[Note: part of the answer is in the photo they provide with the press release below, but they don’t see it. – Anthony]
Greenland melting due equally to global warming, natural variations
The rapid melting of Greenland glaciers is captured in the documentary “Chasing Ice.” The retreat of the ice edge from one year to the next sends more water into the sea.
Now University of Washington atmospheric scientists have estimated that up to half of the recent warming in Greenland and surrounding areas may be due to climate variations that originate in the tropical Pacific and are not connected with the overall warming of the planet. Still, at least half the warming remains attributable to global warming caused by rising carbon dioxide emissions. The paper is published May 8 in Nature.
Greenland and parts of neighboring Canada have experienced some of the most extreme warming since 1979, at a rate of about 1 degree Celsius per decade, or several times the global average.
“We need to understand why in the last 30 years global warming is not uniform,” said first author Qinghua Ding, a UW research scientist in atmospheric sciences. “Superimposed on this global average warming are some regional features that need to be explained.”
The study used observations and advanced computer models to show that a warmer western tropical Pacific Ocean has caused atmospheric changes over the North Atlantic that have warmed the surface by about a half-degree per decade since 1979.
“The pattern of the changes in the tropical Pacific that are responsible for remarkable atmospheric circulation changes and warming in Greenland and the Canadian Arctic are consistent with what we would call natural variability,” said co-author David Battisti, a UW professor of atmospheric sciences.
Researchers say it’s not surprising to find the imprint of natural variability in an area famous for its melting ice. In many of the fastest-warming areas on Earth, global warming and natural variations both contribute to create a “perfect storm” for warming, said co-author John “Mike” Wallace, a UW professor of atmospheric sciences.
The natural variations in the new study related to an unusually warm western tropical Pacific, near Papua New Guinea. Since the mid-1990s the water surface there has been about 0.3 degrees hotter than normal. Computer models show this affects the regional air pressure, setting off a stationary wave in the atmosphere that arcs in a great circle from the tropical Pacific toward Greenland before turning back over the Atlantic.
“Along this wave train there are warm spots where the air has been pushed down, and cold spots where the air has been pulled up,” Wallace said. “And Greenland is in one of the warm spots.”
In previous studies, Wallace and Battisti have documented the existence of decades-long climate variations in the Pacific Ocean that resemble the well-known shorter-range El Niño variations.
This particular location in the tropical Pacific may be a sweet spot for generating global atmospheric waves. A series of studies led by co-author Eric Steig, a UW professor of Earth and space sciences, working with Ding and Battisti, showed that waves starting in the same place but radiating southward are warming West Antarctica and melting the Pine Island Glacier.
Researchers can’t say for how long the tropical Pacific will remain in this state.
“Our work shows that about half of the warming signal in Greenland comes from the predictable part – forcing of climate by anthropogenic greenhouse gases – but about half comes from the unpredictable part,” Steig said.
This makes shorter-term forecasts difficult, but helps scientists to make more accurate long-range projections.
“Nothing we have found challenges the idea that globally, glaciers are retreating,” Battisti said. “We looked at this place because the warming there is really remarkable. Our findings help us to understand on a regional scale how much of what you see is human-induced by the buildup of CO2, and how much of it is natural variability.”
The dramatic message of “Chasing Ice” remains true, authors say.
“There’s nothing in this paper that negates the message in the movie,” Wallace said. “Ice appears to be exquisitely sensitive to the buildup of greenhouse gases, more than we ever would have thought.” Natural variations could either accelerate or decelerate the melting rate of Greenland’s glaciers in coming decades, he said, but “in the long run, the human-induced component is likely to prevail.”
The research was funded by the National Science Foundation, UW’s Quaternary Research Center, the National Basic Research Program of China and the APEC Climate Center. Other co-authors are Lei Geng at the UW; Ailie Gallant at Australia’s Monash University; and Hyung-Jin Kim at South Korea’s APEC Climate Center.
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Note the photo provided with the press release, here it is in full resolution: http://www.washington.edu/news/files/2014/05/Greenland2010-5.jpg
And my enlargement of a section of it:
Note the black at the bottom of the melt pool, that’s carbon soot. That’s something the UW authors aren’t paying attention to.
