See also: “Interactive: $1 Billion U.S. Extreme Storm Disasters, 2011–2017^[1]”

Five years ago, Superstorm Sandy cut a destructive path up the East Coast of the United States, taking 117 lives, leaving thousands of people homeless, and causing more than $71 billion in damage. Experts described it as a 1-in-260-year event, meaning that a storm of that caliber had a 0.3 percent chance of happening in any given year .¹ However, extreme weather is more frequent and widespread than this statistic suggests. In 2016 alone there were more than 15 extreme weather and climate events with losses exceeding $1 billion per event in the United States. Thus far, there have already been 15 events with losses totaling at least $1 billion each in 2017.²

In total, from 2011 to the present, there have been 84 extreme weather events in the United States causing at least $1 billion each in damage. Seventy-two of these disasters were extreme storms and floods; tropical cyclones such as hurricanes; or severe winter weather. U.S. counties have issued more than 13,000 major disaster declarations as a result of $1 billion events during this period—there are only 3,144 counties and county equivalents in the country. Total damage from these events tops half a trillion dollars—an estimated $675 billion, when taking into account preliminary estimates from the 2017 hurricane season. And some 2,000 Americans have died from extreme weather events over this time period—a number that will surely increase before the year is out.³

Climate change is already costing taxpayers dearly. A report from the nonpartisan Government Accountability Office—which is consistently conservative in its calculations—recently found that the federal government has spent $350 billion over the last 10 years in responding to climate-related disasters, and that those costs could reach $35 billion annually by 2050. Those figures do not include state and local government expenditures, costs to businesses, or costs borne by families and individuals.⁴

While varying topography, populations, and government decision-making influence how well a city or region can withstand and recover from extreme weather, one fact remains constant: Extreme weather events tend to most severely harm families who live paycheck to paycheck, because they are least able to prepare for and recover from these disasters.

Forty-six percent of Americans say that they do not have enough money to cover an unexpected $400 expense, according to a study conducted by the Federal Reserve.⁵ The costs of preparing for or evacuating in advance of a disaster can quickly top that amount: plywood to board up windows; food and emergency supplies for possible days of sheltering in place; last-minute plane tickets or multiple tanks of gasoline to drive hundreds of miles; a room in a hotel that can accommodate family pets, since many emergency shelters do not.⁶ Then, following a major disaster, even those who are eligible for federal aid may face weeks or months of delays for home inspections, flood insurance payments, and even small grants to help meet day-to-day expenses—all while grappling with the loss of thousands of dollars of property.⁷ Some of the most vulnerable populations never see federal aid at all. In Immokalee, Florida, which was devastated by Hurricane Irma, thousands of migrant farmworkers who grow and pick many of the tomatoes consumed in the United States live in “trailers so insecure that they say they can’t even apply for homeowner’s insurance,” according to the Miami Herald.⁸ Furthermore, undocumented immigrants do not qualify for cash aid or disaster-related unemployment assistance from the Federal Emergency Management Agency (FEMA).⁹

The Center for American Progress has analyzed $1 billion disasters between 2011 and 2017 to date alongside data on the median income of households in affected counties. The results of this analysis find that extreme weather’s impacts are typically felt more severely by low- and middle-income communities that have fewer resources to recover and rebuild their lives.

Extreme storm events on average affected counties where the median income is below the U.S. national median income:

• On average, extreme storms and floods led to disaster declarations in counties with median incomes 1.17 percent lower than the national median.

• On average, severe winter weather led to disaster declarations in counties with median incomes 3.58 percent below the national median.

• Tropical cyclones such as hurricanes and tropical storms appear at first to be the exception: Between 2011 and 2017, these events led to disaster declarations in counties where median incomes are on average 8 percent higher than the national median.¹⁰

However, when a few unusual extreme weather events are treated as outliers, the picture for hurricanes and tropical storms changes. Tropical cyclones do not typically affect the Northeast—at least not at full strength. Most recorded landfalls of tropical cyclones occur in the Southeast, along the Gulf Coast, Florida, or the Carolinas.¹¹  But in 2011, Hurricane Irene marched up the Eastern Seaboard, resulting in emergency or major disaster declarations from counties whose average median household income was 8 percent higher than the national median. Similarly, 2012’s Superstorm Sandy slammed directly into the New York-New Jersey metropolitan area, one of the country’s wealthiest regions.¹²

