Communicating uncertainty in climate science
When the media talk about climate change scepticism, they usually mean that people are uncertain in some way about the reality or seriousness of climate change.
A number of polls of public attitudes towards climate change have documented an increase in the degree of perceived uncertainty about climate change over the past three years (BBC, 2010; Pew Research Centre, 2009; Spence, Venables, Pidgeon, Poortinga & Demski, 2010). These data on public opinion about climate change can be contrasted with a recent survey of active and publishing climate scientists. Among this group, Doran and Zimmerman (2009) found 97% agree that human activity is contributing to climate change. On the basic question of whether human activity is influencing the global climate there is very little uncertainty among climate scientists.
But despite the overwhelming amount of scientific evidence that shows human activities are causing the earth to warm, debates about climate change are still characterised by an enormous amount of uncertainty (Zehr, 2000). The everyday meaning of uncertainty is negative – and so when it comes to climate change, people tend to infer that scientists do not know anything about a topic, just because they do not know everything about it. Uncertainty about climate change is a major barrier to public engagement.
Perhaps the most important task for communicating climate change effectively is being clear that uncertainty is not an enemy of science that holds it back – it is actually a stimulus that drives it forward. Just like any area of complex science, uncertainty is a feature of climate science that will never go away. Science doesn’t deal in certainties – it weighs up the evidence and tells you which of several possible answers has the most support. Where uncertainties remain, scientists know where to put their efforts into what to investigate next. Getting the message across that uncertainty is not a bad thing, and that we make decisions every day based on less than certain information is an important place to start for climate change communicators.
So how much uncertainty is there about climate change?
On the basic question of whether the earth is warming, and whether human activity is causing this to happen, there is very little uncertainty – but on more specific questions about when, where and how soon the impacts of climate change will take place, there is still a great deal that is unknown.
The British Royal Society has produced a guide to the science of climate change that describes the areas where the science is well established, where there is still some debate, and where genuine uncertainties remain. Although it is clearly written, it is aimed at people who have some understanding of the science. But the basic message is very clear: there is strong and reliable evidence that human activity has caused the earth to warm over the past 50 years – on this critical point, there is next to no uncertainty. Emphasising that uncertainty in science is normal will help to combat the belief that uncertainty should equal inaction.
As a communicator, it is critical to explain to people the difference between scientific uncertainty (that is, the extent to which scientists agree about the answer to a particular question), and uncertainty that comes from deciding how to respond to what the climate science tells us. In his book, Why we disagree about climate change, the climate scientist Mike Hulme shows how easy it is to confuse the different types of uncertainty that surround climate change (Hulme, 2009).
No matter how much science is conducted, it will never tell us which of a set of different policies to choose. A scientist can tell you how much carbon is in the atmosphere, and calculate the effectiveness of different methods of reducing it (e.g. reducing the number of cars on the road vs. regulating emissions from cement factories). But a scientist cannot tell you which of these is the right choice to make – this is a decision for citizens and politicians. Being as clear as possible about the difference between climate science, and the choices we make based on that science, is essential for effective communication – otherwise, these different types of uncertainty become confused.
For people interested in communicating more specific aspects of uncertainty in climate science – for example, how confident scientists are that a particular impact will occur during the next 20–30 years – there is now some guidance available. The Intergovernmental Panel on Climate Change (IPCC) has attempted (not always successfully) to quantify and communicate the uncertainties around climate science in their Assessment Reports for policy makers. In the most recent report, in 2007, they specified numerical probability ranges (e.g. 90% or more) at the outset of the report, linked them to specific terms (e.g. “very likely”) and then used these terms throughout the report. Based on the most recent assessment of the climate science evidence, the IPCC concluded that it was ‘very likely’ that human activity was causing climate change.
However, when psychologists from the University of Illinois (Budescu, Broomell & Por, 2010) ran an experiment to test how people interpreted these written terms, they found a big discrepancy between the meaning the IPCC had intended, and the conclusion people actually drew. The numerical ranges that people actually assigned to the verbal expressions were often not the ones the IPCC had used. The authors of the study concluded that written expressions such as ‘very likely’ need to be accompanied by the probability range they refer to if they are to be effective: otherwise people will interpret the same term in very different ways. For communicators wishing to talk about specific events, using numerical information as well as a verbal term is likely to convey more accurate information.
Media-generated controversy is often cited as a reason for scepticism about climate change – because media reports exaggerate the uncertainty about the basic questions of climate change. Radio, television and newspaper reports have been criticised for interpreting too simplistically the notion of providing a ‘balanced’ set of views, which can lead to competing points of view on a scientific issue being presented as equally supported when in fact they are not (Boykoff, 2007; Ward, 2008; Zehr, 2000). This creates the impression that the causes of climate change are more controversial than they actually are.
Climate change communicators can try to combat this problem by using examples of other subjects where a ‘balanced’ news report would not mean giving equal space to opposing points of view (e.g. the health impacts of smoking). Emphasising that ‘balance’ doesn’t mean ‘equal’ but ‘representative of the evidence’ is one way of explaining to people why media coverage of climate change can often paint an unrealistic picture of the underlying science.
