The changing climate is more complicated to model than we assumed. There are interrelated variables that work together to amplify the effects.
For example, as summer sea-ice and snow shrink back in the Arctic, the number of summertime extreme weather events in the middle latitudes of the Northern Hemisphere is increasing, according to research published recently in Nature Climate Change by two Chinese scientists and their Rutgers colleague.
Its becoming increasingly clear, I think, that the loss of sea ice and snow cover is setting up the conditions that jump-start summer, said Jennifer Francis, research professor at the Institute of Marine and Coastal Sciences in Rutgers’ School of Environmental and Biological Sciences. The soil dries out earlier and that allows it to get hotter earlier. This phenomenon is also changing circulation patterns in the atmosphere.
The jet stream — the fast-moving ribbon of air that encircles the Northern Hemisphere — has a profound impact on weather in the middle latitudes, Francis explained. Temperatures in the Arctic warm faster than in the middle latitudes because of the retreating ice and snow. Because the north-south temperature difference is the main driver of the jet stream, a smaller temperature difference means that the west-to-east winds of the jet stream are weakening.
This weakening also causes the jet stream to meander more, north and south. Because these waves in the jet stream control the movement and formation of storms, an increased meandering means that weather conditions — hot or cold — will be longer-lasting. Previous studies by Francis and her colleagues have shown that rapid sea-ice loss in fall and winter affects winter weather patterns and cold extremes in the mid-latitudes, as well.