Ag Weather Forum
Bryce Anderson DTN Ag Meteorologist and DTN Analyst

Tuesday 12/10/13

New Study On Impact Of Arctic Warming

Following is the text of an article by Andrew Freedman of Climate Central which summarizes findings in a new study of far northern latitude warming and extreme weather occurrences. The study, for the first time, connects the two.--Bryce

Twitter @BAndersonDTN

Study Adds To Arctic Warming, Extreme Weather Debate

A new study for the first time found links between the rapid loss of snow and sea ice cover in the Arctic and a recent spate of exceptional extreme heat events in North America, Europe, and Asia. The study adds to the evidence showing that the free-fall in summer sea ice extent and even sharper decline in spring snow cover in the Northern Hemisphere is reverberating throughout the atmosphere, making extreme events more likely to occur.

The study, published Sunday in the journal Nature Climate Change, is the first to find correlations between rapid Arctic warming and extreme summer weather events, since previous research had focused on the links between Arctic warming and fall and winter weather patterns.

While the study adds to the body of evidence pointing to the outsized role the Arctic is playing in shaping weather patterns, it won't end the debate within the scientific community over whether and how what is happening in the Far North could be having such far-reaching impacts.

There is virtually no controversy among climate scientists and meteorologists that massive changes have occurred in the Arctic environment during the past three decades, and that those changes are largely due to manmade greenhouse gas emissions.

Since the 1980s, Arctic sea ice extent has dropped at a rate of about 8 percent per decade during September, which is when the sea ice cover reaches its annual minimum. A record minimum was set in 2012. For a size comparison, consider that the area of summer sea ice lost since the 1980s would cover about 40 percent of the continental U.S., the study said.

Spring snow cover extent loss during June has dropped even more precipitously than sea ice cover, the study found, at a rate of about 18 percent per decade since 1979.

The reasons why the Arctic is warming so quickly — a phenomenon known as Arctic amplification — has to do with factors that are unique to the Arctic environment, involving feedbacks between sea ice, snow, water vapor and clouds. As the area warms in response to manmade greenhouse gases, melting ice and snow allow exposed land and water to absorb more of the Sun’s heat, which melts more ice and snow, and so on. A relatively small amount of initial warming can be greatly magnified in the Far North.

It is also widely agreed that the world has seen a spate of extreme heat events in recent years, such as the 2011 Texas heat wave and drought and the deadly 2010 heat wave in Russia, and that global warming made some of these events more likely to occur and more severe.

But scientific consensus breaks down when it comes to the issue of whether Arctic warming is altering weather patterns in the northern mid-latitudes, stacking the deck in favor of extreme weather events.

On one side of the issue are some meteorologists and climate scientists who in their studies have found correlations between the vanishing Arctic sea ice and snow cover (collectively known as the cryosphere) and weather patterns that can lead to extreme weather events.

On the other side are other climate scientists and meteorologists who, while convinced that manmade climate change is having profound impacts on the planet, don’t yet see clear physical science evidence showing that Arctic warming is changing the already chaotic nature of weather patterns, and leading to extreme weather events.

James Overland, a researcher at the National Oceanic and Atmospheric Administration (NOAA), said the split in the scientific community is an unusual one.

“The skeptics (of the link between Arctic warming and extreme weather events) actually tend to be some of the real top mid-latitude dynamics climate scientists,” Overland said in an interview. “They’re looking at the chaos of the long-wave atmospheric pattern and it’s really hard to see why modest additional forcing in the Arctic can overwhelm all the energy that’s in that chaotic pattern.”

The case for a connection between Arctic warming and summertime extreme weather events rests on the Arctic’s crucial role as a pacesetter and shape-maker of the jet stream, the powerful ribbon of upper level winds that steer weather systems from west to east across the Northern Hemisphere.

