The heat dome that enveloped Washington, D.C. for much of the last week, so miserable it even prompted Metro to temporarily lift its ban on passengers drinking water aboard its trains, also broke a long-standing heat record.
For over five and a half days, the temperature was least 80 degrees in D.C. This 138-hour streak is the longest on record, dating back to 1871, and besting the 128-hour streak of two years ago.
As Jason Samenow of the Capital Weather Gang notes, this record is just the latest in an “astonishingly long list” of heat-related milestones amassed over the past four summers, including: hottest three Julys, hottest three summers, most 100-degree days in a month, and longest uninterrupted stretch above 100 degrees.
Last week’s heat, combined with stifling humidity, also broke multiple records for highest minimum temperature and came close to matching the highest known dew point ever recorded.
D.C.’s warming trend over the past few years is remarkable. Capital Weather Gang found that “daily heat records have outnumbered cold records in the nation’s capital by a 7 to 1 ratio since the year 2000 and by nearly 16 to 1 in the past 3.5 years.”
The nation’s capital was not suffering alone last week. In fact, much of the country was sweltering in above-average heat. On Thursday, at least one location in each of the Lower 48 states hit 90 degrees or higher.
Temperatures in the Northeast were five to ten degrees above normal, with New York City experiencing the highest above-normal temperatures of any place in the country. Unsurprisingly, on Friday, NYC broke its all-time record for energy use.
A study released last year by Dr. James Hansen, one of the world’s foremost global warming researchers, and his colleagues at NASA, examined the recent uptick in heat and drought across the U.S. and identified a single culprit: man-made climate change.
In an op-ed published in the Washington Post, Hansen wrote:
This is not a climate model or a prediction but actual observations of weather events and temperatures that have happened. Our analysis shows that it is no longer enough to say that global warming will increase the likelihood of extreme weather and to repeat the caveat that no individual weather event can be directly linked to climate change. To the contrary, our analysis shows that, for the extreme hot weather of the recent past, there is virtually no explanation other than climate change.
Hansen and his colleagues found that from 1951-1980, extremely hot summers occurred only in 0.1 to 0.2 percent of the globe in a given year. But since 1981, extremely hot summers have baked about ten percent of the earth’s land area annually and in recent years, that percentage has been even higher.
In addition to posing a major threat to the nation’s energy supply and related infrastructure, increasingly common and severe extreme weather events, such as heatwaves, are a serious concern for public health.
Released earlier this year, the government’s draft National Climate Assessment had some stark predictions: Summertime heat waves are projected to become longer and hotter , whereas the trend of decreasing wintertime cold snaps is projected to continue. These changes will directly affect urban public health through increased risk of heat stress, and urban infrastructure through increased risk of disruptions to electric power generation.
Heat stress, a recurrent health problem for urban residents, has been the leading weather-related cause of death in the United States since 1986 when record keeping began. According to the draft assessment, the effects of heat stress are greatest during heat waves lasting several days or more, and heat waves are projected to increase in frequency, duration, and intensity, become more humid and cause a greater number of deaths.