Today’s Times says, “Nasa analysis showing record global warming undermines the skeptics.” However, a closer look at the information which the Times bases its headline on shows that a combination of selective memory and scientific spin play a large role in arriving at it.
The conclusion is based on a new paper written by James Hansen and submitted to Reviews of Geophysics. The paper released by Hansen has not been peer reviewed, and he admits that some of the newsworthy comments it contains may not make it past the referees.
Hansen claims that, according to his Gisstemp database, the year from April 2009 to April 2010 has a temperature anomaly of 0.65 deg C (based on a 1951 – 1980 average) making it the warmest year since modern records began. It is a fractionally warmer than 2005 he says, although an important point to be made is that statistically speaking, taking into account the error of measurement and the scatter of previous datapoints, it is not a significant increase.
The Nasa study said: “We conclude that there has been no reduction in the global warming trend of 0.15-0.20 deg C per decade that began in the late 1970s.”
This is a selective use of a trend line that joins a datapoint in the late 1970’s with the most recent one ignoring the details in the data inbetween. The fact is that one could have taken a datapoint a decade ago and tied it to the same point in the late 1970’s and deduced an even greater rise in temperature per decade. So another way of describing the data is that the rate of increase has actually declined.
Another point to be made is that an increase of 0.2 deg C per decade, if it is real and sustained, is 2.0 deg C per century, an increase not that unprecedented in the climatic record of the past 10,000 years, and substantially less than the widespread predictions of a higher increase.
In the Times article, the Met Office in the form of Vicky Pope, said that their data showed that the past year was “just below” the 12-month record achieved in 1998. Remember, 2009 annual temperature was, according to the Met Office, statistically indistinguishable from every year between 2001–2008.
Vicky Pope then says that Nasa might be right because the Met Office had underestimated the recent warming detected in the Arctic! There are few weather stations in the Arctic and the Met Office, unlike Nasa, does not extrapolate where there are no actual temperature readings. It is curious to hear this given the criticism that Met Office scientists have expressed in the past about the way the Gisstemp dataset is pieced together this way!
Vicky Pope does say however that, “the Met Office continues to predict that 2010 is more likely than not to be the warmest calendar year on record, beating the 1998 record.” This is also a curious statement since she adds that Met Office analysis showed that the four months to the end of April were probably the third warmest for that time of year.
In only the past few weeks however the Met Office has been saying something different.
In the Sunday Times of May 23rd Vicky Pope says that 2010 could be the hottest year on record due to the current El Nino. She also says that the 2010 January – April temperature was the seventh warmest on record meaning that out of the past ten years (allowing for the 1998 El Nino) most of them have been warmer during the January – April period, though not statistically so.
In the Sunday Times article Kevin Trenberth, head of climate analysis at the National Center for Atmospheric Research in Colorado, adds what is missing from the article mentioned earlier: “We have seen rapid warming recently, but it is an example of natural variation that is associated with changes in the Pacific rather than climate change.”
In the Times article poor journalism is compounded with scientific spin from James Hansen’s article to give a misleading impression about the state of the science and what the data actually shows. It will be interesting to see if 2010 breaks any records in the Gisstemp or Met Office datasets. If it does the next question to ask would be, is it statistically significant as one would expect the occasional high point due to errors of measurements causing measured datapoints being scattered around a constant mean (the case post 2001). It would be highly misleading and scientifically fraudulent to look at one datapoint that is higher than the rest yet within the error bars of the previous years and say, “look, a record.” This will not undermine the skeptics but science itself.