Six Big Ways Climate Change Could Impact the United States by 2100 | Science

Climate change will not just affect our future—we’re seeing damage from it now. Extreme forest fires, warmer temperatures and prolonged droughts are just some of the ways climate change has impacted the United States. Scientists agree that burning fossil fuels is the main contributor to greenhouse gas emissions that drive climate change. Emissions like carbon dioxide and methane build up in the atmosphere, absorb sunlight bouncing off the Earth’s surface, and trap heat.

The effects of climate change are only going to get worse. Someone born in 2020 is predicted to experience more climate hazards in their lifetime than someone born in 1965. So what can we expect in the near future? According to the Fifth National Climate Assessment released this year by the U.S. Global Change Research Program, without significant cuts to greenhouse gas emissions, the U.S. faces increasingly severe climate threats. The Climate Assessment considers less and more extreme scenarios, and predicts that the level of warming in the U.S.—how much average surface temperature increases compared with preindustrial levels—will be between 3 and 13 degrees Fahrenheit by the end of the century.

What temperature we reach depends on our choices regarding greenhouse gases now. Here are six ways climate change is predicted to affect our everyday lives throughout the U.S. by 2100, with more severe consequences if emissions remain unchecked.

Dangerous heat waves will hit cities

This summer’s heat waves put about one-third of the U.S. population under heat advisories. A heat wave is a period of hot weather abnormal for the area, usually lasting two or more days, in which temperatures surpass 103 degrees Fahrenheit. Heat waves are happening more often than ever before in the United States—at an average of six per year—and are becoming more intense and longer. The average heat wave season is about 49 days longer today than in the 1960s. Cities are hit especially hard. Because concrete absorbs heat, cities warm up faster and are less able to cool off than other areas.

In June, some Southern states saw heat-related emergency department visits at their highest in five years. According to Claudia Brown, health scientist at the CDC’s Climate and Health Program, an increase in the frequency and intensity of heat events means more cases of heat-related illness. “Higher temperatures are associated with adverse pregnancy and birth outcomes, mental health impacts, cardiovascular disease, diabetes, electrolyte imbalance, renal failure and respiratory outcomes,” says Brown.

Extreme heat events can harm some groups disproportionately, says Brown. Children, older adults, people with disabilities and people without access to air-conditioned spaces are especially susceptible to heat-related health impacts.

By 2100, hot days reaching dangerous conditions are expected to be three to ten times more frequent in the U.S. even if current emissions are limited to meet global climate goals set in Paris in 2015.

Coasts will flood, especially in the Southeast

Two men row a boat down a flooded street in Charleston, South Carolina. The Southeast will be most affected by rising sea levels.

MLADEN ANTONOV / AFP via Getty Images

Coastlines have seen more frequent flooding since the 1950s. The East Coast shows the most frequent flooding, exacerbated by sea level rise: as the ocean rises, flooding happens more, especially during seasonal high tides and storms. The Southeast, from North Carolina to Florida, lost the most land of any coast in the U.S. to sea level rise. In that region about 20 square miles of dry land and wetland—roughly two-thirds the size of Manhattan—became open water between 1996 and 2011.

About 40 percent of Americans live near the coast, putting them at risk. When flooding happens, streets can become submerged, storm drains can stop working, infrastructure can deteriorate, and people can lose their homes.

Continually rising sea levels mean flooding will likely happen more often. Some models project average sea level to rise along U.S. coasts by two feet by 2100 because of emissions to date, but more extreme scenarios show it could rise up to seven feet if we fail to curb future emissions. A sea level rise of just three feet would threaten the homes of 4.2 million people, according to one study. The researchers found the Southeastern U.S. will be most affected by rising sea levels: Florida is severely at risk, and Georgia, South Carolina and Louisiana would have over 10 percent of their population at risk by 2100 under some flood models.

Wildfires will blaze in the West, sending smoke everywhere

Naturally occurring wildfires are important for ecosystem health, but climate change has led to larger wildfires that are more destructive and harder to control. And a longer wildfire season means more frequent wildfires are burning homes and ecosystems.

Matthew Wibbenmeyer, an economist at Resources for the Future, explains that because of climate change, fuel for fires, such as plant material, becomes drier and stays dry for longer parts of the year. Earlier snowmelt contributes to drying earlier in the year, which can also lengthen the fire season. “For wildfires to occur there needs to be fuel, and it needs to be ready to burn,” says Wibbenmeyer. “What we have due in part to forest management in some parts of the Western U.S. is a lot of fuel; and then due to climate, it’s ready to burn. Both of those factors combine to produce the situation we’re in now.”

