This time 10 years ago.....

[Weather-history]

........we were wondering when the next below average month was going to happen, they had become that seldom events. Infact by 1st August 2005, the last month that was below the 1971-2000 average was July 2004, a year before.

If we compare the period 1st January 2001 to 1st August 2005 to the period 1st January 2011 to 1st August 2015 with the number of months that were below the 1971-2000 average, it is quite revealing

1st Jan 01-1st Aug 05: 11

1st Jan 11-1st Aug 15: 24

If we compare last decade, 2000-09 with the current one 2010 to present day and the number of months that were at least 0.5C below the 1961-90 average.

Months at least 0.5C below the 1961-90 average since January 2000

Aug 2014: 14.9

Jun 2013: 13.6

May 2013: 10.4

Mar 2013: 2.7

Feb 2013: 3.2

Oct 2012: 9.7

Sep 2012: 13.0

Jul 2012: 15.5

Jun 2012: 13.5

Apr 2012: 7.2

July 2011: 15.2

Dec 2010: -0.7

Nov 2010: 5.2

Aug 2010: 15.3

May 2010: 10.7

Feb 2010: 2.8

Jan 2010: 1.4

--------------------------------

Dec 2009: 3.1

Jan 2009: 3.0

Dec 2008: 3.5

Oct 2008: 9.7

July 2007: 15.2

Mar 2006: 4.9

Oct 2003: 9.2

Oct 2002: 10.1

Dec 2001: 3.6

Mar 2001: 5.2

Jan 2001: 3.2

Jul 2000: 15.5

There were only 12 such months during the 2000s. There have already been 17 such months during the 2010s and we still got over 4 years of this decade left

------------------------------

The question is why have below average months suddenly increased? I personally think the turning point was the spring of 2008, when the number -NAO months increased from about spring 2008 to January 2011, they were hardly any +ve NAO months in that period. Why did we record so many -ve NAO months? Solar activity? It makes you wonder.

If we compare 1st January 2008 to present day with 1st January 1998 to 31st December 2007 and the number of months below the 1971-2000 average, it is quite stark

1st Jan '98-31st Dec '07: 25

1st Jan '08- present day: 44 and we still got 29 months left before this decadal period is finished.

[4wd]

I'd say we have to conclude it's cooling, probably due to reduced solar activity.

Similarly the previous warming period, which has been played as largely man made, was probably largely due to increased solar activity beforehand.

[BornFromTheVoid]

........we were wondering when the next below average month was going to happen, they had become that seldom events. Infact by 1st August 2005, the last month that was below the 1971-2000 average was July 2004, a year before.

If we compare the period 1st January 2001 to 1st August 2005 to the period 1st January 2011 to 1st August 2015 with the number of months that were below the 1971-2000 average, it is quite revealing

1st Jan 01-1st Aug 05: 11

1st Jan 11-1st Aug 15: 24

If we compare last decade, 2000-09 with the current one 2010 to present day and the number of months that were at least 0.5C below the 1961-90 average.

Months at least 0.5C below the 1961-90 average since January 2000

Aug 2014: 14.9

Jun 2013: 13.6

May 2013: 10.4

Mar 2013: 2.7

Feb 2013: 3.2

Oct 2012: 9.7

Sep 2012: 13.0

Jul 2012: 15.5

Jun 2012: 13.5

Apr 2012: 7.2

July 2011: 15.2

Dec 2010: -0.7

Nov 2010: 5.2

Aug 2010: 15.3

May 2010: 10.7

Feb 2010: 2.8

Jan 2010: 1.4

--------------------------------

Dec 2009: 3.1

Jan 2009: 3.0

Dec 2008: 3.5

Oct 2008: 9.7

July 2007: 15.2

Mar 2006: 4.9

Oct 2003: 9.2

Oct 2002: 10.1

Dec 2001: 3.6

Mar 2001: 5.2

Jan 2001: 3.2

Jul 2000: 15.5

There were only 12 such months during the 2000s. There have already been 17 such months during the 2010s and we still got over 4 years of this decade left

------------------------------

The question is why have below average months suddenly increased? I personally think the turning point was the spring of 2008, when the number -NAO months increased from about spring 2008 to January 2011, they were hardly any +ve NAO months in that period. Why did we record so many -ve NAO months? Solar activity? It makes you wonder.

If we compare 1st January 2008 to present day with 1st January 1998 to 31st December 2007 and the number of months below the 1971-2000 average, it is quite stark

1st Jan '98-31st Dec '07: 25

1st Jan '08- present day: 44 and we still got 29 months left before this decadal period is finished.

 

I'd say the combination of changes in the Arctic with reduced solar activity. Both, it seems, tend to increase blocking highs by producing larger and slower moving Rossby waves, resulting in more extreme months, both warm and cold.

 

The graph below shows the number of months at least 1.0C above and below the 71-00 average, and the total for each year since 1950.

 

 

There's essentially no trend in the total of (>1.0C) above and below average months, just a shift from mainly below to mainly above. Of course, 2014 stands out quite a bit, as does the 1997 to 2008 period for the distinct lack of below average months.

 

The 10 year rolling mean for above average months is currently 3.9 (>1.0C above average months per year), which is still higher than any decade before 1997. The same value for below average months is currently at 1.6 (>1.0C below average months per year), which is still lower than decade before 2002.