Nemo, The Blizzard, Snow, Climate Crisis, The connection
11 February, 2013
Is there connection between Nemo, the blizzard lashing the northeast US, dumping huge amount of snow, and climate crisis the Earth now experiencing? Scientists search for the answer.
Tom Zeller Jr. writes :
The Union of Concerned Scientists has posted an informative breakdown on the connections between the winter storm bearing down on the Northeast and the planet's changing climate.
"It’s Cold and My Car is Buried in Snow. Is Global Warming Really Happening?," notes that storms like this one -- a classic Nor'easter -- are well-known to residents along the nation's North Atlantic coast. But shifts in the climate due in large part, most scientists say, to burning fossil fuels, are likely to make such storms even more fierce and frequent.
In an emailed statement, UCS climate scientist Brenda Ekwurzel explained, citing data from the National Oceanic and Atmospheric Administration (NOAA):
Rising ocean surface temperatures already have increased the temperature and moisture content of the air passing over the United States, setting the stage for heavier snow and rain storms. Global warming has increased the risk of dumping heavier precipitation -- as rain or snow -- over most land regions that experience storms.
In the U.S., the region that has experienced the highest increase in heaviest precipitation is the Northeast over the last half century. According to NOAA, the Northeast saw a 74 percent increase in the amount of precipitation that fell during the heaviest rain and snow events between 1958 and 2011.
The UCS web site goes on to describe just how changes in climate -- a statistical phenomenon measured in decades and centuries -- can affect weather, or what you see and experience when you walk outside.
It also explains, in response to climate contrarians who routinely ask the question behind the title of the UCS post, why the continuation of cold weather and winter storms does not refute fundamental climate science.
The seasons we experience are a result of the Earth’s tilted axis as it revolves around the Sun. During the North American winter, our hemisphere is tilted away from the Sun and its light hits us at a different angle, making temperatures lower.
While climate change won’t have any impact on Earth’s tilt, it is significantly shifting temperatures and causing spring weather to arrive earlier than it used to. Overall, spring weather arrives 10 days earlier than it used to, on average. “Spring creep" is something scientists projected would happen as the globe continues to warm.
"The choices we make today can help determine what our climate will be like in the future," the scientists note. "Putting a limit on heat-trapping emissions, encouraging the use of healthier, cleaner energy technologies, and increasing our energy efficiency are all ways to help us to avert the worst potential consequences of global warming, no matter what the season."
The scientific reality
Union of Concerned Scientists said :
For years, climate contrarians have pointed to snowfall and cold weather to question the scientific reality of human-induced climate change.
Such misinformation obscures the interesting work scientists are doing to figure out just how climate change is affecting weather patterns year-round.
Understanding what scientists know about these effects can help us adapt. And, if we reduce the emissions that are driving climate change, we can dramatically reduce the pace of change and better prepare for the consequences in the future.
What is the relationship between weather and climate?
Weather is what’s happening outside the door right now; today a snowstorm or a thunderstorm is approaching. Climate, on the other hand, is the pattern of weather measured over decades.
NASA and NOAA plus research centers around the world track the global average temperature, and all conclude that Earth is warming. In fact, the past decade has been found to be the hottest since scientists started recording reliable data in the 1880s. These rising temperatures are caused primarily by an increase of heat-trapping emissions in the atmosphere created when we burn coal, oil, and gas to generate electricity, drive our cars, and fuel our businesses.
Hotter air around the globe causes more moisture to be held in the air than in prior seasons. When storms occur, this added moisture can fuel heavier precipitation in the form of more intense rain or snow.
At the same time, because less of a region’s precipitation is falling in light storms and more of it in heavy storms, the risks of drought and wildfire are also greater. Ironically, higher air temperatures tend to produce intense drought periods punctuated by heavy floods, often in the same region.
These kinds of disasters may become a normal pattern in our everyday weather as levels of heat-trapping gases in the atmosphere continue to rise.
The United States is already experiencing more intense rain and snowstorms. The amount of rain or snow falling in the heaviest one percent of storms has risen nearly 20 percent, averaged nationally—almost three times the rate of increase in total precipitation between 1958 and 2007.
Some regions of the country have seen as much as a 67 percent increase in the amount of rain or snow falling in the heaviest storms — and an updated version of this figure from the draft National Climate Assessment suggests this increase may have risen to 74 percent between 1958 and 2011.
The Arctic connection
Winters have generally been warming faster than other seasons in the United States and recent research indicates that climate change is disrupting the Arctic and ice around the North Pole.
The Arctic summer sea ice extent broke all records during the end of the 2012 sea ice melt season. Some researchers are pointing to a complex interplay between Arctic sea ice decline, ocean patterns, upper winds, and the shifting shape of the jet stream that could lead to extreme weather in various portions of northern mid-latitudes — such that some places get tons of snow repeatedly and others are unseasonably warm.
In the Arctic, frigid air is typically trapped in a tight loop known as the polar vortex. This super-chilled air is not only cold, it also tends to have low barometric pressure compared to the air outside the vortex. The surrounding high-pressure zones push in on the vortex from all sides so the cold air is essentially "fenced in" above the Arctic, where it belongs.