Without the two outliers of Superstorm Sandy and Hurricane Irene, hurricanes and tropical storms from 2011 to present affected counties where median incomes average 8.72 percent lower than the national median.¹³

To be sure, there are limitations to the methodology used to produce this report. A map displaying census income data reveals that households with incomes above the national median are disproportionately clustered in and around major metropolitan areas—meaning that there are more counties with incomes below the national median, and those counties are spread across a bigger geographic area.¹⁴ This could bias the results to show that disasters disproportionately affect such households. Meanwhile, while household income data can be refined to the individual census tract level, information on disaster impacts cannot, because disaster declarations occur only on the county level. That means that the data may mask income inequality between a family earning $30,000 in Bedford-Stuyvesant, Brooklyn, compared with one earning 10 times as much in the wealthy Brooklyn Heights area—both neighborhoods in Kings County, New York, which declared disaster after Superstorm Sandy.

Finally, extreme weather events are not random—certain events typically occur in certain geographies. States in the South and Midwest saw the most billion-dollar storm events of all types between 2011 and 2017, while wealthier states in New England and the West saw the fewest.¹⁵ A complete accounting of the 84 extreme weather and climate events costing at least $1 billion from 2011–present, including costs, number of fatalities, and states affected by each event, can be found in the Appendix.

One thing is certain: Extreme weather is a problem that is only going to worsen. Extreme weather regularly affects four times as many U.S. counties today compared with 40 years ago.¹⁶ From 1980 through 2007, the United States averaged four $1 billion disasters per year; since 2007, the country has seen an average of 11 such disasters per year.¹⁷ The latest version of the National Climate Assessment notes that the “global, long-term, and unambiguous warming trend” is expected to continue, and that this warming will create more “record-setting extremes.”¹⁸  Simply put, climate change will continue to cause more intense heat waves, droughts, and wildfires; increasingly severe storms, flooding, and hurricanes; and more severe winter storms that threaten every region of the country.

Even as this issue brief was being prepared, Hurricane Nate made landfall on the Gulf Coast of the United States, the fourth storm to hit the United States this hurricane season. The head of the Mississippi Emergency Management Agency credited the measures that communities have undertaken to build resilience to extreme weather for mitigating the damage from Hurricane Nate, telling The New York Times, “If Nate would have hit us 15 years ago, the damage would have been much more extensive, we would have had loss of life. But we have rebuilt the coast in the aftermath of Katrina higher and stronger.”¹⁹

Devastating storms such as Superstorm Sandy and Hurricane Maria, which cause damage from storm surge, deluges, and destructive winds, tend to dominate news coverage of extreme weather. But the last seven years have also seen the most expensive and destructive wildfire season on record; in 2015, 10.2 million acres burned, costing $1.71 billion to fight.²⁰ By some measures, the 2017 season has been even worse.²¹ Even as this issue brief was being prepared, wildfires broke out in Northern California, torching more than 245,000 acres, destroying more than 8,400 structures, and killing at least 42 people.²² The system of fires was the deadliest in the state’s history.²³ Before that, California had endured five years of drought, which cost farmers billions of dollars, raised electricity prices, and put thousands of farmworkers out of work.²⁴ And earlier this year, a heat wave in the Southwest shattered records; temperatures rose so high that Phoenix Sky Harbor Airport had to ground planes.²⁵

This brief first explores recent trends in extreme weather—specifically, severe thunderstorms, downpours, and floods; tropical cyclones; and winter storms and freezes—and considers how climate change is making each kind of event more severe. The brief then examines how extreme storms disproportionately affect low- and moderate-income Americans. Finally, the brief considers nonstorm events such as droughts, wildfires, and heat waves, which are also being made worse by climate change.

