Extreme cold weather in Atlanta, Ga., on Jan. 3, 2018. AP Photo/David Goldman
Climate change is increasing the frequency and strength of some types of extreme weather in the United States, particularly heat waves. Last summer the U.S. Southwest experienced life-threatening heat waves, which are especially dangerous for elderly people and other vulnerable populations.
More recently, record-setting cold temperatures engulfed much of the country during the first week of 2018. This arctic blast has been blamed for dozens of deaths. Some scientists believe that Arctic warming may be a factor in this type of persistent cold spell, although others question this connection.
In a recent working paper, we studied the effect of temperature extremes on elderly mortality, using comprehensive data from Medicare covering about 35 million beneficiaries. Analyzing daily patterns at the ZIP code level, we estimated how daily temperature changes affect elderly mortality as a way to predict how people may adapt to climate change.
Our key finding is that both heat waves and cold snaps increase mortality rates.
For example, the mortality rate from a day with average temperatures between 90 and 95 degrees Fahrenheit is higher by about 1 death per 100,000 individuals than a day with an average temperature between 65 and 70 degrees. Deaths also increase, by about one-half per 100,000 individuals, on days when the average temperature is less than 20 degrees.
People and communities have many options for adapting to climate change. They can install air conditioning, or change the urban environment – for example, by planting trees to cool city streets. They may improve readiness at health care facilities, or modify public health strategies – for example, by raising public awareness of risks associated with extreme weather.
As regions adapt, one might suspect that hot places like Miami deal well with heat but struggle with cold, while cold places like Fargo, North Dakota, are ready for deep freezes but less prepared for heat waves. This is exactly the pattern we found when we separately analyzed the hottest, middle, and coldest thirds of all U.S. ZIP codes.
In hot places like Miami, cold days have a very large impact on mortality, while the impact of hot days is smaller. In contrast, hot days in Fargo have a very large impact on mortality, but an additional cold day has little effect. In fact, the effect of the hottest days (90 degrees or higher) in the coldest places is about two to three times larger than the effect of the coldest days (less than 20 degrees) in the hottest places.
Next we considered how people and communities may adapt as climate change intensifies. We used predictions of temperatures in 2080-2100 from a set of climate models called the Coupled Model Intercomparison Project Phase 5, which uses 21 different climate models and assumes that global carbon emissions continue to rise through the end of the century.
Using these projections, we predicted how many extra deaths would be caused by temperature extremes across our hot, moderate and cold zones under three different assumptions.