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Thursday, Mar. 03, 2011

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Published: March 2nd, 2011, Last Updated: March 2nd, 2011 in Impacts, Trends, Projections, Climate, Extremes, Snow & Ice, Weather

Loading the Dice for Heavier Snowfall

It’s been a snowy winter across much of the U.S., particularly in the Midwest and in states like Oklahoma and Arkansas, where snowfall records were recently broken. Southern states like California, Georgia, and New Mexico (all but Florida, really) also experienced snow this winter. And with more wintry conditions forecast for the coming weeks (meteorological winter ended on Feb. 28, but calendar year winter continues until March 19), yesterday’s press briefing from the Union of Concerned Scientists (UCS) — that heavier and more frequent snowstorms are consistent with climate change — seems perfectly timed.

Data from the National Weather Service's analysis of snow depth in the U.S., showing how much snow was on the ground following a January 10-12 snowstorm. Credit: NOAA

In reality, it’s probably just lucky timing.

During a telephone press conference, experts at UCS, a non-profit environmental organization, as well as outside the group talked about the heavy snow-climate change connection. The message wasn’t that all this snow could be blamed on global warming. Instead, the experts emphasized that research suggests that snowy winters, like those of 2010-2011 and 2009-2010, could become more common in the future, as the climate warms and more water vapor is put into the atmosphere.

During the call, meteorologist Jeff Masters of Weather Underground, a private weather forecasting company, explained:

"As the Earth gets warmer and more moisture gets absorbed into the atmosphere, we are steadily loading the dice in favor of more extreme storms in all seasons, capable of causing greater impacts on society"

Climate Central has previously highlighted the possible connection between long-term climate change and the greater odds of heavy snowfall events. We’ve also written about recent research suggesting that melting snow and ice in the Arctic might bring more severe winters to the U.S., and the UCS press call drew attention to the same findings.

Scientists are investigating an atmospheric circulation pattern that brings milder-than-average air to parts of the Arctic, while cold air is routed south into North America and Europe during the winter.

According to Mark Serreze, the director of the National Snow and Ice Data Center in Boulder, Co., the continued loss of snow and ice in the Arctic may be contributing to unusually strong atmospheric circulations that are sending a lot of cold air down over the North American and European continents, while leaving the Arctic itself relatively warm:

"It’s still cutting edge research and there’s no smoking gun, but there’s evidence that with less sea ice, you put a lot of heat from the ocean into the atmosphere, and the circulation of the atmosphere responds to that"

UCS has launched a website to rebut the frequent claims from climate skeptics that snowstorms demonstrate the absence of global warming.

Also of note: Jason Samenow of Washington Post's Capital Weather Gang blog posted a commentary on this subject today, criticizing a USA Today story on the UCS-organized press call for mischaracterizing the relationship between a warming climate and the frequency and severity of major snowstorms.

"No Snow does not disprove global warming!"

It’s Cold and My Car is Buried in Snow. Is Global Warming Really Happening?

For years, climate contrarians have pointed to snowfall and cold weather to question the scientific reality of human-induced climate change.

Their annual barrage of 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 avert its worst 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 water evaporation, which fuels heavier precipitation in the form of more intense rain and snow storms.

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 snow storms. 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.

Overall, it’s warming, but we still have cold winter weather.

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 Arctic connection.

Winters have generally been warming faster than other seasons in the United States. However, recent research indicates that climate change is disrupting the Arctic and ice around the North Pole in a particularly interesting way. 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 now (2009/2010 and 2010/2011), the polar vortex has been notably unstable. In addition, another measurement of barometric pressure—the North Atlantic Oscillation (NAO)—has been 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.

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 is also trending toward a strong negative phase.

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.

Is global warming to blame for record snowfall in the USA this year? Jeff Masters, director of meteorology for the Weather Underground, a private weather service, thinks so and he was around to answer your questions, so see his chat transcript below

Blame it on the warming

Wednesday March 2, 2011 At 100 PM ET 12:02 Moderator: Welcome to today's live chat. Go ahead and start submitting your questions or comments. We'll be moderating the conversation virtually. If you don't see your comment right away, it may post during the discussion at 1 p.m. ET.

1:01 Welcome, this is Dr. Jeff Masters with, taking your questions.

1:01 [Comment From netdr ] Does CO2 cause both cold and warm winters ?

1:01 More CO2 in the atmosphere, on average, raises global temperatures. However, the extra CO2 fundamentally alters the behavior of the atmosphere, changing the amount of moisture, the amount of sea ice, and how the winds blow. Thus we might expect that as a result of more CO2 in the atmosphere, the jet stream patterns will change, bringing warmer winters than usual to some preferred regions of the globe, and colder winters than people are used to in other regions. However, when you add together all these warmer and colder than average numbers, the net result is that the planet continues to warm, with the past decade and past year being the warmest on record, globally.

1:03 [Comment From La La Lander ] How do we know what the "world" temperature (To the .1 of a degree) was 50, 100, 500 or 1000 years ago? How do we determine the "world" temperature today to compare?

1:06 When we average together millions of temperature readings from thousands of stations over many decades of time, it is possible to get a precision of 0.1 degrees. We have software that compares readings taken with those from neighboring stations to test to make sure that bad thermometer readings are not occurring. We have data worldwide from mercury thermometers going back to the late 1880s, and these thermometers are very accurate. Before 1871 or so, we do not have good data, and have to rely on tree rings, ice cores, and other indirect methods, which have an accuracy much worse than 0.1 degrees.

