Jim Hansen is Director of the NASA Goddard Institute for Space Studies and Adjunct Professor of Earth and Environmental Sciences at Columbia University’s Earth Institute. His opinions are expressed here, he writes, “as personal views under the protection of the First Amendment of the United States Constitution.”

1.

Animals are on the run. Plants are migrating too. The Earth’s creatures, save for one species, do not have thermostats in their living rooms that they can adjust for an optimum environment. Animals and plants are adapted to specific climate zones, and they can survive only when they are in those zones. Indeed, scientists often define climate zones by the vegetation and animal life that they support. Gardeners and bird watchers are well aware of this, and their handbooks contain maps of the zones in which a tree or flower can survive and the range of each bird species.

Those maps will have to be redrawn. Most people, mainly aware of larger day-to-day fluctuations in the weather, barely notice that climate, the average weather, is changing. In the 1980s I started to use colored dice that I hoped would help people understand global warming at an early stage. Of the six sides of the dice only two sides were red, or hot, representing the probability of having an unusually warm season during the years between 1951 and 1980. By the first decade of the twenty-first century, four sides were red. Just such an increase in the frequency of unusually warm seasons, in fact, has occurred. But most people—who have other things on their minds and can use thermostats—have taken little notice.

Animals have no choice, since their survival is at stake. Recently after appearing on television to discuss climate change, I received an e-mail from a man in northeast Arkansas: “I enjoyed your report on Sixty Minutes and commend your strength. I would like to tell you of an observation I have made. It is the armadillo. I had not seen one of these animals my entire life, until the last ten years. I drive the same forty-mile trip on the same road every day and have slowly watched these critters advance further north every year and they are not stopping. Every year they move several miles.”

Armadillos appear to be pretty tough. Their mobility suggests that they have a good chance to keep up with the movement of their climate zone, and to be one of the surviving species. Of course, as they reach the city limits of St. Louis and Chicago, they may not be welcome. And their ingenuity may be taxed as they seek ways to ford rivers and multiple-lane highways.

Problems are greater for other species, as Tim Flannery, a well-known Australian mammalogist and conservationist, makes clear in The Weather Makers. Ecosystems are based on interdependencies—between, for example, flower and pollinator, hunter and hunted, grazers and plant life—so the less…