20 September 2021
Climate models may be underestimating the impact climate change will have on the UK, North America and other extratropical regions due to a crucial missing element, new research has shown.
Scientists at the University of Reading have warned that current projections of how a warming world will affect regional temperatures and rainfall do not take into account the fact that extratropical winds – which have a strong influence on climate in the mid-latitudes – vary greatly from decade to decade.
The research team used observations of these winds over the 20th century to better represent their variability in climate model predictions of the future. They found that this made the predictions of future climate less certain in the extratropics – particularly in the North Atlantic region and particularly in winter – and that unusually hot, cold, wet or dry decades are projected to be much more likely by the middle of the century in this region than existing climate simulations suggest.
The research is published in the Nature journal Communications Earth & Environment.
Dr Christopher O’Reilly, a Royal Society University Research Fellow in the University of Reading’s Department of Meteorology, said: “Variations between decades in the strength of winds in the more temperate regions of the world are a crucial missing ingredient in projections of the future climate of those regions.
“By adding this extra variability into climate models, we showed that these winds may be an additional source of uncertainty on top of climate change. This could mean that within these regions, temperatures are pushed to relatively extreme highs or lows more often. While in some decades they could counteract increases to temperatures and heavy rainfall caused by climate change, in other periods they could make these extremes even more extreme.
“This is yet another reminder that preparation will be crucial as we face up to more variable regional climates as an impact of climate change in the future.”
The team used wind observation data from the Met Office, Copernicus Climate Data Store and NOAA, among others, to carry out their analysis and bolster the climate model predictions.
The range of temperature and rainfall most likely to occur in future decades increased by 50% across Northern Europe, Northern America and the Mediterranean – with uncertainty nearly doubling in some cases.
This strengthens previous research that suggests rainfall and temperatures that are very unlikely today will fall within the likely range in future due to climate change.
The updated projections showed that the Mediterranean would see a higher frequency of drier-than-average winters. As studies show that dry winters in this region make heatwaves in Europe more common the following summer, this has health and infrastructure implications for several countries.
Full reference
O’Reilly, C.H., Befort, D.J., Weisheimer, A. et al. ‘Projections of northern hemisphere extratropical climate underestimate internal variability and associated uncertainty’. Commun Earth Environ 2, 194 (2021). https://doi.org/10.1038/s43247-021-00268-7
Image caption: From Supplementary Figure 19. Change in projection uncertainty for mid-century climate change
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