And smoke can extend well beyond the fire itself. Wildfire smoke from Canada shrouded the country this past summer, pushing air quality alerts in the Midwest and Northeast to unprecedented levels. Smoke exposure leads to more emergency department visits, hospital admissions and deaths due to respiratory ailments.

By 2100, catastrophic fire events are expected to increase by up to 50 percent globally—including elevated risks in regions that were not previously fire-prone. “All the climate work that I’ve seen points in the direction of increasing wildfire activity,” says Wibbenmeyer, “at least in the Western U.S. and North America, at least in the foreseeable future.”

Our food supply will be less secure

The length of the growing season, or the number of days in a year when plant growth takes place, has increased steadily in the last 30 years. While a longer growing season could be good for some crops in some regions, overall warming is expected to diminish major crop yields. “Killing-degree days,” when temperatures are too hot for crops to grow, are expected to increase. Warming could also encourage the growth of invasive species that harm crops. And pollinators’ habitat range is limited by climate change. Temperature and precipitation act as cues to tell pollinators when to pollinate, and shifts in these cues have already started to push pollinators out of sync with plant blooms. This has widespread impacts because pollinators are necessary for 35 percent of food crops to reproduce—apples, blueberries, tomatoes and pumpkins all need bird or insect pollination.

More heat and changing rainfall patterns are predicted to harm crop yields throughout the U.S. in the coming decade: corn yields in Iowa, soybean yields in Minnesota and wheat yields in Kansas will all be 5 percent lower than without the effects of climate change.

Warming temperatures, along with ocean acidification and algal blooms, will also threaten fisheries. Some fish like cod are moving northward and into deeper waters in response to warmer oceans, and other species like lobster, oysters, clams and mussels are at risk of population decline. A key Northeastern fishery staple, sea scallops are projected to decline by over 50 percent by 2100 under a high climate scenario because ocean acidification, which results from climate change, will limit their growth and survival.

Disease ranges will expand

Black-legged Tick

Black-legged ticks, like this one, carry Lyme disease and are moving into new areas as the climate changes.

Smith Collection / Gado/Getty Images

Climate change is altering the distribution and abundance of vector-borne diseases like Lyme disease and West Nile virus, according to Brown. Because of warmer weather and shorter winters, the favorable climate for the ticks and mosquitoes that carry these diseases is shifting in geographic location: areas that were not previously suitable for them now are.

“In general we are seeing their seasonality become longer, and their abundance higher,” Brown adds.

Tick-borne diseases make up about 80 percent of reported vector-borne diseases in the U.S. and have increased over the last 20 years. Ticks are spreading to new areas and their seasonal activity is expanding, prolonging their exposure to humans. Climate change can also alter the distribution of mosquitoes—which can carry West Nile virus, dengue, Zika and chikungunya. Future warming is projected to lead to the expansion of West Nile virus in the Northeast over the next 50 years.

These risks affect some folks more than others. “People that don’t have proper housing, or even are working outside, or doing activities a lot outside, are exposing themselves more to these climate hazards,” says Brown.

People will move, but exactly where is an open question

Although climate change might not be the reason people give for moving, the number of people who move due to its impacts is underestimated, says Lawrence Huang, climate and migration expert at the Migration Policy Institute. More residents are either choosing to move away from disaster-prone areas or are displaced and then unable to return home. We might see more climate abandonment areas: places that have lost their population because of climate change. Between 2000 and 2020, 3.2 million people moved away from certain areas because of flooding.

Some parts of the country might become more attractive, such as those at higher elevations or with cooler temperatures. While migration isn’t always a bad thing, choosing to leave an area is very different from being displaced. Wealthier people tend to be more able to relocate, and in the longer term to afford homes in areas that are less climate vulnerable, according to Huang. People forced to move after a disaster are more likely to be those who can’t afford homes on higher land or infrastructure that is resilient to weather, says Huang.

Since researchers can’t predict who’s going to live where in 100 years, Huang says we need to prepare infrastructure and services for moving populations. “We need to be looking at schools, health systems, housing, really trying to find ways to make them more resilient and more flexible to movement within the U.S.,” he says. “The U.S. is already a highly mobile country, but climate change can be one reason this mobility becomes increasingly common.”

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