Extreme weather is the new normal

The conclusion that extreme weather events are occurring more frequently and are becoming more severe reflects decades of scientific research and reporting, including the 2017 Climate Science Special Report of the National Climate Assessment, a consortium of scientists from federal agencies and universities throughout the United States. The report reaffirms that high levels of pollution from human activities have warmed the atmosphere and triggered changes to air temperature, sea level, precipitation rates, and drought.²⁶ These changes intensify the impact of extreme weather by as much as 30 percent.²⁷

While it is difficult to claim that any specific event was the result of climate change, it is beyond dispute that climate change has an amplifying effect on extreme storms. “[E]verything in the atmosphere now is impacted by the fact that it’s warmer than it’s ever been,” said Brendan Miller, CNN’s senior meteorologist, in the wake of hurricanes Harvey and Irma. “There’s more water vapor in the atmosphere. The ocean is warmer. And all of that really only pushes the impact in one direction, and that is worse: higher surge in storms, higher rainfall in storms.”²⁸

This issue brief considers each category of extreme storms and the connection to climate change in more detail below.

Floods and severe storms

Floods are the most common natural disaster in the United States, according to FEMA.²⁹ They are also the deadliest extreme weather event, killing more people in the United States in a typical year than tornadoes, hurricanes, or lightning.³⁰

In recent decades, heavy downpours have increased in frequency and severity across the United States, particularly in the Midwest and the Northeast. More frequent and intense rains have triggered an increase in local flooding events, according to the 2014 National Climate Assessment.³¹

The recent flooding caused by Hurricane Harvey in Houston is an extreme example of what the uptick in severe precipitation events could mean for America’s cities. Harvey smashed records, producing more than 3 feet of rainfall across the greater Houston area and as much as 60 inches near Port Arthur, Texas.³² It was the single largest precipitation event since record-keeping began in the United States.³³ Preliminary results from FEMA models indicated that as many as 90,000 residential structures suffered flood damage across three counties as a result of Harvey, with local officials in Harris County, where Houston is located, estimating that 136,000 homes in that county alone had been damaged.³⁴

Hurricane Harvey was a tropical cyclone, a bigger and more powerful storm system than an everyday thunderstorm. But Harvey deserves mentioning here because 2017 was actually the third consecutive year in which Houston suffered a flood so severe that it had a 1 in 500 chance—or lower—of happening in any one year. The 2015 Memorial Day floods in the Houston metropolitan area killed seven people and triggered federal recovery aid from FEMA for 13,000 Houstonians, according to the Houston Chronicle.³⁵ In 2016, Houston’s Tax Day floods killed eight people and were followed by an additional flooding event, once again around Memorial Day.³⁶ Houston’s East Side, home to many of the city’s low-income communities and communities of color, is typically hit hardest by flood events.³⁷

There has also been an increase in coastal flooding events as a result of sea level rise induced by climate change—where high tides can inundate streets and send water rushing into homes and businesses. These so-called nuisance or sunny day floods do not typically cross the billion-dollar threshold for damages and thus are not reflected in the analysis of this issue brief. However, these events can be disruptive and costly for local communities. Miami Beach saw a 400 percent increase in such tidal flooding between 2006 and 2016.³⁸ In response, the city launched a $100 million project earlier this year to build new flood control infrastructure, including higher roads and stronger pumping systems, to deal with the risks posed by rising sea levels.³⁹ Instances of sunny day flooding have increased between 300 and 925 percent on all U.S. coasts since the 1960s, according to the National Oceanic and Atmospheric Administration (NOAA), with the biggest upticks on the East Coast.⁴⁰

Hurricanes and tropical storms

Hurricanes have grown more frequent, intense, and longer-lasting since the 1980s, according to the National Climate Assessment.⁴¹ This 30-year period has seen the most major hurricanes, days with hurricane activity, and energy generated by tropical cyclones’ winds in 167 years of federal record-keeping.⁴² Compared with the entire record, 2003, 2004, 2005, 2008, 2010, 2012, and 2016 saw hurricane seasons that were more intense than usual. According to the Associated Press, “The 2005 season, which included Katrina, Rita, and Wilma, was so active forecasters ran out of names for storms.”⁴³

While multiple factors contribute to the formation of tropical cyclones, sea surface temperatures are a major variable that helps determine the strength of a storm—the hotter the ocean, the more energy available to fuel a tropical cyclone. Globally, ocean temperatures have risen between 1 degree and 3 degrees Fahrenheit during the last 100 years.⁴⁴ As Hurricane Harvey grew to full strength in the Gulf of Mexico, sea surface temperatures were between 2.7 degrees and 7.2 degrees Fahrenheit higher than average, and Hurricane Irma intensified over waters that were 0.9 degrees to 2.25 degrees Fahrenheit higher than average.⁴⁵

