Tuesday, August 2, 2011

Bray and von Storch on Tollefson's piece in nature

RE: ‘The Sceptic Meets His match' (Nature vol 475 28 July 2011: 440-441), Jeff Tollefson.

In the recent issue of nature (vol 475 28 July 2011), Jeff Tollefson reported about a pamphlet of the Heartland Institute from 2007.  Results from our 2003 survey among climate scientists were used for the statement  “The survey clearly shows that the debate over why climate is changing is still underway, with nearly half of the climate scientists disagreeing with what is often claimed to be a ‘consensus view’”. Tollefson goes on to accurately state that “In the survey, nearly 56% of climate scientists agreed that human activity is causing climate change, 14% were unsure and 30% disagreed”.  Tollefson also goes on to state that Bast [founder of the Heartland Institute] “dismisses the findings of a follow up survey by Bray and von Storch [this is our 2008 survey] which found that more than 85% of the responding scientists agreed that human activity is behind climate change.” - also an accurate interpretation of the survey data. Tollefson spoke to one of us (HvS), and we find his research done well.

The full surveys, from 1996, 2003 and 2007 are all available on-line (Bray, D., and H. von Storch, 2010: CliSci2008: A Survey of the Perspectives of Climate Scientists Concerning Climate Science and Climate Change, GKSS Report 2010/9, and Bray, D. and H. von Storch, 2007: Climate Scientists’ Perceptions of Climate Change Science. GKSS-Report 11/2007).

The changing agreement over time among climate scientists about the existence of a warming (manifestation) and about the dominant cause (namely GHGs; "attribution") is displayed in this diagram, which is taken from the 2010-study by Dennis Bray (Bray, D.: The scientific consensus of climate change revisited. Environ. Sci. Policy (2010), doi:10.1016/j.envsci.2010.04.001)

Tollefson’s article talks about ‘dimensions’ of consensus as consensus is not as clear cut as often portrayed.  From our surveys we have learned that some ‘dimensions’ of ‘consensus’ have increased, others have decreased. In particular for the two key dimensions manifestation of climate change, that it is happening regardless of what is causing it, as well as attribution to human activities, consensus has increased among climate scientists since the beginning of our surveying.

What has recently decreased is the “legitimation” of the IPCC as representing this consensus, because in recent years an opposition has formed which asserts that the IPCC is underestimating the severity of the change (see Bray, 2010). From our own observations of discussions among climate scientists we also find hardly consensus on many other issues, ranging from changing hurricane statistics to the speed of melting Greenland and Antarctica, spreading of diseases and causing mass migration and wars.

We will continue surveying climate scientists about their view and opinions on climate change and climate policies.


Stan said...

I think it important to remember, that despite the woeful performance of expert opinion over the course of history, there remains at least a possibility that climate scientists might be correct in some part of these judgments.

Hans von Storch said...

what do you mean with "climate scientists might be correct" - do you mean all, most, some? Which judgments? - that it is getting warmer, that human are causing it, that sea level will rise by about 2 until the end of this century, that ice bears will die out, that climate wars will rage in future?