NCEI/NOAA
As the disasters unfolded, scientists explained the influence of climate change. Here’s what they said about some of the costliest disasters of 2021.
Extreme rainfall in the east, drought in the west
One characteristic that stood out during the disasters of 2021 was a sharp precipitation divide in the U.S.: While most of the west was in severe drought or worse, with the dry vegetation fueling fires, much of the eastern half of the country was getting soaked.
Extreme downpours in August triggered flash floods across Tennessee that swept away homes and vehicles and killed 20 people. A few days later, the remnants of Hurricane Ida crossed the country and hit New York City with record-shattering rainfall that submerged subway stations and basement apartments, killing dozens more.
On the other side of the country, damage from the western drought was much harder to calculate. The extreme dryness shut down a key hydroelectric power plant in California for five months, harmed farms and ranches and led to the first federal water use restrictions for the Colorado River as levels dropped in important reservoirs.
The Hoover Dam intake towers and ‘bathtub ring’ along the edges of the Colorado River’s Lake Mead shows how far the water level has fallen.
Patrick T. Fallon/AFP via Getty Images
Global warming helps fuel both kinds of precipitation extremes, Dayton University climate scientist Shuang-Ye Wu explained.
“Higher temperature increases evaporation from Earth’s surface, drying out vegetation and soils, which can fuel wildfires. It also increases the atmosphere’s capacity to hold moisture at a rate of about 7% per degree Celsius that the planet warms. With more moisture evaporating, global precipitation is expected to increase, but this increase is not uniform,” Wu wrote.
As the planet warms, wet areas are likely to get wetter, and dry areas drier, she said.
Read more:
Devastating Colorado fires cap a year of climate disasters in 2021, with one side of the country too wet, the other dangerously dry
No. 1: Hurricane Ida
Hurricane Ida, which exploded from a weak hurricane to a Category 4 storm over warm water in the Gulf of Mexico, was the most expensive disaster of 2021, with damage in Louisiana and then in the Northeast estimated at around $75 billion.
University of Miami oceanographer Nick Shay explained how the storm passed over a large pool of warm water in the Gulf of Mexico that had spun off from the Loop Current. That warm pool’s heat, extending down about 480 feet, fueled its strength.
Hurricanes are fueled by warm water, so warming surface temperatures will have an effect on them. Climate models suggest that Atlantic hurricane rainfall and intensity will increase, but there won’t necessarily be more of the storms.
Read more:
Hurricane Ida turned into a monster thanks to a giant warm patch in the Gulf of Mexico – here’s what happened
Ida’s route to Louisiana passed over very warm water. The scale shows in meters the maximum depth at which temperatures were at least 78 F (26 C), considered a general threshold for hurricanes to develop.
University of Miami, CC BY-ND
No. 2: The Texas freeze
In February, an Arctic blast sent ice, snow and freezing temperatures through the center of the country. In Texas, the cold blast quickly became a human disaster. The cold weather overwhelmed Texas’ power grid, freezing components at natural gas plants and slowing natural gas supplies. An estimated 69% of the state lost power, and NOAA counted 226 deaths. State officials have attributed 246 deaths to the storm.
That cold wave was the second-most expensive U.S. disaster of 2021, with costs estimated at around $24 billion.
Temperatures in Texas plunged into the teens in February 2021, knocking out power for a population unaccustomed to cold.
Thomas Shea / AFP via Getty Images
While it may seem counterintuitive, rapidly warming temperatures in the Arctic can trigger this kind of southward dip of the jet stream, a strong band of winds at the boundary between colder and warmer air. Research by atmospheric scientists Mathew Barlow at the University of Massachusetts Lowell and Judah Cohen at MIT shows how that can happen as changes in the Arctic are followed by changes in the stratospheric polar vortex, which are followed by cold waves in North America and Asia.
“Our research reinforces two crucial lessons of climate change: First, the change doesn’t have to occur in your backyard to have a big effect on you. Second, the unexpected consequences can be quite severe,” they wrote.
Read more:
How Arctic warming can trigger extreme cold waves like the Texas freeze – a new study makes the connection
No. 3: Devastating wildfires
The heat and dryness in the West contributed to more multibillion-dollar disasters. On Dec. 30, when Colorado would normally be blanketed in snow, a wildfire whipped by powerful winds tore through neighborhoods in abnormally dry Boulder County. Nearly 1,000 homes and several businesses were destroyed in a matter of hours.
The blaze followed devastating fires in California over the summer. Altogether, damage from the 2021 Western fires was estimated at $10.6 billion.
The fires that devastated parts of Boulder County, Colo., were moving so fast officials could do little more than evacuate homes in their path.
