Reading Climate Change From Ice, Mud and Air: Ten Scientists

James Croll, a Scottish scientist born in 1821, linked variations in the shape and orientation of the Earth's orbit to the timing of ice ages. His astronomically based account anticipated the twentieth century orbital theory of climate change later refined by Milutin Milankovic, so the path begins with the idea that ice ages keep time.

Thomas Chrowder Chamberlin founded the Journal of Geology in 1893 and named glacial stages in North America that are still in use. His page also records that in 1899 he published early research on how changes in atmospheric carbon dioxide concentration could affect climate, the first sign on this path that the air itself may steer the ice.

Cesare Emiliani, regarded as the founder of paleoceanography, applied oxygen isotope analysis to the shells of foraminifera in deep sea sediment cores. His marine isotope stage timescale is still used, and his finding that ice ages of the last half million years occur in cycles gave strong support to the Milankovitch hypothesis that Croll had foreshadowed.

Willi Dansgaard, a Danish geophysicist regarded as the founding figure of ice core paleoclimatology, was the first to show that oxygen eighteen and deuterium preserved in glacier ice could be measured to reconstruct past temperature. Access to United States Army drilling at Camp Century in Greenland during the 1960s helped establish deep ice coring as a scientific tool, and he later led isotope analysis of the DYE-3 core, completed in 1981.

In the mid 1970s Veerabhadran Ramanathan discovered that chlorofluorocarbons and other trace gases have a greenhouse effect, broadening climate forcing beyond carbon dioxide alone. He later used the Earth Radiation Budget Experiment to show that clouds exert a substantial cooling effect, and found that black carbon aerosols in atmospheric brown clouds have masked as much as half of the surface heating caused by rising carbon dioxide.

Wallace Broecker, a geochemist at Columbia's Lamont-Doherty Earth Observatory, developed the idea of a global ocean conveyor belt linking the circulation of the world's oceans. He made major contributions to the study of the carbon cycle and to chemical tracers and isotope dating in oceanography, and he is credited with popularizing the term global warming.

Susan Solomon and her colleagues were the first to propose the chlorofluorocarbon free radical reaction mechanism behind the Antarctic ozone hole. Her expeditions to Antarctica in 1986 and 1987 found chlorine oxide levels far higher than expected, and her research helped lay the scientific foundation for the Montreal Protocol on ozone depleting chemicals.

Claude Lorius, a French glaciologist, pioneered the analysis of air bubbles trapped in ancient ice to reconstruct past atmospheric composition. In 1987 his team's analysis of the Vostok ice core in Antarctica extended the climate record back 160,000 years and showed for the first time that atmospheric carbon dioxide and temperature had risen and fallen together through glacial and interglacial cycles.

James Hansen, an American climatologist born in 1941 in Denison, Iowa, is best known for his 1988 testimony to the United States Congress on climate change. That testimony helped bring broad public awareness to global warming, and he has since become an advocate for action against dangerous climate change.

Michael E. Mann pioneered statistical techniques for finding patterns in past climate change and isolating climate signals from noisy proxy data. His reconstruction of the past thousand years of temperature produced the widely known hockey stick graph and made him a lead author on the Intergovernmental Panel on Climate Change Third Assessment Report.