Rainfall impacts of climate warming to persist

Simulation showed temperature falling decades after CO {-2}’s decline

Canada and Russia would receive more rain and snow

Impacts of manmade greenhouse warming on rainfall would endure long after temperatures fell, a study suggests.

The U.K. Met Office scientists constructed a hypothetical future in which carbon dioxide levels rise and then fall, and modelled what might happen to rainfall.

Their computer simulation showed temperature falling decades after CO {-2}’s decline, with changed rainfall going on for several more decades after that.

The study is published in the journal Geophysical Research Letters.

Hypothetical future

The hypothetical future saw concentrations of carbon dioxide in the atmosphere rising to four times pre-industrial levels over 70 years, then returning to the baseline over a similar period.

“This is an idealised situation,” said Vicky Pope, head of climate change advice at the Met Office.

“On the other hand, we could reach atmospheric concentrations of greeenhouse gases equivalent to a quadrupling of CO {-2} by the end of the century.

“So if we allow emissions to increase to the end of the century and then decrease them rapidly, this is the kind of thing you’d expect to see,” she told BBC News.

The computer simulation also suggested that if greenhouse gas levels remained elevated for an extended period, the rainfall changes would then endure for longer after emissions began to decline.

‘Basic physics’

Rainfall changes arise largely through increased temperatures in the ocean.

Evaporation

More water evaporates into the atmosphere. Overall, this means the world would receive more rain — but computer simulations suggest the impacts would be very unevenly distributed.

High latitude countries such as Canada and Russia would receive more rain and snow, whereas other regions such as the Amazon basin, Australia and parts of sub-Saharan Africa would receive substantially less.

Manmade greenhouse effect

As the oceans have huge capacity to store heat, releasing the heat relating to a temporary quadrupling of the manmade greenhouse effect would take many decades.

The Met Office computer model is known to project more drying of the Amazon than most others.

“Details of exactly where the impacts fall would be different in different models because they don’t agree in details,” said Dr Pope.

“But the mechanism is the same in all models, because it’s basic physics. As models improve, we’ll be able to get more confident on this.” — © BBC News/Distributed by the New York Times Syndicate

Richard Black – From THE HINDU

Climate Change Hits the Oceans

When scientists say the planet is warming, they usually point to rising air temperatures as proof. That’s reasonable enough, especially since the warmth of the air temperature affects us directly so we feel the change the scientists are measuring. But it’s also misleading: while the lower atmosphere has been gradually warming over the past 50 years, it happens unevenly, rising sharply for a year or two or even ten, then flattening out. That stutterstep pattern is due to relatively short-lived effects on top of the general warming – an El Nino current in the Pacific making things warmer, for example, or a volcanic eruption like 1991’s Mt. Pinatubo producing a cloud of dust that makes things cooler. Over time, these cancel out, but it can be tempting – though incorrect – to think a temporary flattening means global warming has stopped.

To get a measure of what’s truly going on, scientists look to the oceans – slow to heat up, slow to cool down, and thus less prone to short-term variations. Indeed, says John Lyman an oceanographer at the University of Hawaii, “about 80 or 90 percent of the extra heat absorbed by the planet is absorbed into the oceans.” That being the case, Lyman and several colleagues set about trying to see how the ocean’s heat content has changed over the past couple of decades. The result, appearing in the current issue of Nature, will give little comfort to climate change deniers: the oceans have been warming inexorably since at least 1993, at a rate broadly consistent with what you’d expect from the buildup of greenhouse gases. (See a photo gallery of climate change in Europe.)

There are some uncertainties in the numbers – not surprising, since the new study is essentially a synthesis of earlier papers, done by different groups using different instruments and making different sorts of measurements. “There’s a large amount of error in the data,” admits co-author Josh Willis, of NASA’s Jet Propulsion Laboratory, in Pasadena. “But the signal of global warming is abut six times larger than any uncertainties.” In particular, the so-called “global cooling” climate skeptics claim has been going on since 1998 doesn’t show up. “If you look at our data since 1998,” says Lyman, “it’s warmed significantly.”

The curve does flatten somewhat in 2003 – but that may have to do with things going on in the deep ocean. The sensors involved in the latest research go down only to about 2,300 ft., roughly half the average depth of the world’s oceans. The upper and lower ocean exchange heat just as the ocean and atmosphere do, and nobody really knows what’s happening near the bottom. Less than two months ago, in fact, Kevin Trenberth and John Fasullo, both climatologists at the National Center for Atmospheric Research, in Boulder, Colorado, published a paper in Nature suggesting that some of the extra heat trapped by greenhouse gases has gone missing – and that it might well be hiding in the deep oceans. Part of the problem, Trenberth suggested, was the same sort of incomplete measurements and inconsistencies in data processing Willis and Lyman describe in their own study. (See a special on December 2009’s COP15 Climate-Change Conference.)

