Hurricanes Harvey, Irma and Maria combined with devastating Western wildfires and other natural catastrophes to make 2017 the most expensive year on record for disasters, the National Oceanic and Atmospheric Administration reported Monday.

The disasters caused $306 billion in total damage in 2017, with 16 separate events that caused more than $1 billion in damage each.

“2017 was a historic year for billion-dollar weather and climate disasters,” said Adam Smith, an economist for NOAA, on a media call with reporters.

The record-breaking year raises concerns about the effects of future natural disasters, as scientists fear climate change could make extreme weather events more damaging.

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Hurricane Harvey, which sparked extreme flooding in Houston and the surrounding area in August and September, caused $125 billion in damage, the year’s most expensive disaster. Hurricane Maria, which in September set off a fatal and ongoing humanitarian crisis in the U.S. territory of Puerto Rico and elsewhere, caused $90 billion in damage. Hurricane Irma hit Florida in September and caused $50 billion in total damage, NOAA reports.

The storms also caused 251 combined deaths, the report found. According to Smith, hurricanes Harvey, Irma and Maria join 2005’s Katrina and 2012’s Sandy among the top five most costly U.S. hurricanes on record.

Western wildfires cost $18 billion and 54 lives, the report found. Other large costs came from tornadoes, droughts, severe weather events, flooding and other causes.

The previous most expensive disaster year was 2005, when events such as Hurricane Katrina caused $215 billion in U.S. damage when adjusted for inflation. NOAA’s record of billion-dollar natural disasters goes back to 1980.

According to NOAA, there have been 215 U.S. disasters costing $1 billion or more since 1980, for a total of more than $1.2 trillion in damage. The year 2017 tied 2011 for the largest total number of such events, at 16.

One key question is to what extent climate change may be driving the U.S. toward more numerous or more severe disasters.

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NOAA experts demurred on this question on a media call, declining to apportion how much of the damage could be attributed to a changing climate as opposed to other factors. One key factor also known to be worsening damage is that there is more valuable infrastructure, such as homes and businesses, in harm’s way — along coastlines or in areas vulnerable to wildfire.

“For the purposes especially of this product, we do not try to parse those apart,” said Deke Arndt, chief of the monitoring section at NOAA’s National Centers for Environmental Information. “We’re more interested in quantifying what’s going on. Both the economists and physical scientists will retrospectively look at that, but those sort of happen at the speed of science.”

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