Sunday, January 13, 2013

Ocean Weather

Here is a nice (and useful) description of decadal climate variability as "ocean weather," by the Met Office:
There are strong analogies between weather forecasting for a few days ahead and longer-term decadal forecasts for the next few years. When we make a weather forecast we are predicting what the likely evolution of the atmospheric circulation will be over the next few days; when we make a decadal forecast we are essentially predicting ocean 'weather' - in other words how the oceanic circulation will evolve over the next few years and its subsequent impact on the atmosphere. The different timescales for these forecasts reflects the differences in density and thermal capacity noted above.
Given that, their ensemble prediction (10 individual forecasts) for the rest of this decade is:
Global annual temperature record since 1950 and the latest ensemble of forecasts from the Met Office decadal prediction system produced in December 2012 : This link opens in a new window
In other words, the change in average global surface temperature is forecast to be ±0.2°C by the end of the decade. That is, noise and thermal inertia pretty much precludes making a climatological meaningful forecast on such a short time scale.

I wish this was the last time any of us had to write that, but surely it won't be.

The rest of their article -- about testing their predictions, and about warming over the next 5-10 years, is worth reading too. They conclude:
The latest decadal forecast, issued in December 2012, show that the Earth is expected to maintain the record warmth that has been observed over the last decade, and furthermore a substantial proportion of the forecasts show that new record global temperatures may be reached in the next 5 years.  
That should keep the David Rose's of the world employed for a few more years, at least.

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