Climate engineering off US coast could increase heatwaves in Europe, study finds

A geoengineering technique designed to reduce high temperatures in California could inadvertently intensify heatwaves in Europe, according to a study that models the unintended consequences of regional tinkering with a changing climate.

The paper shows that targeted interventions to lower temperature in one area for one season might bring temporary benefits to some populations, but this has to be set against potentially negative side-effects in other parts of the world and shifting degrees of effectiveness over time.

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Using Earth system computer models of the climate in 2010 and 2050, they simulated the impacts of two cloud brightening operations carried out over different regions of the north-eastern Pacific Ocean, one in the subtropics near California and one in the mid-latitudes near Alaska. Both were designed to reduce the risk of extreme heat on the target region, the US west coast.

Counterintuitively, the more distant operation had the greater impact because it tapped into "teleconnections", links in the climate system between geographically remote parts of the world.

The 2010 simulation suggested the operation near Alaska would lower the risk of dangerous heat exposure in the target region by 55% - equivalent to 22 million people-days per summer - while the closer subtropical test would cause smaller but still significant gains of 16%.

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"There is really no solar geoengineering governance right now. That is scary. Science and policy need to be developed together," she said. "We don't want to be in a situation where one region is forced to do geoengineering to combat what another part of the world has done to respond to droughts and heatwaves."