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Archive for May, 2014

Here Comes the Flood

Friday, May 23rd, 2014

Noah (cropped) Tony Harrison @ Flickr

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National Assessment Finds Climate Change “Has Moved Firmly into the Present”

The effects of human-induced climate change are being felt in every corner of the United States. . . . If greenhouse gases like carbon dioxide and methane continue to escalate at a rapid pace, [scientists] said, the warming could conceivably exceed 10 degrees by the end of this century.

—“U.S. Climate Has Already Changed, Study Finds, Citing Heat and Floods,” New York Times (5/7/14)

Melting of West Antarctic Ice Sheet “Has Passed Point of No Return”

Scientists say that the melting will continue as long as the heat-trapping carbon dioxide in the atmosphere increases. Even if carbon dioxide and temperatures stabilize, the melting and shifting of glaciers will continue for decades or centuries as they adjust to the new equilibrium.

—“The Big Melt Accelerates,” New York Times (5/20/14)

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Two major reports released in recent weeks state emphatically that dramatic changes in climate are under way in the United States and globally, with a 10-degree average temperature rise in the U.S. possible by 2100, and world sea levels likely to rise by 4 to 12 feet or more by the end of the century. Perhaps most ominous of all, according to papers published last week in Science and Geophysical Research Letters, the melting of the West Antarctic Ice Sheet has already “passed a point of no return,” which will lead to alarming sea level rises that will imperil—or render uninhabitable—coastal and low-lying cities around the planet: New Orleans, New York, Miami, Boston, Venice, Shanghai, Mumbai . . .

A good summary by NASA of the Science and Geophysical Research Letters papers’ findings, along with an explanatory video, can be found here.

 


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More Intense, Frequent Extreme Weather Projected for U.S.

The National Climate Assessment, released by the White House on May 6, was conducted by a team of more than 300 experts guided by a 60-member Federal Advisory Committee and reviewed by the National Academy of Sciences. Among the Assessment’s many noteworthy findings: “The intensity, frequency, and duration of North Atlantic hurricanes, as well as the frequency of the strongest hurricanes, have all increased since the early 1980s. Hurricane intensity and rainfall are projected to increase as the climate continues to warm.”

SalonThe Assessment also projects increases in extreme weather generally, both in intensity and frequency: heat waves, droughts, wildfires, along with (in other places) excessive rainfall, flooding, tornadoes “and other severe thunderstorm phenomena,” etc.:

The number of extremely hot days is projected to continue to increase over much of the United States, especially by late century. Summer temperatures are projected to continue rising, and a reduction of soil moisture, which exacerbates heat waves, is projected for much of the western and central U.S. in summer.

In a good summary of 12 points the Obama administration wants the American public to understand from the Climate Assessment, Grist.org includes one point (among others) that this blog takes very seriously: “Infrastructure is being damaged by sea level rise, heavy downpours, and extreme heat; damages are projected to increase with continued climate change.” (See Further Reading below.)

The Climate Assessment’s findings on sea level rise make for chilling reading:

The oceans are absorbing over 90% of the increased atmospheric heat associated with emissions from human activity. Like mercury in a thermometer, water expands as it warms up (this is referred to as “thermal expansion”) causing sea levels to rise. Melting of glaciers and ice sheets is also contributing to sea level rise at increasing rates.

Recent projections show that for even the lowest emissions scenarios, thermal expansion of ocean waters and the melting of small mountain glaciers will result in 11 inches of sea level rise by 2100, even without any contribution from the ice sheets in Greenland and Antarctica. This suggests that about 1 foot of global sea level rise by 2100 is probably a realistic low end. On the high end, recent work suggests that 4 feet is plausible. . . .  some decision makers may wish to use a wider range of scenarios, from 8 inches to 6.6 feet by 2100.

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