U.S. weather disasters are getting costlier as more people move into vulnerable areas and climate change raises the risks of extreme heat and rainfall, the National Oceanic and Atmospheric Administration warned as it released its annual billion-dollar disasters report on Jan. 10, 2023.

Even with an average hurricane season, 2022 had the third-highest number of billion-dollar disasters in the U.S. since 1980.

In all, 18 disasters each caused more than US$1 billion in damage. The list included three hurricanes, two tornado outbreaks, a destructive fire season, several extreme storms and a drought that disrupted sectors across the economy.

It was also the third-costliest year, compared to past years adjusted for inflation, due primarily to Hurricane Ian’s widespread damage in Florida. Together, the 2022 disasters topped $165 billion, not counting the damage still being tallied from December’s winter storms.

Several scientists wrote about the year’s weather disasters and connections to climate change. Here are three essential reads from The Conversation’s archive:

1. Hurricane Ian

The most expensive U.S. weather disaster of 2022 was Hurricane Ian, which grew into a monster of a storm over the warm waters of the Gulf of Mexico in late September.

Ian hit the barriers islands off Fort Myers, Florida, with 150-mph sustained winds, tying for the fifth-strongest wind speed at U.S. landfall on record. Its storm surge swept through coastal neighborhoods, where the population has boomed in recent years, and its rainfall deluged a large swath of the state. Twenty inches of rain fell in Daytona Beach, triggering erosion with devastating consequences.

At least 144 deaths were attributed to the storm in Florida alone, and the total damage neared $113 billion.

Did global warming play a role?

In some ways, yes, but there are still a lot of unknowns when it comes to hurricanes, explained climate scientists Matthew Barlow of UMass-Lowell and Suzana Camargo of Columbia University.

For example, “it is clear that climate change increases the upper limit on hurricane strength and rain rate, and that it also raises the average sea level and therefore storm surge,” Barlow and Camargo wrote.

Less clear is global warming’s influence on hurricane frequency, though research points to an uptick in the strength of storms that do form. “We expect more of them to be major storms,” Barlow and Camargo wrote. “Hurricane Ian and other recent storms, including the 2020 Atlantic season, provide a picture of what that can look like.”

2. The drought

The second-costliest disaster, at over $22 billion, was the widespread drought across much of the U.S. West and parts of the Midwest. It left reservoirs near record lows, disrupted farming in several states and temporarily shut down barge traffic on the Mississippi River.

At one point, 2,000 barges were backed up along the river, where 92% of U.S. agriculture exports travel.

Rivers the size of the Mississippi can be slow to respond to droughts, but during the flash drought of 2022, the river fell 20 feet in less than three months – even though its major tributaries were flowing at normal levels, wrote earth scientists Ray Lombardi, Angela Antipova and Dorian Burnette of the University of Memphis.

They described the dramatic drop in the river’s water levels as a “preview of a climate-altered future.”

“Warmer atmospheric temperatures have the potential to evaporate more water, causing drought, and to hold more water, causing extreme rainfall,” the scientists wrote. “Over the past 100 years, year-to-year changes from very dry to very wet in the Mississippi River Valley have become more frequent. We expect this trend to continue as global temperatures continue to rise because of climate change.”

3. Extreme storms and flooding

Many of 2022’s billion-dollar disasters involved extreme storms, including hail, tornadoes, and a derecho that damaged power lines from Wisconsin to West Virginia.

It was also a summer of flooding, beginning with rain falling on snow that turned the Yellowstone River into a record-shattering torrent. St. Louis, Dallas, eastern Kentucky, southern Illinois and Death Valley were all hit with 1,000-year floods. Storms in the South knocked out Jackson, Mississippi’s fragile water supply for weeks.

Climate models have consistently shown that extreme rainfall events will become more common as the climate warms, wrote University of Dayton climate scientist Shuang-Ye Wu.

Some of that is basic physics – warmer air increases the amount of moisture that the atmosphere can hold by about 7% per degree Celsius. Increased humidity can enhance latent heat in storms, increasing their intensity and leading to heavier rainfall, Wu explained.

Even though humans are becoming more adept at managing climate risks, research published in 2022 found that extreme flooding and droughts are still getting deadlier and more expensive, and the costs are likely to continue to rise.

“This past summer might just provide a glimpse of our near future as these extreme climate events become more frequent,” Wu wrote. “To say this is the new ‘normal,’ though, is misleading. It suggests that we have reached a new stable state, and that is far from the truth.”

This is a roundup of articles from The Conversation’s archives.

Stacy Morford, Environment + Climate Editor, The Conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Rivers of muddy water from heavy rainfall raced through city streets as thousands of people evacuated homes downhill from California’s wildfire burn scars amid atmospheric river storms drenching the state in early January 2023.

