Hi Richard

“The latest annual update to the decadal forecast is;-“

Many thanks Richard I have already been there and that page does illustrate the issue.

That is a new forecast starting in September 2011 not an update of any previous forecast. What I am trying to get at is how did the previous forecasts perform over their full forecast period? This can only be assessed by considering each annual decadal forecast as a single entity and reporting against it throughout the full length of the forecast period.

The “update” you point to has the previous forecasts, which must have had significant differences, merged into a single ongoing line and as such it cannot be a true representation of the previous individual forecasts. The concern is that this does not allow an overview as to whether subsequent forecasts are showing an improvement in skill.

It must be possible to show the individual annual decadal forecasts updated against actual observations. Could you please point me in the right direction?

Regards

Hi Green Sand

Actually, I think you've misunderstood (or it's not been explained very clearly on the website!)

In Figure 1 of the decadal forecast page", the right-hand one of the three red "plumes" (the one from 2005-2014) is actually the entire decadal forecast from 2005. So, this does do what you require - it allows comparison of the 2005 forecast (red plume and white curves) over most of its entire period against observations (black curves). Clearly we haven't quite reached the end of the 2005 decadal forecast yet so don't yet have an full assessment of its skill over the entire period.

The red plume represents the uncertainty, such that the observations are expected to lie within the red plume 90% of the time.

You can see that the central estimate was for global mean temperatures to be rising over the last few years, but the lower end of the uncertainty range was for more of a flat-lining. So far, the observations were just about within the lower end of the uncertainty range.

Thanks for asking this excellent question!

Cheers

Richard

Hi Richard, many thanks for the reply.

“Actually, I think you've misunderstood (or it's not been explained very clearly on the website!)”

No Richard, with respect I do not think I have misunderstood.

“Clearly we haven't quite reached the end of the 2005 decadal forecast yet so don't yet have an full assessment of its skill over the entire period.”

The page shows and states that Decadal forecasting started in 1985 not 2005. So we have numerous decadal forecasts that we do have a full assessment of the skill over their entire period?

In 1985 we had a certain amount of knowledge and computer power, since then our awareness, knowledge and number crunching power has increased and in the latter case by multiple factors.

Therefore we should (must) know whether this gain in ability has shown through in increased skill? (I use the royal “we” as a concerned member of the human race and not to imply being directly involved in the science)

That cannot be assessed from the chart you reference (ps, why does it now start in 1950?).

It can only be assessed by showing each subsequent Decadal Forecast as single entities over the whole of each forecast decadal span and then assessing if the accuracy of subsequent forecasts are improving or not?

With regard to “the red plume” and the “white line” where does the “2009 decadal prediction of global average temperature and validation of past predictions.” fit in?

http://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/decadal-prediction

It appears the “blue line” from 2009 has now been blended in to the ongoing white line in the chart on the page you reference, though I have to admit that is only by applying a grid and eyeballiung.

We constantly talk about “uncertainties” we are all aware that they exist, but we should by now be quantifying the uncertainties, “we expect to be for 90% of the time” does not do this. Surely we should be targeting and monitoring the forecast means against actual observational data? It is well understood that we are not going to hit the target all the time but we need (must) know if we are getting closer or further away from our targeted mean?

Regards

GS

Richard, sorry for rambling even ended up a main point.

"All data are rolling annual mean values. The gap between the black and blue curves arises because the last observed value represents the period November 2010 to October 2011 whereas the first forecast period is September 2011 to August 2012."

Why therefore cannot the forecasts be individually updated with HadCRUT3 actual observational data against forecast mean on the same basis? Month in month out?

"ended up a main point."

Should be "ended up missing a main point"!

Matron says I must have a nap!

Green Sand,

If I may interject a layman's viewpoint of the decadal forecast graph.

The 90% confidence level gives quite a large bandwidth aprox 0.4C generally which is half of the overall rise in temperature over the last 100 years. Commercially, in industry, this would be the catastrophic error margin which would mean if exceeded that you were manufacturing the wrong product.

It is noticeable that the previous two decadal forecasts starting 1985 and 1995 are quite reasonable facsimiles of observed data if the events Mt Pinatubo and 1998 El Nino are respectfully excluded.

With the 2005 decadel forecast, although it has so far resided within the 90% confidence level it is indicative of something major being overlooked as the divergence increases with time.

