The Real News About Mann-Made Global Warming -- Debunking the "hockey stick" of global doom

By Aussiegirl

So much for the hockey stick of doom! It turns out it's nothing more than the hockey puck of hucksterism!

Another fond myth bites the dust of reality. Read the report, you so-called reporters! Of course the earth is warmer now than it has been in 400 years -- we are emerging from the Little Ice Age, and good thing too! Believing the hockey stick of doom is like taking one month's Dow Jones Industrial average and extrapolating it out to some sort of meaningful trend based on one small snapshot of a dynamic process. If you looked at a chart of the Dow Jones just prior to a big crash, you'd swear the darn thing was going to keep rising in perpetuity. Good way to lose a fortune and end up splatted on the pavement below. The climate is dynamic. It changes. Better warmer than colder.

TCS Daily - The Real News About Mann-Made Global Warming

Last week's release of a National Academies of Science (NAS) report entitled "Surface Temperature Reconstructions for the Last 2,000 Years" was the result of a congressional request to look into the controversy surrounding the now-famous "hockey stick" temperature curve. The media portrayed the findings of the NAS review panel as some sort of new statement about how warm the Earth is at present, and totally missed the real news: that the original claim of Mann et al. of unprecedented warmth in the last 1,000 years -- based mostly upon tree ring data, especially from the southwest U.S. -- was dubious at best.

For the last several years, the hockey stick has been a poster prop for manmade global warming. For instance, it figures prominently in Al Gore's new movie, "An Inconvenient Truth." But the statistical and data analysis methods that Mann et al. used to arrive at their 1,000 year temperature reconstruction were strongly criticized by some. The hockey stick played down the warmth of the "Medieval Warm Period" of 1,000 years ago, as well as the later coolness of the "Little Ice Age."

Also, the uncritical acceptance of the hockey stick for inclusion in the U.N.'s Third Assessment Report on global climate in 2001 gave many scientists the impression that the editors of that report wanted to believe the hockey stick more than they were convinced of its validity.

In their attempt to not publicly scold Mann and his coauthors for questionable data analysis methods, the authors of the new report instead chose to restate the evidence for how warm the Earth has gotten recently. What the media didn't notice, however, is that the 1,000 year figure that was central to the whole hockey stick debate had now been replaced in the report by a figure of 400 years. Since most of the last 400 years was dominated by the "Little Ice Age," the warming during the 20th century should be welcomed by humanity.

The report says that surface temperature reconstructions before this period (about 1600) have "less confidence" and that "uncertainties...increase substantially backward in time..." for any of these proxy estimates of ancient temperatures. One review panel member told me that the statisticians on the panel were amazed when it was revealed that the method underlying the hockey stick had essentially no statistical skill when validated.


This is pretty harsh language for an NAS report written by review panel members, several of whom are equivalent to foxes guarding the hen house. Researchers who have bought into the validity of using proxy measures for ancient climate reconstructions aren't about to throw away the "best" method the paleoclimate research community has, even if it can not be validated with real temperature measurements (the thermometer was not even invented until the 1600's).

One rather amazing characteristic of the hockey stick is the so-called "divergence problem": the strong warming in the late 20th century is not even indicated in the tree ring data that were used to reconstruct the last 1,000 years of supposed temperature variations. Much of the 20th century warming (the blade of the hockey stick) represents real temperature measurements, not tree ring reconstructions, since they don't show the warming. This raises a natural question, which the panel shrugged off: If tree rings do not show the strong warming of the late 20th century, how do we know there wasn't a similar temperature spike 1,000 years ago?

Keeping the door open to the possibility that Mann might be right anyway, the new report says that it is at least "plausible" that we are warmer now than anytime in the last 1,000 years. But this is a much lower level of certainty than has been associated with the hockey stick by the media, bureaucrats, and movie stars (like Al Gore).

But what was the biggest news in the media coverage of the NAS report last week? The biased nature of the media coverage. It almost seems like the media covering the report looked for familiar phrases that fit their global warming paradigm (e.g., "...warmer than the previous 400 years..."), without noting the important conclusions that addressed why the report was written in the first place.

Indeed, much of the press coverage managed to connect the words "warmer than" with a report reference to "2,000 years" to come up with widespread statements (not supported by the report) that the Earth is warmer now than when Jesus Christ walked the Earth. Apparently, sound bites are still preferred over truth.


The NAS review panel report admits that it is difficult to conclude that we are warmer now than 1,000 years ago, but that we are very likely warmer than anytime in the last 400 years. Since what this really means is that we are warmer now than any time during the "Little Ice Age" (and thank goodness for that), one wonders whether we really know anything about past climate reconstructions from tree ring data.

Dr. Roy Spencer is a principal research scientist for the University of Alabama in Huntsville and the U.S. Science Team Leader for the Advanced Microwave Scanning Radiometer (AMSR-E) on NASA's Aqua satellite.