Climate change will increase heatwave frequency

A Russian man tries to stop a fire near the village of Dolginino in 2010 during one of the country's most severe heatwave in decades. Picture: Getty

Extreme heatwaves such as those that hit the United States last year and Australia in 2009 are projected to expand into other areas of the globe between now and 2040.

The new study, published in the journal Environmental Research Letters, found that in the first half of the 21st century, increased incidences of extreme weather will occur regardless of the amount of carbon dioxide (CO2) emitted into the atmosphere.

After that, the rise in frequency of heatwaves will depend on how we deal with emissions, the study claims.

Under a low-emission scenario, the number of extremes will stabilise by 2040, but under a high-emission scenario, the land area affected by extremes will increase by one per cent a year after 2040.

The study’s lead author, Dr Dim Coumou, of the Potsdam Institute for Climate Impact Research, said: “We find that up until 2040, the frequency of monthly heat extremes will increase several-fold, independent of the emission scenario we choose to take.

“Mitigation can, however, strongly reduce the number of extremes in the second half of the 21st century.”

Under a high-emission scenario, the projections show that by 2100, extreme heatwaves will cover 85 per cent of the global land area. Dr Coumou said: “A good example of a recent event is the 2010 heatwave in Russia, which expanded over a large area stretching from the Baltic to the Caspian Sea.

“In the Moscow region, the average temperature for the whole of July was around 7C warmer than normal – it was around 25C. In some parts, temperatures above 40C were measured.”

In the study, Dr Coumou and co-author Dr Alexander Robinson, from Universidad Complutense de Madrid, used hi-tech climate models to project changes in the trend of heat extremes throughout the 21st century.

The historic period was also analysed and the results showed that the models can accurately reproduce the observed rise in monthly heat extremes over the past 50 years.

Dr Robinson, said: “Our thresholds are defined by the variability a region has experienced in the past, so the absolute temperatures associated with these types of event will differ in different parts of the world.

“Nonetheless, these events represent a significant departure from the normal range of temperatures experienced in a given region.”

Tropical regions will see the strongest increase in heat extremes, exceeding the threshold that is defined by the historic variability in the specific region, according to the research.

Dr Coumou said the results show that these changes can already be seen when analysing observations between 2000 and 2012.

He added: “Heat extremes can be very damaging to society and ecosystems, often causing heat-related deaths, forest fires or losses to agricultural production.

“So an increase in frequency is likely to pose serious challenges to society and some regions will have to adapt to more frequent and more severe heatwaves  already in the near-term.”