A State-by-State Climate Map

If those New England seasons feel far warmer these days than they were 20 years ago, it’s because they are. So are Florida’s, Arizona’s, and Washington State’s.

A new interactive map released by the group Climate Central summarizes the average temperatures of each of the 48 contiguous United States for the last 100 years. By clicking across the country (try it on the map above), you can see that lately, temperatures have been trending up no matter where you live.

But if you look closely, the story is more complicated than a general upswing in temperatures. Some states are warming more quickly than others. And the rate at which they’re warming depends on what time span you’re looking at.

Trends in climate depend on scales both global and temporal, said Claudia Tebaldi, a climate scientist at Climate Central and the report’s main author. “We are trying to show that at the local level, there might be effects that slowed down or put on hold warming for a while, but the big picture is one of warming,” she said.

The report, which relied on data from the National Climate Data Center, illustrates warming trends over two time spans, 1912 to 2011 and 1970 to 2011.

You might notice that in the 100-year time span, states had average temperature increases per decade that were generally lower than over the shorter time span. Three states – Arkansas, Georgia and Alabama – even show an overall decreasing trend in average temperature per decade. These states sit in what is sometimes referred to as the “warming hole,” a section of the Southeast that has warmed more slowly than most other parts of the country.

Some scientists posit that the warming hole could be explained by air pollution that rose in the postwar industrial boom, said J. Marshall Shepherd, director of the Atmospheric Sciences program at the University of Georgia and president-elect of the American Meteorological Society. The particulate pollution in the air reflects sunlight back into space before it has a chance to warm the atmosphere.

Another theory is that Southeastern tree-planting efforts (afforestation) in the mid-1900s may have slowed warming there by absorbing carbon dioxide, Dr. Shepherd said. Whatever once kept those states cooler, though, has apparently quit working, and “the Southeast is now warming with the rest of the world,” he said.

The second, shorter time span in the report, 1970 to 2011, shows exacerbated warming across the country. Starting in the 70s, the country’s temperatures began to ramp up more quickly than before. Some researchers have paradoxically suggested that this could be due to the enforcement of the Clean Air Act, when government rules resulted in a decline in pollutant particles, allowing more of the sun’s heat to penetrate the atmosphere, Dr. Tebaldi said.

You might also notice that several Southwestern, Great Lakes and Northeastern states have warmed much more quickly than the rest of the country, both over the century-long time range and over the last 40 years. Dr. Shepherd said this might be due to shifts in atmospheric circulation patterns caused by the warming itself. Weather that usually sits over the Southwest was pushed further north, causing less precipitation and cloud cover in that region and more heat, said Dr. Shepherd.

Yet it’s less obvious why the Great Lakes region and New England are heating up more intensely than the rest of the country. “If you look at global warming patterns in general, as you go from the equator to the poles, warming becomes more intense,” Dr. Shepherd said. Yet the northern United States isn’t typically thought of as being close enough to the North Pole to experience this effect. “This is clearly one of those areas where more research is needed,” he said.

The report shows that despite regional variability, the nation is overwhelmingly warming, Dr. Tebaldi said.

Her hope is that people will explore the data behind the climate trends they may have experienced at home and compare it with trends elsewhere across the United States.

 

 

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