Here’s the latest essay by Matti Vooro. Like Ed Caryl, Matti has written some very successful essays. At least two of them have been translated in German and posted at German sites.
Are European Winters Going To Stay Warm? By Matti Vooro
North America’s winters have been getting colder since 2006, and Europe had its two warmest winters ever in 2007 and 2008 as the AO, NAO and AMO were all positive. All this may be changing over the next several decades. Cooling was already evident after 2007 as both the winter AO and NAO went negative.
Figure 1 shows the European winter temperature departures, land and sea, for years 1948 -2009. The graph shows above normal temperature anomalies in the period 1948-1964, followed by a cooler period 1962-1987 when the temperature anomalies were mostly below normal except when they were briefly interrupted by a warm period in the first half of the 1970’s due to a number of years with a warm or positive AO. This was then followed by a warm period 1987-2007. Winter temperatures started to decline after 2007.
Figure 2 shows again the European winter temperature departures (land and sea) together with the winter AO and winter AMO Indices. Europe‘s climate seems to be significantly affected by AO and AMO. The drop in winter temperature deviations as the winter AO went strongly negative is especially noticeable in the winters of 2009, 2010 and 2011. AMO is still positive or warm.
Figure 3 shows a correlation between winter NAO and winter AO and both are reflected in the European winter temperatures. One is a subset of the other. The negative phase of NAO implies high pressure anomaly over Iceland, low pressure anomaly over sub-tropical Atlantic, weakened mid-latitude easterlies, colder over Northern Europe, milder over Greenland, colder and snowier for eastern US. This was the dominant phase from the mid 1950s through late 1970s. The negative AO, NAO and AMO seem to be returning.
The annual and monthly AO data can be found here.
The figures below show how the variation in the number of negative or cool winter NAO’s affected the cool and warm periods in the past.
1920 – 1940: 9 negative or cool winter NAO years [WARM PERIOD]
1950 – 1970: 14 negative or cool winter NAO years [COLD PERIOD]
1980 – 2009: 8 negative or cool winter NAO years [WARM PERIOD]
Figure 4 supplied by the NOAA shows the change in the winter AO from basically being positive from 1989 to 2008 to now becoming strongly negative.
Last cool period for Europe
Figure 5 shows the European winter temperature [land and sea] and the winter AO index for the years 1962-1987, the last cool period in Europe. During this time 17 or 2/3 of the winters were below norm and had an average mean temperature departure of -0.14°C (range of -1.28°C to +0.93°C). During the 22 years after this period , the average mean winter temperature was + 0.63°C with a range of +1.54°C to -0.27° C.
Recent historical European winter temperature departures from 1961-1990 base for the years 1998 -2009
Figure 6 shows the European winter temperature departure [land and sea] and the winter AO and AMO index more recently for the years 1998 -2008. Notice that there has been no significant increase in temperature departures other than 2007-2008 and the temperature anomalies have actually started to decline as the AO stared to decline after 2007 and have done so for the last 3 years and possibly 4 years if 2011 is
I have estimated the 2010 winter anomaly. It is bound to be negative as UK 2010 winter temperature dropped by 1.57 °C over 2009. Table of recent historical European winter temperature departures (land and sea) from 1961-1990 base for the years 1998 -2009
2010 -1.0 (estimated, not available until May 2011)
2011 not available
The average mean winter temperature anomaly during this most recent period of 1998 to2009 was 0.73°C while during the previous cooler period it was – 0.14°C or almost a full degree cooler. La Nina winters have not been exceptionally cold for Europe. Seven of the last La Nina winters have been above normal and the average anomaly for the last four was o.89°C well above the 0.73°C average above. The 2011 winter anomaly will be down because of the cold December 2010
All of the above European winter temperature departure data can be found at the following web page of European Environment Agency.
I find no evidence in the field during the post 2007 period to support the IPCC prediction that “The warming in northern Europe is likely to be largest in winter…”. The flat global temperatures for the last 10 years and the recent cooling since about 2006-2007 seem to be consistent with the cooling taking place now all over Northern Hemisphere, including Europe, as the natural planetary cycles enter their cool mode. Once the North Atlantic ocean SST and AMO start to contribute to the global cooling in a more significant way, the global temperatures of the western coast of Europe and the Arctic will be the cooling more consistently. This cooler period could last 30 years as they have done nearly 20 times during the last 500 years.
Matt Vooro, P.Eng