Hello, Thank you for the email in connection with CET FIGURES 1961-2020

We have received the following response from the team that manages this.

 

At present, as the correspondent has spotted, the HadCET pages on the external HADobs website quote CET statistics w.r.t.the 1961-1990 averaging period.

These pages will be updated when we complete the transition to a new version of HadCet which will be referred to as HadCETvn2, which e hope will be achieved by the middle of this year. At this point, the web pages will be redesigned and will be able to quote statistics w.r.t. either1961-1990 or 1991-2010. At the same time, it is likely that a user interface will be introduced which will allow much more flexibility in what information can be displayed in response to real-time user requests. In the meantime, though, with these future plans in mind, our existing offering is unlikely to be enhanced as these web pages will soon be  "end of life".

I hope this helps and thank you for getting in touch

Weather Desk Met office Exeter Devon

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I'm surprised that they quote 1991-2010 as an option, as I thought that the WMO-approved standard period for climate averages was thirty years, a shorter period presumably being thought to run the risk of being overinfluenced by one or two exceptional years. But perhaps 1991 was just their typo for 1981.

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I'm surprised that they quote 1991-2010 as an option, as I thought that the WMO-approved standard period for climate averages was thirty years, a shorter period presumably being thought to run the risk of being overinfluenced by one or two exceptional years. But perhaps 1991 was just their typo for 1981.

I think its a school-boy error.  30 yrs is the standard.

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Maybe we should move on and accept new modern figures.

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Maybe we should move on and accept new modern figures.

It’s an interesting point. I’ve always accepted that the average is a baseline against which to describe the current weather, ie the conditions relative to what might normally be expected.  Unless the reference period is updated periodically (every decade) then increasingly the baseline becomes a less accurate/relevant reference point.

But in terms of describing the effects of climate change we also need to be showing how temperatures of the 30-year reference periods have increased.  1961-1990 v 1991-2020 is likely to be an eye-opener for some, and a grim confirmation for others, of how fast our climate is shifting (‘fast’ in geological terms).

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One of the problems flagged up elsewhere is that we now report "above average" for the majority of the months because temperatures in the UK are rising so quickly. Therefore, switching to a 20 year measure may have help; however, I personally would stick with the 30 year period because there is a lot of value in seeing how things are changing.

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It’s an interesting point. I’ve always accepted that the average is a baseline against which to describe the current weather, ie the conditions relative to what might normally be expected.  Unless the reference period is updated periodically (every decade) then increasingly the baseline becomes a less accurate/relevant reference point.

But in terms of describing the effects of climate change we also need to be showing how temperatures of the 30-year reference periods have increased.  1961-1990 v 1991-2020 is likely to be an eye-opener for some, and a grim confirmation for others, of how fast our climate is shifting (‘fast’ in geological terms).

Read your post after making mine. This is exactly the point. 

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I vaguely remember it took forever for the Met Office to switch from the 61 - 91 average to the 71 - 01 average.

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It’s an interesting point. I’ve always accepted that the average is a baseline against which to describe the current weather, ie the conditions relative to what might normally be expected.  Unless the reference period is updated periodically (every decade) then increasingly the baseline becomes a less accurate/relevant reference point.

But in terms of describing the effects of climate change we also need to be showing how temperatures of the 30-year reference periods have increased.  1961-1990 v 1991-2020 is likely to be an eye-opener for some, and a grim confirmation for others, of how fast our climate is shifting (‘fast’ in geological terms).

This table shows the running 30 year CET average (annual) since the 1961-1990 period. 

30 year base		30 year avg
1961	1990	9.51
1962	1991	9.49
1963	1992	9.54
1964	1993	9.57
1965	1994	9.60
1966	1995	9.65
1967	1996	9.64
1968	1997	9.67
1969	1998	9.71
1970	1999	9.75
1971	2000	9.77
1972	2001	9.78
1973	2002	9.83
1974	2003	9.86
1975	2004	9.89
1976	2005	9.91
1977	2006	9.93
1978	2007	9.96
1979	2008	9.98
1980	2009	10.02
1981	2010	10.00
1982	2011	10.05
1983	2012	10.05
1984	2013	10.03
1985	2014	10.07
1986	2015	10.12
1987	2016	10.17
1988	2017	10.22
1989	2018	10.25
1990	2019	10.24
1991	2020	10.25
1992	2021	10.27

From: https://www.metoffice.gov.uk/hadobs/hadcet/cetml1659on.dat

On average, there is about a 0.02/3c increase in each consecutive 30 year period with an upward trend that is pretty much consistently linear. 

 

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One of the problems flagged up elsewhere is that we now report "above average" for the majority of the months because temperatures in the UK are rising so quickly. Therefore, switching to a 20 year measure may have help; however, I personally would stick with the 30 year period because there is a lot of value in seeing how things are changing.

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Hello, Thank you for the email in connection with CET FIGURES 1961-2020

We have received the following response from the team that manages this.

 

At present, as the correspondent has spotted, the HadCET pages on the external HADobs website quote CET statistics w.r.t.the 1961-1990 averaging period.