The evacuations at one point included all of Montecito, home to around 8,000 people – and the site of the state’s deadliest mudslide on record exactly five years earlier.

Wildfire burn scars are particularly risky because wildfires strip away vegetation and make the soil hydrophobic – meaning it is less able to absorb water. A downpour on these vulnerable landscapes can quickly erode the ground, and fast-moving water can carry the debris, rocks and mud with it.

With more storms expected through mid-January, officials warned of a risk of debris flows near several recently burned areas, including near Santa Barbara and Los Angeles, Monterey and Santa Cruz counties and the Shasta Trinity National Forest.

I study cascading hazards like this, in which consecutive events lead to human disasters. Studies show climate change is raising the risk of multiple compound disasters, including new research showing increasing risks to energy infrastructure.

When storms hit burn scars

Five years ago, on Jan. 9, 2018, a deadly cascading disaster struck Montecito, a community in the coastal hills near Santa Barbara.

The cascade of events had started many months earlier with a drought, followed by a wet winter that fueled dense growth of vegetation and shrubs. An unusually warm and dry spring and summer followed, and it dried out the vegetation, turning it into fuel ready to burn. That fall, extreme Santa Ana and Diablo winds created the perfect conditions for wildfires.

The Thomas Fire began near Santa Barbara in December 2017 and burned over 280,000 acres. Then, on Jan. 9, 2018, extreme rainfall hit the region – including the burn scar left by the fire. Water raced through the burned landscape above Montecito, eroding the ground and creating the deadliest mudslide-debris flow event in California’s history. More than 400 homes were destroyed in about two hours, and 23 people died.

These kinds of cascading events aren’t unique to California. Australia’s Millennium Drought (1997-2009) also ended with devastating floods that inundated urban areas and breached levees. A study linked some of the levee and dike failures to earlier drought conditions, such as cracks forming because of exposure to heat and dryness.

Individually, they might not have been disasters

When multiple hazards such as droughts, heat waves, wildfires and extreme rainfall interact, human disasters often result.

The individual hazards might not be very extreme on their own, but combined they can become lethal. These types of events are broadly referred to as compound events. For example, a drought and heat wave might hit at the same time. A cascading event involves compound events in succession, like wildfires followed by downpours and mudslides.

With compound and cascading events likely to become more common in a warming world, the ability to prepare for and manage multiple hazards will be increasingly essential.

Climate change intensifies the risk

Several research studies have shown that compound events that include both drought and heat waves have become more severe and frequent in recent years. Studies have also shown that droughts and heat waves increase the likelihood of wildfires. And wildfires can also trigger other cascading hazards, turning otherwise unexceptional events into human disasters.

At the same time, extreme rainfall events are expected to intensify in a warming climate. A warmer atmosphere can hold more moisture, leading to wetter storms. This means more burned acres could be exposed to potentially extreme rainfall events in a warmer world.

Cascading hazards are not limited to rain over burned areas. For example, soot and ash deposits on snowpack can increase snowmelt, change the timing of runoff and cause snow-driven flooding.

It’s also important to recognize that human activities and local infrastructure can affect extreme events. Urbanization and deforestation, for example, can intensify flooding and worsen mud or debris flow events and their impacts. That was evident in the videos of muddy water pouring through streets in Santa Barbara County on Jan. 9, 2023.

In a recent study, colleagues and I also looked at the risks to energy infrastructure from cascading disasters involving intense rain over burn areas, focusing on natural gas pipelines and other infrastructure. Our results showed that not only will natural gas infrastructure be increasingly exposed to individual hazards, creating the potential for fires, the chances of cascading hazards are expected to increase substantially in a warming climate.

Managing multiple disasters and climate change

About a year after the devastating Montecito mudslide in 2018, I visited a location where damage to a natural gas pipeline hit by the mudslide led to a fire that burned multiple homes. Looking upstream, I could see many hills next to one another with similar burned scars, slopes and vegetation cover. Each one can be the ground zero for the next human disaster.

\Despite the high risk when extreme rainfall and droughts interact, most research in this area focuses on only rainfall or drought, but not both. Different government agencies oversee flood and drought monitoring, warning and management, even though both are extremes of the same hydrological cycle.

Recent disasters and research show a strong need to integrate management and risk reduction strategies of droughts and flood. Having one agency focus on one hazard can have unintended consequences for another hazard. For example, maximizing reservoir storage when expecting a drought can increase the flood risk.

Emergency response has improved since the 2018 Montecito disaster, but it’s clear that communities and government agencies still aren’t fully prepared for the scale and potential impacts of future events.

This article was updated Jan. 10 with the Montecito evacuation lifted. The article is an update to a version published Oct. 24, 2021.

Amir AghaKouchak, Professor of Civil & Environmental Engineering and Earth System Science, University of California, Irvine

This article is republished from The Conversation under a Creative Commons license. Read the original article.