1:06 [Comment From Ted Wagner ] Ten years ago the predictions were that global warming would result in less snow. Did those predictions change, and if so, when and why?

1:14 How concerned are you about global warming?

Very concerned 44% A little concerned 38% Not at all concerned 19%

1:14 I'm not sure of the exact prediction you are talking about, I assume it is the 2001 IPCC report that predicted a decrease in heavy snows. I'm not sure we have the data globally to say how heavy snows have changed, so I don't know to what degree this prediction is right or wrong. We do know that the U.S. has had very heavy snows the past two winters, and that the snow EXTENT (not depth) over the whole Northern Hemisphere was also unusually high the past two winters.

1:14 [Comment From HAL2007 ] What do you think would happen if we stopped human emissions within 5 years (if this were possible)? Would we see continued rise and effects of global warming or would we see things "taper" so to speak?

1:19 The oceans are very slow to respond to heating, and there is about a 30 year lag between the time we emit CO2 and when the planet fully responds. If we stopped emissions now, there is at least 0.5C (0.8F) of warming "still in the pipeline." This is probably enough to cause a major shift in climate that would greatly alter rainfall patterns and cause significant disruptions to society, since we are adapted to the current climate. That amount of warming is also probably enough to partially melt the Greenland and West Antarctica Ice Sheets and trigger sea level rise of at least 1 – 2 meters ( 3 – 6 feet) by 2200.

1:19 [Comment From netdr ] DAvid Viner of CRU predicted that snow would be a thing of the past.

1:22 We have to be wary of looking at too short a period of time to see what the climate is doing. Two consecutive cold and snowy winters in the U.S. and Western Europe are not enough to say that this is the new climate norm we can expect to see. Viner's prediction was based on looking at too short a period of time to make his forecast. The climate is moving towards a new and overall warmer state, but there will be many surprises along the way that we do not anticipate.

1:23 [Comment From netdr ] The warming seems to have stopped for the last 12 years and the water vapor seems to have gone down. How do they account for that ?

1:26 The warming during the 2000s is less than in the 1990s, it is true, and a recent research paper showed that a decrease in moisture in the stratosphere–for unknown reasons–may have been partially responsible. We don't know why the warming was less in the 2000s. However, keep in mind that on a decadal time scale, the 2000s were by far the warmest decade on record, and 2010 was tied with 2005 as the warmest year on record.

1:30 [Comment From HAL2007 ] Dr. Masters thank you for your time and responses today. One final question….do you feel based on all available information that this climate changes has no natural component that is being enhanced by our GHG emissions?

1:34 The weather is willy variable, and a large reason why we got so many extreme events in 2010 was because we started with a strong El Nino and ended with a strong La Nina. Whenever those natural climate patterns enter their extreme phase, you can expect extreme weather somewhere. But when you overlay those natural swings in weather on top of a climate that is changing in unprecedented ways, with more energy in the system due to a hotter atmosphere and ocean, you have the opportunity for a really remarkable year. We are loading the dice in favor of more extreme weather events, and I believe that cliamte change was a major reason why 2010 was so remarkable.

1:35 [Comment From Rodney Smith ] What I don't understand is this year we are seeing the arctic hitting record warm temps yet we see record cold snaps across the world at lower latitudes. Is there any science that supports warming in the arctic will increase the mass and ferocity of storms at lower latitudes.

1:39 Sure, there is a well-known pattern called the Arctic Oscillation that affects weather. Usually, the Arctic is dominated by low pressure and winds that circle the pole, but sometimes this pattern breaks down, and we get winds that flow from the south to the pole, warming it, and from the pole back to the south, letting all the cold air spill out of the Arctic into the mid-latitudes. This pattern took on its most extreme value in 145 years of record keeping in the winter of 2009 – 2010, giving us our wacky winter that year. There is research that suggests that record loss of Arctic sea ice could contribute to that pattern, though we don't know for sure.

1:39 [Comment From Jonnysmoke ] Why isn't there more concern about adapting to our changing climate instead of trying to mitigate it? As you said to another poster, there is still 30 years or more in the pipeline would spending time and efforts on adapting and preparing for things like SLR make more sense for our species survival?

1:40 Absolutely, we need to stop building in flood plains and on barrier islands, and prepare for the coming increase in floods and sea level rise.

1:41 [Comment From Chuck Abrams ] From Facebook: Here in MN, the weather folks say La Nina, or El Nino or whichever it was is the source of the weather patterns and we can actually track that from past events. Nothing else to blame.

1:45 La Nina and El Nino are hugely important, no question. We can't say how much human-caused climate change might influence a particular event without doing a specific study that takes years to complete. In many cases, such studies will probably conclude that a particular event would have happened anyway without climate change. However, there have been 2 studies, one for a UK flood and one for the European heat wave of 2003 which showed that climate change significantly raised the odds of the event, by a factor of 2 – 4 in the case of the European heat wave of 2003.

1:47 Thanks for attending the chat session, I've enjoyed talking with you all!

1:48 [Comment From Ted Wagner ] You have used the clause "warmest on record" a few times. What is the extent of "on record"? (How far back, and what data set(s)?)

1:48 This is the last question I'll answer, and we have good global temperature records going back to 1871.

1:53 Moderator: Thanks to Dr. Masters and all that participated in the chat. Have a good day!

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