Extreme weather

One of the most robust measures of Earth’s changing climate is that winter is warming more quickly than other seasons. The cascade of changes it brings, including ice storms and rain in regions that were once reliably below freezing, are symptoms of what I call “warming winter syndrome.” Wintertime warming represents the global accumulation of heat. During winter, direct heat from the Sun is weak, but storms and shifts in the jet stream bring warm air up from more southern latitudes into the northern U.S. and Canada. As global temperatures and the oceans warm, that stored heat has an influence on both temperature and precipitation. The U.S. has been feeling this warming in the winter of 2023-24, the warmest on record for the Lower 48 states. Snowfall has been below average in much of the country. On the Great Lakes, the ice cover has been at record lows. Late February saw a wave of summerlike temperatures spread up into the central and eastern U.S., along wi...

Winter storms can easily become billion-dollar disasters as the snow piles up on interstates and collapses roofs and power lines. Yet, while canceled flights and business interruptions can’t be avoided, what turns a snowstorm into a disaster often can be. I have worked on engineering strategies to enhance disaster resilience for over three decades and recently wrote a book, “The Blessings of Disaster,” about the gambles humans take with disaster risk. Snowstorms stand out for how preventable much of the damage really is. Stay off the roads The easiest storm costs to avoid involve human behavior, including driving during snowstorms. Successfully plowing the snow off a highway requires repeated passes to prevent snow from accumulating to the point where it piles up faster than it can be removed. However, that simple concept breaks down when an accident blocks the lanes, and traffic – including commerce and emergency vehicles – grinds to a halt. W...

Extremely cold Arctic air and severe winter weather swept southward into much of the U.S. in mid-January 2024, breaking daily low temperature records from Montana to Texas. Tens of millions of people were affected by dangerously cold temperatures, and heavy lake-effect snow and snow squalls have had severe effects across the Great Lakes and Northeast regions. These severe cold events occur when the polar jet stream – the familiar jet stream of winter that runs along the boundary between Arctic and more temperate air – dips deeply southward, bringing the cold Arctic air to regions that don’t often experience it. Surface temperatures at 7 a.m. EST on Jan. 16, 2024. Temperatures below freezing are in blue; those above freezing are in red. The jet stream is indicated by the light blue line with arrows. Mathew Barlow/UMass Lowell, CC BY An interesting aspect of these events is that they...

Millions of Californians were under flood alerts as a powerful atmospheric river brought heavy rain to the West Coast in early February 2024. Los Angeles saw one of its wettest days on record with over 4 inches of rain on Feb. 4. Other communities were hit by more than 12 inches of rain and reported widespread flooding. Debris and mudslides shut down sections of highways and roads into Malibu. It was the latest in a series of atmospheric rivers to bring extreme rainfall to the West Coast. While these storms are dreaded for the damage they can cause, they are also essential to the region’s water supply, particularly in California, as Qian Cao, a hydrologist at the University of California, San Diego, explains. What are atmospheric rivers? An atmospheric river is a narrow corridor or filament of concentrated water vapor transported in the atmosphere. It’s like a river in the sky that can be 1,000 miles long. On average, atmospheric rivers have about twice the regul...

National weather analysts released their 2023 billion-dollar disasters list on Jan. 9, just as 2024 was getting off to a ferocious start. A blizzard was sweeping across across the Plains and Midwest, and the South and East faced flood risks from extreme downpours. The U.S. set an unwelcome record for weather and climate disasters in 2023, with 28 disasters that exceeded more than US$1 billion in damage each. While it wasn’t the most expensive year overall – the costliest years included multiple hurricane strikes – it had the highest number of billion-dollar storms, floods, droughts and fires of any year since counting began in 1980, with six more than any other year, accounting for inflation. 2023’s billion-dollar disasters. Click the image to expand. NOAA The year’s most expensive disaster started with an unprecedented heat wave that sat over Texas for weeks over...