A woman digs out potatoes Tuesday in her former garden, ravaged by wildfires that also burned her house, in Verkhnyaya Vereya village, Russia. Source: European Pressphoto Agency
"When the great air streams in the sky above us get disturbed by climate change, this can have severe effects on the ground," says lead-author Dim Coumou. "While you might expect reduced storm activity to be something good, it turns out that this reduction leads to a greater persistence of weather systems in the Northern hemisphere mid-latitudes. In summer, storms transport moist and cool air from the oceans to the continents bringing relief after periods of oppressive heat. Slack periods, in contrast, make warm weather conditions endure, resulting in the buildup of heat and drought."
This troubling new information from the Potsdam Institute for Climate Impact Research (PIK) shows that climate change will continue to weaken summer circulation patterns causing more intense heat waves.
"Unabated climate change will probably further weaken summer circulation patterns which could thus aggravate the risk of heat waves," says co-author Jascha Lehmann "Remarkably, climate simulations for the next decades, the CMIP5, show the same link that we found in observations. So the warm temperature extremes we've experienced in recent years might be just a beginning."
Science Daily explains:
Rapid warming in the Arctic might be the driver of the observed changes in circulation, according to the study. Greenhouse-gas emissions from burning fossil fuels make temperatures rise globally, but in the high North the warming is faster. Since the Artics' sea-ice cover is shrinking due to global warming, the polar region takes up more heat. The ice-free dark sea-surface reflects less sunlight back to space than white ice would do. Warmer waters then warm the air, which reduces the temperature difference between the cold polar region and the warmer rest of the Northern hemisphere. Since the temperature difference drives air motion, the reduction of this difference weakens the jet-stream, something the scientists also observed. Furthermore, they link this weakening to the observed reduction in storm activity.
"From whichever angle we look at the heat extremes, the evidence we find points in the same direction," Coumou says. "The heat extremes do not just increase because we're warming the planet, but because climate change disturbs airstreams that are important for shaping our weather. The reduced day-to-day variability that we observed makes weather more persistent, resulting in heat extremes on monthly timescales. So the risk of high-impact heat waves is likely to increase."
5:24 PM PT: I had to revisit the embed code. The video is a must watch, Jeff Masters explains the weather science behind the human induced climate change we have been seeing.