Will distorted Jones' comments about warming and statistical significance

From Will's February 21 Washington Post column:

Global warming skeptics, too, have erred. They have said there has been no statistically significant warming for 10 years. Phil Jones, former director of Britain's Climatic Research Unit, source of the leaked documents, admits it has been 15 years. Small wonder that support for radical remedial action, sacrificing wealth and freedom to combat warming, is melting faster than the Himalayan glaciers that an IPCC report asserted, without serious scientific support, could disappear by 2035.

Jones echoed scientific consensus in pointing to long-term warming trend

RealClimate.org: Media are distorting Jones comments about statistically significant warming. In a February 15 post, RealClimate.org's staff, which is comprised of several working climate scientists, stated that a Daily Mail article had distorted Jones' comments when it claimed Jones “admits...[t]here has been no global warming since 1995.″ RealClimate.org stated that ”[w]hat Jones actually said is that, while the globe has nominally warmed since 1995, it is difficult to establish the statistical significance of that warming given the short nature of the time interval (1995-present) involved." From the post:

Yesterday, the Daily Mail of the UK published a predictably inaccurate article entitled “Climategate U-turn as scientist at centre of row admits: There has been no global warming since 1995″.

The title itself is a distortion of what Jones actually said in an interview with the BBC. What Jones actually said is that, while the globe has nominally warmed since 1995, it is difficult to establish the statistical significance of that warming given the short nature of the time interval (1995-present) involved. The warming trend consequently doesn't quite achieve statistical significance. But it is extremely difficult to establish a statistically significant trend over a time interval as short as 15 years-a point we have made countless times at RealClimate. It is also worth noting that the CRU record indicates slightly less warming than other global temperature estimates such as the GISS record.

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Update 2/16/10. Phil Jones has confirmed to us that our interpretations of his comments in the BBC interview are indeed the correct ones, and that he agrees with the statements in our piece above.

Jones: “Achieving statistical significance in scientific terms” is “less likely for shorter periods” but “much more likely for longer periods.” Indeed, contrary to Will's suggestion that Jones' comments undermine the scientific consensus that humans are warming the planet or somehow indicate that warming has stopped, Jones said that 15 years was generally too short a time period to achieve statistically significant results, and that statistical significance is “much more likely for longer periods.” When asked in the BBC interview, “Do you agree that from 1995 to the present there has been no statistically-significant global warming,” Jones stated:

Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods.

Jones: “I'm 100% confident that the climate has warmed.” Later in the same interview, Jones pointed to longer-term, multi-decade warming. Asked, “How confident are you that warming has taken place and that humans are mainly responsible,” Jones stated:

I'm 100% confident that the climate has warmed. As to the second question, I would go along with IPCC Chapter 9 -- there's evidence that most of the warming since the 1950s is due to human activity.

Met Office: Climate shows “continued variability, but an underlying trend of warming in the previously steady long-term averages.” The U.K. Met Office states: “In 1998 the world experienced the warmest year since records began. In the decade since, however, this high point has not been surpassed. Some have seized on this as evidence that global warming has stopped, or even that we have entered a period of 'global cooling'. This is far from the truth and climate scientists have, in fact, recognised that a temporary slowdown in warming is possible even under increasing levels of greenhouse gas emissions.” [Met Office, accessed 9/22/09] The Met Office further notes:

After three decades of warming caused by man-made greenhouse gas emissions, why would there suddenly be a period of relative temperature stability -- despite more greenhouse gases being emitted than ever before? This is because of what is known as internal climate variability. In the same way that our weather can be warm and sunny one day, cool and wet the next, so our climate naturally varies from year to year, and decade to decade.

Before the twentieth century, when man-made greenhouse gas emissions really took off, there was an underlying stability to global climate. The temperature varied from year to year, or decade to decade, but stayed within a certain range and averaged out to an approximately steady level.

In the twentieth century we have had continued variability, but an underlying trend of warming in the previously steady long-term averages. This is what we observed in the 1970s, 1980s, and 1990s. Now we have seen a decade of little change in the average global temperature -- but that doesn't mean climate change has stopped, it's just another part of natural variability.

2000-2009 was warmest decade on record. NASA's Goddard Institute for Space Studies, the National Climatic Data Center of the National Oceanic and Atmospheric Administration, the U.K. Met Office, and the World Meteorological Organisation have all stated that 2000-2009 was the warmest decade on record for the globe.