Incomplete though the numbers are, however, the results seem reasonably robust – and they’re corroborated by another, entirely different set of measurements. As the oceans warm, they expand; indeed, up to half of sea-level rise comes not from melting glaciers or disappearing ice caps, but from the physical expansion of seawater as it heats up. And like the ocean’s heat content, the rise in sea level is gradual enough that over time, the year-to-year or even decade-long ups and downs disappear into a steady, long-term increase. “A century ago,” says Willis, “sea level was rising at about one millimeter per year. Fifty years ago it was two. And now it’s rising at three millimeters per year.”

In short, the oceans are currently doing the heavy lifting in absorbing trapped heat. Ultimately, though, some of that heat will be transferred back to the air, continuing to warm the places we live even if we manage to stop generating greenhouse gases at such a great rate. That makes it crucial to understand exactly what’s going on offshore. If scientists can refine their measurements, writes Trenberth in a commentary on this week’s Nature paper, “ocean heat content is likely to become a key indicator of climate change.” That key, in turn, may be one more tool to help slow the damage.

From Yahoo

Warmest Temperature recorded in JUNE 2009

Ocean surface temperatures around the world were the warmest on record for the month of June, according to federal scientists, though they caution that one month doesn’t necessarily imply global warming.

The warmer temperatures do confirm that an ocean phenomenon known as El Nino is building in the Pacific Ocean.

Junes record ocean warmth worries fishermen, environmentalists

June's record ocean warmth worries fishermen, environmentalists

Some scientists think the rising temperatures hint at broader changes, perhaps resulting from global climate change. Environmentalists and fishermen are wary of what it may mean.

“It’s really kind of disturbing,” said Zeke Grader, the executive director of the Pacific Coast Federation of Fishermen’s Associations, based in San Francisco. “What we’ve seen right offshore here is a real variation in temperature. But we don’t know what to expect in the future.”

So far, the year has been among the warmest on record for ocean temperatures, ranking sixth based on January through June. The June temperature averaged 62.56 degrees Fahrenheit; the 20th-century average was 61.5 degrees. The National Oceanic and Atmospheric Administration has been keeping the records since 1880.

“The high ocean temperatures can threaten coral reefs, provide more energy to hurricanes, cause thermal expansion, which would raise sea level and inundate coasts, force the relocation of some aquatic species and thus impact fisheries,” said Ahira Sanchez-Lugo, a climate scientist with NOAA.

The hottest spots were the north Pacific south of Alaska, along the U.S. West Coast and the Atlantic Ocean off New England. Overall, the Pacific was the warmest. The measurements were taken for every 5 degrees of latitude, however, and an overall temperature for each ocean wasn’t calculated, said Deke Arndt, a climate scientist with NOAA in Ashville, N.C.

“Individually, no single month can be attributed to long-term global warming,” Arndt said, though he added that this June marked the 33rd consecutive June with a temperature above the 20th-century average, which may provide an indication of global warming.

In addition to having the warmest waters, this June saw the second warmest combined ocean and land temperature on record, 61.02 degrees, which was more than a degree above the 20th-century average of 59.9.

Though some climatologists dismiss the June heat as an anomaly, others say it’s part of a traditional El Nino pattern. Occurring roughly every three to eight years, El Nino is a warming of water in the eastern Pacific Ocean, which can disrupt usual weather patterns. During an El Nino year, the Southwest United States tends to be wetter, the Northwest drier and there’s an increased chance of severe weather, such as hurricanes, in the Southern United States.

“Current conditions and trends, as well as the majority of dynamic climate models, are suggesting that (El Nino) will indeed occur,” said Karsten Shein, another climate scientist with NOAA.

Grader said fishermen were worried about their catches, and he, for one, thinks that it isn’t just El Nino that’s causing the higher ocean temperatures.

“Colder water fish will go north,” he said. “It’ll affect phytoplankton and krill production. You’ll see salmon getting smaller.”

Other fishermen aren’t as concerned.

“We’ve fished El Ninos before,” said Larry Collins, 52, a commercial fisherman based at Fishermen’s Wharf in San Francisco. “There’s good and bad things about El Ninos for the California coast. Nature will throw you a curveball.”

From KansasCity