How Hot is Hot?

By Michael Rohwer

When I complain about the DC heat to my Austin-bred housemate, he likes to remind me that I, a native Michigander, don’t know what hot really is.

But just the other day, I caught that same housemate saying “it is sweltering in DC.” AHA, it IS hot here, and getting hotter! It would be easier to refrain from saying “I told you so” if I didn’t also have the proof to back it up: EPA’s Climate Change Indicators in the U.S. Report, using data from the National Oceanic and Atmospheric Administration’s National Climatic Data Center, shows the DC region has warmed at a faster rate than all of Texas over the last century.

Since 1901, the average surface temperature across the contiguous 48 states has risen at an average rate of 0.13°F per decade, which means that it gets warmer by 1.3°F per century. But that’s not the whole story. Temperatures haven’t risen at a constant pace over time or in different parts of the country. Average temperatures have risen more quickly since the late 1970s and seven of the top 10 warmest years on record for the contiguous 48 states have occurred since 1990. Some parts of the U.S. experienced more warming than others. The map below shows how quickly temperatures are changing across the country. The map is a darker red in DC (and Michigan) than it is in Texas. This means it is getting hotter faster in those areas than in Austin.

Concentrations of heat-trapping greenhouse gases are increasing in the Earth’s atmosphere. In response, the climate is changing and, among other things, average temperatures at the Earth’s surface are rising. But those changes haven’t happened uniformly, and regional differences are expected to continue with future warming. The North, the West, and Alaska have seen temperatures increase the most, while some parts of the Southeast have experienced little change.  Temperature is a fundamental measurement for describing the climate and the temperature in particular places can have wide-ranging effects on human life and ecosystems. For example, increases in air temperature can lead to more intense heat waves, which can cause illness and death, especially among children and the elderly.

So sure, Texas is still hot, but it’s growing warmer faster here in DC.  Maybe my housemate and I are both right?

How does the map look where you live?

About the author: Michael Rohwer is an ORISE Fellow supporting the communications team in the Climate Change Division within the Office of Air and Radiation. When he’s not pursuing a career in protecting human health and the environment, you can find him enjoying gardening and sports.

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