Met Office Scraps Seasonal Forecasts

Bishop Hill reports that the Met Office reports that seasonal forecasts have been scrapped:

• The Met Office is to abandon its long-term and seasonal forecasting after criticism for failing to predict extreme weather.
  

Bishop Hill then asks the natural question how it is possible for the Met Office to make long-time

predictions of the climate, if seasonal predictions are impossible. I have discussed this question in previous posts on Short-Time vs Long-Time Accuracy, with the conclusion that only in very special cases is it possible that long-time accuracy is possible without short-time accurcay.

The Met Office maybe should scrap also its long-time climate forecasts, and stick to its main mission of daily forcasts.

But the Met Office counters the scrapped seasonal forecasts by sending out renewed long-time AGW alarm: Climate Change Human Link Even "Stronger".

Compare Warmists overwhelmed by fear, panic and deranged hatred as their 'science' collapses.

What does the Royal Swedish Academy of Sciences say? No collapse of any AGW science in sight?

Short-Time vs Long-Time Accuracy 2

The question of short-time vs long-time accuracy of climate models plays an important role in the debate on climate change.

Roger Pielke Sr. takes a critical look the recent article by Ed Hawkins and Rowan Sutton, 2009: The Potential to Narrow Uncertainty in Regional Climate Predictions. Bulletin of the American Meteorological Society. DOI: 10.1175/2009BAMS2607.1. 1095–1107.

Pielke questions the claim illustrated in the above figure of the article, that modeling errors decrease with increasing time. We posed a similar question in the blog post Short-Time Accuracy vs Long-Time Accuracy.

We noticed that a good deal of happy cancellation must be present in order for modeling errors to decrease with time. It is doubtful if this is the case in a complex dynamical system like the global climate. This means that if climate models are not short-time accurate, they have a small chance to be long-time mean-value accurate. If this is true then, the accuracy of climate models can be tested on short-time predictions, which can be checked in short-time, say 2 years.

Compare with Earth Cools, and Fights over Warming Heats Up.

Short-Time vs Long-Time Accuracy 1

The question of short-time vs long-time accuracy of climate models  is discussed in a recent article in New York Times by Andrew Revkin. What does the plateau in global temperature seen over the last decade tell us? That global warming is over? Maybe, maybe not. But it tells that climate models are inaccurate over a decade since the plateau was not predicted. Does it then follow that climate models are accurate over long-time over a century?  Not necessarily. A short-time inaccurate model may be long-time inaccurate as well.

What is then the mathematical nature of models which are short-time inaccurate but long-time accurate. Are there such models? Yes, if you put a rapid short-time oscillation on top of a long-time slow motion, then a model that discards the rapid short-time oscillation will have this property. 

Can you then draw the conclusion that a simple model with some form of damping of short-time variations, will be long-time accurate? Sometimes yes, but then only under very special conditions: regular short-time oscillation and linearity, which allows a lot of cancellation to take place. But in a non-linear system this may not be the case at all, since cancellation maybe lost.

The idea that climate models can be allowed to be short-time inaccurate, without jeopardizing long-time accuracy,  thus seems questionable. Of course, a climate model will be short-time inaccurate if some unknown major natural variation is not taken into account, and if that unknown natural variation would disappear, then the model may recover long-time accuracy but then together with short-time accuracy. The combination of short-time-inaccurate with long-time-accurate seems very special.

Altogether, it seems reasonable to ask climate models to be short-time accurate. If they are not, it probably signals that they are also long-time inaccurate. Compare the recent post by Roger Pielke Sr.  stating in particular:

• Societally useful (i.e., reliable, accurate, etc.) climate  prediction requires that all of the feedbacks and other physical processes included in weather prediction be  presented in the climate prediction model. In addition, longer-term feedback and physical processes must  be included. This makes climate prediction amuch more difficult problem than weather prediction.
  

We learn that climate models also have to be weather models, and thus have to be short-time accurate in order to have a chance to be long-time accurate. It follows that the accuracy of 

climate models can be tested over short-time. What is the result of such tests?