Small local changes make a big difference as the temperature soars. And the European Union’s existence once cooled a vicious heatwave.
LONDON, 9 August, 2019 − Of all the political plaudits or economic brickbats hurled at the European Union, this might be the least expected: simply because it existed, it somehow ameliorated or damped down the worst of the 2003 heatwave.
This moment of extreme summer heat is believed to have caused an estimated 40,000 excess deaths and cost the European economy more than €13 billion in economic losses and infrastructure damage.
And yet it could have been worse. Had what is now a 28-nation political and economic behemoth not been formed in 1993, the way the member nations used their land would not have changed, and the heatwave might have been more intense, more severe and more destructive still.
The formation of the EU with its single market and customs union wasn’t the only political shift. The end of the Cold War and the collapse of the Soviet Union in 1991 also played a role in determining how farmers, graziers, foresters, conservationists and ministerial managers used the terrain of the European continent.
And – without thinking much about future climate shifts – farmers and foresters collectively began a series of changes that meant that what had once been farmland was abandoned, in Portugal and Spain, in eastern Europe and in Italy, as intensive production shifted to other economic zones.
“Our results suggest that if this land use change had not occurred, the 2003 heatwave may have been more severe”
As more than 8% of what had been ploughed land reverted to grassland and scrub, the shallow groundwater in the abandoned soil began to act in unexpected ways. There was more evapotranspiration, which meant more cloud, which meant more reflectivity, which meant that lower levels of radiation actually scorched the landscape.
And, in turn, temperatures, as torrid as they were in the unprecedented heat that August, were damped down.
Samuel Zipper, then of the University of Victoria in Canada, now at the University of Kansas, and colleagues from Belgium and Germany report in the journal Environmental Research Letters that they used what they call “bedrock to atmosphere” computer models to simulate the way water and energy cycles shifted over western Europe between 1990 and 2010. They then made an estimate of what might have happened had there been no changes in the way the land was used.
“What we think is happening is that the agricultural abandonment led to an increase in the amount of water that plants transpired into the atmosphere, which caused increased cloud formation,” Dr Zipper said.
“Our results suggest that if this land use change had not occurred, the 2003 heatwave may have been more severe.”
They found in addition that the changes in land use overall had some effect on local climate even in those places where land had not been abandoned.
They found that even France – the nation most harshly hit by the extremes of heat that summer – experienced less heat than it would have without shifts in land use further south and east.
And they confirmed that soil moisture, especially in the first metre or so of ground, played a powerful role in moderating atmospheric temperatures that in that region in that year, and in other places exposed to heat extremes since, put the very young, the elderly, the already ill and the poorly housed at ever greater risk of death in dangerous temperatures.
The scientists completed their research long before the unprecedented temperatures recorded in Western Europe this 2019 summer. Such what-if studies based on alternative histories arrive with inherent uncertainties. There is no way to conduct any convincing real life experiment that replicates the same heat wave under different landscape changes.
But the research confirms what climate scientists have been arguing for decades, and that is that the way land is used inevitably contributes to local shifts in temperature, and therefore to overall annual average warming, and inevitably to long-term, lethal and potentially catastrophic extremes. − Climate News Network