Because the temperature contrast between the frigid Arctic and the milder mid-latitudes is what drives the powerful jet stream winds that guide weather systems, what happens in the Arctic is bound to have some sort of influence on the world’s weather.

The new study, along with other previously published research, showed that the decline in sea ice and snow cover has slowed the west-to-easterly component of the jet stream, thereby enhancing the north-to-south waviness of the jet, which leads to the creation of more stagnant or “blocked” weather patterns. In addition, the new study found an association between sea ice and snow cover decline and a northward shift in the jet stream, which allows more warm air to move into the U.S. and Europe during the summer.

Paradoxically, other studies, including work by the same team of researchers, has shown that Arctic warming can actually enhance cold weather extremes in the U.S. and Europe during the winter.

Jennifer Francis, a meteorologist at Rutgers University, co-author of the new study, and the most prominent proponent of the hypothesis that Arctic warming is leading to more extreme weather events, told Climate Central that this study adds further evidence to the growing body of research supporting her team’s conclusions.

“While an observational study cannot pin down the mechanistic cause of the response, our results show a strong relationship between ice and snow losses during summer with heat waves in mid-latitude continents where billions of people are affected,” Francis said in an email conversation.

But the lack of statistically significant results and, more important, the absence of evidence pointing to a smoking gun — a physical mechanism in the climate system that ties Arctic changes to extreme events — has left many top climate researchers unconvinced that rapid Arctic warming is a major player in causing extreme weather events outside of the Arctic itself.

The result, some of these scientists told Climate Central, is a series of hypotheses that have not yet been fully tested.

“I would have more confidence in the linkage being ‘real’ if there was a well-understood and proven mechanism to support the correlations,” James Screen, a climate researcher at the University of Exeter in the U.K., said in an email. “The arguments presented are plausible, but in my opinion the evidence presented is far from conclusive (to put it mildly).”

Kevin Trenberth, a senior scientist at the National Center for Atmospheric Research in Boulder, Colo., said the new study and others like it have failed to show statistically significant results. Additionally, he said they lack the physical evidence of what are known as “dynamical links,” — physical ties within elements of the Earth’s climate system, such as the upper oceans and lower atmosphere — between Arctic warming and extreme events.

“There is no plausible physical mechanism or analysis of how the atmosphere is forced to behave in this manner,” Trenberth said in an email.

Further adding to the divide within the climate science community is the fact that many of the climate models that Trenberth and others often use do not show the sorts of changes in the jet stream that the new study and others like it have pointed to, including the more frequently stagnated or “blocked” weather patterns that Francis cited. In fact, many of the newest generation of climate models show that atmospheric blocking will become less common in the North Atlantic than it is now.

“We need more case studies, and more direct dynamics studies rather than just correlation studies,” Overland said.

Overland pointed to the International Arctic Science Committee, which is making this a key focus of its research agenda during the next year. The International Arctic Science Committee is part of the World Meteorological Organization.

Judah Cohen, lead seasonal weather forecaster at AER, a weather and climate consulting firm, said the possibility that Arctic climate change is leading to more extreme weather patterns has initiated a flurry of new studies. “I can tell you that I am busier now reviewing journal papers than I have ever been in my career and they are all on sea ice” he said in an email. “I think this will be a dominant area of research and discourse for years to come.”

For her part, Francis is continuing to keep a wary eye on the weather map, convinced that the evidence for Arctic-induced weather extremes will continue to mount.

“As we continue to emit ever-increasing amounts of greenhouse gases into the atmosphere and as the Arctic continues to warm faster than mid-latitudes, we will see the case for the linkage strengthen,” Francis said. “I expect that with every year we will see a clearer response of weather patterns in all four seasons, and new modeling experiments will help elucidate the links in the chain, as well.”

