Winter has held North America and Northern Europe in a relentless grip for months, and scientists are saying that we may have to get used to experiencing such prolonged periods of bad weather. Recent research presented at the annual meeting of the American Association for the Advancement of Science (AAAS) in Chicago suggests that this is occurring as a result of Arctic warming, where temperatures are increasing at two or three times the rate of the rest of the world. The region has seen a rise of 2°C since the 1970s, resulting in a 40 per cent drop in the amount of summer ice coverage across the Arctic Ocean. This becomes a vicious cycle as open water then absorbs more heat than ice, thereby increasing sea temperatures even further especially on the side of the Arctic near Alaska and Siberia, which is losing the most ice.
Ian Eisenman is a member of a team from the Scripps Institute of Oceanography in La Jolla, California who have examined data from NASA's CERES satellite.
"Arctic sea ice retreat has been an important player in the global warming that we've observed during recent decades," he said. "I think this is an important piece in the climate change story, but there are lots of other pieces we need."
The team found that the albedo in the arctic Ocean - that is, the fraction of sunlight that the water reflects back to the sky - had dropped from 52 per cent in 1979 to 48 per cent in 2011. This small decrease has had a large impact, as it may result in an increase in the energy absorbed, equivalent to 25 per cent of the energy generated by escalating atmospheric carbon dioxide during the same period.
"That is big – unexpectedly big," said Eisenman
"It reaffirms that albedo feedback is a powerful amplifier of climate change, maybe even more so than is simulated by the current crop of climate models," agreed Mark Flanner of the University of Michigan in Ann Arbor.
It is likely that, in the future, the Arctic seas could be free from ice altogether during the summer months.
"Right now we have very little ability to predict Arctic ice two months or 30 years out,"said Eisenmann.
But how do rising Arctic sea temperatures affect our global weather systems?
The main culprit directly affecting the weather is the jet stream which is fuelled by differentials in temperatures between the Arctic and middle latitudes. If there is a marked disparity in temperature this increases the speed of the jet stream, which then carries weather systems briskly along, but as the oceans are warming and the driving differential has been reduced, the jet stream has slowed down to a meandering pace.
The slowed-down jet stream is allowing weather systems to linger, resulting in the prolonged periods of bad weather seen recently in the UK and the US.
Prof Jennifer Francis of Rutgers University in New Jersey explained: "This does seem to suggest that weather patterns are changing and people are noticing that the weather in their area is not what it used to be. We can expect more of the same and we can expect it to happen more frequently.”
If the jet stream continues to behave in this way, we can expect weather patterns to becoming locked over areas for weeks at a time. Other effects are that cold weather is driven further south and warm weather further north, such as the exceptionally warm winter conditions experienced in Alaska and Scandinavia this year with temperatures 4-5C above the norm across much of Norway, Sweden and Finland. Animals have been emerging from their hibernation early, and reindeer are struggling to feed as snow melted by the warm temperatures has re-frozen as ice, preventing them from grazing on the solid ground.
In Britain also, though the first half of winter was 1.5C above average, the temperatures are now increasingly mild, causing spring flowers to push their heads tentatively above ground only to be met by the worst and most intense storms for 20 years, and a deluge of rainfall 50% above normal levels. Across the Atlantic, much of the US and Canada has been assaulted by record low temperatures as low as minus 27C (-16.6F). The lazy jet stream allowed the a band of freezing Arctic air to filter down across North America, even drifting down as far as the Sunshine State, Florida, and southern U.S. cities like Atlanta, who experienced rare snowstorms and freezing weather.
So is global warming going to result in "endless winter" or increased temperatures?
It seems certain that the effects of rising sea temperatures on the jet stream will result in bands of weather hanging around, but what of the overall trend in weather for the future? Will we experience greater precipitation or will temperatures rise and rise, resulting in drier conditions?
The answer, it appears, is probably both. Behind the stormy weather experienced recently in the US, another serious environmental situation is unfolding as many states are experiencing severe drought conditions.
Climate change has been cited as the cause of this, and President Obama suggested that the rest of the country may start to endure similar conditions as global warming increases.Climate scientists are not so quick to make the same judgement, however, as there is not sufficient evidence available to make this connection, which could be due merely to normal variations.
“I’m pretty sure the severity of this thing is due to natural variability,” said Richard Seager, a climate scientist who studies water issues at the Lamont-Doherty Earth Observatory of Columbia University.
It cannot be disputed that, in drought-stricken California, 2013 was the driest year on record but it is not the first time that the state has experienced such severe dry conditions. In 1976-77, intense droughts occurred not just in the US but in other parts of the world including the UK, but the trend across the world does seem to suggest that drought conditions are becoming more common, consistent with the prediction that global warming would result in dry areas becoming drier and wet areas seeing yet more rainfall.
It is possible that natural variations are being worsened by the effects of climate change, intensifying the effects. The warmer climate is causing more rain and less snowfall in winter, eliminating the melting snowpack that usually irrigates dry states through the summer months.
“We are going through a pattern we’ve seen before, but we’re doing it in a warmer environment,” said Michael Anderson, the California state climatologist.
The White House science adviser, John P. Holdren, said in a briefing last week: “Scientifically, no single episode of extreme weather, no storm, no flood, no drought can be said to have been caused by global climate change. But the global climate has now been so extensively impacted by the human-caused buildup of greenhouse gases that weather practically everywhere is being influenced by climate change.”
The pattern seems to correlate with a computer model developed ten years ago by scientists at the University of Californiain Santa Cruz. Study leader, Jacob O. Sewall, forecast the effects on climate if there was a significant reduction in Arctic sea ice.
“The surprise jumped out that, wow, all of a sudden it got a whole lot drier in the western part of North America,” Dr. Sewall recalled.
He and his peers have agreed that lower ice coverage is allowing heat to escape from the Arctic, disturbing weather patterns and resulting in the type of extreme weather now being seen in many parts of the world in the form of furious storms and droughts. Dr. Sewall now calls the correlation “frightening.”
Other studies conducted since Sewalls have reached the same conclusion - that the western US will become drier -but caused instead by more dry air from the tropics, and that there may be more precipitation in these areas in winter. As global warming is an unprecedented event, there is a great deal of uncertainty, and scientists can only make predictions based on computer models and reasonable hypotheses, but so far weather events do appear to be unfolding in a textbook fashion and the world could now be seeing glimpse of its future climate.
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