Tuesday, February 19, 2013

Bacci's "Delusional Dribble"

MobyT | 2:57 PM Feel free to comment!

Talking "dribble" on climate models and tea leaves

This is (probably not) for people who listen to fake skeptics science mockers like bacci, who writes:

Image of Bacci post saying climate models are bunkum
Source: HotCopper.com

Bacci starts off talking about modelling complex systems. He says the idea that 'we' can model the climate in 100 years is 'delusional'.  (I'd have to agree that any attempt by Bacci and mates to model complex systems would indicate delusion on their part, going by his posts.  Using his own imagery, bacci tends to dribble his drivel like a drip.)

He then shifts to weather forecasting, saying that in order to 'prove' a model of centennial trends in climate, one needs to model monthly weather.

Predicting monthly trends in weather

Actually, most people (Bacci excepted) don't need a model to broadly predict weather on the monthly scale.  Next month is the start of autumn down here and we know from experience that autumn brings milder temperatures (but it can still get a bit hot).  We can even predict with reasonable accuracy that in five months time (July) the average monthly temperature in southern Australia will be cooler than the average for this month (February) and there will likely be snow on the ranges, while in the northern hemisphere the ice in the Arctic will be melting.

Feel free to check back in July and tell me how wrong my prediction is!

One source for an indication of likely rainfall patterns in eastern and south-eastern Australia on a short term scale (weeks to months) is the Bureau of Meteorology's seasonal outlooks and also their ENSO wrap up.

Fake skeptic predictions

Fake skeptics have not done very well in their predictions. Some have even been so far off target with short term predictions that the 'delusional' descriptor may be appropriate.

John McLean's Delusional Drop

For example, bacci could have been talking about computer technician John McLean.  Back in March 2011, he 'predicted' that "2011 would be the coolest year since 1956, or even earlier".  He was forecasting a drop of 0.8 degrees Celsius in the average global surface temperature in a single year, from the record high of 2010. (The global average surface temperature has risen by about 0.8 degrees Celsius in the past century.  In 2010 it was 0.62 degrees above the twentieth century average.)

As it turned out, 2011 was the 11th warmest year on record and the warmest La Nina year on record.  So much for that fake skeptic's delusion.  2011 was 0.51 degrees Celsius above the twentieth century average, whereas the average temperature in 1956 was about 0.18 below the twentieth century average.  He was out by a whopping 0.69 degrees Celsius!

NCDC/NESDIS/NOAA Jan-Dec global mean temp chart 1880 to 2011

Click here to go to the NOAA source.

Other fake skeptics' tea leaves

Bacci says he might as well read tea leaves.  Maybe that's what fake skeptics do.  SkepticalScience.com has an animated gif comparing the predictions of 'skeptics' with IPCC temperature projections and actual observations.  Fake skeptics 'tea leaf' predictions don't stack up at all well, while the different years' IPCC projections have so far all been much closer to what was actually recorded.

Animated gif from skepticalscience comparing skeptic/IPCC/observed temperatures

The skepticalscience.com article goes into more detail and is worth a read.   It discusses some of the weaknesses of IPCC projections, such as the fact that sea levels may be rising faster and the fact that Arctic ice is definitely disappearing much faster than expected.

Realclimate.org does an annual comparison of models too, looking at global surface temperature, ocean heat content and summer Arctic sea ice cover as well as early projections from James Hansen.

To sum up, complex models based on physics and constructed by experts in climate science have been very good predictors of global trends and even of regional trends.  They are not perfect but as computing power increases along with knowledge of climate the models also improve.

Important factors that climate scientists have more difficulty in predicting in the medium to longer term are the amount of greenhouse gases and aerosols we choose to pour into the atmosphere.  (Also significant volcanic eruptions that might occur in the future.) That's why they use scenarios to model climate under different permutations of future pollution.

Isaac Held's blog is a really good place to peep under the hood of climate modelling.

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