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Superstorm Sandy, which made landfall on the East Coast a month ago yesterday, wasn’t a particularly powerful storm. But what it did have was water—lots of it. Sandy pushed record storm surges in places like lower Manhattan, and it was the flooding triggered by those surges—much more than the winds accompanying the storm—that caused the tens of billions of dollars in damages attributed to the Superstorm.

But our coastlines were already primed for those kinds of catastrophic floods, thanks in part to the gradual rise in sea level over the past century caused chiefly by man-made global warming. Sea levels have risen by about half a foot over the past century—and are likely rising even faster along the U.S. Northeastern coast—which amplified the effects of Sandy’s storm surges. That’s why scientists are so worried about the impacts that climate change to come may have on sea levels. The higher the seas rise, the more devastating coastal storms will become.

Unfortunately, trying to predict how rapidly the seas will rise as the climate warms is extremely difficult. We know that as ocean temperatures increase—which goes hand in hand with global warming—water expands and sea levels rise. But the big X factor is the polar ice sheets chiefly found in Greenland and Antarctica. As that massive land ice melts, the water flows directly into the seas, causing the water to rise. By contrast, sea ice melting—which has been occurring at a record pace in the Arctic this summer—does not raise the sea levels, just as the melting of an ice cube in a glass of scotch doesn’t raise the overall level of liquid.

In a new paper published in the November 29 Science, a team of researchers have gone through all of those estimates and come to a broadly agreed conclusion. The new analysis means that polar ice sheets are melting three times faster today than they did in the 1990s, with much of the ice loss happening in Greenland. Most of that melting appears to be happening to the Greenland ice sheet, which holds nearly 700,000 cu. miles of ice, although the even more massive Antarctic ice sheet is melting as well.

In the 1990s, the two ice sheets combined on average to lose 110 billion tons of ice a year. That sounds like a lot—actually, that is a lot—but keep in mind that it takes about 10 trillion tons of ice melting to raise sea levels by an inch. But that rate increased to 379 billion tons a year between 2005 and 2010—and the Science paper doesn’t include information from 2012, when the Greenland ice sheet experienced a record thaw.

Of course, what the data doesn’t tell us is what we should actually be doing about ice-sheet melting, sea-level rise and climate change. But we shouldn’t kid ourselves that there won’t be major costs if we fail to slow the pace of warming—and that we’ll eventually have to pay the bill. Sandy helped teach us that.Much more, including facts and figures, at http://science.time.com/2012/11/30/climate-change-polar-ice-sheets-mel
ting-faster-raising-sea-levels/]
For just a bit of perspective, Arctic Sea Ice Larger Than U.S. Melted This Year alone. ( http://science.time.com/2012/11/28/arctic-sea-ice-larger-than-u-s-melt
ed-this-year/

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Dryland Farmers Work Wonders without Water in U.S. West

A generation of extremely efficient farmers increasingly sees irrigation as a non-viable alternative while mulling over a switch from water-intense cotton and wheat to rain-fed sorghum and grains

In the long rain shadow of the Cascade Mountains, where dryland wheat farmers have eked out livings for more than a century, climate change is very much an issue of the present.

The rain gauge is always in the back of the mind for Mike Nichols, a wheat farmer cultivating 20,0000 acres across two counties in south-central Washington state.

It has to be: Nichols doesn't irrigate, and with less than six inches of precipitation a year, his wheat crop is already on the edge of what's considered possible for dryland farming. When drought hits or if, as expected, the West gets drier, his operation will be in trouble.

"The last eight years have been pretty good," said Nichols. "But we are putting some [cash] aside, because down the line we know we're going to go through another drought."

Although Nichols remains stoic about the potential that climate change could eventually have on his livelihood, his innovative dryland farming methods enable his crops to better handle low moisture conditions.

But there are legions of farmers in the West and Midwest dependent on dwindling aquifers and over-subscribed rivers for irrigation. If today's drought conditions continue, a whole new generation of growers may join Nichols and return to wholly rain-fed farming.

To cope with Washington's aridity, Nichols crops on a rotating two-year period, leaving half his fields remaining fallow at any given time. Partly as a result, Nichols currently averages 18 bushels an acre. The average in Washington – where most wheat farms are dryland – is closer to 53 bushels per acre.

Nichols and others like him continue to wring profits from their yields through the practice of extremely efficient farming, using no-tillage methods to preserve moisture and soil, while leaving at least half the ground fallow at any given time.

Such dryland farming practices represent an ever-evolving science; albeit, one that the rest of the country may increasingly heed.

Irrigation is increasingly seen as a non-viable alternative in many areas. In Washington state, farmers tapping into the depleted Odessa aquifer may be forced into dryland agriculture to survive. Unless these farmers get permission to recharge such aquifers with waters from the Columbia River, in a decade's time the Odessa is projected to dry up.

Aquifer depletion is also affecting the southern Great Plains and West Texas.

With lower water levels in the Ogallala Aquifer, West Texas cotton farmers are already switching from irrigation to dryland cropping, which could cut their yields by at least half – from about 600 pounds to 300 pounds of cotton per acre.

Dryland farmers save money on irrigation, But other production costs remain about the same even as yields drop, said Jerry Hatfield, laboratory director at the USDA's National Lab for Agriculture and the Environment in Ames, Iowa. That means an economic hit for growers turning from irrigated to dryland agriculture.

But many farmers don't have a choice. Some 12 million acres are already under such cultivation in the western U.S. alone, a number set to rise in the near future.

Part of that is water management: Atop the Ogallala aquifer in Texas and eastern Kansas, some groundwater levels have dropped so much that it's cost prohibitive to pump water to irrigate crops, said Brian Fuchs, a climatologist at the National Drought Mitigation Center at the University of Nebraska at Lincoln.

Farmers there are switching back to traditional crops, like sorghum and wheat more suited to a semi-arid environment.

But part of the transition is due to a changing climate, scientists say.

Arizona has been in a drought since the mid-1990s. Farmers around Phoenix, which averages only 8 inches of rainfall a year, continue to produce some of the country's highest-yielding cotton by flooding their fields with water from a huge local reservoir system. Nancy Selover, Arizona's state climatologist in Tempe, says that climate change is already eating into mountainous snow packs needed to replenish water reservoirs and aquifers during the state's long hot summers.Much more at http://www.scientificamerican.com/article.cfm?id=dryland-farmers-work-
wonders-without-water-us-west

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