Climate Warming’s Past and Future Trends Diverge in Many US States

August 31, 2022

States where temperatures gained the most in the past, in part due to climate change, won’t necessarily be the ones showing the fastest rates of increase in the future.

Since 1970, some of the greatest increases in mean annual temperature have been in Southwestern states Arizona and New Mexico, and in parts of the Northeast, including Massachusetts, Vermont, and New Jersey.
While these states will show further temperature gains by 2050, their rates of warming will be below the US average, according to Gro’s Climate Risk Navigator for US People and Economy. (Schedule a demo with our sales team to learn more about the Gro Navigator.)
California and Texas especially stand out, warming by 2050 at a pace well below the national average, even as temperatures in these states increased at above average rates in the past.
By contrast, several states with the smallest temperature increases in the past 50 years, such as North and South Dakota, will see faster than average gains in the future.

Gro’s Climate Risk Navigator for US People and Economy, which incorporates temperature projections from the Gro Climate Ensemble Model, allows users to view US climate statistics and projections at the county, state, and national levels, weighted by population, economic activity, and land area, through the end of the century under five climate change scenarios typically used by the Intergovernmental Panel on Climate Change (IPCC). Gro’s parallel application, Climate Risk Navigator for Global People and Economy, provides projections for any location in the world.

This chart from Gro’s Climate Risk Navigator shows projected mean daily high temperatures for the US out to 2100, under two prominent climate change scenarios known as SSP2-4.5 and SSP3-7.0. For individual US states, projected temperature increases vary considerably, and often don’t mirror warming trends seen in the past.

For our analysis, we relied on two IPCC climate projection scenarios — SSP2-4.5, the so-called “middle of the road” warming scenario, and SSP3-7.0, the IPCC’s medium-to-high emissions scenario. Currently, the IPCC's trajectory estimate for global warming falls between these two scenarios. For estimates of increases in mean annual temperatures since 1970, we relied on an analysis by Climate Central.

We estimate that for the US as a whole, the average increase in mean daily high temperature by 2050 will be 1.2°C under SSP2-4.5 and 1.7°C under SSP3-7.0. That follows a gain since 1970 in the average US mean annual temperature of 2.6° Fahrenheit (1.4°C).

View a display in Gro’s Climate Risk Navigator of temperature projections for the US, weighted by land area. (Displays for individual states are linked below.)

Arizona and Massachusetts have both warmed since 1970 by 1.8°C, faster than the US overall. But by 2050, temperatures in both states will increase by 1.0°C under SSP2-4.5 and by 1.4°C under SSP3-7.0, below the national average.
California, where temperatures rose 1.6°C since 1970, will warm at an even slower pace — by 0.9°C under SSP2-4.5 and by 1.2°C under SSP3-7.0.

The temperature differences appear small, often just a fraction of a degree, in part because they represent calculations for an entire state or country, which reduces the impact of localized weather extremes.

Several states that in the past 50 years saw relatively small temperature increases will warm at above average rates by 2050.

Mean daily high temperatures in South Dakota, for example, will increase by 1.4°C under SSP2-4.5 and by 2.0°C under SSP3-7.0. The state’s mean annual temperature rose by 1.0°C since 1970, well below the national average.
Some states along the Mississippi River warmed at below average rates in the past, but by 2050 Iowa’s warming pace will surpass the US average, while Missouri will match the US average.
In the Great Lakes region, Michigan, Wisconsin, and Minnesota weren’t among the past half-century’s fastest warming states, but they nevertheless warmed at above-average rates. Looking out to 2050, these states will continue warming at about the same pace as the US overall.
One outlier: Alaska saw the greatest temperature increase in the past 50 years — up 2.4°C — and will continue to outpace the US average, rising by 2050 by 1.7°C under SSP2-4.5 and by 2.2°C under SSP3-7.0.

Gro’s Climate Ensemble Model combines data from the best climate models around the world to estimate the rate of change in climate conditions under various GHG emissions scenarios between the present time and the next 50 to 100 years.