A new paper in PNAS, called Observational determination of albedo caused by vanishing sea ice, reminds me of scientific work Peter Wadhams published a year and a half ago wherein he showed Arctic ice melt is 'like adding 20 years of CO2 emissions'. He based this assertion on calculations, as can be read in this BBC article from around that time.
This new paper by Pistone et al., however, is based on observations (as it says in the title) and similarly concludes that the "decrease in albedo is equivalent to roughly 25 percent of the average global warming currently occurring due to increased carbon dioxide levels"
I've taken this last quote from a livescience article. Here's more:
Warming from Arctic Sea Ice Melting
More Dramatic than Thought
Since as early as the 1960s, scientists have hypothesized that melting sea ice amplifies global warming by decreasing Arctic albedo. Researchers have since devised climate models to demonstrate this phenomenon but, until now, nobody had relied entirely on satellite data to confirm this effect through time. [See Stunning Photos of Earth's Vanishing Ice]
Now, scientists based at the University of California, San Diego have analyzed Arctic satellite data from 1979 to 2011, and have found that average Arctic albedo levels have decreased from 52 percent to 48 percent since 1979 — twice as much as previous studies based on models have suggested, the team reports today (Feb. 17) in the journal Proceedings of the National Academy of Sciences.
The amount of heat generated by this decrease in albedo is equivalent to roughly 25 percent of the average global warming currently occurring due to increased carbon dioxide levels, the team reports.
"Although more work is needed, a possible implication of this is that the amplifying feedback of Arctic sea ice retreat on global warming is larger than has been previously expected," study co-author Ian Eisenman told Live Science.
Previous models of Arctic albedo have suggested the reflectiveness of white cloud cover could potentially mitigate a portion of albedo loss due to melting ice; but these new observations show that cloud cover has had a negligible effect on overall Arctic reflectivity, the team says.
While Arctic sea ice will not likely return to 1979 values in the near future, the ice does change from year to year and might still experience some comeback this century, though the extent to which this might happen remains unclear, Eisenman said.
Read the rest here.
Here's another quote from the September 2012 BBC article mentioned above:
The melting ice could have knock-on effects in the UK. Adam Scaife, from the Met Office Hadley Centre told Newsnight it could help explain this year's miserable wet summer, by altering the course of the jet stream.
"Some studies suggest that there is increased risk of wet, low pressure summers over the UK as the ice melts."
There may be an effect for our winters too: "Winter weather could become more easterly cold and snowy as the ice declines," Mr Scaife said.
The increased risk of wet summers in the UK has shown its ugly face already in recent years. As fellow blogger Chris Reynolds shows on his Dosbat blog, 4 of the 10 wettest summers since 1910 all occurred in the last 7 years. The chance that this is due to natural variation, is 0.14%.
In fact, Chris says: "The UK is experiencing cooler wetter summers, likely as a result of sea ice loss. And this has lead to damaging flooding events in 2007, and 2012. This is not happening by chance, it is climate change, ongoing and causing damaging consequences to lives, property and agriculture."
Nevertheless, there's a lot of ongoing brouhaha in the deniosphere over the Met Office giving conflicting forecasts. It could be that what the Met Office isn't getting, and fake skeptics will probably never (want to) get, is that the very real risk for now is that weather systems get stuck because of changes in the jet stream.
Coincidentally, the BBC published another article a couple of days ago, explaining how this works:
The meandering jet stream has accounted for the recent stormy weather over the UK and the bitter winter weather in the US Mid-West remaining longer than it otherwise would have.
"We can expect more of the same and we can expect it to happen more frequently," says Prof Francis
The jet stream, as its name suggests, is a high-speed air current in the atmosphere that brings with it the weather.
It is fuelled partly by the temperature differential between the Arctic and the mid-latitudes.
If the differential is large then the jet stream speeds up, and like a river flowing down a steep hill, it ploughs through any obstacles - such as areas of high pressure that might be in its way.
If the temperature differential reduces because of a warming Arctic then the jet stream weakens and, again, like a river on a flat bed, it will meander every time it comes across an obstacle.
This results in weather patterns tending to becoming stuck over areas for weeks on end. It also drives cold weather further south and warm weather further north. Examples of the latter are Alaska and parts of Scandinavia, which have had exceptionally warm conditions this winter.
Perhaps the most spectacular example has been on Svalbard in the last 30 days (besides the fact that Svalbard is circumnavigable in February!) where the average temperature was -1.0 °C, 15.0 °C above the normal. This is Europe's northernmost territory, just 10 degrees latitude from the Pole. According to NOAA all of the Arctic Circle could be heading towards this kind of anomaly as the century progresses.
So, when you get easterly cold and snowy, you keep getting easterly cold and snowy. When you get westerly storms and rainy, you keep getting westerly storms and rainy, as some folks in the UK have been noticing this winter.
Again, from the BBC article:
With the UK, the US and Australia experiencing prolonged, extreme weather, the question has been raised as to whether recent patterns are due to simple natural variations or the result of manmade climate change? According to Prof Francis, it is too soon to tell.
"The Arctic has been warming rapidly only for the past 15 years," she says.
"Our data to look at this effect is very short and so it is hard to get a very clear signal.
"But as we have more data I do think we will start to see the influence of climate change."
Prof Francis was taking part in a session on Arctic change involving Mark Serreze, the director of the US National Snow and Ice Data Center in Colorado.
He said the idea that changes in the polar north could influence the weather in middle latitudes - so-called "Santa's revenge" - was a new and lively area of research and somewhat controversial, with arguments for and against.
"Fundamentally, the strong warming that might drive this is tied in with the loss of sea-ice cover that we're seeing, because the sea-ice cover acts as this lid that separates the ocean from a colder atmosphere," Dr Serreze explained.
"If we remove that lid, we pump all this heat up into the atmosphere. That is a good part of the signal of warming that we're now seeing, and that could be driving some of these changes."
Which brings us back again, full circle. Or perhaps I should say full meander.