Winter weather has been especially harsh this year, as it was last year. Scientists have long predicted that weather across the Northern Hemisphere could get colder with global warming. How might this work?
Some commentators have invoked changes in atmospheric circulation over Siberia to explain the severe winter weather besieging Europe and parts of the U.S. But there is another part of this puzzle lying closer to our own shores. Warming may be leading to cooling via melting Arctic ice.
For the past 16 months a climate phenomenon known as the North Atlantic Oscillation (NAO) has been locked in one mode; a negative phase, an unusually long stretch with unusually high atmospheric pressures over the Arctic, and low pressure to the south.
Highs persist over cold areas, for cold air is heavy and sinks. Lows, meanwhile, form over warm regions, for hot air rises. And winds and weather fronts flow "downhill," as it were, from highs to lows.
So why might a High pressure system be locked in over the North Atlantic?
During the past decade Arctic ice (where the North Pole sits) has melted and thinned much faster than models predicted. (The floating North Polar cap is only several feet thick.) In addition, many Greenland outlet glaciers are melting from above, calving from below (as they meet warmer seas), and sliding and slipping along their bases into the sea. This melting ice spreads cold, fresh water across the North Atlantic Ocean surface, contributing to a North Atlantic High.
To the south in the Atlantic, the Azores bask in warm sea surface temperatures, as does most of the globe, for the world ocean is where heat has built up over the last century. Indeed, since the late 1950s, the world ocean has accumulated 22 times as much heat as has the atmosphere, and the warmed ocean is the engine for changing weather patterns globally.
Meanwhile, in the Middle East, unusually hot and dry conditions have become the new norm (ask our soldiers and the residents), creating persistent Lows in that region. It is the large gradient between the Atlantic High and the Middle East Low that pushes and pulls the bitter winds and weather fronts now whipping off the North Atlantic across Europe.
For the U.S, the North Atlantic High is a blocking high, deflecting fingers of the Jet Stream deep down into the south, bringing lots of continental polar air to usually temperate and sub-tropical states. And with warming seas and atmosphere overall, there's plenty of water vapor evaporating to generate large amounts of snow, sleet and rain.
The details of this argument are not critical. What is important is that global warming (of the atmosphere and oceans) is causing climate change -- meaning changing temperatures and weather patterns. Weather has become more extreme -- drier and hotter in some areas and wetter and cooler in others -- and precipitation is coming in heavier downpours across the globe. And the warming world ocean and shrinking ice cover are playing leading roles in driving the weather extremes.
Changes in winds and weather patterns with global warming, we have begun to discover, are not limited to the warm seasons. Winter weather anomalies are an emerging feature of climate change and result in orthopedic injuries and travel accidents, deaths, crop failures, power outages, business interruptions, and insured and uninsured losses. Harsh winter weather may, in the future, play an even more disruptive role to society than the heatwaves and spread of infectious disease more commonly considered.
Climate instability -- with greater volatility and wider swings to extremes -- raises the risks of major anomalies that threaten our health and economies. "God does not play dice," Albert Einstein famously said (as he grappled with the uncertainty of quantum mechanics). With regard to weather it seems we have stepped into a high stakes global casino.
But there is hope. An unstable system can re-stabilize and establish a new equilibrium. But we must back off the forces changing Earth's climate -- burning fossil fuels and felling forests -- and fast. We can hope that growing recognition of the mounting risks of climate change help spur a new level of commitment, domestically and internationally. Bold measures are needed, backed by global funds, to stabilize Earth's climate and provide new impetus for a healthy global economy.
Paul R. Epstein, M.D., M.P.H. is associate director of the Center for Health and the Global Environment at Harvard Medical School. He and science writer Dan Ferber are co-authors of the forthcoming book, Changing Planet, Changing Health, to be published this spring by the University of California Press.
Rabbi Or Rose: Life on Planet Eaarth: An Interview with Environmental Activist Bill McKibben
Maybe it's also because the sun is in a rather deep solar minimum, sunspot activity has been very low. I just read a paper that says the thermosphere recently collapsed due to the solar minimum:
http://science.nasa.gov/science-news/science-at-nasa/2010/15jul_thermosphere/
And how is it that previous cold winters similar to the one we are having this year not due to AGW? Put another way, why is this cold winter, similar to the ones we've had years ago, from AGW and those others not from AGW?
Remember, Britain, Ireland, and other nations of Northwestern Europe are at the same latitude as Labrador.
What keeps Europe warmer than it would otherwise be is the Gulf Stream. But a sudden dump of cold fresh water would essentially shut the ocean current down -- and thus the "warming planet" could actually "freeze" Northwestern Europe.
The real point is that everything is so complex, that it is not easy to develop computer models.
What is disturbing, though, is that virtually every estimate and prediction has UNDERSTATED the effects of rising global temperature. The ice is melting far faster than was thought would happen. That is just one example.
As for your suggestion that climate models are being "adujusted to try to explain it", I don't suppose you have anything to back up that statement?
