Talking about climate change in terms of U.S. averages is like saying, 'My head is in the refrigerator, and my feet are in the oven, so overall I'm average.'
Risky Business Project Co-Chair Tom Steyer 9
Our risk assessment begins with the straightforward fact that human-induced climate change leads to rising temperatures.
If we continue along our current path, with no significant efforts to curb climate change, the U.S. will likely see significantly more days above 95°F each year. By the middle of this century, the average American will likely see 26 to 50 days over 95°F each year—from double to more than triple the average number of 95°F days we've seen over the past 30 to 40 years. Climate change impacts only accelerate with time, so that by the end of this century we will likely see 45 to 96 days per year over 95°F. That's between one and a half and three months of the year at what are now considered record hot temperatures. To put this in context, by the end of the century, Oregon, Washington, and Idaho could well have more days above 95°F each year than there are currently in Texas.
These are only the most likely scenarios; there are possible lower and higher estimates outside the most likely range. Within that range, there are also disparities, of course: As the maps that follow demonstrate, some regions of the country will be far harder hit by extreme heat than others, and some will experience rising temperatures in terms of warmer winters rather than unbearable summers.
What matters isn't just the heat, it's the humidity—or, in this case, a dangerous combination of the two. One of the most striking findings in our analysis is that increasing heat and humidity in some parts of the country could lead to outside conditions that are literally unbearable to humans, who must maintain a skin temperature below 95°F in order to effectively cool down and avoid fatal heat stroke. The U.S. has never yet seen a day exceeding this threshold on what we call the “Humid Heat Stroke Index," but if we continue on our current climate path, this will change, with residents in the continental U.S. experiencing 1 such day a year on average by century's end and nearly 17 such days per year by the end of the next century.
Heat is a critical issue for the health of businesses as well as that of human beings. On their own, rising temperatures can have significant negative impacts on health and also labor productivity. But high temperatures are also at the root of several other important climate impacts that have long been recognized by scientists:
- Hotter air on the Earth's surface leads to higher ocean temperatures, which causes ocean expansion and sea level rise;
- Higher temperatures accelerate the rates at which land ice melts, further elevating average sea levels;
- A warmer atmosphere makes extreme precipitation more likely, which is expected to make wet regions even wetter, but could also make dry regions even drier.
Because the U.S. is such a large and geographically diverse country, it will experience every one of these climate impacts in the next century. Even the individual sectors we studied have regional variations: For agriculture, for instance, the national story is one of an industry able to adapt by changing where and what farmers plant; at the same time, the story within particular regions is quite different, as individual farmers potentially abandon traditional crops or move away from the farming business altogether. For the energy industry, the story in the warming North is starkly different than in the increasingly unbearably hot South. Sea levels, too, vary significantly across the U.S., and even across cities along the same coastline: For example, sea level rise at New York will likely be higher than at Boston, and sea level rise at San Diego will likely be higher than at San Francisco.
As in a standard business risk assessment, we looked at the data to see exactly where the greatest risks lie, and confirmed that some regions and economic sectors face extreme and unacceptable risks. These are some of our gravest concerns:
- Rising seas and greater coastal storm damage already threaten the financial value and viability of many properties and infrastructure along the Eastern Seaboard and Gulf Coast. If we stay on our current climate path, some homes and commercial properties with 30-year mortgages in places in Virginia, North Carolina, New Jersey, Alabama, Florida, and Louisiana and elsewhere could quite literally be underwater before the note is paid off.
- Rising temperatures will also reduce labor productivity, as some regions—especially the Southeast and Southwest—become too hot by mid-century for people to work outside during parts of the day.
- Heat will also put strains on our energy system, simultaneously decreasing system efficiency and performance as system operators struggle to cool down facilities, and increasing electricity consumption and costs due to a surge in demand for air conditioning.
- As parts of the nation heat up, the worst health impacts will be felt among the poor—many of whom work or even live outdoors or can't afford air conditioning at home—and among those too elderly or frail to physically withstand the heat or get themselves to air-conditioned facilities.
More than any other factor, our direct economic exposure to climate change will be determined by where we do business. For that reason, we present our findings below in terms of the major regions of the U.S., and then identify how climate change will affect critical sectors within those regions. Still, as any business person knows, these impacts won't be contained within regional boundaries; the ripple effects are likely to resonate throughout the economy. Put another way, just because it's not hot where you are doesn't mean you won't feel the heat of climate change.
Explore the Regions
9 Tom Steyer, video interview for the Risky Business Project, May 14, 2014.