Washington’s natural summer climate is abysmal. Downtown and the federal government sit a mere few feet above sea level, between two major shallow estuaries (the Chesapeake Bay and the Potomac River) that heat up early in the summer. Those water bodies drive dewpoint temperatures — a very good measure of the total amount of moisture in the air — into the mid-70s. (The dewpoint is the temperature at which moisture will condense if a parcel of air is cooled. The greater the moisture, the higher the dewpoint.) This is where it should be called the don’t point, meaning don’t jog, don’t play softball, and don’t do anything without a jug of Gatorade nearby.

But D.C. also has one of the worst “urban heat island” effects in the nation. The bricks, buildings, and pavement absorb more solar radiation than the long-gone natural vegetation, and their uneven surface impedes the flow of ventilating winds at night. Non-air-conditioned brownstones here would do Hansel and Gretel proud. But most homes, and all commercial buildings, are air conditioned, and the heat that is removed inside goes somewhere — i.e. outside, adding more fuel to the fire.

July 2011 was the hottest month ever recorded here. It should be no surprise that our greener friends, like the London Guardian, immediately blamed global warming. One of my local friends, who works for I‑can’t-tell-you-who, grumbled that “maybe now the politicians will finally listen.”

Climate-related pronouncements like these are really hypotheses posing as truth, and it is easy to check whether this warming is a result of the heat island or something forced by dreaded climate change. One can do this by looking at nearby weather stations whose environs have changed little over time, both in terms of the surrounding ground cover and urbanization. In Figure 1 we compare Washington’s temperature to Woodstock and Dale Enterprise, Va. Woodstock is a small town in the middle of the Shenandoah Valley that has been surrounded by cornstalks since the 19th century. Dale Enterprise is in rolling country that only recently has become a bit suburban as nearby Harrisonburg, Va. expanded. Both are considered very reliable stations by climatologists.

Another interesting comparison is to see how temperature departures from normal in Washington correlate with those in the Northern Hemisphere during the era of global warming putatively from greenhouse gas emissions.

There have been two separate warming periods since 1900. The first was from approximately 1910 through 1945. It is hard to blame that warming on human carbon dioxide emissions because the vast majority of global emissions occurred after World War II. The second warming period began in 1976–1977 with something known as “The Great Pacific Climate Shift” and ended with a gigantic El Nino in 1997–1998. Los Ninos release the tropical Pacific Ocean’s heat to the atmosphere and create temporary spikes in the temperature history. The 1997–1998 one was so great that global temperatures have yet to beat the 1998 record, something that may or may not mean anything about prospective warming in this century. Figure 2 shows a comparison between Washington, D.C. and Northern Hemisphere temperatures since 1977.

Figure 3 offers a scatterplot of D.C. vs. Northern Hemisphere temperatures, and manfully shoots the last of the big fish in this very small barrel. In the figure, “explained variance” is the amount of statistical correspondence between the Northern Hemisphere’s departure from normal and Washington’s. The explained variance of 2.5 percent is statistically indistinguishable from zero for a sample of this many years.

The bottom line is there is just no relationship between Washington’s misery and global warming. Of course, if and when Washington does get with the global temperature program, D.C.‘s summer temperatures will go from their current hell to even hotter.