Met Office 2013 annual global temperature forecast released warmer than the long-term average predicted

[loafer]

So why don't they use the 1971-2000 mean then?

[UV-RAY]

So why don't they use the 1971-2000 mean then?

A quick sortie back in here and this is a very good question, those sceptical know the answer already but I'm sure those who want to protect what's precious to them will have the answers.

[BornFromTheVoid]

My thinking is that the 61-90 average is much more representative of the 20th century climate norm, even if it is a little warmer, as can be seen in the graph below. It is also the earliest time that we had global coverage with modern instruments.

But that's not controversial enough, hmmmm... I got it! The WMO set 61-90 as the baseline because it's warmer than all preceding 30 year periods, and that way they can further their "coolist" agenda and trick the world into thinking global warming ain't happening too quickly!

Am I doing this right!?

[loafer]

I rather expected you to come up with a good reason. As it is, it seems to be entirely arbitrary at best.

Like I say, if there is no good reason, why not publish against several different measures, including longer term and more recent?

[Methuselah]

Maybe we should all become 'good sceptics' and agree on 2061-90?

[BornFromTheVoid]

I rather expected you to come up with a good reason. As it is, it seems to be entirely arbitrary at best.

Like I say, if there is no good reason, why not publish against several different measures, including longer term and more recent?

It's only arbitrary if you blindly ignore the reasoning behind it..

Edited December 22, 2012 by BornFromTheVoid

[loafer]

In all of the businesses I run or am involved in we use KPIs. We don't choose a single one, or compare to a single period, because this doesn't tell us the whole picture. I certainly understand the need for consistency, but you haven't come up with a single reason why a range of comparators wouldn't be used, which I think is very odd.

[Thundery wintry showers]

Weather forecasts and anomalies are based on the most recent climatological mean, i.e., 30 year mean to smooth out the short term variability..

For climate data, you need a constant baseline temperature so that whether your looking at temperatures from 1 million years ago or temperatures 100 years into the future, you have a standard baseline to which they can all be compared and standardised anomalies generated.

Makes perfect sense to me at least?

I agree with the general premise (for a climatological type of analysis it makes far less sense to keep updating the reference period than when, say, reporting the latest month's weather) but think that the World Meteorological Organisation's idea of having a 30-year mean updated every 30 years for that purpose is far from ideal. I would suggest a longer-term baseline such as 1951-2000, or maybe even 1901-2000 if the pre-1950s station networks were reliable enough back then.

I remember when analysing the Central England Temperature series, finding that the period 1981-2010 had anomalously cold Decembers (relative to the other months, in the context of longer-term averages) and the 1961-1990 period had anomalously warm Octobers, whereas extending the average to 1951-2000 largely drowned out the short-term variability.

[BornFromTheVoid]

I agree with the general premise (for a climatological type of analysis it makes far less sense to keep updating the reference period than when, say, reporting the latest month's weather) but think that the World Meteorological Organisation's idea of having a 30-year mean updated every 30 years for that purpose is far from ideal. I would suggest a longer-term baseline such as 1951-2000, or maybe even 1901-2000 if the pre-1950s station networks were reliable enough back then.

I remember when analysing the Central England Temperature series, finding that the period 1981-2010 had anomalously cold Decembers (relative to the other months, in the context of longer-term averages) and the 1961-1990 period had anomalously warm Octobers, whereas extending the average to 1951-2000 largely drowned out the short-term variability.

I agree to an extent, ideally a longer baseline for climatology studies would work better. Perhaps the pre 60s station distribution wasn't good enough though? And global satellite coverage didn't become consistent enough until the late 70s,

I wouldn't agree with using the 90s though. Being the second warmest decade on record, it would likely skew the comparisons more than any slightly anomalous months. I doubt anomalously cold or warm months over a 30 year period globally is as much of an issue as with a small area such as the CET zone.

[Guest pjl20101]

Well the cold PDO apparently is going to lose power so it's a possibility.

[Gray-Wolf]

As we continue to warm then so will the oceans. There seems to be another sceptical idea that we are not seeing ocean warming but the scientist in the field appear to strongly disagree noting both surface and deep ocean warming. As such the old index's for things like PDO will be at risk from becoming of lss use if the 'negative' phase becomes increasingly dominated by neutral and positive temps.

The start of this PDO-ve now appears to have been pushed back again to starting in 2010! Historically we define the phases once they have ended so we may well find that once we return to positive that the negative began far earlier than 2010 and the lower temps we see now reflect the middle of the phase and not the start?

With the 2010 Nino driving such high global temps I have to wonder about the Enso influence once we move into a more neutral PDO? As it is global temps under Nina are now higher than past Nino years! This year being one such, with a top ten global temp year even though classed as a Nina year, means that most all of the past recorded Nino years had lower global temps yet we are still to believe we are cooling?

Next year with a neutral ENSO should surely do better , temp wise, than a Nina year?

[Thundery wintry showers]

I doubt anomalously cold or warm months over a 30 year period globally is as much of an issue as with a small area such as the CET zone.

A good point- the anomalies relating to short-term synoptic variability will even out more readily over the globe as a whole. There may still be minor anomalies (e.g. a strongly positive NAO can cause enhanced warmth by a few tenths of a degree in the Northern Hemisphere, due to concentration of warm anomalies over the continents) but the magnitude of the anomalies will be somewhat smaller. Some good points also about reliability of earlier records and the anonalous warmth of the 1990s.

I forgot to mention that the NCDC compares global temperatures with the twentieth-century average, which drowns out the warmth of the 1990s more effectively than a 1951-2000 base period but the downside is that the earlier years of that period have relatively limited data in parts of the globe. That said, the resulting anomalies are very similar to those relative to 1961-1990, perhaps fractionally greater due to the colder temperatures in the first three decades of the century, so it doesn't appear to make a significant difference (unlike, say, moving to 1981-2010 which would dramatically mask the warm anomalies).

Edited December 24, 2012 by Thundery wintry showers