Mathematicians Urged to Confront Climate Change

June 19, 2008

In April 2007, the Mathematical Sciences Research Institute (MSRI) sponsored the symposium "Climate Change: From Global Models to Local Action." Its aim was to involve mathematicians with the latest research and thinking about climate change and to single out the kinds of mathematical opportunities and challenges offered by the subject.

Seventy-five climate scientists and mathematicians from around the country took part. An illustrated record of their key discussions and ideas is now available from MSRI: a 28-page booklet (or pdf) titled "Mathematics of Climate Change: A New Discipline for an Uncertain Century," by Dana Mackenzie.

"Mathematics and statistics already play a central role in this as in any sort of modeling effort," former MSRI director David Eisenbud said. "Likewise, computer science must have a say in the effort to simulate the Earth's environment on the unprecedented scale of petabytes. With a problem of this complexity, new mathematical tools will undoubtedly be needed to organize and simplify our thinking."

Exploring ways to attract mathematicians to what is—for many of them—an untapped branch of science, Mary Lou Zeeman of Bowdoin College noted in a SIAM News report on the symposium, "We need a stamp of approval that tells mathematicians, especially young mathematicians, that this is an okay program of research."

Keynote speaker Inez Fung of the University of California, Berkeley made the scientific case for global warming: the tight correlation between historical carbon dioxide levels and historical climate, as determined from ice-core samples; the increase in measured concentrations of carbon dioxide; isotopic evidence that additional carbon dioxide has come from fossil-fuel burning; an observed increase in average temperature in recent years; and climate models forecasting an increase in temperature over the next century.

The issue of global warming, however, melts into ambiguity when climate modelers are asked to predict the future. "There are demands being made on these climate models that the models weren't constructed for," said Doug Nychka of the National Center for Atmospheric Research.

A number of speakers expressed their belief that this ambiguity could be overcome mathematically. Statisticians, for instance, might develop better ways to combine models than by simple averaging. "Tuning" could be done by defining the parameter spaces in which the values are being chosen. "My suspicion," Nychka said, "is that there will be a continuum of models, and a person will have to make a choice, or else cast the results as a distribution."

The symposium included examples of mathematical climate analysis. Ben Santer of the Lawrence Livermore National Laboratory explained how to attribute climate change to nonhuman factors (solar fluctuations or volcanoes, for example) versus human factors by combining several different climate variables into an "anthropogenic warming pattern." Berkeley's Max Aufhammer merged economics and climate science to quantify the effects of aerosols and temperature increases on rice harvests in Asia.

"Mathematicians can serve as translators," Zeeman said, by helping atmospheric scientists talk with oceanographers, for example, or facilitating the formulation of climate models in terms of economic risk.

According to Hans Kaper of the National Science Foundation, economists and businesspeople should also be involved in the study of climate change. "Their input will give you credibility to the outside world," Kaper said.

Mackenzie concluded that the symposium had made the case that there were "many opportunities for collaboration between mathematicians and climate scientists."

MSRI is sponsoring a three-week climate change summer school, July 14-Aug. 1, 2008, for graduate students and postdocs.

Source: Mathematical Sciences Research Institute, May 2008; SIAM News, June 12, 2007.