You may also view the article at this link: http://bit.ly/…

(ES/)

Posted at 3:45PM CST 12/10/13 by Bryce Anderson
Comments (9)
Has modeling ever failed? I like the idea of historical correlations. The Heartland Institute published a graph of the last 29,000 years which shows that our "extreme" weather is a figment of our imagination. Anyway, if we can determine pre-industrial age atmospheric carbon dioxide levels from glacial ice thousands of years old, we should be able to geologically put together other pieces of the puzzle and make historical comparisons. Or would that take away someone's grant?
Posted by Curt Zingula at 7:04AM CST 12/11/13
@Curt...models absolutely do fail, and the group of models that the IPCC bases their warming predictions on have failed miserably. Extreme weather events have not increased, our perception of them has. We have better weather tracking capabilities plus the weather news is heard around the world now through the internet and cable television, when 30 years ago information traveled by snail mail and local television outlets. I'll give you two examples of extreme weather that occurred before the industrial revolution...the tri-state tornado of 1925 which is the longest track tornado in recorded history as far as I know, and the Galveston Hurricane of 1900 which I believe is the deadliest US disaster in history. You can google each one for specific info but those are two record holders that will be tough to beat. A lot of weather is 'extreme' but not abnormally so.
Posted by Eric Apel at 2:07PM CST 12/11/13
Most people's historical context is contained to what has happened in their lives. That being said, a huge event is about to occur that hasn't happened in centuries, and that is the cancelling of Christmas. That is what Santa in the commercial for Greenpeace says, due to the elves and reindeer floating away due to the melting of the ice at the North Pole. Perhaps they should move to the South Pole, where the coldest ever recorded temperature just occurred...that is, unless water doesn't freeze below 32 degrees anymore. The way "science" is these days, that may just be the case.
Posted by Brandon Butler at 4:53PM CST 12/11/13
When liberal leftist ideas and theories start to go to where it will never freeze they just get more hysterical. It is really quite fun to watch.
Posted by GORDON KEYES at 5:37PM CST 12/11/13
Ice on the dog dish this morning, proof again there is no global warming,, who needs an education, just listen to Rush Limbo! Those pesky lefty libs, think they need to have an education to do some figuring! How can burning 90 million barrels of oil a day change anything with the climate? You can't even see carbon, how can anything you can't see hurt you?
Posted by Jay Mcginnis at 9:48PM CST 12/11/13
I sense some sarcasm... Here is my $.02. It seems today most people and "scientists" are in agreement about this "Global warming/Climate Change"bs. If it truely is changing like they say it is, fine, so be it. What I have a hard time believing is that it is man made climate change. That is where they loose me, because there is only speculation, not proof. You can all read the numbers how you want, it all depends on how you interpret them. All of you Global Warming believers, remember that these scientists are getting federal funding and such, they are going to make sure they keep getting that funding. It is job security. The day they lose all public funding is when they will regain credibility.
Posted by RJZ Peterson at 9:17AM CST 12/12/13
Jay, the master of red herrings.
Posted by Brandon Butler at 9:43AM CST 12/12/13
The one source of our global heat is always ignored and that is the power of the sun. A person can't see the radiation from it but we know it exists. It easy to access the power of the sun and its phases currently its in a calm cycle and giving off less energy. Geee I wonder why global warming took a pause? Solar cycle 24 is predicted to be low in activity. What if its lower than predicted. The leftys are gonna staring into the cold harsh reality of the sun and yet will be blinded by their ideology... good grief Charlie Brown.
Posted by Paul Beiser at 9:10AM CST 12/17/13
I am waiting for a comment on the Russian ship full of global warming scientists traveling to the south pole to study the melting ice It's summer in the southern hemisphere. Ice should be melting. I guess it was so warm the ice refroze so fast it trapped the ship. It must have something to do with hot water freezing faster than cold water. I do think the earth is slowly warming but man has little to do with it. A erupting volcano puts more gases in the air in a day then all the people in the world do in a hundred years. All these green house gases actually cool the earth off rather then making it warmer.
Posted by FRANK FULWIDER at 1:34PM CST 01/02/14
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