RJ Sangosti/MediaNews Group/The Denver Post via Getty Images
As rising global temperatures dry out vegetation, forest managers are dealing with increasing wildfire risks and costs. Fighting huge wildfires, like the Dixie and Caldor fires in California that destroyed much of Greenville and Grizzly Flats in 2021, depletes funds needed for fire prevention efforts, such as forest thinning and prescribed burns, University of California forest and fire experts Susan Kocher and Ryan Tompkins wrote.
“To manage fires in an era of climate change, where drier, hotter weather creates ideal conditions for burning, experts estimate that the area treated for fuels reduction needs to increase by at least an order of magnitude,” they said.
Read more:
Moving beyond America's war on wildfire: 4 ways to avoid future megafires
What about the tornadoes?
Tornadoes, like the deadly outbreak that created another multibillion-dollar disaster across Kentucky and nearby states in early December, haven’t been clearly connected to global warming, but climate models can still provide some insight, as Central Michigan University meteorology professor John Allen explained.
Tornadoes ripped a 250-mile path of destruction across Kentucky and neighboring states in December.
Scott Olson/Getty Images
“There are certainly signals pointing in the direction of a stormier future,” Allen said, “but how this manifests for tornadoes is an open area of research.”
Read more:
Tornadoes and climate change: What a warming world means for deadly twisters and the type of storms that spawn them
Editor’s note: This story is a roundup of articles from The Conversation’s archives. It has been updated with NOAA’s disaster map.
References^ US$145 billion in damage (www.ncdc.noaa.gov)^ one of the hottest (twitter.com)^ 4th hottest year in the U.S. (www.ncei.noaa.gov)^ Not every weather event (theconversation.com)^ rising temperatures affect the climate (theconversation.com)^ amplify heat waves (www.worldweatherattribution.org)^ is caused by greenhouse gases accumulating in the atmosphere from burning fossil fuels (www.metoffice.gov.uk)^ NCEI/NOAA (www.ncei.noaa.gov)^ record-shattering rainfall (theconversation.com)^ shut down a key hydroelectric power plant (water.ca.gov)^ harmed farms and ranches (www.fsa.usda.gov)^ water use restrictions for the Colorado River (theconversation.com)^ Patrick T. Fallon/AFP via Getty Images (www.gettyimages.com)^ fuel both kinds of precipitation extremes (theconversation.com)^ Shuang-Ye Wu (scholar.google.com)^ expected to increase (theconversation.com)^ Devastating Colorado fires cap a year of climate disasters in 2021, with one side of the country too wet, the other dangerously dry (theconversation.com)^ exploded from a weak hurricane to a Category 4 storm over warm water (theconversation.com)^ estimated at around $75 billion (www.ncdc.noaa.gov)^ Nick Shay (scholar.google.com)^ down about 480 feet (isotherm.rsmas.miami.edu)^ warming surface temperatures (www.globalchange.gov)^ rainfall and intensity will increase (nca2018.globalchange.gov)^ Hurricane Ida turned into a monster thanks to a giant warm patch in the Gulf of Mexico – here’s what happened (theconversation.com)^ CC BY-ND (creativecommons.org)^ overwhelmed Texas’ power grid (theconversation.com)^ freezing components (www.texastribune.org)^ 69% of the state lost power (uh.edu)^ 246 deaths (www.dshs.texas.gov)^ Thomas Shea / AFP via Getty Images (www.gettyimages.com)^ rapidly warming temperatures in the Arctic (doi.org)^ Mathew Barlow (scholar.google.com)^ Judah Cohen (scholar.google.com)^ shows how that can happen (theconversation.com)^ How Arctic warming can trigger extreme cold waves like the Texas freeze – a new study makes the connection (theconversation.com)^ abnormally dry Boulder County (theconversation.com)^ RJ Sangosti/MediaNews Group/The Denver Post via Getty Images (www.gettyimages.com)^ Fighting huge wildfires (www.redding.com)^ Greenville (inciweb.nwcg.gov)^ Grizzly Flats (inciweb.nwcg.gov)^ forest thinning and prescribed burns (www.gov.ca.gov)^ Susan Kocher (scholar.google.com)^ Ryan Tompkins (celassen.ucanr.edu)^ order of magnitude (theconversation.com)^ Moving beyond America's war on wildfire: 4 ways to avoid future megafires (theconversation.com)^ can still provide some insight (theconversation.com)^ John Allen (scholar.google.com)^ Scott Olson/Getty Images (www.gettyimages.com)^ Tornadoes and climate change: What a warming world means for deadly twisters and the type of storms that spawn them (theconversation.com)Authors: Stacy Morford, Environment + Climate EditorRead more
