A disastrous hurricane season combined with wildfires and other extreme weather events inflicted a record-setting toll on the U.S. in 2017, with 16 billion-dollar weather and climate events costing a total of $306 billion in damage. These events caused 362 direct deaths.

These figures come from a new report from the National Oceanic and Atmospheric Administration (NOAA), released on Monday morning.

The previous costliest year for the U.S. was 2005, when losses totaled $215 billion, largely due to the three major hurricane strikes of Hurricanes Katrina, Rita, and Wilma.

The number of billion-dollar events tied 2011 for the most such disasters in a single year. The Western wildfire season alone, which scorched California in particular, cost at least $18 billion, NOAA said, tripling the previous record annual wildfire toll.

Temperature departures from average during 2017 for the contiguous U.S. Image: noaa/ncei

Hurricane Harvey, which caused the most extreme rainstorm ever observed in the U.S., had total costs of $125 billion, just behind Hurricane Katrina in the 38-year period of record for billion-dollar disasters. Insurance companies are still tallying the damage for some of these events, so these costs may yet rise further.

Hurricanes Maria and Irma had total costs of $90 billion and $50 billion, respectively, and Hurricane Maria, which demolished Puerto Rico's power grid, ranks as the third-costliest weather and climate disaster on record for the nation.

The spike in costs for 2017 may have some link to global warming, since numerous recent studies have found that extreme heat, wildfire, and rainfall events are becoming more likely and more severe due to climate change. This could, in turn, make such disasters more expensive, depending on how vulnerable the impacted areas. However, NOAA did not make a determination on global warming's role in billion-dollar disasters for this report.

In deluging Houston with up to 60 inches of rain in just a few days time, Hurricane Harvey, for example, hit one of the most flood-prone metro areas in the U.S., where rampant urban development did not take into account the threat of heavy rainfall.

The NOAA cites both increased vulnerability to disasters, in part due to a growing population and more infrastructure in harms' way, as well as climate change for causing an increase in the number of billion-dollar disasters since 1980.

"Climate change is also paying an increasing role in the increasing frequency of some types of extreme weather that lead to billion-dollar disasters," wrote Adam B. Smith of NOAA in a blog post. "Most notably the rise in vulnerability to drought, lengthening wildfire seasons and the potential for extremely heavy rainfall and inland flooding events are most acutely related to the influence of climate change."

There is some uncertainty associated with the billion-dollar event estimates, given that NOAA is drawing from about a dozen databases, from private insurance company figures to public data from the federal government. The costs do not include ancillary costs of these events, such as health care, including mental health care that may be needed for storm survivors for years after an event.

Furthermore, the death toll from Hurricane Maria is still being tabulated, as are the costs, so these figures are likely to be updated in the future.

"They really are a low point to the true costs that are probably harder to calculate," Smith said during a press conference from the American Meteorological Society annual meeting in Austin, Texas.

A strong wind blows embers at the Thomas Fire on Dec. 16, 2017 in Montecito, California. Image: David mcnew/Getty Images





Third-warmest year for the U.S.

The NOAA report also found that 2017 was the third-warmest year on record for the lower 48 states, with an average annual temperature that was 2.6 degrees Fahrenheit above the 20th Century average. This was slightly cooler than 2012 and 2016, but it marks the 21st straight warmer-than-average year for the country.

In other words, if you were born in the U.S. in 1997 and remained here since, you've never experienced a cooler-than-average year in the U.S. In fact, the globe has not experienced a cooler-than-average month since December of 1984.

Strikingly, the five warmest years on record for the contiguous U.S. have all occurred since 2006, NOAA found.

This year, every state across the lower 48 and Alaska had an above-average annual temperature, and five states — Arizona, Georgia, New Mexico, North Carolina, and South Carolina — had their warmest year on record. This is the third-straight year in which every state across the lower 48 states has had an above-average annual temperature, said Jake Crouch, a climate scientist at NOAA's National Centers for Environmental Information in Asheville, North Carolina.

Thirty-two additional states, including Alaska, had a top-10 warmest year.

One way that NOAA measures extreme weather is via the Climate Extremes Index, which takes into account temperatures, precipitation, tropical storms and hurricanes, and other factors. In 2017 it had the second-highest value in the 108-year period of record, which was more than double the average.

Only 2012 had a higher value on this index, NOAA said. Extremes in warm maximum and minimum temperatures, one-day precipitation totals, days with precipitation and landfalling tropical cyclones contributed to the elevated extremes index, NOAA found.

According to NOAA, during the past 38 years, the U.S. has sustained 219 weather and climate disasters where the overall damage costs reached or exceeded $1 billion. The cumulative costs for these 219 events exceed $1.5 trillion, when adjusted to current levels using the Consumer Price Index.

This story has been updated to state more explicitly that some of the billion-dollar events may have some climate change connection to them.