Europe’s freak weather, explained

Europe’s freak weather, explained

SOURCE: Politico DATE: August 16, 2018 SNIP: We’ve all become increasingly used to reports of extreme weather over the past few years. But this summer’s raft of dramatic weather events is significant: Not only does it show what warming can do, it points to the potential large-scale trouble that lurks in the disruption of the planet’s winds and ocean currents. That global warming leads to more heat extremes is not rocket science and has been confirmed by global data analysis. We’re seeing five times more monthly heat records — such as “hottest July on record in California” — now than we would in a stable climate. It’s not just that the weather is doing what it always does, except at a higher temperature level. Rather, there is growing evidence that the dynamics of weather itself are changing. This is currently one of the hottest topics in climate research. The basic idea is that the jet stream — a band of high winds around the Northern Hemisphere that significantly influences our weather in the mid-latitudes — is changing. This phenomenon has been confirmed by data: Researchers showed in 2015 that the jet stream has actually slowed down significantly in recent decades and undulates more. The cause is probably the strong warming of the Arctic, as the jet stream is driven by the temperature contrast between the tropics and the Arctic. Because this temperature difference is getting smaller and smaller, the jet stream is weakening and becoming less stable. The weaker summer circulation means fewer weather changes, so the weather is becoming more persistent. But the atmosphere is not the only...
Climate change is supercharging a hot and dangerous summer

Climate change is supercharging a hot and dangerous summer

SOURCE: Washington Post DATE: July 26, 2018 SNIP: In the town of Sodankyla, Finland, the thermometer on July 17 registered a record-breaking 90 degrees, a remarkable figure given that Sodankyla is 59 miles north of the Arctic Circle, in a region known for winter snowmobiling and an abundance of reindeer. This is a hot, strange and dangerous summer across the planet. Greece is in mourning after scorching heat and high winds fueled wildfires that have killed more than 80 people. Japan recorded its highest temperature in history, 106 degrees, in a heat wave that killed 65 people in a week and hospitalized 22,000, shortly after catastrophic flooding killed 200. Ouargla, Algeria, hit 124 degrees on July 5, a likely record for the continent of Africa. And the 109-degree reading in Quriyat, Oman, on June 28 amazed meteorologists because that wasn’t the day’s high temperature. That was the low . It was the hottest low temperature ever recorded on Earth. The brutal weather has been supercharged by human-induced climate change, scientists say. Climate models for three decades have predicted exactly what the world is seeing this summer. And they predict that it will get hotter — and that what is a record today could someday be the norm. The proximate cause of the Northern Hemisphere bake-off is the unusual behavior of the jet stream, a wavy track of west-to-east-prevailing wind at high altitude. The jet stream controls broad weather patterns, such as high-pressure and low-pressure systems. The extent of climate change’s influence on the jet stream is an intense subject of research. If nothing is done to curb greenhouse-gas emissions,...
Heavy Rainfall Has Increased by Up to 70 Percent in Parts of the U.S. Since the 1950s, and It Will Only Get Worse, Experts Say

Heavy Rainfall Has Increased by Up to 70 Percent in Parts of the U.S. Since the 1950s, and It Will Only Get Worse, Experts Say

SOURCE: Weather.com DATE: June 9, 2018 SNIP: Heavy rainfall from storms has increased by up to 70 percent in some areas of the United States since the 1950s and will only get worse in the coming years, thanks to global warming, scientists say. The 2014 National Climate Assessment reported that downpours from storms are dumping more water across the nation than ever before, with the Midwest, Pacific Northwest and the Upper Plains receiving the greatest increase in heavy rainfall. The Environmental Protection Agency notes that heavy rainfall events have increased by 70 percent in the Pacific Northwest over the past six decades or so, more than any other region in the United States. Andreas Prein of the University Corporation for Atmospheric Research (UCAR) and the National Center for Atmospheric Research (NCAR) says peak rain rates, which arrive when the core of a storm is overhead, have increased across the country by 30 percent over the past 60 years. And while some areas will continue to get wetter from heavy downpours, other regions will get drier. “The combination of more intense rainfall and the spreading of heavy rainfall over larger areas means that we will face a higher flood risk than previously predicted,” Prein said in a press release. “If a whole catchment area gets hammered by high rain rates, that creates a much more serious situation than a thunderstorm dropping intense rain over parts of the...
Is Arctic warming influencing the UK’s extreme weather?

Is Arctic warming influencing the UK’s extreme weather?

SOURCE: University of Lincoln DATE: January 4, 2018 SNIP: Severe snowy weather in winter or extreme rains in summer in the UK might be influenced by warming trends in the Arctic, according to new findings. Climate scientists from the UK and the US examined historic data of extreme weather events in the UK over the past decade and compared them with the position of the North Atlantic polar atmospheric jet steam using a measure called the North Atlantic Oscillation (NAO) index. The NAO indicates the position of the jet stream – which is a giant current of air that broadly flows eastwards over mid-latitude regions around the globe – through a diagram which shows ‘negative’and ‘positive’ spikes, similar to how a heart monitor looks. The researchers highlight that the exceptionally wet UK summers of 2007 and 2012 had notably negative readings of the NAO, as did the cold, snowy winters of 2009/2010 and 2010/2011, while the exceptionally mild, wet, stormy winters experienced in 2013/2014 and 2015/2016 showed pronounced positive spikes. The scientists also highlighted a correlation between the jet stream’s altered path over the past decade – so-called jet stream ‘waviness’ – and an increase during summer months in a phenomenon called Greenland high-pressure blocking, which represents areas of high pressure that remain nearly stationary over the Greenland region and distort the usual progression of storms across the North Atlantic. Increased jet waviness is associated with a weakening of the jet stream, and the accompanying ‘blocking’ is linked to some of the most extreme UK seasonal weather events experienced over the past decade. The strength and path of the...
It’s Not the Heat. It’s the Humidity.

It’s Not the Heat. It’s the Humidity.

SOURCE: Slate and Columbia University DATE: December 22, 2017 SNIP: “It’s not the heat that kills you. It’s the humidity.” As climate change progresses, this is likely to become gruesomely true, according to a new study published Friday in Environmental Research Letters. Climate change–induced increases in humidity could actually exacerbate the effects of heat to the point of making certain places in the world uninhabitable later this century. By 2080, the researchers predict, we’ll see measurements of heat and humidity that go far beyond safe thresholds in which individuals can still function normally. For individuals too poor to afford cooling systems, who have no housing, or anyone with poor health already, the humidity could be lethal. The study’s model predicts that in many places in the world, under worse estimates for global warming rates, those temperatures could stretch for up to 100 to 250 days a year by 2080. [H]undreds of millions could experience a staggering 95 degrees Fahrenheit at 100 percent humidity—which is literally off the charts on the heat index. In “dry” heat terms, this would feel like 170 degrees...