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2009-2010 winter saw record cold spells

What the science says...

The cold snap is due to a strong phase of the Arctic Oscillation. This is causing cool temperatures at mid-latitudes (eg - Eurasia and North America) and warming in polar regions (Greenland and Arctic Ocean). The warm and cool regions roughly balance each other out with little impact on global temperature.

Climate Myth...

2009-2010 winter saw record cold spells
"Britain's big freeze is the start of a worldwide trend towards colder weather that seriously challenges global warming theories, eminent scientists claimed yesterday. The world has entered a 'cold mode' which is likely to bring a global dip in temperatures which will last for 20 to 30 years, they say." (Daily Mail)

Through December 2009 and January 2010, a dramatic cold spell swept across Eurasia, England and parts of North America. The most spectacular image capturing this phenomenon is a satellite photo revealing the whole of Britain covered in snow. Does this mean global warming has stopped? To determine this, one needs to step back and look at the broader picture. For starters, here is a temperature map of the entire Arctic circle and beyond:


Figure 1: Map of temperature anomalies for December 2009 at roughly 1000 metres altitude for the region north of 30°N (NSIDC). Areas in orange and red correspond to strong warm anomalies. Areas in blue and purple correspond to cool anomalies.

Eurasia and North America are experiencing unusually cold conditions. On the other hand, Greenland, eastern Siberia and the Arctic ocean are experiencing unusual warmth. The warmest regions (more than 7° Celsius above average) are over the Atlantic side of the Arctic, including Baffin Bay and Davis Strait. Unsurprisingly, sea ice extent was below average in this region.

These strong contrasts in temperature are the result of a strongly negative phase of the Arctic Oscillation.  This is caused by opposing patterns of atmospheric pressure between the polar regions and mid-latitudes. During a negative phase, pressures are higher than normal over the Arctic and lower than normal in mid-latitudes. In December 2009, the Arctic Oscillation index was -3.41, the most negative value since at least 1950. Note the blue dot in the bottom right corner representing December 2009.

Arctic Oscillation Index
Figure 2: Blue dots are monthly Arctic Oscillation Index. Red line is one year running mean (sourced from Andrew Revkin, plotted by Ignatius Rigor).

An even broader picture is a global map of temperature anomaly in the last week of December 2009. Here we see that much of the planet is experiencing warmer temperatures than usual, including North-east America, Canada, North Africa, the Mediterranean, and south-west Asia.


Figure 3: Map of global temperature anomalies, December 26 to January 1 (Met Office).

To conclude that global warming has ended based on recent cold snaps is another example of the misleading practice of focusing on small pieces of the puzzle while ignoring the broader picture. Interestingly, Roger Pielke Sr takes the opposite approach when assessing global temperature in December 2009 as measured by satellites. Despite the regional cold weather, global temperature has not shown a dramatic drop in December, leading Pielke to conclude (with original emphasis included):

"This data shows why the focus needs to be on the regional scale and that a global average is not of much use in describing weather that all of us experience."

After taking a broader look at global temperature, Pielke is forced to conclude that it's preferable to focus on small pieces of the puzzle than the bigger picture. Better that is, if the global picture isn't giving you the result you're looking for.

Last updated on 26 June 2010 by John Cook.

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Comments

Comments 1 to 17:

  1. Could the deep solar minimum that we had for the past few years have been the cause of the extreme negative phase of the Arctic Oscillation? Because I read paper(I don't recall the name) suggesting that low solar activity lowers the Arctic Oscillation index. Or could it have been Arctic warming that triggered the extreme negative phase of the Arctic Oscillation? A paper that I came across, Francis et al(2009)suggests that reduced sea ice extent weakens the equator to pole temperature gradient and lowers the Arctic Oscillation and North Atlantic Oscillation indexes, allowing arctic air to spill into mid latitudes. If so, will the Arctic Oscillation index trend more negative in coming decades, and could this outstrip the influence that stratospheric cooling from increases in greenhouse gases have on the Arctic Oscillation index(which tends to raise the Arctic Oscillaion index)? Do you have any answers?
  2. As the oceans are heat capacitors of the planet and there are 3 of them, Pacific, Atlantic and the Indian ocean it is reasonable to suggest cold intrusions from either pole will affect the weather systems over them. This combined with the Walker circulation and ENSO might produce an uneven rythm on the weather patterns over land areas, even without the GW effect. There was a paper recently of the significance to the warming of the S Atlantic of Agulhas current, but of course I've lost the link. Similar patterns would be the Indonesian throughflow (linked to ENSO and IOD) and the cold water intrusion to N Atlantic (likely linked to NAO). In combination these likely produce the teleconnection patterns the values of which are usually evaluated after they've happened, but which also have a limited amount of predictive value.
  3. jyyh
    the paper you quote should be Turney and Jones 2010. Please not that they call the Agulhas current effect a feedback, not a forcing.
  4. (From Positives & Negatives of Global Warming)

