December 2010 Archives

Why is Europe cold?

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londonsnow.jpg
Short answer: it's winter.
Longer answer: it's the NAO, and no it doesn't mean global warming is a hoax.

Winter is always an interesting time for climate researchers. The oceanographer in me has always been fascinated with how the ocean's memory (encoded as the distribution of temperature and salinity) has a tendency to remember winter and forget summer.  As someone interested in climate change and how it is perceived and portrayed, winter is when the crazy comes out.  It's easy for people to conclude the earth might be warming when they're baking in a July heat wave.  It's a much harder sell when you're shoveling snow.


The recent spate of cold weather in Europe is a great example.  Last winter, Europe was colder than it had been in recent memory, and this year seems off to a similar start.  Winter weather in Europe is strongly correlated with the North Atlantic Oscillation (NAO) Index.  The NAO is essentially a measure for the size and strength of the cold, high pressure region centered over Iceland and the warm, low pressure region centered over the Azores.  During the "positive" state of the NAO, the low is lower, the high is higher, and the high pressure area expands northward.  This brings mild weather to most of Europe and pushes the track of winter storms over Scandinavia.  When the NAO is in its "negative" state, the low pressure area expands southward, bridging colder air over Europe.  For reasons that are still unclear (at least to me), the NAO can often get locked into one of these states, with positive or negative conditions persisting for several months.  This is what happened last year--the monthly NAO was strongly negative from October 2009 to now.  This year looks to be headed in the same direction, and the recent strongly negative NAO conditions are the proximal explanation for Europe's cold spell.  

nao.mrf.obs.jpg


Whether the negative NAO will stick around and keep Europe frozen all winter is anyones guess.  Regardless, it has almost nothing to do with climate change.  The main global warming hypothesis, namely, that increased CO2 in the atmosphere causes global mean temperatures to rise, is fundamentally about the total amount of heat on the planet.  Europe can be cold, but if the rest of the world is warmer, the global mean temperature will go up.  This is exactly what happens with the NAO.  Cold conditions in Europe are often associated with warmer conditions in the Canadian Maritimes, and often in New England.  Based on the weather here in Portland (still haven't dug the snow boots out of the garage, and Walt is still wearing shorts), we could write an article about the dire consequences from global warming.  Of course, this would be equally wrong as some of the stories coming from Europe.  Before anyone declares that climate change is not occurring because it snowed in London, they should do their homework.  If it's also colder in New York, Tokyo, Mumbai, Sydney, Cape Town, and Palmer Station, then they might have something.  


Weather or Climate?

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Yesterday, in Rimouski and all along the coast of Bas-St-Laurent and Gaspésie (Québec), it was very rainy and very windy with gusts around 80 to 100 km/h.  A depression was installed just over the St-Lawrence estuary.  Combine that to some really high spring tides and we ended up with hundreds of displaced people, thousands of damaged properties along the shore and millions of $ in damages (and don't argue that's Canadian $, it worth the same now!).

 


Just imagine that beyond the rolling waves, there should be a 4m tall wall, with a large beach, and then the waters...


Would it be unfair to blame that on climate change?  I agree it is more about weather here, but it's been observed that hitching a ride with climate change, extreme weather events are on the rise.  And it's not just climatologists: some old folks in their 80's told yesterday in the news that they don't remember something like that...  and that it should have been snowing at this time of year!  We grow wary having to wait to prepare our country-skiing trails!

 

Moreover, it was the same pattern earlier this year when the Gulf of St-Lawrence seal's breeding and subsequent hunting seasons were a disaster due to the record low sea-ice condition.  Other old folks said they did not remember years... oh no, wait, they remembered one year in the 50's, of no hunting season because there was no ice at the horizon!  And strangely, no need to be an old folk to remember 2007 and 2002, which were really bad, too...


GSL_ice_anomaly_Feb15_2010.gif

 

 And this is the real deal.  Less sea-ice, less land-fast ice especially.  Huge coastal lands have already been lost to erosion everywhere along the Gulf of St-Lawrence coasts, because there is less and less ice to protect the shore from the raging winter waves.  And during the past 50 years or so, several cycles of positive/negative NAO, El-Nino/La-Nina occurred... but the trend remained, and increased steadily.

 

Climate change can severely harm cute fluffy harp seals pups, sure, but it definitely affect the life of people, climate sceptics and environmentalists alike, if they happen to live in the wrong place, which used to be the best places not so long ago.

Climate focus for early 2011

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bears.jpgPrompted by Fred's post, I've decided to emphasize climate variability and change over the next few months.  Keep an eye out for commentary on winter weather conditions, especially as they relate to the North Atlantic Oscillation (an old buddy of mine) and the current La Nina in the Pacific.  This will hopefully include a forecast or two for copepods and right whales for the next few years.  I am also in the process of boning up on my understanding of the climate change controversy, and I plan to post reviews of several recent books on the topic:

  • Jim Hansen's "Storms of My Grandchildren"
  • Roger Pielke, Jr.'s "The Climate Fix"
  • James Hoggan's "Climate Cover-up: The Crusade to Deny Global Warming"
  • Roy Spencer's "The Great Global Warming Blunder: How Mother Nature Fooled the World's Top Climate Scientists"
Hansen is a climate scientist at NASA and has made very strong claims about the potential severity of climate change, and thus the need for action.  Pielke is a political scientist at U. Colorado, and my understanding (haven't read the book, yet) is that he acknowledges evidence for a changing climate but is less action-oriented than Hansen.  Hoggan is a journalist and his book is supposed to be an exploration of the effort by big companies to shift the climate change debate.  Finally, Spencer is a well-respected scientist who takes a dim view of the science behind global warming.  I'm hoping this will provide a good cross section of how different groups view climate change.  I'll try to give each viewpoint a fair shake.  Stay tuned...

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