Unless the MO have managed to model ENSO on a multi year timescale and there is a large EL NINO in the pipeline then this decadel forecast is not going to achieve anything like the previous ones.

My suspicions are that the quietening Sun since the turn of the century is having a greater effect than allowed for. If this is going to have an effect for the next couple of decades then the 2015 forecast will be an interesting release, particularly when AR5 is due and an election year where policies mean points votes.

The thick blue line forecast is basically an EL NINO forecast which I am dubious of even starting in the next twelve months let alone of having any effect, but that is just my two penneth worth I am sure that Richard and colleagues will keep us informed.l

Mar 1, 2012 at 3:06 PM | Lord Beaverbrook

My dear Lord you are more than welcome and thanks! Your point re error margins in manufacturing ring very true and I have the scars to prove it.

But they are not yet my concern and neither am I anywhere near any consideration regarding the actual issues of ENSO, Volcanoes, sunspots etc.

At first I feel it is necessary to understand what the forecasts have been and how they have performed.

From the present chart it would appear that previous forecasts that overlapped have been merged to show the single “white line”. PS I doubt that there will have only been 4 – 1985, 1995, 2005 and “the latest”. I would be very surprised if the MO did not carry out an annual update of their decadal forecast, I know I would and Richard did previously point me to “The latest annual update to the decadal forecast is”, though to be fair he could be just using a figure of speech.

By illustration what happened to:-

2009 http://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/decadal-prediction

There is an individual forecast “thick blue line” and the previous forecast “white line, note the overlap another such is shown on the latest chart.

Also there appears to be a variation in the value of the “white line” between 2009 and the present?

I am probably missing something and I am hoping that Richard can help with further clarification.

Hi Richard

I am aware that this does not relate directly to the Met Office but it must have a huge bearing on current research.

Does the following sort of report cause the Met Office any concern or is it too way off beam to merit any attention? I refer to this article

http://notrickszone.com/2012/03/01/data-tamperin-giss-caught-red-handed-manipulaing-data-to-produce-arctic-climate-history-revision/

I quote from the opening paragraph

GISS and the GHCN are preoccupied with the Arctic, bestowing large “corrections” on the few and far northern stations. The raw data of the Arctic did not tell the story they wanted to hear, and so GISS took it upon themselves to rewrite it.

In general, is this sort of gross adjustment ever warranted and if so, should the fact that it has happened be more transparent instead of being done by a replacement of old data?

As this is topical to posts on this thread there is an excellent new post at Climate Etc looking at models.
What can we learn from climate models? Part II

I remember a BBC program many years ago where an MO guy was going into a room where models where being created and saying to the camera something like "of course models only predict what you program them to predict" so we dont really take them too seriously.
Today the MO takes them so seriously that they are willing to try and predict climate as well as weather. I think the following post on TGWPF says it all:

Today In The Annals Of Settled Science
Sunday, 04 March 2012 09:47 Walter Russell Mead, The American Interest
E-mail Print PDF

According to a new study reported in Scientific American and published in Nature Medicine, it turns out that your biology textbook was wrong about the basic facts of the human body:

A study led by Jonathan Tilly of the Massachusetts General Hospital overturns the decades-long idea that women are born with all the eggs they will ever have. It reports that women of reproductive age carry ovarian stem cells, meaning that they can produce new eggs.

So, to recap: after centuries of intensive scientific research we are still learning amazing and surprising things about our bodies. But climate science is settled once and for all and no further questions need to be asked.

Got it?

Body snatchers, doctors and medical scientists have had hundreds of years of available live and dead human beings to study but they still dont know the half of it. However doctors make no predictions about how long it will take them to understand everything, they just get on with finding out more that will help save lives.
The truth about predicting weather and predicting climate is that it is not currently possible because our knowledge is in its infancy. The discussions in this thread are at about the same level as two early adopters discussing whether wood or stone would be best if one was to make a wheel. Then on the back of that discussion to predict that man would invent a nuclear weapon.
Why is it so hard to admit that we dont know enough? Considering the amount of tax payers money being spent on the basis of predictions of climate and weather I believe we deserve better from our public servants.

