Main

Archive by category: Hans von Storch

Bookmark in Connotea

Climate scientists' views on climate change: a survey

Hans von Storch and Dennis Bray

In 1996 and 2003 we surveyed the opinions on climate change held by climate scientists. The results of these surveys have been subject to many misuses and erroneous claims. Some have selected individual statements out of context (scroll down to number 5) to bolster their claims, while others have argued that the 2003 part of the survey would be strongly biased by skeptics misusing the online-sampling for multiple submissions.

With respect to the latter – the survey was conducted first in 1996 with a mail-out format, which nobody claimed could be biased and the results were published in the Bulletin of the American Meteorological Society. The second survey from 2003 was conducted on the internet, a procedure that in principle could have been misused by multiple submissions by those skeptical or alarmist on climate change who shared the password. However, the 2003 results are internally consistent with the 1996 results. In 2003 scientists expressed increased satisfaction and agreement with the IPCC and increased confidence in the tools of the science. In comparison to 1996, no anomalies were found in the response to questions.

On the skeptical side, the survey has often been used to create the impression that most scientists were not in support of anthropogenic causes of ongoing climate change: Specifically, it was noted that “For example more climate scientists ‘strongly disagree’ than ‘strongly agree’ that climate change is mostly the result of anthropogenic causes.” This interpretation is certainly biased.

We had requested responses on a scale from 1-7 to the question “Climate change is mostly the result of anthropogenic causes.” – with 1 representing “strong agreement” and 7 “strong disagreement”. Thus, scales 1-3 signal agreement, 4 an ambivalent position, and 5-7 disagreement. The frequency distribution for the two surveys in 1996 and 2003 are:
chart.JPG
Thus, the statement, that more respondents strongly disagree than strongly agree is technically correct (10% vs. 9%), but highly misleading. If we pool the 1-3 positive responses to “agreement”, and 5-7 to disagreement, then the ratio in 1996 was 41:45 in favor of disagreement; in 2003, however, this ratio has become 56:30 in favor of agreement; all scales 1-3 have seen strong increases in frequency, while 5-6, with the notable exception of scale 7, have seen marked reductions.

Continue reading "Climate scientists' views on climate change: a survey" »

Posted by Olive Heffernan on August 08, 2007
Categories: Communicating Climate Change, Hans von Storch, In the News, Opinion | | Comments (13) | TrackBacks (2)

Bookmark in Connotea

The decay of the hockey stick

(Posted by Olive on behalf of Hans)

In October 2004 we were lucky to publish in Science our critique of the ‘hockey-stick’ reconstruction of the temperature of the last 1000 years. Now, two and half years later, it may be worth reviewing what has happened since then.

The publication in 2004 was a remarkable event, because the hockey-stick had been elevated to an icon by the 3rd Assessment Report of the IPCC. This perception was supported by a lack of healthy discussion about the method behind the hockey-stick. In the years before, due to effective gate keeping of influential scientists, papers raising critical points had a hard time or even failed to pass the review process. For a certain time, the problem was framed as an issue of mainstream scientists, supporting the concept of anthropogenic climate change, versus a group of skeptics, who doubted the reality of the blade of the hockey stick. By framing it this way, the real problems, namely the ‘wobbliness’ of the shaft of the hockey-stick, and the suppressing of valid scientific questions by gate keeping, were left out.

Hopefully, sociology of science will later study this unfortunate period of climate science, but we may conclude now that science itself has indeed corrected claims of premature knowledge. We see now a healthy and broad discussion of the issue. We had the opportunity to respond to no less than four comments on our 2004 Science paper, but unfortunately only two comments were published. Similarly, Michael Mann and his coworkers had to respond to at least 2 comments to their Journal of Climate article in 2005.

At the EGU General Assembly a few weeks ago there were no less than three papers from groups in Copenhagen and Bern assessing critically the merits of methods used to reconstruct historical climate variable from proxies; Bürger’s papers in 2005; Moberg’s paper in Nature in 2005; various papers on borehole temperature; The National Academy of Science Report from 2006 – al of which have helped to clarify that the hockey-stick methodologies lead indeed to questionable historical reconstructions. The 4th Assessment Report of the IPCC now presents a whole range of historical reconstructions instead of favoring prematurely just one hypothesis as reliable.

When looking back we are satisfied with what has been achieved – namely an open, open-minded exciting discussion about the merits and problems related to different methods; an atmosphere where mere claims about the informational content of proxy-data meet a more critical response; an evolving practice of testing the skill of reconstruction methods in the laboratory of millennial forced global climate model simulations, where the formation of proxy-data is simulated in - so far too simplified - models.

Hans von Storch and Eduardo Zorita

Posted by Olive Heffernan on May 03, 2007
Categories: Climate Science, Hans von Storch, Palaeoclimate | | Comments (36) | TrackBacks (1)

Current content

For the latest comment, analysis, news and features, go to Nature Reports Climate Change, Nature’s online resource dedicated to in-depth coverage of climate science and the implications for policy, the economy and society.

Search