If humanity stays near our current greenhouse gas emissions path, then Americans face hell – every state will be red:

The thermometer in this landmark U.S. government report puts warming at 9 to 11°F over the vast majority of the inland U.S. – and that is only the average around 2090 (compared to 1961-1979 baseline).  On this emissions path, the IPCC’s A2 scenario, most of the inland United States will be warming about 1°F a decade by century’s end.  Worse, we are on pace to exceed the A2 scenario (which is “only” about 850 ppm in 2100):  See U.S. media largely ignores latest warning from climate scientists: “Recent observations confirm … the worst-case IPCC scenario trajectories (or even worse) are being realised” – 1000 ppm.

So this part of my not-so-well-funded analysis appears to hold up well:  “Yes, the science says on our current emissions path we are projected to warm most of U.S. 10 – 15°F by 2100.”

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But I’m getting ahead of the story.  On Tuesday at 1:30 PM, the US Global Change Research Program is releasing its long-awaited analysis of Global Climate Change Impacts in United States with NOAA as lead agency.

But impatient CP readers need look no further than here for the third draft of the report, which has been online since April 27.  That’s where I got the figure above from. [You can see the letters F and T from “DRAFT” stamped across the figure. I’ll update this post with the final figures when they are online.]

How hot will it be?  Here’s another stunning figure from the report:

The average number of days per year when the maximum temperature exceeded 90°F from 1961-1979 (top) and the projected number of days per year above 90°F by the 2080s and 2090s for lower emissions (middle [550 ppm]) and higher emissions (bottom).  Much of the southern United States is projected to have more than twice as many days per year above 90°F by the end of this century.

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Look at Kansas.  By 2090, it’ll be above 90°F some 120 days a year – more than the entire summer. Much of Florida and Texas will be above 90°F for half the year.  These won’t be called heat waves anymore.  It’ll just be the “normal” climate.

Again, this isn’t news to CP readers.  Last July I summarized the very modest U.S. “heat wave” literature as follows (see “When can we expect extremely high surface temperatures?“):

Bottom line: By century’s end, extreme [i.e. peak] temperatures of up to 122°F would threaten most of the central, southern, and western U.S. Even worse, Houston and Washington, DC could experience temperatures exceeding 98°F for some 60 days a year.

So this is truly Hell – to match the High Water: Greenland ice sheet melting faster than expected and could raise East Coast sea levels an extra 20 inches by 2100 – to more than 6 feet.

The time to act is long past.

I will have much more to blog on this essential report this week.

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