These pages will be updated when we complete the transition to a new version of HadCet which will be referred to as HadCETvn2, which e hope will be achieved by the middle of this year. At this point, the web pages will be redesigned and will be able to quote statistics w.r.t. either1961-1990 or 1991-2010. At the same time, it is likely that a user interface will be introduced which will allow much more flexibility in what information can be displayed in response to real-time user requests. In the meantime, though, with these future plans in mind, our existing offering is unlikely to be enhanced as these web pages will soon be  "end of life".

I hope this helps and thank you for getting in touch

Weather Desk Met office Exeter Devon

A big thanks and well done for doing this.

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This table shows the running 30 year CET average (annual) since the 1961-1990 period. 

30 year base		30 year avg
1961	1990	9.51
1962	1991	9.49
1963	1992	9.54
1964	1993	9.57
1965	1994	9.60
1966	1995	9.65
1967	1996	9.64
1968	1997	9.67
1969	1998	9.71
1970	1999	9.75
1971	2000	9.77
1972	2001	9.78
1973	2002	9.83
1974	2003	9.86
1975	2004	9.89
1976	2005	9.91
1977	2006	9.93
1978	2007	9.96
1979	2008	9.98
1980	2009	10.02
1981	2010	10.00
1982	2011	10.05
1983	2012	10.05
1984	2013	10.03
1985	2014	10.07
1986	2015	10.12
1987	2016	10.17
1988	2017	10.22
1989	2018	10.25
1990	2019	10.24
1991	2020	10.25
1992	2021	10.27

From: https://www.metoffice.gov.uk/hadobs/hadcet/cetml1659on.dat

On average, there is about a 0.02/3c increase in each consecutive 30 year period with an upward trend that is pretty much consistently linear. 

 

Thanks very much for posting those stats

Just goes to show the cet is steadily and consistantly rising year on year.

And we wonder why we dont get cold winters anymore,along with the odd lengthening each year as well on getting one

 

This table shows the running 30 year CET average (annual) since the 1961-1990 period. 

30 year base		30 year avg
1961	1990	9.51
1962	1991	9.49
1963	1992	9.54
1964	1993	9.57
1965	1994	9.60
1966	1995	9.65
1967	1996	9.64
1968	1997	9.67
1969	1998	9.71
1970	1999	9.75
1971	2000	9.77
1972	2001	9.78
1973	2002	9.83
1974	2003	9.86
1975	2004	9.89
1976	2005	9.91
1977	2006	9.93
1978	2007	9.96
1979	2008	9.98
1980	2009	10.02
1981	2010	10.00
1982	2011	10.05
1983	2012	10.05
1984	2013	10.03
1985	2014	10.07
1986	2015	10.12
1987	2016	10.17
1988	2017	10.22
1989	2018	10.25
1990	2019	10.24
1991	2020	10.25
1992	2021	10.27

From: https://www.metoffice.gov.uk/hadobs/hadcet/cetml1659on.dat

On average, there is about a 0.02/3c increase in each consecutive 30 year period with an upward trend that is pretty much consistently linear. 

 

Thanks for researching that CP.  As you say, about 0.25c per decade, which puts us on track to see the 30-year average above 11c by mid-century.

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Thanks very much for posting those stats

Just goes to show the cet is steadily and consistantly rising year on year.

And we wonder why we dont get cold winters anymore,along with the odd lengthening each year as well on getting one

Thanks from me too.

Rather splitting hairs, but it doesn't quite show that the CET is steadily rising year on year. What it does show is that each new year that is added at the end of the 30-year period is consistently warmer than the year 31 years earlier that has dropped out. That's still pretty alarming, as it shows that a relatively chilly year by current standards is warmer than a relatively mild year by the standards of 30 years earlier.

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I'm surprised that they quote 1991-2010 as an option, as I thought that the WMO-approved standard period for climate averages was thirty years, a shorter period presumably being thought to run the risk of being overinfluenced by one or two exceptional years. But perhaps 1991 was just their typo for 1981.

It wouldn't be the same though without one of Arty's typos (I know that Caz will agree with me on that one).

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Thanks from me too.

Rather splitting hairs, but it doesn't quite show that the CET is steadily rising year on year. What it does show is that each new year that is added at the end of the 30-year period is consistently warmer than the year 31 years earlier that has dropped out. That's still pretty alarming, as it shows that a relatively chilly year by current standards is warmer than a relatively mild year by the standards of 30 years earlier.

Perhaps ‘decade on decade’ would be more accurate, but there’s no disputing the relentless signal.

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Perhaps ‘decade on decade’ would be more accurate, but there’s no disputing the relentless signal.

Agree. Year on year comparisons are useful in their own right but as you say, it is better to look at longer term trends as this will smooth out the loud noise that short term comparisons often produce. For example, if this year was to finished below average (which is highly unlikely) or cooler than 2021, it still wouldn't have a noticeable impact on the longer term rising trend.

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I'm still confused, is the new baseline period going to be 1991-2010 (20 years, unlikely), 1981-2010 or 1991-2020? I would have thought 1991-2020 as that is the decade we have just completed.

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I'm still confused, is the new baseline period going to be 1991-2010 (20 years, unlikely), 1981-2010 or 1991-2020? I would have thought 1991-2020 as that is the decade we have just completed.

In the past, updating the 30-year reference period seems to have lagged by quite a bit (eg when going from 1961-1990 to 1971-2000). So based on that, I'd have thought that 1981-2010 was more likely.

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