The last five years have been the hottest on record globally. But this past winter, plunging temperatures, snowstorms and torrential rains throughout the country have a lot of people questioning the reality of climate change. If the planet is warming up, they say, then why is it so darn cold outside?
“The challenge is explaining that to people that there is this warming signal, but there's also going to be natural variability,” says climate scientist Ben Santer. “Human caused global warming does not invalidate winter; we’re still going to have winter.”
Santer was part of a panel of climate scientists, communicators and educators convened to explain the basics of climate change and to debunk some popular myths. Or, as host Greg Dalton jokingly referred to it, “Climate 101.”
“When we put CO2 into the atmosphere it's like a blanket around the surface of the earth,” Mach explains. “And we’re switching now from a lightweight summer blanket to a down comforter, and that effect is cranking up the temperature of the planet.”
This effect can’t be written off to natural causes, added Santer. In teasing out the magnitude of mankind’s contribution, “our best understanding is that over the last 60 or 70 years -- say since 1950 -- the human contribution to global warming far outstrips any natural effect due to changes in the sun, volcanoes, natural cycles.”
According to the most recent IPCC report, Santer says there’s a “greater than 95% probability that we’re right that humans are responsible for most of the warming since roughly 1950.”
Mach and Santer went on to unpack several more truths about the ways that climate change is affecting our world, from air travel to the Arctic ice shelf; from food production to California wildfires to the number of home runs in major league baseball.
As for those unseasonably cold spells and extra-wet winters? All part of the new climate normal, says Mach.
“We know for sure that a warmer atmosphere holds more water, so we can get much heavier downpours,” she explains. “There's some parts of the northern U.S. where we’re actually seeing some years with more extreme snowfall. Similarly, atmospheric rivers smacking the West Coast of the U.S. are increasing in frequency and intensity.
“So all these things that we think of as cold winter actually can be interconnected in this really complex dynamic system.”