Weatherdem's Weblog

Bridging climate science, citizens, and policy

Current & Future U.S. Heat Waves

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A substantial portion of the U.S. population experienced a heat wave during the past week.  Due to the number of people affected, the media spent some time on the topic.  As opposed to places like Las Vegas or Phoenix, where the “heat is supposed to happen”, folks normally accustomed to rather pleasant summer conditions experienced real heat again.  Heat waves of various intensity happen every year.  This  heat wave is rather intense – it is breaking some heat records.  Some interesting factoids:

Temperatures at Newark Liberty Airport in New Jersey were recorded at 98 degrees at 1 p.m. local time on Friday, as the mercury hit 93 in Central Park. John F. Kennedy Airport in Queens, New York, recorded temperatures of 100 degrees on Thursday, beating out the previous record set for that date a year ago, and on Friday the heat index there reached 108.

Electricity usage soared to an all-time high in New York City as the work week closed out, provider Con Edison announced, as service hit a peak of 13,214 megawatts around 2 p.m. local time. The previous record was 13,189 megawatts on July 22, 2011, according to the company.

So, some serious heat and serious energy consumption.  The latter proves interesting to look at in more detail: if warming trends continue, power plants will be unable to operate like we expect them to due to water and infrastructure cooling requirements.  That spells trouble for people: the worst heat waves of the future might be accompanied by temporary brownouts and blackouts.  How manageable will heat waves be with no A/C?

What about the warming trend?  If we stay on our current greenhouse gas emissions pathway (the highest considered by climate models), look at the potential number of weeks with 100°F+ temperatures in 2090-2099:

 photo A1FI-warming.gif

Figure 1. Projection of A1FI emissions pathway-derived number of weeks (2090-2099) per with daily maximum temperatures exceeding 100°F.

With this heat wave fresh in mind, imagine what it will be like later this century when there is more than one excessive heat wave per year in the Midwest and along the east coast.  Instead of five days of misery, what will 25 days be like?  How about 50 days of 100°F heat in Virginia, North Carolina, Kentucky, Illinois, Iowa, and Nebraska?  When 100°F daytime heat dominates one, two, or even three months every year and high nighttime temperatures accompany it, this week’s heat wave will seem refreshing by contrast.

That’s how we feel in Denver, CO this year.  Instead of 73 total 90°F+ days – 13 of those days at 100°F+ – in 2012 (with June 2012 7.6°F warmer than normal), summer 2013 has been closer to average.  Yes, it’s been warm and only one 100°F day occurred so far this year, but it feels almost pleasant in comparison to last summer when the heat was relentless for months on end.

Three days of excessive heat is difficult to experience.  Three months is currently unimaginable.  How much worse future heat waves get is mostly within our control.  The sooner we significantly cut greenhouse gas emissions, the better things will end up for all of us.  But as the above graph demonstrates, the future could be quite hot if we continue along our current emissions pathway too much longer.

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