Understanding more about the drivers of heatwaves could help weather forecasters make better predictions and give people more time to prepare. Now, thanks to large ensembles of climate models, researchers are probing the co-occurrence of atmospheric blocking and summer temperature extremes – a relationship that has been difficult to study due to limited observations.
During atmospheric blocking, a persistent and stationary high-pressure system diverts the usual westerly flow at mid-latitudes for a few days to several weeks. It’s a scenario that can lead to extreme events such as heatwaves.
The researchers used simulations for 1979–2015 to determine that there is a significant correlation between the magnitudes of summer heatwaves and the number of days influenced by atmospheric blocking in Northern Europe and Western Russia.
After demonstrating agreement with historical records, the group – which includes scientists from the Canadian Centre for Climate Modelling and Analysis, ETH Zurich and the European Commission’s DG Joint Research Centre – examined how the relationship might hold for the rest of this century.
Although heatwaves are projected to become more intense and last longer with continued global warming, the relationship between heatwaves and blocking appears to remain the same, the researchers found.
Considering multiple, large ensembles of climate models is an advantage from a statistical perspective. “They seem to represent the relationship between blocking and heatwaves correctly, and in a similar manner to that of the real world,” says Nathalie Schaller of the Centre for International Climate Research in Norway.
Schaller and colleagues suggest that under present-day climate conditions we could experience even larger heatwaves than the one observed in Central Europe in 2003. The group is keen to develop the approach, examining aspects such as the return period of prolonged periods of high-temperature.
“If blocking events or their probability of occurrence could be more skillfully predicted in monthly to seasonal forecasts, this would be particularly useful to increase our preparedness for extreme heatwaves in the future,” writes the team in Environmental Research Letters (ERL).
Such information could aid decision-makers in planning disaster risk reduction and adaptation to climate change.