Hot days warming faster in the tropics

Climate change will be amplified on the hottest days in tropical regions, new research from the University of St Andrews has found.

The paper, recently published in Nature Geoscience (21 October) shows that in the tropics, hot days will warm substantially more than on the average day. For example, the hottest 5% of days are expected to warm 20% more than on the average day. This amplified warming of extreme temperatures will have severe impacts across large parts of Africa, Asia and the Americas.

Study author, Dr Michael Byrne of the School of Earth and Environmental Sciences at the University of St Andrews, uses concepts from atmospheric dynamics to explain the accelerated warming of hot days. In particular, he shows that two aspects of the tropical climate – namely frequent thunderstorms (that is, convection) and the weak influence of Earth’s rotation at low latitudes – control how hot days respond to a changing climate.

Dr Byrne said: “The paper introduces a simple yet quantitative theory to understand the processes controlling extreme temperatures over tropical land in a changing climate.

“According to the theory, warming is amplified on hot days because those days are dry: this is termed the ‘drier get hotter’ mechanism.

“This theory fills an important gap in our understanding of tropical climate and heatwaves and I hope the study spurs new research, using theory as well as climate models and observations, to expand understanding of extreme weather across the tropics and beyond.”

Official paper link here; link to read-only version here