"Only when the last tree has died and the last river been poisoned and the last fish been caught will we realize we cannot eat money" -- Cree Native American Teaching
"We are the most dangerous species of life on the planet, and every other species, even the earth itself, has cause to fear our power to exterminate. But we are also the only species which, when it chooses to do so, will go to great effort to save what it might destroy" -- Wallace Stegner
This is the part where his bias shows. Up until this, he had a plausible theory. Then to top is off it ends with a plug of his "forthcoming" book. Maybe the climate is cycling but the cause is not known.
I believe in adopting greener technologies and living greener but not destroying our economy by forcing industries out. If our govt/economy collapses we will make China's pollution look like a camp fire.
It tells me you are more concerned about your backyard than the planet. Global warming (if its actually man made) will occur faster! Geeeeee Thanks!
How about spending more money and time on pollution controls and cleaner processes instead?
There is likely to be a decline in the frequency of cold air outbreaks (i.e., periods of extreme cold lasting from several days to over a week) in NH winter in most areas
In other words, increased CO2 may have nothing to do with these events. We may simply be experiencing the same weather as earlier centuries did. Presumeably this change in the weather is simply part of natural weather cycles that have existed for thousands of years.
Tieing this winter weather to global warming/climate change/climate disruption/climate challenges is just a hypothesis, like the alternative one.
Which one is better supported by the evidence? Hopefully mature adults can discuss this issue openly and civily, thanks in part to the freedom of speech guaranteed by our constitution.
I don't recall any government climate hearings where witnesses warned the government to prepare for heavy snows around Christmas, shortages of de-iceing fluids at airports, and shortages of snow removal equipment for our streets and highways. Perhaps you can reference some of them?
I thought Dr. Hansen's predictions about New York City involved sharply higher sea levels flooding some highways, and all the birds in Central Park being tropical species, instead of those adapted to cold winters.
I don't recall any demonstrations demanding additional storage facilities for de-iceing fluids, or more runway clearing equipment, or snow removal vehicles. It seems like hindsight is 20/20.
The fact is that an individual event is impossible to conclusively tie to global warming. The predicted increase in the frequency of extreme weather events is possible to confirm and to use as confirmation of AGW.
The melting of the ice as described provides a clear possible causal chain linking the cold winters to the global warming we are experiencing. That does not mean that this particular causality has been proven. It is simply a statement of how the extra cold winters are not contradictory to the evidence that average global temperatures are increasing.
You obviously missed a whole bunch of the predictions from the climate scientists about the increases in extreme weather events that were to occur due to climate change. You also have missed the fact that the insurance industry has noticed vastly increased payouts due to these events and have raised their premiums.
You should wait until the predictions fall due before you comment on their accuracy. For example I predict that Xmas will occur on 25th of December this year, and this is in no way proven false by the fact that I wake up tomorrow, and it is not Xmas yet.
There is no proven link between global warming and extreme weather events and no evidence that extreme events are increasing. It is a hypothesis only.
Massive cold fronts and excessive snow have been recorded in the northern hemisphere in 78-79, 62-63, and 46-47 to name a few very bad winters.
Nothing to see here, please move along, only random weather striking again.
Likewise, the Dickens December in England was the second coldest in 350 years, and the coldest since 1890. Again, please check the record.
Hopefully these facts will help you see that the issue of of whether or not man-made global warming is real is more complex and less certain than you make it.
Ignorance is easier!
Where is this said or implied?
"Yet they do not know that because climate and weather records have only been kept since the 1880's."
There is no way to know anything about climate before the 1880's because, you claim, that is the earliest records were kept? Wow, you've just discarded history and paleoclimatology in one sentence. Solid work.
You are wrong. Good weather data is available through parts of Europe going back to the 1800s. The Armagh, Northern Ireland observatory has been recording weather continuously since 1796. Unlike most weather stations which have have cities built around them and are subject to the urban heat island effect, Armagh remains a rural area and the dataset relatively pure. The same cannot be said for the vast majority of weather station data around the world.
When using 1880 or 1900 as a baseline, the Armagh data indicate a slight warming during this century. Using a baselind of 1796, no significant warming is identified during the last 200 years.
ttp://star.arm.ac.uk/preprints/445.pdf
Enjoy.
A large body of evidence supports the conclusion that human activity is the primary driver of recent warming. This evidence has accumulated over several decades, and from hundreds of studies. The first line of evidence is our basic physical understanding of how greenhouse gases trap heat, how the climate system responds to increases in greenhouse gases, and how other human and natural factors influence climate.
The second line of evidence is from indirect estimates of climate changes over the last 1,000 to 2,000 years. These estimates are often obtained from living things and their remains (like tree rings and corals) which provide a natural archive of climate variations. These indicators show that the recent temperature rise is clearly unusual in at least the last 1,000 years.
The third line of evidence is based on comparisons of actual climate with computer models of how we expect climate to behave under certain human influences. For example, when climate models are run with historical increases in greenhouse gases, they show gradual warming of the Earth and ocean surface, increases in ocean heat content, a rise in global sea level, and general retreat of sea ice and snow cover. These and other aspects of modeled climate change are in agreement with observations.
“Global Climate Change Indicators”, National Oceanic and Atmospheric Administration, National Climatic Data Center
http://www.ncdc.noaa.gov/indicators/