As I explain here http://wattsupwiththat.com/2010/11/03/greenland-ground-zero-for-global-soot-warming/
…it has a big effect on albedo, and thus absorbed solar insolation, likely far more so than CO2 forcing, as explained here: http://wattsupwiththat.com/2013/08/13/in-the-arctic-nearby-soot-may-be-a-larger-forcing-than-co2/
UPDATE: Here is a map showing albedo change, the text is from the link below:
http://www.climate.gov/news-features/understanding-climate/greenland-ice-sheet-getting-darker
Map of changes in the percent of light reflected by the Greenland Ice Sheet in summer (June-July-August) 2011 compared to the average from 2000-2006. Virtually the entire surface has grown darker due to surface melting, dust and soot on the surface, and temperature-driven changes in the size and shape of snow grains. Map by NOAA’s climate.gov team, based on NASA satellite data processed by Jason Box, Byrd Polar Research Center, the Ohio State University.
![MODISalbedo_greenland2011_610[1]](http://wattsupwiththat.files.wordpress.com/2014/05/modisalbedo_greenland2011_6101.jpg?quality=83)
You may well be right but at least the point being made is that some of the lost albedo on Greenland ice not down to man? Where it is down to man it could originate from coal powered stations or industrial pollution. My point is that it perhaps has less to do with co2 than other factors such as wild fires (natural or arson?).
TimTheToolMan, here are the Warmists at ‘Skeptical Science’ on soot on Greenland ice lowering albedo. See their graph “Greenland Ice Accumulation Area Albedo, July 2000 – 2012”.
Here is yet another paper showing a warmer Greenland in the first half of the 20th century.
Find my earlier peer reviewed references for this observation HERE.
Funny thing, their graph (and its blatant ask-for-money trick in Skeptical Science) …
See, the ACTUAL measured day-by-day albedo of the nearby Arctic sea ice across the summer days by Curry during her SHEBA experiments shows a variation of the arctic sea ice albedo between a high of 0.93 and a low of 0.45 in mid-July.
Thus, NOT a 0.75 – 0.72 year-to-year variation – ASSUMING these people actually DID measure summer ice albedo at the same day-of-year each of the years! – but a actual variation of arctic surface ice albedo of 0.93 – 0.45. Do we call that a 50% decrease in albedo from April through July then back to 0.93 in late August and September? Or a 100% variation in albedo?
A mere 2 weeks difference in sample dates each season would account for the difference they plotted on January 1 each year.
Katherine says:
May 8, 2014 at 4:18 pm
This makes shorter-term forecasts difficult, but helps scientists to make more accurate long-range projections.
If they can’t the short-term forecasts right, how can they be confident of getting the long-range projections right? Is that like going east to get to the west, or north to go south?
Katherine, according to Steve Mosher “”they” know more about what happens after 2060 than before”
steven mosher | February 17, 2013 at 3:27 am over at J. Curry’s.
The physics of climate are such that we know more about what happens after 2060 than before. Strange but true.
Mosher apparently wrote “The physics of climate are such that we know more about what happens after 2060 than before. Strange but true.”
But the physics of climate change due to increased CO2 only says that the temperature of the ERL must increase and doesn’t say anything about what happens below that and definitely doesn’t say what must happen all the way down to ground level.
Nevertheless the AGW believers all assume warming to ground level which then feeds back positively with increased water vapour. If only they could see their assumptions for what they are…
To me it seems as if the glaciers have some sort of self-cleaning mechanism: soot comes down and blackens the surface, then the sun heats the blackened surface and the soot is washed away by the thus generated water until the surface is white again.
The sun at these latitudes doesn’t shine in winter at all. But the soot comes down incessantly. If it isn’t washed out of the air by precipitation, then it comes down by the force of gravity, some day. If the amount of soot exceeds the self-cleaning capacity of these glaciers, then all glaciers ought to be grey or even black and the sun in summer will thaw and thaw and thaw. Finally, even during summer, soot will not cease to come down. So there must be some sort of balance between soot and precipitation like snow and rain. Is the current amount of precipitation sufficient to maintain that balance? If it is, then soot can’t be a significant factor for an assumed thawing of that glacier ice, else: gotcha – at least one of the suspects.
“Ice appears to be exquisitely sensitive to the buildup of greenhouse gases…”
How would anyone who makes such a stupid, anti-scientific statement as that expect to be taken seriously?
A good picture of black volcanic dust.
http://themetapicture.com/the-demons-are-breaking-loose/