Climate science is an example of post-normal science. This is the application of science to “public issues where facts are uncertain, stakes are high and decisions urgent”. (1) Normal science seeks to observe, theorise and experiment in order to establish facts. Post-normal science happens in a context of a lot of uncertainties where it’s impossible to experiment, so it deals with uncertainties rather than established facts. This is the situation that climate scientists work in.

Intergovernmental Panel on Climate Change secretariat building

Some climate science uncertainties

One of the key uncertainties in current climate science is how much global warming is likely to increase, and what the consequences are likely to be. There are various reasons for these uncertainties.

First, scientists don’t fully understand how specific aspects of the physical climate system work. For instance, climate scientists don’t understand things like how the deep ocean affects surface heat exchanges, or how aerosols in the atmosphere affect temperature.

Second, large complex systems like the global atmosphere and oceans are unpredictable, so scientists can only estimate the probability of something occurring (in the same way as weather forecasting).

Third, some of the uncertainty is about how humans will act in the future, so scientists have to create different scenarios for different possible human choices, and then work out what’s likely to happen in each scenario.

How post-normal science deals with uncertainties

Scientists on the Intergovernmental Panel for Climate Change (IPCC) use two main methods for dealing with their uncertainties when it comes to identifying cause and effect climate change relationships, and making predictions about the future climate and what to do about it. They:

• adopt a Bayesian belief system (named after Thomas Bayes) – this is a scientist’s statement of their subjective level of confidence or belief about a given outcome, when uncertainty exists about the processes that give rise to a future outcome, so the outcome itself is also uncertain

• accept consensus building as a way of establishing scientific knowledge

The way that the IPCC arrives at a consensus opinion is complicated and sometimes the consensus positions seem to paper over cracks in scientists’ opinions. For example, the 2007 4th IPCC Assessment Report position on the likely future of the Greenland  ice sheet basically said there was so much uncertainty and lack of data about what might happen to the Greenland ice sheet, that there was no basis for a Bayesian statement, so they weren’t going to make any prediction. Later, some of the IPCC scientists disputed this view and made quite dire predictions that the Greenland ice sheet would melt, even though they had gone along with including the consensus view in the Report.

 Why we need to recognise climate science uncertainties

On top of the uncertainties of post-normal science, there are additional uncertainties that are part and parcel of any kind of science – normal or not. Scientific knowledge is a human construct – it’s affected by things like scientists’ world views, their cultural contexts and institutional arrangements, such as what funding is available for specific kinds of research. So uncertainty is bound up with science, and science “is most useful to society when it finds good ways of recognising, communicating and managing uncertainty.”(2)

On top of these uncertainties, climate scientists and government policy makers  also have to allow us, the public, to scrutinise and engage with their work. This is because the stakes are high and we have a right to know and have a say in what scientific work is going on. So post-normal scientists and the policy makers who use their science knowledge need to think carefully about communicating their knowledge – and uncertainties – to us. And we need to know how to assess and engage with these science policy communications.

Sources of information

1) Funtowicz, SO & Ravetz, JR (1993), Science for a post-normal age. Futures 25, 739-55, cited in Hulme, Mike (2009), Why we disagree about climate change. Cambridge, Cambridge University Press

2) Hulme, Mike (2009), Why we disagree about climate change. Cambridge, Cambridge University Press