Extreme weather events to intensify rapidly over next two decades, study finds

Nearly three-quarters of the world’s population can expect strong and rapid changes in extreme temperatures and precipitation over the next 20 years unless greenhouse gas emissions are drastically reduced, a new study finds.

Led by scientists at the CICERO Centre for International Climate Research and supported by the University of Reading, the study shows that 20% of the population could face extreme weather risks if emissions are cut enough to meet the goals of the Paris Agreement, compared to 70% if limited action is taken.

The article, published in the journal Geosciences of nature, shows how global warming can combine with normal weather variations to produce multi-decade periods of very rapid changes in extreme temperatures and precipitation.

Few studies have explored the impact that extreme weather events will have on different countries. Dr Carley Iles, lead author of the research at CICERO, said: “We focus on regional changes, because of their greater relevance to the experience of people and ecosystems compared to the global average, and identify regions that are expected to experience substantial changes in rates of one or more extreme event indices over the coming decades.”

Unprecedented conditions

Large-scale climate model simulations were used in the study to show that large parts of the tropics and subtropics, encompassing 70% of the current population, are projected to experience large rates of joint change in combined temperature and precipitation extremes over the next 20 years under a high-emissions scenario. With strong emissions mitigation, this figure is projected to fall to 20%, or about 1.5 billion people.

Rapid changes increase the risk of unprecedented conditions and extreme events that are currently responsible for a disproportionate share of the real impacts of climate change. For example, heat waves can cause heat stress and excessive mortality in people and livestock, disrupt ecosystems, reduce agricultural yields, make power plants difficult to cool, and disrupt transportation.

Similarly, extreme precipitation events can cause flooding and damage to homes, infrastructure, crops and ecosystems, increase erosion and reduce water quality. Society therefore appears particularly vulnerable to high rates of change in extremes, especially when multiple hazards occur simultaneously.

Risks associated with cleaning

Dr Laura Wilcox, co-author at the University of Reading, said: “We also find that rapid clean-up of air pollution, mainly in Asia, is leading to accelerated and co-localised increases in hot extremes and influencing the Asian summer monsoons.

“While air cleaning is essential for health reasons, air pollution has also masked some of the effects of global warming. But the necessary cleaning could combine with global warming to lead to very significant changes in extreme conditions over the coming decades.”

Although the new paper focuses on the likelihood of rapid change, the authors stress that the findings have important implications for climate adaptation.

“In the best case scenario, we estimate that rapid changes will affect 1.5 billion people. The only way to cope is to prepare for a situation with a much higher probability of unprecedented extreme events, already in the next one to two decades,” says Dr. Bjørn H. Samset of the Center for International Climate Research CICERO. Samset contributed to the newly published study.