In a paper that was published in the journal Nature Climate Change, the social scientists Nick Pidgeon and Baruch Fischhoff suggest that the best way to deal with uncertainty is to talk about climate change as a risk. Although this might not seem a major difference, framing the issue as being about risk (rather than a set of predictions about the future) turns the problem into something that most people are used to dealing with (and that social scientists know a fair amount about): perceiving and managing risks. It is also the language of the insurance, health and national security sectors. Pidgeon and Fischhoff suggest that the more the risks of climate change can be brought to life through vivid ‘mental models’, the better (using clear practical examples of the risk of sea level rise, or the risk of melting glaciers).
An academic paper by psychologists from the University of Exeter in the UK showed that uncertainty is not necessarily a barrier to communication if the right ‘framing’ of the problem is used (Morton et al, 2011). They gave people short messages to read that contained uncertain information, but framed in either a positive or negative way. So, half the participants in the experiment read a message describing an 80% risk of abrupt changes to Monsoon patterns (negative framing), while the other half of the participants read a message describing a 20% chance of avoiding abrupt changes to Monsoon patterns (positive framing). The researchers found that when uncertainty was used to indicate that losses might not happen if cautious action is taken to prevent them (i.e. the positive frame), then people were more likely to indicate stronger intentions to act in a pro-environmental way. The authors concluded that uncertainty is not an inevitable barrier to action, provided communicators frame climate change messages in ways that trigger caution in the face of uncertainty .
A good practical example of an attempt to communicate uncertainty in climate science is the UK Climate Impacts Programme. It contains a great deal of information about the probable outcomes of climate change for different regions in the UK, and is a tool for national and local governments. The last major assessment, in 2009, used visual images and probability information to communicate complex uncertainty information. Resources and reports can be downloaded from their website.
Beyond uncertainty in climate science, there is also a problem with public perceptions of disagreement among climate scientists. One study in Nature Climate Change (Ding et al, 2011) directly studied the link between people’s sense of whether there was a ‘consensus’ on climate change among scientists, and their support for climate policies. Using survey data from the US, the study found that perceptions of consensus were directly linked to a range of key beliefs (including whether humans were causing climate change), which in turn determined whether people supported policies for reducing carbon. The message from this study is important – repeatedly stating that the vast majority of scientists agree that humans are causing climate change is one way of overcoming perceptions of uncertainty.
Boykoff, M. (2007). Flogging a Dead Norm? Media Coverage of Anthropogenic Climate Change in United States and United Kingdom, 2003–2006. Area 39(4) 470–481.
British Broadcasting Corporation. (2010). BBC climate change poll – February 2010.
Budescu, D. V., Broomell, S., & Por, H. (2009). Improving communication of uncertainty in the reports of the Intergovernmental Panel on Climate Change. Psychological Science 20, 299–308.
Ding, D., Maibach, E.W., Zhao, X., Roser-Renouf, C. & Leiserowitz (2011). Support for climate policy and societal action are linked to perceptions about scientific agreement. Nature Climate Change doi:10.1038/NCLIMATE1295
Doran, P.T. & Zimmerman, M.K. (2009). Examining the scientific consensus on climate change. EOS, Transactions American Geophysical Union 90(3) 22–23.
Hulme, M. (2009). Why we disagree about climate change: Understanding controversy, inaction and opportunity. Cambridge: Cambridge University Press.
Morton, T.A., Rabinovich, A., Marshall, D. & Bretschneider, P. (2010). The future that may (or may not) come: How framing changes response to uncertainty in climate change communication. Global Environmental Change 21 (1) 103–109.
Pew Research Centre for the People and the Press. (2009). Fewer Americans See Solid Evidence of Global Warming.
Pidgeon, N.F and Fischhoff, B. (2011) The role of social and decision sciences in communicating uncertain climate risks. Nature Climate Change. 1, 35–41.
Spence, A., Venables, D., Pidgeon, N., Poortinga, W. and Demski, C., (2010). Public Perceptions of Climate Change and Energy Futures in Britain: Summary Findings of a Survey Conducted in January-March 2010. Technical Report (Understanding Risk Working Paper 10–01). Cardiff: School of Psychology.
Ward, B. (2008). A higher standard than ‘balance’ in journalism on climate change science. Climatic Change 86, 13–17.
Zehr, S. (2000). Public representations of scientific uncertainty about global climate change. Public Understanding of Science 9, 85–103.
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- Communicating climate change
- Communicating climate science
- Encouraging sustainable behaviour
- Visual communication of climate change
- Making climate science simple & understandable
- Communicating uncertainty in climate science
- Why are people still sceptical about climate change?
- Social norms & social networks
- Using scare tactics: does it work?
- Resources for communicating climate change
- Breaking bad habits & creating good ones
- How to go beyond social marketing
- Language: words & phrases
- Values & frames
- Uncertainty & the IPCC
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- Climate change scepticism and the media