Meeting Abstract
Warming mean temperatures have shifted distributions, altered phenology, and increased extinction risks of diverse organisms, and have impacted human agriculture and health. However, knowledge of mean temperatures alone does not provide a complete understanding either of changes in climate itself or of how changing climate will affect organisms. Temporal temperature variation, primarily driven by daily and annual temperature cycles, has profound effects on organism physiology and ecology, yet changes in temperature cycling are still poorly understood. Here we estimate global changes in the magnitudes of diurnal and annual temperature cycles from 1975-2013 from an analysis of over 1.4 billion hourly temperature measurements from 7906 weather stations. Increases in daily temperature variation since 1975 in polar, temperate, and tropical regions parallel increases in mean temperature. Concurrently, magnitudes of annual temperature cycles decreased by in polar regions, increased in temperate regions, and remained largely unchanged in tropical regions. Stronger increases in daily temperature cycling relative to changes in annual temperature cycling in temperate and polar regions mean that, with respect to diurnal and annual cycling, the world is flattening as temperate and polar regions converge on tropical temperature cycling profiles. These shifts in temperature cycling will likely have profound and, as yet, unknown biological impacts.
