http://4.bp.blogspot.com/_D9-JNTtRKgs/S4vWQB3OjdI/AAAAAAAAAfo/s_H8YtRL_Sw/s400/Picture+688.pngNumber of days annually over 100F in the recent past, and under high emissions in 2080-2099 according to p90 of Global Climate Change Impacts in the United States
So, I ended up spending much of my weekend going through Global Climate Change Impacts in the United States, and I have to say I'm pretty gutted by the experience. I'm just amazed that I didn't know about this report, despite regularly reading the NYT and a variety of progressive and moderate-conservative blogs at the time it was issued. Realclimate never mentioned it. Grist covered it, and the NYT did in fact mention it, but the NYT story has a flavor of "the government released a big long boring report with nothing new in it" and Grist mostly posts a long video of the press conference with little clue as to why you should watch it. And neither coverage item, had I seen them, would have given me the slighest clue at how dynamite some of the contents are once I started reading and thinking for myself. I think this report should be far higher profile in the public discourse than it is. In fact, every citizen ought to read it.
Let me try to go through a few of the things that seemed particularly significant to me. At some abstract level, I knew most of this stuff, but the maps and charts in here really made the scale of the problem much more clear to me.
EDIT
Hmmm. But, obviously, these places are deserts now not just because it's hot, but because it's dry, right? If it was this hot but wet, it would be a jungle, not a desert. True enough. Here's annual precipitation in the United States (from here).
http://4.bp.blogspot.com/_D9-JNTtRKgs/S4vgVQx96_I/AAAAAAAAAgI/IBU92NM1dDM/s400/Picture+697.pngIndeed, you can see that the Sonora/Mojave deserts are places that get less than 10 inches of rain each year. Of course, there's a lot of the west that's similarly dry, or only a little bit wetter. Ok, so what's going to happen to US precipitation under high emissions? Now we turn to p31 of the report:
http://4.bp.blogspot.com/_D9-JNTtRKgs/S4viUBf-wGI/AAAAAAAAAgQ/Y7oc5V__DY8/s400/Picture+698.pngSo basically, in the winter, the northern half of the country gets more rain/snow, while the southern half gets less rain. But in the summer, the whole country will get less rain, and in the case of the Pacific Northwest and the Southeast, a lot less rain.
So, roughly, summers are going to be completely hellish to be outside throughout a lot of the country - comparable to conditions in the Sonora/Mojave deserts now. The desert areas of the southwest are going to undergo a major expansion in all directions, the dry-mediterranean climate of Northern California is going to push up into Oregon and Washington, while California itself increasingly desertifies, the southeast is going to get much dryer and hotter, etc, etc. I think it should be obvious that under these circumstances, just about every landscape in the country is going to change radically. For those of us who like to get out and hike/bike/kayak, there's just about no place you might love that isn't going to undergo massive wrenching change. For example, on p81, we see the Eastern half of the country, under a mid range warming scenario (so on the present trajectory, it's likely worse than this):
http://3.bp.blogspot.com/_D9-JNTtRKgs/S4vlIvbT0VI/AAAAAAAAAgY/_IVVREtktXQ/s400/Picture+699.pngEDIT
http://earlywarn.blogspot.com/2010/03/us-in-high-emissions-scenario.html