09 January 2014

The Science of Informed Uncertainty

Written by Published in Sustainability Science
Image: Ken Slade Image: Ken Slade

Uncertainty is inevitable in scientific research, especially around global issues of sustainability, so why do we find it so difficult to know that we don't know?

In this age of big data and constant information you might think scientific knowledge would bring more certainty to our lives, but greater insight can paint a more complex and sometimes cloudy picture.  Last year’s Intergovernmental Panel on Climate Change (IPCC) report is a well-known example.  It provided an in-depth analysis of trends in the Earth's surface temperature, ice sheet mass, sea level, glacier retreat and greenhouse gas emissions. It used a huge variety of data ranging from the concentration of CO2 molecules to satellite pictures as well as information stored in rocks, tree rings and fossils. In other words it brought together a lot of different data by a lot of different scientists on a very big subject.

Amongst this exhaustive analysis, one of the more heated (no pun intended) discussions was around the recent slowdown in the rising temperature trend. The IPCC report acknowledged this and suggests that it is a temporary pause. To quote directly it says, ‘Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850’. Although not worded particularly clearly this seems to suggest that, even if there has been a relatively recent slowdown, over the long-term the rate of warming is still increasing. The report also provided possible reasons for this phenomenon such as the storage of heat in oceans, a lower level of solar activity and the cooling effect of small droplets of liquid in the atmosphere caused by volcanic eruptions.

Despite these explanations, the issue remains that this slowdown was not predicted by the previous 2009 report, causing many sceptics to cast (continuing) doubts on the ability of the models to do their job. The details of the IPCC models are beyond the scope of this blog and, to be honest, probably my understanding. What I do know is that as scientists have accumulated more and more data over the years, the models have become increasingly complex and each set of data brings it’s own level of ambiguity. Strangely, it seems to be the case that the more we know, the less certain we become.

Communicating this is a problem, especially when all people tend to want to know is the answer to the question: ‘Are we the cause and will things get worse?’ We want either absolution or blame, hope or disaster but not something drifting in between. The report states that it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. Although terms such as ‘likely’ and ‘extremely likely’ are more accessible than probabilities and error bars, they are still difficult to get our heads around. We don’t like uncertainty and we don’t expect it from science. And, if we do have to endure it, we want it in a form we can compare to something in our everyday lives, which can be difficult .

Yet uncertainty is an inherent part of scientific research, particularly when working at the level of the IPCC. The global climate system is far bigger than any laboratory or test tube and hence contains all kinds of variables. Although our capacity to measure and analyse may have improved, that doesn’t mean the fundamental problems of controlling or removing influences have changed.

So perhaps we need to allow ourselves to be a bit more at ease with uncertainty when seeking to make informed choices and decisions, knowing that not in all cases the information at hand will be black-and-white. After all, many of us would hate to think that our life or even the next sixty seconds are predictable so why expect it from science? Just like any superhero, science has its Achilles Heel and, the more responsibility it’s given, the more vulnerable it becomes. Surely that just makes it more human?

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