New pattern: back-to-back heatwaves and droughts in Eurasia
The number of extreme heatwaves followed by periods of drought has risen over the past 300 years in Eurasia. This vicious cycle increases the risk of forest fires and affects agriculture and water resources, according to new research from the University of Gothenburg and others.
“The pattern of combined heat waves and droughts has intensified in recent times and it is far beyond natural variations. This development is an effect of human activity on Earth and global warming,” says Hans Linderholm, Professor of Physical Geography at the University of Gothenburg and one of the authors of the study.
“This is a major threat to water resources, agriculture and forestry. It leads to major socio-economic damage and imposes costs on society," he adds.
Eurasia is the contiguous landmass made up of the continents of Europe and Asia, home to 70% of the world's population. The international study from the region is based on weather observations from 1979 to 2022, and 300 years of climate data from tree rings. By analyzing tree rings, researchers from Sweden and Korea were able to map the evolution of temperature and precipitation conditions in Eurasia since 1741.
Curbing the new trend a must
According to the study, the most affected areas in Eurasia are western Russia, Mongolia and northern China. Hans Linderholm points out that summers are getting drier in Sweden also.
"The extreme summer of 2018 was a result of drought and heatwave and it is likely that we will experience more similar events."
According to the study, the new weather patterns are a result of global warming, which affects the planet's climate system. One example is the jet stream, which is affected by the warming of the sea surface in the north-west Atlantic. The jet stream has large-scale waves, known as Rossby waves, which in turn drive weather systems. As the climate changes, Rossby waves can have larger swings and lower speeds. This causes high and low pressure to stay in the same place for longer, which affects the weather for a longer period of time and can lead to extreme weather such as heatwaves or floods.
Historical climate provides insights into the future
Using the historical climate data, the researchers simulated what a future climate will be like under global warming. The forecast shows that weather patterns will become even more severe towards the end of this millennium. The authors of the study call for long-term national adaptation strategies to mitigate the trend.
“The most important thing is to slow down the temperature increase by reducing greenhouse gas emissions. Then land use needs to be adapted to possibly reduce the effects of increased summer temperatures,” says Hans Linderholm.
The study “Emerging Trans-Eurasian Heatwave-Drought Train in a Warming Climate” is published in the scientific journal Science Advances: https://doi.org/10.1126/sciadv.adr7320
For more information about the study, please contact:
Hans Linderholm, Professor in Physical Geography, Department of Earth Sciences, University of Gothenburg, email: hansl@gvc.gu.se
It was the Swedish-American meteorologist Carl-Gustaf Rossby who, in 1939, made the remarkable discovery about the effect of the Earth's rotation on the movement of the atmosphere.
A Rossby wave or planetary wave is a large-scale wave between two nearly parallel layers that are almost perpendicular to an axis of rotation. Rossby waves occur in the Earth's atmosphere and in the oceans. Their length can be around 5-10 000 kilometers.
Source: Wikipedia
- On the National Ocean Service website you can see a video explaining Rossby waves: https://oceanservice.noaa.gov/facts/rossby-wave.html
