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If you do a search at this blog site for ‘hockey stick’, Google will provide you with about 70 links and the first will link to a question I posted a year ago:

“What is the evidence for the medieval warm period? My understanding is that the Vikings were able to settle Greenland and grow grapes in Canada over several hundreds of years because the climate was significantly warmer. Yet this period is not evident in the famous ‘hockey stick’ graph.”

The Graph

[from BBC News]

The graph was the creation of Dr Michael Mann, et al, and was used by the United Nation’s Intergovernmental Panel on Climate Change (IPCC) to conclude in their influential 2001 assessment report that the 1990s was the warmest decade and 1998 the warmest year of the last millenium.

Indeed the ‘hockey stick’ has emerged as something of an icon for believers in anthropogenic global warming (AGW), while global warming skeptics have dismissed it as shoddy science and another example of ‘believers’ using models to support a position at odd with the evidence in particular the existence of the medieval warm period.

Now a prominent statistician who is also a Univeristy Professor, Chair of the National Academy of Sciences Committee on Applied and Theoretical Statistics, and a member of the board of the American Statistical Association, has published a rather damning report on the hockey stick. As Paul Williams commented in the thread following my blog post last Friday, “… the hockey stick has just been hit for six”!

Following are some of the conclusions from Dr Edward Wegman as summarized by the US House Committee on Energy and Commerce:

1. Mann et al., misused certain statistical methods in their studies, which inappropriately produce hockey stick
shapes in the temperature history. Wegman’s analysis concludes that Mann’s work cannot support claim that
the1990s were the warmest decade of the millennium.

Report: “Our committee believes that the assessments that the decade of the 1990s was the hottest
decade in a millennium and that 1998 was the hottest year in a millennium cannot be supported by
the MBH98/99 analysis. As mentioned earlier in our background section, tree ring proxies are
typically calibrated to remove low frequency variations. The cycle of Medieval Warm Period and
Little Ice Age that was widely recognized in 1990 has disappeared from the MBH98/99 analyses,
thus making possible the hottest decade/hottest year claim. However, the methodology of
MBH98/99 suppresses this low frequency information. The paucity of data in the more remote past
makes the hottest-in-a-millennium claims essentially unverifiable.”

2. A social network analysis revealed that the small community of paleoclimate researchers appear to review
each other’s work, and reuse many of the same data sets, which calls into question the independence of peerreview and temperature reconstructions.

Report: “It is clear that many of the proxies are re-used in most of the papers. It is not surprising that
the papers would obtain similar results and so cannot really claim to be independent verifications.”

3. Although the researchers rely heavily on statistical methods, they do not seem to be interacting with the
statistical community.

Report: “As statisticians, we were struck by the isolation of communities such as the paleoclimate
community that rely heavily on statistical methods, yet do not seem to be interacting with the
mainstream statistical community. The public policy implications of this debate are financially
staggering and yet apparently no independent statistical expertise was sought or used.”

4. Authors of policy-related science assessments should not assess their own work.

Report: “Especially when massive amounts of public monies and human lives are at stake,
academic work should have a more intense level of scrutiny and review. It is especially the case
that authors of policy-related documents like the IPCC report, Climate Change 2001: The Scientific
Basis, should not be the same people as those that constructed the academic papers.”

5. Policy-related climate science should have a more intense level of scrutiny and review involving statisticians.
Federal research should involve interdisciplinary teams to avoid narrowly focused discipline research.

Report: “With clinical trials for drugs and devices to be approved for human use by the FDA, review
and consultation with statisticians is expected. Indeed, it is standard practice to include statisticians
in the application-for-approval process. We judge this to be a good policy when public health and
also when substantial amounts of monies are involved, for example, when there are major policy
decisions to be made based on statistical assessments. In such cases, evaluation by statisticians
should be standard practice. This evaluation phase should be a mandatory part of all grant
applications and funded accordingly.”

6. Federal research should emphasize fundamental understanding of the mechanisms of climate change, and
should focus on interdisciplinary teams to avoid narrowly focused discipline research.

Report: “While the paleoclimate reconstruction has gathered much publicity because it reinforces a
policy agenda, it does not provide insight and understanding of the physical mechanisms of climate
change… What is needed is deeper understanding of the physical mechanisms of climate change.”

Read the full report here: http://energycommerce.house.gov/108/home/07142006_Wegman_Report.pdf .

Hollywood blockbuster ‘The Day After Tomorrow’ was an apocalyptic tale about the Gulf Stream — the ocean current which circulates warm water from the tropics to the Northern Hemisphere — being disrupted by global warming. In the following guest blog post, Rog summarises the latest research findings from Richard Seager on the Gulf Stream. This research suggests even if the Gulf Stream slows, New York won’t freeze over.

Oh well, I enjoyed the movie.

Rog writes:

There has been considerable speculation that changes to the body of water known as the “Gulf Stream” can alter climates on a local and global scale. Tim Flannery in his book ‘The Weather Makers’ speculates that the sudden drop of five degrees centigrade in Greenland ice cores was due to changes in the flow of the Gulf Stream.

Tim Flannery then goes on to state that changes to the Gulf Stream constitute a “tipping point” in global climate change.

The Pentagon shares Flannery’s views, in a study published in 2003 they warned that changes to the direction of the flow of the Gulf Stream could result in northern latitudes becoming suddenly colder and tropics much warmer leading to floods of desperate immigrants. The study notes that: “The dramatic slowing of the thermohaline circulation is anticipated by some ocean researchers, but the United States is not sufficiently prepared for its effects, timing, or intensity”.

However, in a recent article in the American Scientist, Richard Seager from Columbia University’s Lamont-Doherty Earth Observatory disputes all these scenarios. He claims:

“..temperatures will not drop to ice-age levels, not even to the levels of the Little Ice Age, the relatively cold period that Europe suffered a few centuries ago. The North Atlantic will not freeze over, and English Channel ferries will not have to plow their way through sea ice. A slowdown in thermohaline circulation should bring on a cooling tendency of at most a few degrees across the North Atlantic—one that would most likely be overwhelmed by the warming caused by rising concentrations of greenhouse gases. This moderating influence is indeed what the climate models show for the 21st century and what has been stated in reports of the Intergovernmental Panel on Climate Change. Instead of creating catastrophe in the North Atlantic region, a slowdown in thermohaline circulation would serve to mitigate the expected anthropogenic warming!”

Note that Richard Seager’s revelation was not founded on any new evidence.

“..All Battisti and I did was put these pieces of evidence together and add in a few more illustrative numerical experiments. Why hadn’t anyone done that before? Why had these collective studies not already led to the demise of claims in the media and scientific papers alike that the Gulf Stream keeps Europe’s climate just this side of glaciation? It seems this particular myth has grown to such a massive size that it exerts a great deal of pull on the minds of otherwise discerning people.

This is not just an academic issue. The play that the doomsday scenario has gotten in the media—even from seemingly reputable outlets such as the British Broadcasting Corporation—could be dismissed as attention-grabbing sensationalism. But at root, it is the ignorance of how regional climates are determined that allows this misinformation to gain such traction.”

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Comment/guest posts welcomed from others readers of this blog, email jennifermarohasy@jennifermarohasy.com .