What’s Up With This Weather?

While most of the nation bakes, California keeps its cool–and not just along the coast

Climate scientist Phil Duffy and meteorologist Jan Null joined Michael Krasny on KQED’s Forum to discuss California’s cooler-than-usual summer and what it might reveal about climate change in the region. The upshot? We don’t really know.

“I think we’re seeing plain old climate variability,” said Duffy, who is a visiting scholar at Stanford and the Carnegie Institution for Science and chief scientist for Climate Central, a Climate Watch content partner.

Null agreed with Duffy, saying that in any given year, “stuff happens,” which can’t necessarily be attributed to a larger trend.

“It’s hard to take an individual year and say ‘This is the result of climate change’,” said Null. “It could be just the roll of the dice. If we see a lot of stuff happening over the next decades, then we’re talking about climate change.”

Null said this summer’s cool weather is due to a persistent trough of low pressure along the west coast.

“Anytime you have that for an extended period of time, you get what people call ‘unusual’ or ‘freakish’ weather,” he said.

Duffy said there is a theory that ties colder weather on the California coast to human-caused climate change, which he thinks has merit. That theory argues that as inland areas (which are already much hotter than the coast) heat up due to climate change, they’ll warm faster than the coastal areas. This could make the existing sea breeze stronger, pulling the cool marine air further inland. Duffy says that there is some research that suggests this is already happening.

However, he said, that’s not what we’re seeing this summer here in the Bay Area. This summer, cooler than average temperatures are present as much as a 1,000 miles inland, he said, which doesn’t fit this theory.

Regardless, said Duffy, what’s happening here in the Bay Area this year is not representative of the rest of the country or the world, which are experiencing record heat in many places. And even if we can’t attribute the weather in one particular year to climate change, he said, that doesn’t mean scientists are uncertain about climate change in general.

“There is a lot we do know,” he said. “We know increased greenhouse gases cause warming overall, changes in precipitation, and an increased frequency in certain types of extreme weather events…It’s frustrating that we can’t explain every weather variation, but the point is that when humans emit greenhouse gases, it does push things in a certain direction.”

You can listen to the entire episode on the Forum website.