Past climates

Leona Marshall Libby is credited as an early figure in modern climate research, a discipline that picked up considerable momentum in the late twentieth century, largely because of its potential to forecast coming climate patterns. Her research introduced notable methods for studying long-term shifts in rainfall and temperature, which broadened what scientists knew about climates of the past.

The book includes a passage from Professor Rainer Berger, who describes how tree ring records now supply temperature data reaching well beyond the written records historians rely on. Analysts can use Fourier transforms to pick out repeating cycles, and the climate shifts recorded in tree rings line up closely with historical documents. Berger notes that forecasts are growing more reliable over days, weeks and months, and that very long-range projections spanning tens of thousands of years have been attempted, while the period of decades and centuries in between has remained poorly understood. He argues that tree ring thermometry is well placed to address that gap.

Berger also points to the practical stakes of this work, including agricultural yields worldwide, water supplies, heating demand, stockpiling decisions, construction planning, and political and military considerations.