By Karl Ritter
Saturday March 30, 2013
STOCKHOLM -- Is it Easter or Christmas? Many Europeans would be forgiven for being confused by winter’s icy grip on lands that should be thawing in springtime temperatures by now.
Britain is on track for the coldest March since 1962, according to national weather service the Met Office, which also says daily low temperatures in London are going to remain below freezing through the Easter holiday. The mean temperature in Britain from March 1-26 was 2.5 C (36.5 F) -- three degrees below the long-term average.
In Berlin, Good Friday saw a new round of snowfall and temperatures just above freezing. The city’s popular lakeside beach opened for the season as planned, though it wasn’t exactly beach weather. Some visitors built a snowman and few ventured into the freezing water.
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What’s going on?
As always when you talk about weather, natural variability is a big factor. But an increasing body of research suggests that cold spells like the one that has lingered in northern and central Europe for much of March could become more common as a result of global warming melting the Arctic ice cap.
Q: Why is it so cold in much of Europe right now?
A: Normally, European winters are kept relatively mild by wet, westerly winds from the Atlantic. But in March, the wind has been blowing mostly from the northeast, bringing freezing Arctic air down over much of Europe.
Q: So why are the winds coming from the northeast?
A: The winds are driven by atmospheric circulation patterns which in turn are affected by differences in air pressure between northern and southern latitudes. For much of March this circulation has been in a negative state, meaning the pressure difference is small. That weakens the westerly Atlantic winds and paves the way for cold air to sweep down over Europe from the Arctic and Siberia.
Q: What does that have to do with Arctic sea ice?
A: Global warming is melting the ice cap over the Arctic Ocean. Last September, it reached its lowest extent on record. Climate models show that the loss of sea ice -- which acts as a lid on the ocean, preventing it from giving off heat -- triggers feedback mechanisms that shake up the climate system further. A series of studies in recent years have shown that one such effect could be changes in atmospheric circulation, resulting in more frequent cold snaps in Europe.
Q: How would melting Arctic ice lead to cold snaps?
A: The theory is the loss of sea ice means more heat is released from the open ocean, warming the layer of polar air over the water. That reduces the temperature and air pressure differentials with more southern latitudes, increasing the likelihood of a negative state in the atmospheric circulation. Experts stress that winter weather is affected by many other factors, but several studies have shown the Arctic melt loads the dice in favor of colder and snowier winters in Europe. One study by scientists at the Potsdam Institute for Climate Impact Research in Germany showed European cold snaps could become three times more likely because of shrinking sea ice.
Q: What’s the impact on the jet stream?
A: Some studies suggest that the shrinking sea ice also shifts the polar jet stream, a high-altitude air current that flows from west to east. Bigger waves in the meandering jet stream allow frigid air to spill southward from the Arctic, they say. Other climate experts are uncertain about this effect, saying more research is needed.
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http://water-is-life.blogspot.com/2013/03/major-loss-in-arctic-sea-ice-volume-it...
Also See:
http://www.nature.com/nature/journal/v458/n7242/full/nature08017.html
Nature 458, 1158-1162 (30 April 2009) | doi:10.1038/nature08017; Received 25 September 2008; Accepted 25 March 2009
Greenhouse-gas emission targets for limiting global warming to 2 °C
See associated Correspondence: Victor, Nature 459, 909 (June 2009)
Malte Meinshausen1, Nicolai Meinshausen2, William Hare1,3, Sarah C. B. Raper4, Katja Frieler1, Reto Knutti5, David J. Frame6,7 & Myles R. Allen7
1.Potsdam Institute for Climate Impact Research, Telegraphenberg, 14412 Potsdam, Germany
2.Department of Statistics, University of Oxford, South Parks Road, Oxford OX1 3TG, UK
3.Climate Analytics, Telegraphenberg, 14412 Potsdam, Germany
4.Centre for Air Transport and the Environment, Manchester Metropolitan University, Chester Street, Manchester M1 5GD, UK
5.Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland
6.Smith School of Enterprise and the Environment, University of Oxford, Oxford OX1 2BQ, UK
7.Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
Correspondence to: Malte Meinshausen1 Correspondence and requests for materials should be addressed to M.M.
Abstract
More than 100 countries have adopted a global warming limit of 2 °C or below (relative to pre-industrial levels) as a guiding principle for mitigation efforts to reduce climate change risks, impacts and damages1, 2. However, the greenhouse gas (GHG) emissions corresponding to a specified maximum warming are poorly known owing to uncertainties in the carbon cycle and the climate response. Here we provide a comprehensive probabilistic analysis aimed at quantifying GHG emission budgets for the 2000–50 period that would limit warming throughout the twenty-first century to below 2 °C, based on a combination of published distributions of climate system properties and observational constraints. We show that, for the chosen class of emission scenarios, both cumulative emissions up to 2050 and emission levels in 2050 are robust indicators of the probability that twenty-first century warming will not exceed 2 °C relative to pre-industrial temperatures. Limiting cumulative CO2 emissions over 2000–50 to 1,000 Gt CO2 yields a 25% probability of warming exceeding 2 °C—and a limit of 1,440 Gt CO2 yields a 50% probability—given a representative estimate of the distribution of climate system properties. As known 2000–06 CO2 emissions3 were ~234 Gt CO2, less than half the proven economically recoverable oil, gas and coal reserves4, 5, 6 can still be emitted up to 2050 to achieve such a goal. Recent G8 Communiqués7 envisage halved global GHG emissions by 2050, for which we estimate a 12–45% probability of exceeding 2 °C—assuming 1990 as emission base year and a range of published climate sensitivity distributions. Emissions levels in 2020 are a less robust indicator, but for the scenarios considered, the probability of exceeding 2 °C rises to 53–87% if global GHG emissions are still more than 25% above 2000 levels in 2020.
1.Potsdam Institute for Climate Impact Research, Telegraphenberg, 14412 Potsdam, Germany
2.Department of Statistics, University of Oxford, South Parks Road, Oxford OX1 3TG, UK
3.Climate Analytics, Telegraphenberg, 14412 Potsdam, Germany
4.Centre for Air Transport and the Environment, Manchester Metropolitan University, Chester Street, Manchester M1 5GD, UK
5.Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland
6.Smith School of Enterprise and the Environment, University of Oxford, Oxford OX1 2BQ, UK
7.Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
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Planting trees is great and we are all for it. However, in concert with that we need laws and we need to keep the oil and tarsands IN THE GROUND as well as preserving what we already planted. An "all of the above" energy policy will also NOT bring us to the goal outlined in this peer reviewed paper.
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JanforGore
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