Climate v Weather: Climate Services
Simon Mason [email protected]
The Climate-Weather Connection New York, NY, U. S. A., 24 September 2014
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Date: Friday 24 September 1993 Request: forecasts for Saturday 23 and 30 April 1994
Climate Services
The academic The sleazy salesman The equivocator The voice of authority
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Climate v Weather “Climate is what you expect; weather is what you get.”
Ed Lorenz
What if you do not know what to expect?
What if you expect almost anything can happen? The Bri2sh, he thought, must be gluSons for sa2re: even the weather forecast seemed to be some kind of spoof, predic2ng every possible combina2on of weather for the next twenty-‐four hours without actually commiTng itself to anything specific.
David John Lodge, Changing Places
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Spot the Ball Compe33on Where is the ball now?
Where will it be in 20 seconds? Who will win the match?
What is the current weather?
What will it be on Saturday? Will winter be unusually wet?
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Sources of Predictability
• We can make forecasts at different 2mescales because there are different reasons why the predic2ons can work:
– days: current weather – months: sea-‐surface temperatures – years: sub-‐surface ocean temperatures
– decades: atmospheric composi2on
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Making seasonal forecasts I: Models of past sta3s3cs -‐ correla3ons
How have past El Niño events affected the weather?
Typical El Niño impacts during December -‐ February
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Making seasonal forecasts II: Models of the physics – causa3on
How might this El Niño affect weather?
Run lots of forecasts, ideally using a selec2on of models. Do many of the forecasts agree?
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Do seasonal forecasts work?
How well can we predict seasonal rainfall totals?
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Climate Services
It is in the very nature of probability that improbable things will happen.
Aristotle, Rhetoric
Climate services involve specifying precisely how improbable the improbable is, by: • understanding the past; • analyzing the present; • predic2ng the future.
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