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2010 not 'warmest year ever' - close but no banana

By John McLean - posted Monday, 24 January 2011


Even if 2010 was colder than the general temperature near the start of the trend period it would not have altered the trend from warming to cooling. Only if the average annual temperature in 2010 was 7 degrees below the 1961-90 average would the rising trend since 1950 have disappeared. Because of the mathematics used, a 2010 temperature of 3.2 degrees below the average, not 3.5, would have halved the rate of warming, and in comparison there's been a range of just 0.9 degrees in annual average temperatures since 1950.

The other point about trends is that they mask individual years, and temperatures in those years, months and days are subject to all kinds of natural forces. Since 1987 we've had several El Nino events and fewer La Nina events, and there have been several volcanic eruptions to cause cooling. These all contribute to the monthly and annual average temperatures that the WMO talks about and therefore they help drive the data trends, those trends that are frequently cited as evidence of man-made warming.

The problem with all averages is that they mask any variation in the data. In 2010 the November average was 0.44 degrees above the 1961-90 average, but December was only 0.25 degrees warmer than the average for that month.

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The sudden fall in temperature in December is no surprise. It takes about 7 months for changes in the Pacific Ocean to appear in changes in global temperature and it was back in April 2010 that the Pacific abruptly changed from El Nino to a strong La Nina. Forget the so-called experts saying that 2010 was warm despite the La Nina; it's just that the influence of the La Nina on temperatures came too late to have much impact on the annual average.

Various modelling suggests that the current La Nina will last at least until the end of March and that means cooler weather, with plenty of rain, can be expected right through until November.

On this basis I expect a far cooler 2011 than 2010 and around this time next year I doubt that there will be much crowing, from the ABC or any other media outlets, about annual average temperatures in 2011.

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About the Author

John McLean is climate data analyst based in Melbourne, Australia.

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