Dangerous Climate Change, Reconsidered

If we take the dangers of future global warming seriously, then nothing is more important for curbing them than to immediately begin significant annual reductions in carbon dioxide emissions from fossil fuels. That was my first reaction on reading the new paper by climatologist James Hansen of Columbia University’ Earth Institute and his colleagues being published today by PLOS ONE, “Assessing Dangerous Climate Change: Required Reductions of Carbon Emissions to Protect Young People, Future Generations and Nature” (doi: 10.1371/journal.pone.0081648).

The paper, which is very large in scope, sets out to do several things. Its most noteworthy ambition is to make a case, based primarily on paleoclimate data and the Earth’s planetary energy balance, that the 2 degree Celsius target that climate strategists often use as a limit for allowable warming is too high. That much warming would not only be worse than is commonly projected, the authors argue, but would commit the world to catastrophic levels of further warming thereafter. The paper also offers some projections about how rapidly CO2 from burning fossil fuels needs to fall to keep the total amount of global warming below crucial thresholds.

For many readers, however, the great value of this paper may be that it serves as a broad summary of the current state of climate science relevant to the warming challenge. Hansen conceived of the paper as a brief that might be understood by a judge or other authority who needed to understand the rationale for restraining carbon emissions.

I imagine that the report’s focus on developing appropriate plans for the future was why PLOS ONE’s editors chose to publish it in conjunction with the new PLOS Collection “Ecological Impacts of Climate Change” and accompanied it with a call for papers offering constructive responses to climate change.

Its comprehensiveness also offers a good opportunity for examining a number of particular climate change issues and ideas. I am planning to publish a variety of posts in the days ahead that tee off of this paper, but which may not be restricted to what Hansen et al. wrote, including criticisms of the paper’s recommendations and a more considered reflection on my first reaction. To kick off the series, here are a couple of items:

I’ll add more links to this page as new posts appear.


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