Friday 05 March 2021

Ever hotter heatwaves are not recognised by weather models: KNMI

Photo: Odi Busman

Models used to predict the weather are ‘totally underestimating the trend of ever hotter heatwaves,’ weather bureau KNMI has said.

The current heatwave, accompanied by exceptionally warm nights, will last for an unprecedented seven or eight days and is the first of its kind in the Netherlands.

‘Heatwaves have been getting more extreme over the last three years. But I had not expected one as extreme as this and it is worrying we did not see it coming,’ KNMI climate researcher Jan van Oldenburgh told broadcaster NOS.

‘Our climate models, which we use to predict what will happen in the future are underestimating this trend completely,’ Van Oldenburgh said. While the models are showing an average rise of 1.5 degrees in temperature, during a heatwave the thermometers have shot up by 3 degrees.

‘We can’t really explain the difference. We need to do more research and find out why things are accelerating,’ Van Oldenburgh told the broadcaster.

The exceptionally warm nights are the most unusual feature of the heatwave, Van Oldenburgh said. ‘The highest average weekly night time temperature we ever measured was 18 degrees but this week it will be over 20 degrees. That is unprecedented for the Netherlands.’

Research done by the weather bureau has found that the number of warm nights has tripled in the last 20 years, particularly in the south and on the coast. The reason for this is clear, Van Oldenborgh said. ‘We are experiencing the greenhouse effect. As long as we continue to emit greenhouse gases the world will get warmer.’

It’s worrying the models are not correctly predicting the severity of the heatwaves, Van Oldenborgh said, because it means measures to make the country ‘heat proof’ will not be taken.

The impact of heatwaves should not be underestimated, he said. ‘Heatwaves are killers. In 2003 tens of thousands died in Europe because of extreme heat. In the Netherlands thousands died in 2006.’

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