As the Arctic region warms faster than most other places, however, the Arctic sea ice melts more rapidly and for longer periods each year, and is unable to replenish itself in the briefer, warmer winter season. This can destabilize the polar vortex and raises the barometric pressure within it.
For two winter seasons (2009/2010 and 2010/2011), the polar vortex was notably unstable. In addition, another measurement of barometric pressure — the North Atlantic Oscillation (NAO) — was in negative mode, weakening part of the barometric pressure "fence" around the polar vortex. This instability allows the cold Artic air to break free and flow southward, where it collides with warmer, moisture-laden air. This collision can produce severe winter weather in some regions and leave milder conditions in other parts of the northern hemisphere.
The winter of 2009/2010 recorded the second lowest negative phase of the NAO since the 1970s, which helps to explain the record snowfalls across the northeastern United States. The 2010/2011 winter also trended toward a strong negative phase.
During the 2011/2012 winter, there was a shift in the position of the jet stream, which separates cold arctic air from warmer air. Typically New England, the Great Lakes, and parts of the Great Plains sit north of the jet stream and remain cold in the winter season. However, the 2011/2012 winter jet stream position meant these regions were south of it for most of the winter, which helped produce the fourth warmest U.S. winter on record.
It’s not clear how much impact this trend will have in the future, especially as the Arctic ice continues to lose mass.
It’s not too late
The choices we make today can help determine what our climate will be like in the future. Putting a limit on heat-trapping emissions, encouraging the use of healthier, cleaner energy technologies, and increasing our energy efficiency are all ways to help us to avert the worst potential consequences of global warming, no matter what the season.
A lot of moisture
Lynne Peeples writes :
Storms like the nor'easter lashing the East Coast happen with some regularity. But the amount of snow the storm called "Nemo" ultimately dumps, and the extent of flood damage it leaves in its wake, may well have ties to global warming, climate scientists suggested.
Michael Mann, a climatologist who directs the Earth System Science Center at Pennsylvania State University, compared a major storm like Nemo -- or Hurricane Irene or Superstorm Sandy, for that matter -- to a basketball slam-dunk with a lower net.
"If you take the basketball court and raise it a foot, you're going to see more slam-dunks," Mann said. "Not every dunk is due to raising the floor, but you'll start seeing them happen more often then they ought to."
The two key ingredients in a big snow: just cold-enough temperatures and a lot of moisture. Combine the chilled air converging on the East with the massive moisture coming from the Gulf of Mexico region and you've got the "perfect setup for a big storm," Kevin Trenberth, of the Climate Analysis Section at the National Center for Atmospheric Research in Colorado, told The Huffington Post in an email.
As Trenberth explained, the ideal temperature for a blizzard is just below freezing -- just cold enough to crystallize water into snow. Below that, the atmosphere's ability to hold moisture to create those snowflakes drops by 4 percent for every one degree Fahrenheit fall in temperature.
"In the past, temperatures at this time of year would have been a lot below freezing," Trenberth said. In other words, it's been too cold to snow heavily. But that may become less of an obstacle for snow in the Northeast.
In addition to warming the air, climate change is adding moisture to it.
Sea surface temperatures are about two degrees Fahrenheit warmer than they were before 1980, raising the potential for a big snow by about 10 percent, according to Trenberth. And any individual storm, including this nor'easter, will pick up more moisture as it spins across a warmer ocean. What's more, as Mann explained, a warm ocean clashes with cold air masses from the Arctic. A bigger contrast in temperatures may mean a bigger storm, he said.
Michael Oppenheimer, a climate change expert at Princeton University, said global warming is increasing extreme storms. "Storms like this tend to be heavier than they used to be," he told HuffPost. "That's a fact."
Still, connecting any specific weather event to global warming remains inexact. A new area of study called "event attribution science" is mining data in an attempt to make more definitive links, or at least better gauge the odds of an extreme event in the context of climate change that results partly from human activities, including burning fossil fuels. But the field is young.
And, truth is, nor'easters happen.
In fact, Jeff Masters, a climatologist and founder of Weather Underground, noted that the number of intense nor'easters hasn't increased over the last three or four decades. A warmer climate, he explained, can decrease the length of the snowy season, and therefore the time window for nor'easters.
Further, nor'easters are defined not only by heavy snowfall, but by high winds. There's less evidence for links between winter winds and climate change. Warm weather storms, such as Hurricane Irene and Superstorm Sandy, are another story. "Since hurricanes are heat engines, they drive power from ocean waters," said Masters.
Another climate-linked ingredient could propel this weekend's storm into the history books: rising sea levels.
"A three-foot storm surge, on top of a higher sea level, will do more damage," Masters said, noting that sea levels in Boston, expected to bear the brunt of the nor'easter with an historic storm surge, have risen a foot in the last 90 years.
Penn State's Mann also likes to use baseball metaphors when describing climate's influence on major storms -- "home runs," he calls them. "What we're seeing now with climate change is weather on steroids."
 02/08/2013, “'Nemo' And Climate Change Connection: Scientists Weigh-In”,
 Global Warming, last revised: 02/08/13, “It’s Cold and My Car is Buried in Snow. Is Global Warming Really Happening?”,
 02/09/2013, “Climate Change And The Blizzard: Nor'easters More Fierce With Global Warming, Scientists Say”,
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