Findings from Swiss-American team present nuanced view of how climate change affects weather extremes
FRISCO — Adding more fuel to the debate over climate change and extreme weather, Swiss and American scientists this week said their new study shows that global warming tends to reduce temperature variability.
The cold and snowy weather that gripped much of the eastern U.S. this winter was probably not linked to Arctic amplification and increased waviness of the jet stream, according to the scientists with ETH Zurich and the California Institute of Technology.
Changes in the north-south difference in temperatures play a greater role in modifying temperature variability than changes in the jet stream, the researchers said.
Tackling the question from a different angle, the scientists used climate simulations and theoretical arguments to show that in most places, the range of temperature fluctuations will decrease as the climate warms. They concluded there will be fewer cold snaps because fluctuations from the warming mean temperature will be smaller, the scientists wrote in the latest issue of the Journal of Climate.
The researchers started with the baseline concept that higher latitudes are warming faster, which means that the temperature difference between the equator and the poles is decreasing. As that contrast shrinks, air masses would start having more similar temperatures, regardless of whether they flow from the south or north.
Using a highly simplified climate model, they examined various climate scenarios to verify their theory. It showed that the temperature variability in mid-latitudes decreases as the temperature difference between the poles and the equator diminishes.
Climate model simulations by the Intergovernmental Panel on Climate Change (IPCC) showed similar results: as the climate warms, temperature differences in mid-latitudes decrease, and so does temperature variability, especially in winter.
None of this means there will be no temperature extremes in the future.
“Despite lower temperature variance, there will be more extreme warm periods in the future because the Earth is warming,” said study leader Tapio Schneider.
The researchers limited their work to temperature trends. Other extreme events, such as storms with heavy rain or snowfall, can still become more common as the climate warms, as other studies have shown.
Schneider wants to explore the implications these results have in further studies. In particular, he wants to pursue the question of whether heatwaves in Europe may become more common because the frequency of blocking highs may increase. And he wants to find why these high pressure systems become stationary and how they change with the climate.