    Argus wrote, quoting from WEEKLYSTANDARD.COM : "In the middle of the month, the German Weather Service quietly acknowledged that the country was experiencing record cold: some 3-5 degrees Celsius below the long-term averages."


    "Quietly acknowledged", as in notified by press release by the German Met Office :


    Germany weather in May 2010 - Very cool, very wet, and how rarely the sun shone.
    Deutscher Wetterdienst


    Meanwhile, the rest of the highlights for May show why the odd low temperature was of less interest :


    The combined global land and ocean average surface temperature for May 2010...the warmest such value on record since 1880.

    For March–May 2010, the combined global land and ocean surface temperature was...the warmest March-May on record.

    The combined global land and ocean average surface temperature for January–May 2010 was the warmest on record.

    The worldwide ocean surface temperature for May 2010 was the second warmest May on record...

    The seasonal (March–May 2010) worldwide ocean surface temperature was the second warmest such period on record...

    The global land surface temperatures for May and the March–May period were the warmest on record...

    In the Northern Hemisphere, both the May 2010 average temperature for land areas, and the hemisphere as a whole (land and ocean surface combined), represented the warmest May on record. The Northern Hemisphere ocean temperature was the second warmest May on record. The average combined land and ocean surface temperature for the Northern Hemisphere was also record warmest for the March–May period.

    State of the Climate Global Analysis May 2010

    Why do some not seem to see the difference between a cold record which goes back maybe two or three decades (at most, normally - since 1991 in this German case), and warm records that are the warmest or second warmest in records going back 130 years ?
  5. JMurphy: "Why do some not seem to see the difference between a cold record which goes back maybe two or three decades (at most, normally - since 1991 in this German case), and warm records that are the warmest or second warmest in records going back 130 years ?"

    Am I "some"? - I know nothing about Germany in May - it just slipped into a comment because I quoted an article about an all-time low in an Antarctic station. I also, in an earlier comment, quoted recent all-time lows in Wales and N. Ireland for November - coldest "since records began".

    In Stockholm the weekend offered the coldest temperatures since 1965 (for November), and it is expected (according to today's newspapers) that records from either 1904 (-17) or 1884 (-18) will be beaten this week.

    But it's all due to NAO-, so I guess it doesn't count at all.
  6. Argus wrote : "Am I "some"? - I know nothing about Germany in May - it just slipped into a comment because I quoted an article about an all-time low in an Antarctic station. I also, in an earlier comment, quoted recent all-time lows in Wales and N. Ireland for November - coldest "since records began"."


    You do seem to be one of those who like to point out cold temperature records (no matter how significant or relevant), as if they meant anything. What do you think they mean ?

    Perhaps this should be discussed over on Does cold weather disprove global warming?

    Have you read that thread ? If so, what point do you believe you are trying to make by highlighting scarce cold records from individual locations ?

    How about this thread ?
  7. argus.
    These October maps give a good indication of the (im)balance between hot and cold temperatures. It's fairly certain that the large blue dots include some all-time record low temps, but they are far outnumbered by the large red dots in many more places.

    http://www.ncdc.noaa.gov/sotc/service/global/map-blended-mntp/201010.gif
  8. JMurphy,
    You, on the other hand, "do seem to be one of those who like to point out" hot temperature records (no matter how significant or relevant), as if they meant anything. And, at the same time, you like to neglect all cold temperature records (because they don't fit in nicely?).

    The fact is that 2010 has been a very warm year, with many national records beaten, especially during the summer in the northern hemisphere. Wikipedia lists 14 heat records and no cold ones. Dr. Jeff Masters' WunderBlog lists 17 heat records and only one cold (in Guinea).

    This is unusual, but how much does one year mean? What do you think? Does one year's weather constitute proof of a change in climate, or does it take several continuous years of records? What if 2011 turns out to be one of the coldest years ever? What will the climate experts say then (my guess is that it would become yet another proof of AGW, somehow)?

