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Regular observers of the climate scene will know it’s that time of year again. The end of the year is in sight and with it another annual global data point to add to the others to see if the world is warming, or if it is not.

It’s always unwise to speculate too much on data that hasn’t yet been measured, as unwise as it is to count chickens, but even though it’s been quite an interesting year temperature wise (heat waves in Eastern Europe, droughts and fires in Moscow), it does however not appear to be anything unusual. It will probably be like all the other years since 2001, no change and statistically identical to each other. But that’s only an impression; we still have two months to go.

But caution about data that hasn’t been collected yet is not shared by all, and those unwise enough to make predictions earlier this year are having to go back on them. Unless that is such predictions were statements of the obvious.

The dominant factor in this year’s annual temperature has been the strong warming El Nino event in the early part of the year and the transition to cooling La Nina event in the latter part of the year. Specifically the most recent El Nino began around June 2009, peaked in Jan/Feb 2010 and continued to about May/June 2010.

Since we live in the warmest decade of the past few hundred years, and the global average temperature hasn’t increased in a decade, then an El Nino event occurring in the past year is likely to elevate temperatures to almost record levels (depending on whether it exceeds the 1998 strong El Nino event.) So it is hardly surprising that statistics compiled by Nasa’s Goddard Institute for Space Studies showed the period between October 2009 and September 2010 was the warmest ever, according to their GISS database at least.

This record temperature says nothing about anthropogenic global warming, but that hasn’t stopped some distorting the science and claiming, directly and indirectly, that it has.

Vicky Pope, head of climate science advice for the Met Office told the British media, “The high temperatures this year are a clear symptom of a long-term increase in global temperatures, probably caused by greenhouse gas emissions from human activities.”

2010 the hottest?

Despite fears (or hopes) to the contrary, according to James Hansen, the director of NASA’s Goddard Institute for Space Studies (GISS), 2010 may not wind up being the hottest year in the modern temperature record after all. Hansen has said recently that the onset and intensification of La Nina conditions in the Pacific Ocean have cooled global average surface temperatures, and despite the record heat in the first eight months of the year, 2010 may wind up either tied with or behind 2005, currently the warmest year in the GISS analysis.

Even that might not be clear-cut. Other climate research institutions that keep temperature records, such as the U.S. National Oceanic and Atmospheric Administration (NOAA) look as if hey will see this year differently. For example, in the GISS analysis, June-July-August 2010 was the fourth warmest on record, but according to NOAA’s methods it was the second warmest.

What this all boils down to is that 2010 is not going to be an exceptional year when compared to the past decade. Hansen: “It is likely that the 2005 and 2010 calendar year means will turn out to be sufficiently close that it will be difficult to say which year was warmer, and results of our analysis may differ from those of other groups.” (Later statements by Hansen suggested that 2010 might actually be cooler than 2009, although not statistically significantly so!)

This is perfectly reasonable, but then Hansen correctly states the obvious about the recent El Nino leaving the clear implication in the reader’s mind that mankind has something to do with the temperature record, “What is clear, though, is that the warmest 12-month period in the GISS analysis was reached in mid-2010.”

According to Hansen, the calendar year temperature ranking is not as relevant to monitoring long-term global climate change as the 12-month running mean — which did hit a record high this year. This is an extreme example of cherry picking as choosing a running mean that covers an El Nino will give a false elevation in temperature. By contrast there is something to be said about calendar year averages if they (admittedly crudely) even out the El Ninos and the La Ninas.

Perhaps the long awaited record will come next year, or the year after that. The plain fact is that if the global warming theories are correct the world’s annual average temperature will have to start increasing soon. Because of the La Nina (which seems of moderate strength) we are experiencing, and which will stretch into next year; Hansen suggests that 2012 currently looks like a record year, err possibly. “It is likely that 2012 will reach a record high global temperature…the principal caveat is that the duration of the current La Nina could stretch an extra year, as some prior La Ninas have.”

…or maybe not

But what a difference a La Nina makes. Back in March it was a different story. Hansen said that his draft analysis predicted that 2010 will likely set a new global temperature record, as well as being “virtually certain” that a new 12-month running mean global temperature record would occur sometime in year. Making the record running mean prediction in March was, frankly, a no-brainer.

We will have to wait and see where 2010 comes in the ranking of recent warm years. But even if it is a record (doubtful) it will still not be evidence of warming as it is just one datapoint and one would expect, if the temperature was constant, a spread above and below the mean. So it will take several years of an upward trend to be sure the temperature is rising.

There will no doubt be some comment between now and when the temperature figures for 2010 are released, particularly from those awaiting the further warming of the world among them those who will strain the significance of an additional datapoint if it does. But already some scientists have misled the public about the interaction between an El Nino and a running mean.