Why do so many doubt the science on climate change?

Wednesday, August 10, 2011

Despite the voluminous evidence and near unanimity of climate experts, large numbers of North Americans remain sceptical about global warming. Studies suggest that one factor is an entrenchment of views along political lines

by HENRY HENGEVELD

I quite enjoyed reading Terry Daynard's opinion column in the April issue of Better Farming. In particular, I was gratified by his strong endorsement of the credibility of scientists involved in writing the voluminous climate science assessment report released by the Intergovernmental Panel on Climate Change (IPCC) in 2007. This endorsement was both appropriate and timely. 

However, it seems that most North Americans, including many within the farming community, don't share his confidence. Take, for example, their thoughts on the IPCC conclusions about the magnitude and causes of recent trends in global climate. 

The 2007 Working Group I report states unequivocally that:

• Global mean surface temperatures have risen by 0.74 C ± 0.18 C when estimated by a linear trend over the last 100 years (1906–2005). The rate of warming over the last 50 years is almost double that over the last 100 years (0.13 C ± 0.03 C vs. 0.07 C ± 0.02 C per decade).

• It is extremely unlikely (a less than five per cent chance) that the global pattern of warming during the past half century can be explained without external forcing, and very unlikely that it is due to known natural external causes alone. The warming occurred in both the ocean and the atmosphere and took place at a time when natural external forcing factors would likely have produced cooling.  

• Greenhouse gas forcing has very likely caused most of the observed global warming over the last 50 years. This conclusion takes into account observational and forcing uncertainty, and the possibility that the response to solar forcing could be underestimated by climate models. It also stands up to the use of different climate models, different methods for estimating the responses to external forcing and variations in the analysis technique.

However, a U.S. Gallup poll taken in March 2010 indicated that 49 per cent of Americans believe that scientists have serious doubts about the evidence for global warming. In fact, 38 per cent believe most scientists are unsure about whether or not global warming is occurring at all.  Furthermore, 46 per cent believe that warming of the past century is due to natural causes.

Canadians are somewhat less sceptical. An Angus Reid poll taken in October of 2010 suggests that 80 per cent of Canadians agree that there is solid evidence for global warming during the past 40 years, and 60 per cent agree that this warming was caused by human emissions of greenhouse gases.

Canadians are also far more willing to become engaged in action to reduce the risks of climate change. In concurrent surveys of Americans and Canadians undertaken by Christopher Borick and fellow researchers at Muhlenburg College, the University of Michigan and University of Montreal in late 2010 and early 2011, 65 per cent of Canadians polled thought there should be a great deal of national government involvement in addressing climate change, compared to only 43 per cent of Americans.

Canadians are also more willing to pay for action to address climate change. For example, 58 per cent of Canadians surveyed support the concept of a cap and trade system for reducing greenhouse gas emissions, while 50 per cent were also willing to pay a carbon tax. The American support for such measures was 39 per cent and 32 per cent, respectively.

Needless to say, the reluctance of the North American public to accept the key conclusions of the international scientific assessment by experts has caused considerable head-scratching and concern within the science community. Several related studies on this subject have now been published in major scientific journals.

In one of these, Stanford University researcher William Anderegg and colleagues undertook an analysis of the extent of agreement of experienced climate system researchers with the above IPCC conclusions. They evaluated the position of 1,372 such scientists from around the world who had published 20 or more related research papers in peer-reviewed science journals.

In their report, published in the American Proceedings of the National Academies of Science, they noted that 97-98 per cent of these "experts" support the IPCC conclusions about human-induced climate change. They also found that the 2.5 per cent of the researchers who were unconvinced by the evidence for climate change had, on average, published about half the number of related papers that the vast majority of "convinced" experts had. These results are consistent with those published in other similar analyses.

I, like many others in the climate science community, used to think that better communication of the evidence that climate scientists have provided to support the IPCC conclusions would help address this discrepancy between expert and public confidence in such evidence. Several recent new studies suggest otherwise.

Scientific confidence in the reality of a significant warming of the Earth's surface temperatures over the past century and the role that humans have played in this warming has progressively increased from the first major assessment issued in 1990 to the fourth assessment released in 2007. Yet, despite reasonably competent media reporting of these assessments, these studies note that public confidence has changed little or even decreased.

For example, a study of British climate change sceptics published by Cardiff University psychologist Linda Whitmarsh in the journal Global Environmental Change showed little change in their opinions on climate change over time. In her research, Whitmarsh noted that acceptance or rejection of the evidence was to a large measure based on the world views held by the people polled.

Those who were less concerned about the natural environment and more conservative in their socio-political perspectives tended to be more likely to reject the evidence than those who appeared to be more pro-environment and more liberal in their world views.

Thus, individual opinions become entrenched. Whitmarsh argues that many of the sceptics are actually "contrarians" and that better communications of evidence is unlikely to change their opinion.

The Borick et al. study comparing Canadian and American opinions discussed above shows similar entrenchment of opinions along political lines. It found that, in the United States, Republican voters were much more likely to reject the scientific evidence than Democrats. In Canada, only 64 per cent of polled individuals who vote Conservative believed the evidence for warming, while between 84 and 91 per cent of Liberal, NDP, Green and Bloc Quebecois supporters indicated they believed the evidence. 

The bottom line is that communicating the need for action on what many climate experts consider to be the greatest threat facing our planet today needs to involve far more than scientists. As Anderegg and his colleagues note, the encouragement of behavioural change also needs to engage educators, social psychologists, behavioural economists, political scientists, historians, ethicists and experts in other disciplines.
Are we prepared to do so? BF


Henry Hengeveld is Emeritus Associate, Science Assessment and Integration Branch/ACSD/MSC, Environment Canada