From The Washington Post (Joel Achenbach and Angela Fritz):
In the United States, 35 weather stations in the past month have set new marks for warm overnight temperatures. Southern California has had record heat and widespread power outages. In Yosemite Valley, which is imperiled by wildfires, park rangers have told everyone to flee.
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 old records belong to a world that no longer exists,” said Martin Hoerling, a research meteorologist at the National Oceanic and Atmospheric Administration.
It’s not just heat. A warming world is prone to multiple types of extreme weather — heavier downpours, stronger hurricanes, longer droughts.
“You see roads melting, airplanes not being able to take off, there’s not enough water,” said Katharine Hayhoe, director of the Climate Science Center at Texas Tech University. “Climate change hits us at our Achilles’ heel. In the Southwest, it’s water availability. On the Gulf Coast, it’s hurricanes. In the East, it’s flooding. It’s exacerbating the risks we already face today.”
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.
This summer, the jet stream has undulated in extreme waves that have tended to block weather systems from migrating. The result has been stagnant high-pressure and low-pressure systems with dire results, such as heat waves in some places and flooding elsewhere.
“When those waves are very big — as they have been for the past few weeks — they tend to get stuck in place,” said Jennifer Francis, a professor of atmospheric science at Rutgers University. Last year, scientists published evidence that the conditions leading up to “stuck jet streams” are becoming more common, with warming in the Arctic seen as a likely culprit.
Gone are the days when scientists drew a bright line dividing weather and climate. Now researchers can examine a weather event and estimate how much climate change had to do with causing or exacerbating it…
Said Hayhoe: “The biggest myth that the largest number of people have bought into is that ‘climate change doesn’t matter to me personally.’ ”
The heat waves have hit hard where people don’t expect them — the Netherlands, Sweden, Britain, Ireland and Canada.
“Our office doesn’t have air conditioning. I do have a fan,” said Geert Jan van Oldenborgh, a climate researcher at the Royal Netherlands Meteorological Institute. He spoke by phone from the city of Gouda, where the temperature hit 96 degrees Thursday…
Human activity, primarily the burning of fossil fuels, has added greenhouse gases to the atmosphere, trapping heat and making extreme weather events even more extreme. The amount of carbon dioxide in the atmosphere reached 410 parts per million in May, the highest the Mauna Loa Observatory in Hawaii had measured since Charles David Keeling started keeping records in 1958. NASA estimates Earth has warmed almost one degree Celsius (1.8 degrees Fahrenheit) since the late 1800s. Of that, half a degree (around one degree F) has accrued since 1990 alone…
Overall precipitation has decreased in the South and West and increased in the North and East. That trend will continue. The heaviest precipitation events will become more frequent and more extreme. Snowpack will continue to decline. Large wildfires will become even more frequent.
Kevin Trenberth, a climate scientist with the National Center for Atmospheric Research, said even modest heat from global warming can build up over time.
“The accumulated energy over one month is equivalent to a small microwave oven at full power for six minutes over every square foot of the planet,” Trenberth said. “No wonder things catch on fire.”