From the Met Office:

Will also misrepresented Jones' statements on Medieval Warm Period

From Will's column:

Jones also says that if during what is called the Medieval Warm Period (circa 800-1300) global temperatures may have been warmer than today's, that would change the debate. Indeed it would. It would complicate the task of indicting contemporary civilization for today's supposedly unprecedented temperatures.

Jones said current warming cannot be explained by solar and volcanic forcing. Contrary to Will's suggestion that Jones' statements on the Medieval Warm Period (MWP) undermine man-made global warming, Jones stated that warming after the 1950s is likely human-caused because “we can't explain the warming from the 1950s by solar and volcanic forcing.” From the Q&A:

D - Do you agree that natural influences could have contributed significantly to the global warming observed from 1975-1998, and, if so, please could you specify each natural influence and express its radiative forcing over the period in Watts per square metre.

This area is slightly outside my area of expertise. When considering changes over this period we need to consider all possible factors (so human and natural influences as well as natural internal variability of the climate system). Natural influences (from volcanoes and the Sun) over this period could have contributed to the change over this period. Volcanic influences from the two large eruptions (El Chichon in 1982 and Pinatubo in 1991) would exert a negative influence. Solar influence was about flat over this period. Combining only these two natural influences, therefore, we might have expected some cooling over this period.

[...]

G - There is a debate over whether the Medieval Warm Period (MWP) was global or not. If it were to be conclusively shown that it was a global phenomenon, would you accept that this would undermine the premise that mean surface atmospheric temperatures during the latter part of the 20th Century were unprecedented?

There is much debate over whether the Medieval Warm Period was global in extent or not. The MWP is most clearly expressed in parts of North America, the North Atlantic and Europe and parts of Asia. For it to be global in extent the MWP would need to be seen clearly in more records from the tropical regions and the Southern Hemisphere. There are very few palaeoclimatic records for these latter two regions.

Of course, if the MWP was shown to be global in extent and as warm or warmer than today (based on an equivalent coverage over the NH and SH) then obviously the late-20th century warmth would not be unprecedented. On the other hand, if the MWP was global, but was less warm that today, then current warmth would be unprecedented.

We know from the instrumental temperature record that the two hemispheres do not always follow one another. We cannot, therefore, make the assumption that temperatures in the global average will be similar to those in the northern hemisphere.

H - If you agree that there were similar periods of warming since 1850 to the current period, and that the MWP is under debate, what factors convince you that recent warming has been largely man-made?

The fact that we can't explain the warming from the 1950s by solar and volcanic forcing - see my answer to your question D.

I - Would it be reasonable looking at the same scientific evidence to take the view that recent warming is not predominantly manmade?

No - see again my answer to D.

Will is routinely criticized for distorting climate data

Will criticized for “misrepresentation of the data” after distorting World Meteorological Organisation (WMO) data about global temperatures. Will wrote in an April 2, 2009, column that "[r]educing carbon emissions supposedly will reverse warming, which is allegedly occurring even though, according to statistics published by the World Meteorological Organization, there has not been a warmer year on record than 1998." Will presented the WMO data as evidence that global warming may not be occurring despite the fact that WMO Secretary-General Michel Jarraud criticized him for similarly writing in a February 15, 2009, column that according to the organization, "[T]here has been no recorded global warming for more than a decade." Jarraud called Will's February 15 assertion “a misrepresentation of the data and of scientific knowledge.”

Will distorted Arctic Climate Research Center (ACRC) about sea ice. Previously, Will twice misused sea ice data to falsely suggest that the data undermine the overwhelming evidence that humans are causing global warming. In a February 27, 2009, column, Will falsely claimed that in his February 15 column, he “accurately reported” on the contents of an ACRC document. In fact, the document he cited rebutted the very argument he was making: the ACRC document that Will relied on actually stated that the sea ice data are consistent with the outcomes projected by climate-change models. In the words of TPM Muckraker's Zachary Roth, Will's new column “amounts to a stubborn defense of the amazing global warming denialist column he published earlier this month, that was ripped apart by just about everyone and their mother." On April 6, 2009, NASA and the National Snow and Ice Data Center (NSIDC) released new data on Arctic sea ice levels that further discredited Will's statements.

Will columns criticized by Post colleagues. Will's global warming columns have also been criticized by Washington Post editorial board member and cartoonist Tom Toles, Post weather columnist Andrew Freedman, and Post ombudsman Andrew Alexander. His fellow editorial columnist Eugene Robinson also said that Will “cross[ed] the line” in spreading global warming misinformation.