The Months That Buck The Trend!

[Isolated Frost]

Of course, temperatures have slowly been rising in the last few decades, but are there months that buck the trend?

Example:

December - 1961-1990 (3.9C)

December - 1971-2000 (4.3C)

December - 2001-2009 (4.1C)

Here are some stats from Durham Observatory, showing that, December has been cooler in the last decade, than in the period between 1971-2000. Anything below 2.5C as the mean for this December would mean that on a whole, this decade's December's have been as cold (or even colder) than the 61-90 period.

Another one:

October - 1961-1990 (9.8C)

October - 1971-2000 (9.5C)

Of course, the temperatures in October are also reflected in the CET average, with 71-00 also being cooler.

May - 1961-1990 (9.9C)

May - 1971-2000 (9.9C)

May, is an oddity, a summer month which has the same average.

However, there are some months with obvious warming trends.

November - 1961-1990 (5.7C)

November - 1971-2000 (6.0C)

November - 2001-2009 (7.2C!)

Do you keep any records of your temperatures, or have records nearby? Do you have months that buck the trend?

[reef]

The ten-year averages in this location have shown a marked increase from the 1990s to the 2000s with the exception of March which is marginally cooler. My records begin in 1982 so the 80s are incomplete, however these are also rather cooler than the 90s, so a clear warming trend:

Month Average (80s/90s/00s) (1971-2000 in brackets)

JAN: 3.5 / 4.3 / 5.2 (4.2)

FEB: 2.8 / 5.0 / 5.3 (4.6)

MAR: 5.2 / 6.9 / 6.8 (6.5)

APR: 7.1 / 8.4 / 9.2 (8.2)

MAY: 10.5 / 11.3 / 12.2 (11.4)

JUN: 13.8 / 14.0 / 15.3 (14.2)

JUL: 16.4 / 16.7 / 17.0 (16.7)

AUG: 15.6 / 16.7 / 17.2 (16.6)

SEP: 13.5 / 13.7 / 14.9 (14.3)

OCT: 10.5 / 10.4 / 11.5 (10.8]

NOV: 6.5 / 7.1 / 7.5 (7.0)

DEC: 5.4 / 4.4 / 4.8 (5.1)

ANN: 9.2 / 9.9 / 10.6 (10.0)

(1980s covers period June 1982 - December 1989)

Also interesting about these figures is the mean minima has warmed by 0.9C between the '80s' and '00' decadal averages, yet the mean maxima by 1.8C in the same period.

[Isolated Frost]

The ten-year averages in this location have shown a marked increase from the 1990s to the 2000s with the exception of March which is marginally cooler. My records begin in 1982 so the 80s are incomplete, however these are also rather cooler than the 90s, so a clear warming trend:

Month Average (80s/90s/00s) (1971-2000 in brackets)

JAN: 3.5 / 4.3 / 5.2 (4.2)

FEB: 2.8 / 5.0 / 5.3 (4.6)

MAR: 5.2 / 6.9 / 6.8 (6.5)

APR: 7.1 / 8.4 / 9.2 (8.2)

MAY: 10.5 / 11.3 / 12.2 (11.4)

JUN: 13.8 / 14.0 / 15.3 (14.2)

JUL: 16.4 / 16.7 / 17.0 (16.7)

AUG: 15.6 / 16.7 / 17.2 (16.6)

SEP: 13.5 / 13.7 / 14.9 (14.3)

OCT: 10.5 / 10.4 / 11.5 (10.8]

NOV: 6.5 / 7.1 / 7.5 (7.0)

DEC: 5.4 / 4.4 / 4.8 (5.1)

ANN: 9.2 / 9.9 / 10.6 (10.0)

(1980s covers period June 1982 - December 1989)

Also interesting about these figures is the mean minima has warmed by 0.9C between the '80s' and '00' decadal averages, yet the mean maxima by 1.8C in the same period.

Interesting note about March, it was only just marginally warmer here in the last 10 years than before.

The fact that maxima have gone up more than minima, would indicate increased sunlight (and clearness) as minima of course are usually cooler under clear skies and maxima are warmer. Wouldn't it?

[Isolated Frost]

Very interesting statistic here:

At Durham Observatory, the period between 1971 and 1980 gave December an average temperature of 4.2C, in the period, 2001-09, our average in December is 4.0C. Using this, we've found that, a mean temperature of 5.9C this coming December would make the 81-10 figure less than 71-00 figure.

So, December's have been cooler in the noughties than in the seventies.

[Thundery wintry showers]

...unless we get a December like that of 1988, which had a mean temperature of 7.3C at Durham!

[Isolated Frost]

...unless we get a December like that of 1988, which had a mean temperature of 7.3C at Durham!

Yep, but that is actually the only December that had mean maxima above 10C (10.1C) since Records Began in the late 1800's.

5.9C is extremely do-able and it would be interesting in 10 years, as this decade has been colder than average, the 80's were above average, so if the next decade is below average, 91-20 could be very cool indeed.

[AderynCoch]

For the period 1988-2009 inclusive, December has actually been the coldest winter month (Dec = 4.82C, Jan = 4.94C, Feb = 5.06C). This is rather strange when you consider how January and February are supposed to be the "meat" of the winter.

Thanks to a cold January and February this year, December 2010 needs to come in at below 3.9C to be the coldest month for the period 1988-2010 (3.9C exactly will place it equal with January). However, for the period 1989-2010 it will need to be above 6.0C to not be the coldest month (6.1C exactly will place it equal with January), thanks to the very mild December of 1988 being wiped off the slate.

Edited October 25, 2010 by AderynCoch

[Isolated Frost]

For the period 1988-2009 inclusive, December has actually been the coldest winter month (Dec = 4.82C, Jan = 4.94C, Feb = 5.06C). This is rather strange when you consider how January and February are supposed to be the "meat" of the winter.

Thanks to a cold January and February this year, December 2010 needs to come in at below 3.9C to be the coldest month forthe period 1988-2010 (3.9C exactly will place it equal with January). However, for the period 1989-2010 it will need to be above 6.0C to not be the coldest month for this period (6.1C exactly will place it equal with January), thanks to the very mild December of 1988 being wiped off the slate.

So your value was really distorted by the 1988 figure!

Overall, it looks like December is the real stand-out month for most people.