Scientists have proposed that climate change could be altering the jet stream in a way that leads to intense flooding, droughts, heat waves, and other extreme weather events.
The new work shows that man-made climate change is not just leading to more extreme weather through the usual mechanisms, including warmer temperatures and added air moisture.
The Jet Stream And Extreme Weather Events
Pennsylvania State University’s Dr. Michael Mann and his colleagues reported that climate change is directly impacting extreme weather events via changing the jet stream’s movement.
Jet streams, ribbon-like air currents snaking across the northern section of the globe up to 7 miles above Earth’s surface, are driven by contrasting cold polar air and tropical climes. The path of these massive air flows forms weather patterns, such as pressure systems that lead to hot or cold spells.
The team suggested that the climate-driven change in the jet stream influenced specific events: the 2003 European heat wave, the Pakistan flooding and a Russian heat wave in 2010, and the 2011 Texas heat wave.
The team looked at historical atmospheric data to better analyze the conditions under which these extreme events formed and continued. They saw that these occurred when the jet stream turned stationary, the peaks and troughs remaining locked in place.
When jet streams become stationary or slow, weather systems can turn more extreme, resulting in extended spells of heat or precipitation. Even quite small changes to the jet stream, according to coauthor Dim Coumou of VU University Amsterdam, can have significant impact on weather and events it causes.
The Role Of Climate Change
The giant air flows can naturally stall due to a small temperature difference found between tropical and Arctic air. This, however, has happened more often as climate change occurs on the planet.
"The warming of the Arctic, the polar amplification of warming, plays a key role here," said Mann in a statement. "The surface and lower atmosphere are warming more in the Arctic than anywhere else on the globe.”
The Arctic has warmed over twice as fast over the past half-century as the global temperature average, climbing by 3.6 degrees Fahrenheit. Air hovering over land masses, too, has warmed more rapidly than over the world’s oceans.
Just recently, the National Snow and Ice Data Center in Colorado reported that Arctic sea ice levels have come down to a record low of 5.57 million square miles.
“Climate change is changing the behavior of the jet stream in a way that favors more extreme persistent weather anomalies,” Mann told Christian Science Monitor.
Using surface temperature records as far back as 1870 and combining them with computer models to derive patterns, the team found that conditions paving the way for the jet stream’s stalling have rose by around 70 percent since the industrial period started, when humans began filling the atmosphere with greenhouse gases.
Most of the change, too, has occurred in the past 40 years, rendering the persistent, more frequently occurring winding jet stream a quite recent occurrence.
The findings were discussed in the journal Scientific Reports.
