In 2001, when the Intergovernmental Panel on Climate Change produced its third set of reports examining the causes and consequences of global warming, it included a fascinating illustration, called the “burning embers” diagram, showing gradients of rising risk with rising temperatures. It was part of the panel’s evolving effort to provide policymakers with a clear sense of what was known about potential impacts from various levels of warming and also what was uncertain.
An updated version of the diagram was created for the panel’s momentous 2007 report on climate, but it met resistance from some scientists who thought the color bars were too vague or subjective and from some governments, which thought the artwork was too unnerving, according to interviews with the lead authors.
Now 15 authors of the 2007 report, many of whom were authors on the 2001 report as well, have written a paper salvaging the I.P.C.C. diagram of climate risk that was dropped. It vividly shows how, in many areas of concern, the transition to big problems is much closer than research implied eight years ago. The paper, “Assessing Dangerous Climate Change Through an Update
of the IPCC ‘Reasons for Concern’,” is being published this week in the online edition of the Proceedings of the National Academy of Sciences.
But there are no clean thresholds and there is still substantial uncertainty, particularly in the category given the understated name “Risks of Large Scale Discontinuities.” These are risks like the unstoppable loss of big portions of Greenland and West Antarctic ice sheets.
This evolving picture of a clarifying, but still uncertain, threat leads back to a persistent question confronting scientists who eager for action by society. As Ralph J. Cicerone, the president of the National Academy of Sciences (and an award-winning atmospheric scientist) put it in an interview two years ago: “Does it take a crisis to get people to go along a new path or can they respond to a series of rational, incremental gains in knowledge?”
UPDATE, 11 p.m.: The M.I.T. Joint Program on the Science and Policy of Global Change has published a different type of global warming risk barometer that includes the odds of various levels of warming with and without policies on emissions (hat tip to the Capital Weather Gang).
One reader was so incredibly unimpressed with the embers diagram that I was inspired to consider holding a contest to see what other ways readers can devise to illustrate climate risks accurately but also in a way that captivates. What do you think?