The Atlantic Ocean also undergoes natural variation in sea surface temperatures, which has led to disputes among scientists about how much of the increase in recent hurricane activity can be attributed to human-caused climate change. However, climate models developed by the National Center for Atmospheric Research show that the changes in Atlantic sea surface temperature exceed what is expected from the natural oscillation cycle.⁴⁶

2017 has also already seen four major hurricanes that intensified rapidly—Harvey, Irma, Jose, and Maria. Hurricane Maria underwent a particularly startling transformation, with wind speeds increasing from a tropical storm with 65 mph winds at 2 p.m. ET on Sunday, September 17, to a Category 5 hurricane with 160 mph winds by 7:45 p.m. ET the following day.⁴⁷ Kerry Emanuel, a hurricane expert at the Massachusetts Institute of Technology (MIT), has found that climate change may make these rapidly intensifying storms more frequent.⁴⁸

Winter storms

In February 2015, Sen. Jim Inhofe (R-OK) brought a snowball onto the Senate floor. “In case we have forgotten because we keep hearing that 2014 has been the warmest year on record,” said Sen. Inhofe, who is a notorious denier of the mainstream science of climate change. Inhofe continued, “I asked the chair, do you know what this is? It’s a snowball just from outside here. So it’s very, very cold out. Very unseasonable.”⁴⁹ While 2014 was indeed the hottest year on record at that time, it has since been replaced by 2015 and then by 2016, and the 10 hottest years ever recorded have all occurred since 1998.⁵⁰

Not only does the continued existence of winter not disprove the science of climate change, but there is evidence that climate change actually makes some kinds of winter storms more severe. Winter storms have become more frequent and more intense since the 1950s, according to the National Climate Assessment.⁵¹ Specifically, the second half of the 20th century saw about twice as many extreme snowstorms as the first half, according to NOAA.⁵²

In fact, years with above-average temperatures tend to see winters with more snowstorms, not fewer.⁵³ And while average snowfall is expected to decrease in a warmer world, some studies predict an increase in extreme snowfall events for the same reasons as other extreme precipitation events are expected to increase.

“People may know the expression, ‘It’s too cold to snow’—if it’s very cold, there is too little water vapor in the air to support a very heavy snowfall,” said Peter O’Gorman, a professor at MIT and the author of one such study, in 2014.⁵⁴ Warmer air holds more water vapor, meaning that the snowstorms that do occur will have more fuel. And in extreme cases, large bodies of freshwater could either not freeze or only partially freeze in a warmer winter, leading to an increase in lake-effect snow—snowstorms occurring as a result of cold air moving over relatively warmer, open, unfrozen water.⁵⁵ Just such an increase happened in 2006, when Lake Erie did not freeze over for the first time in recorded history.⁵⁶

Additionally, some studies have concluded that climate change may even be altering the patterns of the jet stream that helps direct weather patterns throughout the United States. “Enhanced warming of the Arctic affects the jet stream by slowing its west-to-east winds and by promoting larger north-south meanders in the flow,” a NOAA-led study concluded in 2012.⁵⁷ The reduction in Arctic sea ice cover also appears to be contributing to a weakening of the polar vortex, which in recent years has contributed to extreme cold temperatures in late winter.⁵⁸

Middle- and lower-income Americans are more vulnerable to extreme weather events

Extreme weather events affect entire communities, but they are by no means social equalizers, as some assume. Extreme weather disproportionately harms families who struggle to make ends meet, including low- and middle-income households who have the fewest resources to prepare for and respond to disasters. Additionally, extreme weather events can also exacerbate existing racial and socioeconomic inequities around housing, access to services, and economic opportunity.

This disparity is borne out both in the immediate aftermath of a disaster and in the long-term recovery of a community. For instance, when Superstorm Sandy hit New York City, some 375,000 New Yorkers lived in mandatory evacuation zones—but only about 6,800 showed up at emergency shelters.⁵⁹ As Cathleen Kelly and Tracey Ross from the Center for American Progress recounted in their 2014 report, “One Storm Shy of Despair,” federal emergency workers soon discovered why: