Biden incorrectly links derechos to climate change

Source: By Thomas Frank, E&E News reporter • Posted: Monday, October 5, 2020

Joe Biden drew attention to the little-known and often destructive weather phenomenon called a “derecho” at last week’s presidential debate but said mistakenly that they have been linked to climate change.

The Democratic presidential nominee cited the derecho that demolished a wide swath of Iowa in August as evidence of the cost of a warming planet.

“Look what’s happened just in the Midwest with these storms that come through and wipe out entire sections and counties in Iowa. They didn’t happen before. They’re because of global warming,” Biden said.

Biden’s assertion that such events are new is wrong, and his attribution to global warming is not supported scientifically.

“We really don’t know what climate change is going to do to derechos,” Villanova University atmospheric scientist Stephen Strader said. “We don’t know if there are going to be more or less. Our models are not very good.”

The Fourth National Climate Assessment in 2018 said that the U.S. “has experienced several” derechos in recent years but downplayed any link to climate change.

“There are not enough observations to determine whether there are any long-term trends in their frequency or intensity,” according to the assessment, which uses the word “derecho” exactly once.

NOAA says on its “About Derechos” webpages that while a warmer planet “at first glance would appear to be more conducive to the development” of derechos, other climate trends such as increased cloudiness in the lower atmosphere hinder their development.

“How might climate change affect derecho frequency and distribution? The short answer is: No one can be sure,” NOAA says.

Derechos are fast-moving bands of thunderstorms with powerful winds that can be as destructive as a hurricane or tornado but which move forward in one direction instead of rotating.

The derecho that hit Iowa on Aug. 10 wiped out much of the state’s corn and soybean crops and caused an estimated $4 billion in damage. Twenty-three of the state’s 99 counties were declared a federal disaster.

The recent derecho was the first such incident to gain national attention since June 2012 when one such storm swept from Illinois to the East Coast where it caused extensive damage in Washington.

Derechos are rare, and their infrequency makes it difficult to track trends that might be driven by climate change, said Alan Czarnetzki, a meteorologist at the University of Northern Iowa and a leading derecho researcher.

“In Iowa, we probably have a derecho every couple of years,” Czarnetzki said. “Sometimes we have two in a year, but sometimes none for 10 years.”

“When an event is not particularly common to begin with, it’s a little difficult to untangle natural variability from some sort of a [climate] trend that might be there,” Czarnetzki added. “I don’t know that we have seen an increase in the frequency of them.”

Despite Biden’s statement that derechos “didn’t happen before,” scientists have known about the phenomenon since the late 19th century when a researcher in Iowa coined the term to distinguish straight-line wind damage caused by tornadoes, according to NOAA. “Derecho” is Spanish for “direct” or “straight ahead.”

Meteorologists used the term briefly in the late 19th century, but it “disappeared from use for nearly 100 years until resurrected by severe weather meteorologists in the mid-1980s,” NOAA says.

Meteorologists are struggling to understand the effect of climate change on derechos because they are difficult to incorporate into climate models.

“They’re such relatively small phenomena dependent on a lot of criteria,” said Strader of Villanova. “We’re talking about small events that models are just now getting to the point that we can look at them.”

Biden cited the recent devastation in Iowa as he was explaining the need to address climate change in part to deal with the growing cost of disasters.

“We spend billions of dollars now — billions of dollars — on floods, hurricanes, rising seas,” Biden said, citing three types of disasters whose increasing intensity has been linked to climate change. “We’re in real trouble.”

During the same segment of the debate, President Trump repeated his call for better management of forests in the western U.S. to reduce wildfires.

While forest managers agree that wildfire intensity could be reduced by thinning out forests, scientists agree that the wildfires that have devastated the U.S. and Australia in recent years are due in part to increasing heat and dryness that result from climate change.

A recent report that analyzed 116 papers on climate change and wildfire said that climate change has played an “unequivocal and pervasive role” in the increase and intensification of wildfires.