Absent a time machine, it’s hard to truly wrap your head around what the future climate will be like. Climate projection numbers carry a lot of information, but those numbers can seem abstract—what does 2.5º warmer actually feel like?

One way to understand that information is to hop in the car (even if it’s not a DeLorean). There are a huge variety of local climates around the world, and it’s possible to find a location today that ought to feel a lot like your hometown will in a few decades. A new study by Matt Fitzpatrick and Rob Dunn applies this “climate analog” approach to 540 cities in the US and Canada—which means about 250 million people can use a Web map to look for an analog to their future climate.

Present and future climates

There are multiple ways you could imagine defining such a comparison. In this case, the researchers broke the data down by season, calculating minimum/maximum temperatures and total precipitation averaged over 1960-1990. This is basically the seasonal weather you’re used to.

To see what future climate change is expected to bring, the researchers averaged the results of 27 different climate models. For each point around North and Central America, they calculated seasonal temperatures and precipitation for 2070-2099. This was done for two scenarios of future greenhouse gas emissions—a high-emissions scenario where nothing is done to reduce emissions and a middle-emissions scenario that would halt warming a couple degrees Celsius sooner.

For each present-day city, the researchers then analyzed the models for a point where the future climate variables were a close match. For the purposes of the Web map, they pick the closest possible match, even if it fails to meet their statistical threshold for good analogs. (There is an option to show degree of similarity on the map.)

In general, a warming climate means you have to head south to find your climate analog. Portland, Maine, for example, would have a climate similar to Baltimore by the 2080s without emissions reductions—considerably warmer and wetter than what Mainers are accustomed to. Beyond human expectations of the weather, you can think about how the climate-adapted ecosystems in these two areas differ.

Going the distance

There are additional factors to consider, though, like elevation. High-elevation cities can find their warmer future analog simply by coming down closer to sea level. As a result, the match for some cities can even be to their north. And of course, comparisons are otherwise constrained by what exists south of you. Coastal cities in Florida, for example, have no real choice but to jump the Gulf to Central America, which may not contain a great comparison.

Overall, the average analog in the middle-emissions scenario ends up over 500 kilometers (over 300 miles) away—a number that grows to 850 kilometers (530 miles) at higher emissions. Cities in the Northeast generally have to look toward the southern Midwest and more humid Southeast to find analog climates, while cities in the West have to look toward the drier Southwest.

In the middle-emissions scenario, most cities have a close analog that passes the statistical threshold. The exception is the coastal West and Southeast, which has a harder time. But in the high-emissions scenario, only 17 percent of cities can find a truly close match. The change in climate is too large to easily find anything similar, so you have to relax your standards and settle for whatever's closest.

The other way to look at this, as the researchers put it, is that “if we continue on our current trajectory, the climate of many urban areas could become unlike anything present within the study domain, whereas keeping warming within the 1.5°C goal set by the Paris Agreement could reduce the exposure of urban areas to climate novelty.”

Washington, DC, for example, can find its future analog in Paragould, Arkansas for a middle-emissions scenario. But if we don’t reduce our emissions, the closest analog (a poorer match) is in Greenwood, Mississippi. So any denizens of the District who like the South's climate have a choice: they can move there now, or they can stay put for a few decades and let the climate come to them.

Open Access at Nature Communications, 2019. DOI: 10.1038/s41467-019-08540-3(About DOIs).