Hi Richard

"The red plumes for 1985-1994 and 1995-2004 are hindcasts"

Thanks Richard, I missed that, must improve my reading skills! I will need to re-think about “hindcasts”

"You are right that others have been done starting at other years since 2005"

What I actually said was that decadal forecasting started in 1985 so there must be numerous that have run full extent and therefore their subsequent individual performances can be assessed. Assessed very simply forecast against actual, were we better in the 90s than we were in the 80s etc? Are we gaining skill as we gain resource?

"so the 2005 forecast remains the best one for testing "out of sample", ie: the one that was actually done as a forecast, not a hindcast"

But surely they were all originally done as forecasts, how did they do against actual?

But hey ho, as you point out we do have the 2005 decadal forecast up and running, so we will continue to observe. As HadCRUT3 reports as an 1961-1990 anomaly and the decadal forecast is 1971-2000 is it possible to get an official MO “conversion factor”?

The other concern re the 2005 forecast is the imminent arrival of HadCRUT4. I take that 2005 will be reported against HadCRUT3?

Richard I know you are very busy and I am sorry for being a pain, but if you get chance could you get somebody to shed light on the following?

Some days ago you pointed at the following MO page to explain the HadCRUt3 /Arctic issues:-

“Global-average annual temperature forecast”

http://www.metoffice.gov.uk/research/climate/seasonal-to-decadal/long-range/glob-aver-annual-temp-fc

At the bottom of the page is:-

Figure 3: The difference in coverage of land surface temperature data between 1990-1999 and 2005-2010. Blue squares are common coverage. Orange squares are areas where we had data in the 90s but don't have now and the few pale green areas are those where we have data now, but didn't in the 90s. The largest difference is over Canada.

Why do we no longer have the Canadian land surface temperature data? I am not aware of any of the stations being closed? If they have been could somebody please point me in the right direction?

Many, many thanks for your replies and contribution.

Regards

matthu,

Just to clarify where I think the misunderstanding lies.
From what I understood Richard has said, the 2005 forecast was the first forecast using the current model. The 1985 and 1995 plumes are hindcasts to validate the model output, but there weren't any previous forecasts prior to 2005 using this model.
The first end of the decadal forecasts will then be in 2014. There have been subsequent forecasts post 2005 but obviously the decadal end of the forecasts are rolling on. The accuracy of this model output against observational data over the full forecast period can only then be assessed post 2014.
That's what I understood from the comments but I'm more than willing to be corrected if I'm wrong.

Above, Richard Betts wrote "It is the Arctic that's the issue. The model forecasts covers the Arctic, but the observations do not, so it's not comparing like with like."

Seems to me that the GISS data for arctic warming is badly skewed. At this hyperlink: http://data.giss.nasa.gov/gistemp/maps/ clicking on the "Make Map" button displays a livid red Arctic. But if the user changes the settings to "Polar" rather than "regular", and "250km" rather than "1200km" a very different image is generated. These utterly different images use the selfsame source data.

The distorted Mercator projection (big fat Greenland) combined with unwarranted extrapolation (it's as if a thermometer in Nice were used to declare UK temperatures) allows GISS to perpetuate the myth that global warming is concentrated in the Arctic and the citizen who judges GW by looking out of the window is being parochial.

Lord B

Quantifying solar variations/forcings is one of life's mysteries to me. There appears to be many, many solar “jockeys” each with different mounts and sometimes in what seems to be different races!

Don’t know if you have seen this, apologies if you have, but I would appreciate any comments you may have TIA:-

The magnitude of the solar forcing, which varies about 0.25 W/m2 from solar minimum to solar maximum, is much smaller than the forcing by human-made greenhouse gases. However, the most relevant comparison of the solar forcing is with Earth's energy imbalance, 0.58±0.15 W/m2 (Hansen et al., 2011), because the combined effect of all forcings is less than that of greenhouse gases alone, and much of the greenhouse gas forcing has been "used up" in causing the warming of the past century. It is apparent that the solar forcing is not negligible in comparison with the net climate forcing.

It is under “Solar Cycle” here:-

http://data.giss.nasa.gov/gistemp/2011/

My initial question amongst many – is the 0.25 W/m2 relevant if “the current prediction for Sunspot Cycle 24 gives a smoothed sunspot number maximum of about 59 in early 2013.”?

http://solarscience.msfc.nasa.gov/predict.shtml