By Jim Bloch
If you think the rainiest days are rainier than they used to be, you’re probably right.
A new study by Climate Central, the nonprofit organization dedicated to probing and publicizing the effects of a warming world, has found that the top one percent of precipitation events is getting more intense across the United States.
The organization released its findings May 1.
“As the climate has warmed over recent decades, the most extreme precipitation days have become more intense across the U.S.,” the study said. “In the Northeast and Midwest, the amount of precipitation falling on the heaviest 1% of days has increased 60% and 45 %, respectively, from 1958 to 2021 according to the Fifth National Climate Assessment. The heaviest rainfall events have become wetter across all other major regions of the continental U.S. from 1958 to 2021 as well, led by: the Southeast (+37%); the Northern Rockies and Plains (+24%); and the South (+21%).”
The world has warmed by about two degrees Fahrenheit since the start of the industrial revolution in 1750, when humans began burning of fossil fuels in earnest to generate electricity, heat homes, run factories and power transportation. The U.S. has warmed 2.6 degrees F since 1970.
For each one degree rise in temperature, the atmosphere can hold four percent more water, which must go somewhere. In the U.S., the air may now hold 10 percent more water at any given time than it did 50 years ago. All that water returns to earth as increased snow and rain.
Among the consequences: Heavier downpours coming faster, which in turn means more flash floods, landslides, washed out farm fields, damaged roads and bridges, increased contaminants in the runoff and more people forced from their homes and businesses.
A warmer future will be a wetter future.
The study estimated that about a third of the cost of recent flood damages may be laid at the doorstep of climate change.
“Inland flooding in the U.S. caused $230 billion in damages from 1988 to 2021. Over one-third (37%) of those damages are attributed to precipitation changes due to climate warming,” the report said. “That’s $84 billion in past flood damage due to warming-induced rainfall intensification.”
The biggest downpours cause the most damage.
“Hourly rainfall intensity has also increased since 1970 — by 13% on average across 150 U.S. locations analyzed by Climate Central,” the report said.
The organization looked at 3,111 counties in the U.S.
If the temperature increase hits 3.6 degrees F, 85 percent of those counties will see at least a 10 percent increase of precipitation on the wettest of days; on average, the increase will be 17 percent.
“Counties likely to experience at least a 30% increase in extreme precipitation are concentrated in: Tennessee, Alabama, Georgia, Mississippi, Maine, North Carolina, and Kentucky,” the report said. “Alaska and Hawaii are likely to experience some of the highest levels of extreme precipitation intensification (43% and 30%, respectively) at 3.6°F of global warming.”
The world is poised to continue warming.
The National Oceanic and Atmospheric Administration said carbon dioxide, the main heat-trapping gas, saw its fourth fastest annual increase in 2023, rising to 419 parts per million, about 50 percent more than 1750.
As the New York Times puts it: “Carbon dioxide acts like Earth’s thermostat. The more of it in the air, the more the planet warms.”
And the more intense become the most intense rainstorms.
Jim Bloch is a freelance writer based in St. Clair, Michigan. Contact him at bloch.jim@gmail.com.