    As for the suggestion, "Perhaps this should be discussed over on 'Does cold weather disprove global warming?'" - well, I don't know. I have already been directed to this thread once, from another one that wasn't appropriate enough. Perhaps there are too many threads on this site.
  9. Argus wrote : "You, on the other hand, "do seem to be one of those who like to point out" hot temperature records (no matter how significant or relevant), as if they meant anything. And, at the same time, you like to neglect all cold temperature records (because they don't fit in nicely?)."


    None of that is true because :

    The temperature records I point out are significant - check the positions in the records and see how many are in the top 5, but mainly in the top 2. They are also mainly relative to global or regional records.
    Compare and contrast with your cold records.

    They are relevant because they are further evidence of a warming world, especially as hot records outstrip cold ones, and have been doing so since at least the 80s - as shown for America here.

    Cold records have been noted by myself on previous occasions, especially on the other thread I mentioned previously.

    Cold records are still possible in a warming world (why shouldn't they be ? Are cold days impossible during Summer ?), so there is no assertion by me that they "don't fit in nicely".


    Argus wrote : "The fact is that 2010 has been a very warm year, with many national records beaten, especially during the summer in the northern hemisphere. Wikipedia lists 14 heat records and no cold ones. Dr. Jeff Masters' WunderBlog lists 17 heat records and only one cold (in Guinea)."

    Actually, to be more updated, there were NO cold records.

    And 2010 just joins a long list of record-breaking years and decades. And October also joins the long list of record-breaking months, even under conditions that include a la Nina and an inactive sun. See the relevance again ?



    Argus wrote : "This is unusual, but how much does one year mean? What do you think? Does one year's weather constitute proof of a change in climate, or does it take several continuous years of records? What if 2011 turns out to be one of the coldest years ever? What will the climate experts say then (my guess is that it would become yet another proof of AGW, somehow)?"


    Not unusual at all, and when you add it to lots of years (not wanting to base everything on one year, of course), a pattern seems to be developing. And you can't see it yet ?

    There is nothing stopping 2011 being "one of the coldest years ever". Unlikey but certainly not impossible and certainly not another final nail in the coffin of AGW. For that, you will need..."several continuous years of records" - let's go for 30, shall we ?
  10. Check out the cool satellite shot of snow blanketing the UK (from Science Daily).


  11. The image @10 is somewhat misleading; note the "snow" in the English channel, North Sea and Irish Sea. The area where I live appears to be covered in snow, but there was none. Clouding the issue perhaps ? (Ouch, sorry)
  12. #11: "The image @10 is somewhat misleading"

    Indeed. This thread is about winter 2009-2010; the photo date puts it in winter 2010-2011.
  13. Re: Rob Painting (10)

    Here's one from January 7th, 2010

  14. 11 & 12 - Sure it's not winter 2009-2010, but given the change in Arctic weather patterns, it may become an annual skeptic talking point.
  15. #14: "become an annual skeptic talking point. "

    It already has. Try searching 'coldest November in living memory'.

    But here is some interesting anecdotal perspective on historic winters in the UK.
  16. Muoncounter - I'm talking about the cold winter UK, in particular, being a regular occurrence, based on changes in the Arctic Oscillation. Not the "but there's record cold in Wagga Wagga" or whatever line the skeptics cling to.

    Sure it's likely to be a transient phase (the rest of the world will still be getting warmer) but I expect a similar future break-down in the circum-polar winds around Antarctica (Southern Annular Mode) will lead to similar outbreaks of cold weather. Living in New Zealand, that may affect me personally, but I probably won't be around when that happens.

  17. A new study (Sept 2011) confirms and extends the thesis of this post to winter 2010-2011. Link to pdf.

    Recent warm and cold daily winter temperature extremes in the Northern Hemisphere

    While some parts clearly experienced very cold temperatures, the NH was not anomalously cold. Extreme warm events were much more prevalent in both magnitude and spatial extent. Importantly, the persistent negative state of the North Atlantic Oscillation (NAO) explained the bulk of the observed cold anomalies, however the warm extremes were anomalous even accounting for the NAO and also considering the states of the Pacific Decadal Oscillation (PDO) and El Niño Southern Oscillation (ENSO). These winters’ widespread and intense warm extremes together with a continuing hemispheric decline in cold snap activity was a pattern fully consistent with a continuation of the warming trend observed in recent decades.
    -- emphasis added

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