Much is understood about the causes of the ice ages. It takes many thousands of years to descend into an ice age, allowing time for ecosystems and humans to adapt. The present human-caused climate change differs because it is occurring too fast for normal human or ecological adaptation.

Does Dyson seriously believe that climate scientists, in their projections of climate change, ignored or overlooked the issues he raises?

We are dismayed by the limited understanding and short-sighted interpretation of basic elements of climate science exhibited in Freeman Dyson’s Dec. 4 opinion piece “Questionable beliefs and misunderstandings.”

We have good measurements of the effect of the sun on climate. For example, solar radiative flux and magnetic activity have actually declined slightly since 1980 and hence cannot be responsible for the warming observed since then. Research on longer-term changes in solar activity show that they can indeed have a detectable impact on climate, which is why we are concerned about the much larger effects of long-lived greenhouse gases.


The proposal that the "main effect of carbon dioxide is to make the planet greener" overlooks the constraints imposed by the availability of other nutrients and the disruption of the biosphere caused by the direct effects of climate change.

Dyson says we must choose between economic development and action on the climate problem. Yet technical advances in renewable energy, in energy efficiency, and in developing safe and secure nuclear energy offer the prospect that economic development and a transition to a low-carbon economy can go hand in hand.

Contrary to Dyson's statement, the Intergovernmental Panel on Climate Change does not assert that "the science of climate change is settled and understood." Indeed, scientists continually question their assumptions and conclusions and continually work to improve their observations, theories, and models. They are not "fanatics . . . ranting about climate change."

The IPCC report presents strong evidence that more than half of the climate change seen in recent decades is human-driven, and that there is a great risk that increasing greenhouse gases will result in future climate change with destructive consequences for humanity and the natural environment. The report provides the legitimate basis for evaluating the origins of climate change and for formulating policies to avoid, ameliorate, or adapt to its effects.


Like Dyson, we too are environmentalists concerned with many problems, including global warming. None of them should be ignored.

Dyson made important contributions to physics in the past, but his perspective on the earth's changing climate is woefully misguided.

Robert L. Jaffe, professor of physics

Kerry A. Emanuel, professor of atmospheric science

Massachusetts Institute of Technology, Cambridge

This letter was cosigned by the following professors at MIT: Elfatih A. B. Eltahir, John E. Fernández, Daniel Kleppner, Ronald Prinn, Susan Solomon, and Washington Taylor.