very soon in Atmospheric Physics and Chemistry (an-open-to-public peer-reviewed journal), will be drawing a great deal of attention – as it should.

Dr. Hansen has suspected that the sensitivity of our climate to changes in our greenhouse gases has been significantly underestimated in climate models, to date, and this most recent paper supports that notion.  New insight into the magnitude of climate change is provided in this paper by its inclusion of ice sheet dynamics – a factor not previously understood well enough to be included in models.  A key and possibly controversial point made in this paper is that the amount of fresh water being produced from the melting of glaciers in Greenland and Antarctica will increase exponentially – rather than linearly – with time if our planet continues on its current course of warming.

As a result of this additional insight, the authors argue that our goal for limiting future global temperature increase should be changed from +2.0 C to +1.5 C because an increase of 2.0 C will prove to be far too distressful to our present civilization. Specifically, the authors predict that an increase of 2.0 C will cause sea levels to rise about 10 feet by the year 2100 instead of 3 feet, as was previously predicted by the IPCC. A sea level rise of 10 feet would obviously cause horrific damage, making numerous coastal cities, including New York, London, and Shanghai, uninhabitable.

So who is this guy, again, who brings us this most distasteful news at a point in time when we are not even on track for limiting future warming to 2.0 C?   Ever since James Hansen first sounded the global warming alarm in his historic testimony to the US Congress back in 1988, he has consistently been ahead of the scientific curve. His predictions have generally been both more dire and more accurate than those of the IPCC.  This new paper also offers some “good news”, however.  That is. it explains what we can do to avoid temperatures in excess of 1.5 C. Perhaps the moment has finally come when Congress will do more than ignore his advice. We will soon see. Time for needed action appears to be running out.

For a preview of the paper in question, see   Keep an eye out for its impact in the next week or so.  Also note that this paper has not yet gone through the normal scientific review process which will very likely take several weeks and result in at least some modifications of the initial version.

(note added on 7/27/2015).  Dr. Hansen has now provided an op ed in which he describes his recent paper in a condensed and lay-public friendly manner while also providing a link to the full paper.  I highly recommend that you have a look at:

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