The Washington Post

Federal climate report predicts spike in hot days for Washington, D.C.

Increase in number of days above 95 degrees by mid-century (2041-2070 compared to 1971-2000) under high emissions scenario (NCA)

The draft National Climate Assessment (NCA) posted Friday afternoon says the punishing, record-setting streak of 11 straight days above 95 D.C. experienced last summer is exactly the kind of event that may occur with increasing regularity in the future.

Link: Effects of climate change will be felt more deeply in decades ahead, draft report says

“Much of the southern portion of [the Northeast], including the majority of Maryland, and Delaware, and southwest West Virginia and New Jersey, are projected to experience more than 15 additional days per year above 95°F [by mid-century],” the draft NCA says.

More hot weather is a common theme in the report, the third in a series that started in the late 1990s.

“The chances of record-breaking high temperature extremes will continue to increase as the climate continues to change,” the NCA executive summary reads.

While the report highlights the prospects for a dramatic increase in oppressive heat, it projects a remarkable decrease in subfreezing overnight low temperatures in the Mid-Atlantic region.

Change in number of nights below 32 degrees by mid-century (2041-2070 compared to 1971-2000) under high emissions scenario (National Climate Assessment, adapted by CWG)

Under a scenario in which greenhouse gases continue to rapidly increase, the number of days when low temperatures drop below 32 degrees decreases by more than 20 between today’s climate and mid-century. That’s about a 25 percent reduction.

Overall, in the Northeast, the average warming projected by 2080 ranges from 3 to 10 degrees and 2 to 6 degrees for the Southeast (by 2100). (Warming projections and their impacts for the Washington, D.C. region overlap two chapters in the NCA - the Northeast and Southeast.).

For the U.S. as a whole, the average warming projected by 2100 ranges from 3 to 10 degrees F, depending on greenhouse gas emissions scenario (and the climate’s response to greenhouse gases, the so-called climate sensitivity).

Link: Report: We’re on pace to heat the U.S. by 10°F

The lengthy report also provides precipitation and sea level rise projections while discussing the impacts of climate change on the various U.S. regions, economic sectors, human health and ecosystems. Over 240 authors contributed to the report’s 30 chapters.

White House science advisor John Holdren and NOAA administrator Jane Lubchenco say the report is intended to assist Americans “who need information about climate change in order to thrive—from farmers deciding which crops to grow, to city planners deciding the diameter of new storm sewers they are replacing, to electric utilities and regulators pondering how to protect the power grid.”

Reactions to the draft report, thus far, have been predictable.

Carol Browner, a former Obama Administration official who now works at the Center for American Progress - which advocates for stronger climate policies, said the report is a call for action to reduce greenhouse gas emissions:

“The draft climate assessment released today confirms what the science says and what our eyes are telling us: It’s getting hotter, and that carbon pollution is driving climate change, fueling more violent and frequent weather events and threatening public health,” Browner said in statement. “The time to act is now.”

Georgia Tech atmospheric scientist Judith Curry, who frequently stresses the need for qualifying climate projections, blogged that the report needs to more comprehensively communicate uncertainty.

“I am very concerned that the highly confident story being told here has enormous potential to mislead decision makers,” she wrote.

Roger Pielke Jr., an environmental studies professor at the University of Colorado, who has criticized past federal and international assessments for - in his view - overselling connections between climate change and extreme weather, also found flaws in this report’s characterization of these links. He called them “selective” and “incomplete”.

“Good thing it is a draft, but still poor form,” Pielke Jr. tweeted

Pielke Jr. and others have the benefit of a 90-day public comment period - which opens today - to express their concerns/complements.

Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.


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