MAKING SENSE of UNCERTAINTY Why Uncertainty Is Part of Science CONTRIBUTORS
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SENSE ABOUT SCIENCE MAKING SENSE OF UNCERTAINTY Why uncertainty is part of science CONTRIBUTORS The contributors met over 2012 to review what is being said about scientific uncertainty in the media, policy and public life; to identify the misconceptions in these discussions and share insights that help to dispel these; and to draft and edit the guide. With thanks to everyone who reviewed all or part of the guide, or gave contributions on specific questions, including: Dr Suzanne Aigrain, Dr Nina Alphey, Dr Richard Betts, Professor Sheila Bird, Professor Andy Challinor, Dr Nathan Green, Professor Joanna Haigh, Professor Mike Hulme, Christian Hunt, Richard Johnston, Dr Shelly Lachish, Professor John Mitchell, Professor Peter Sammonds, Dr Emily Shuckburgh, Dr Juliet Stevens, Dr Matthew Sullivan, Dr Tom Wells, Dr Ben Wheeler; and for valuable input from the Royal Society meeting ‘Handling uncertainty in weather and climate prediction’ convened by Professor Tim Palmer in October 2012. We are grateful to the BBSRC, Clark Bradbury Charitable Trust, John Innes Centre, NERC, University of Reading and the Walker Institute for supporting the production and distribution of this guide. PETER GIBBS MICHAEL HANLON PROF. PAUL DR ED HAWKINS PROF. AVERIL BBC weather presenter, Journalist HARDAKER Climate scientist in MACDONALD Met Office Chief Executive, Institute NCAS-Climate, JJ Thomson Physical of Physics; Chairman, Department of Laboratory, University Sense About Science Meteorology, University of Reading of Reading KATHY MASKELL HEATHER MAYFIELD PROF. ANGELA DR ELIZABETH DR KEN MYLNE Walker Institute Deputy Director, MCLEAN FRS MORRIS OBE Head of Weather for Climate Science Museum Professor of Scott Polar Research Science Numerical System Research Mathematical Biology, Institute, Cambridge Modelling, Met Office All Souls College, University of Oxford DR MARK NAYLOR PROF. TIM PALMER FRS PROF. SIR MICHAEL DR KATHERINE ROYSE PROF. LEONARD Scottish Government Royal Society Research RAWLINS Science Director SMITH and Royal Society Professor, University of Chair, National Environmental Modelling, Director, Centre for of Edinburgh Oxford; Co-Director Institute of British Geological Survey; the Analysis of Time Oxford Martin Programme Personal Fellow Clinical Excellence NERC Knowledge Series, LSE on Modelling and Exchange Fellow Predicting Climate DR EMILY SO PROF. DAVID DR DAVID PROF. IAN DR CHRIS TYLER Lecturer, Department of SPIEGELHALTER FRS STAINFORTH STEWART FRS Director, Parliamentary Architecture, University Winton Professor of the Senior Research Fellow, Emeritus Professor of Office of Science and of Cambridge Public Understanding Grantham Research Institute Mathematics, University Technology (POST) of Risk, University on Climate Change and the of Warwick of Cambridge Environment, LSE DR FRANK DE VOCHT TRACEY BROWN DR TABITHA Lecturer in Occupational Managing Director, INNOCENT and Environmental Sense About Science Scientific Liaison, Health, University Sense About Science of Manchester INTRODUCTION why make sense of uncertainty? Scientific uncertainty is prominent in research This conflict frustrates us at Sense About that has big implications for our society: could Science, and we know that it frustrates the Arctic be ice-free in summer by 2080? researchers we work with and the public we Will a new cancer drug be worth its side hear from. Some clearer ideas about what effects? Is this strain of ‘flu going to be a researchers mean by scientific uncertainty – dangerous epidemic? and where uncertainty can be measured and where it can’t – would help everyone with how Uncertainty is normal currency in scientific to respond to the uncertainty in evidence. research. Research goes on because we don’t know everything. Researchers then have to This guide has brought together specialists in estimate how much of the picture is known many areas – climate science, clinical research, and how confident we can all be that their natural hazard prediction, public health, findings tell us what’s happening or what’s biostatistics and epidemiology. We asked them going to happen. This is uncertainty. for the reasons why they are not automatically so troubled by the presence of uncertainty in But in public discussion scientific uncertainty is the most heated debates. presented as a deficiency of research. We want (even expect) certainty – safety, effective We have looked at what uncertainty means public policies, useful public expenditure. and doesn’t mean in science, how it is Uncertainty is seen as worrying, and even a measured, when it can’t be measured and how reason to be cynical about scientific research that might change through research into the – particularly on subjects such as climate big questions. Above all we asked how other science, the threat of disease or the prediction people can grapple constructively with of natural disasters. In some discussions, advances in knowledge and changes in uncertainty is taken by commentators to mean thinking, instead of despairing at ‘those that anything could be true, including things uncertain scientists’. that are highly unlikely or discredited, or that nothing is known. TRACEY BROWN TABITHA INNOCENT SENSE ABOUT SCIENCE CONTENTS THOSE UNCERTAIN DO WE EVEN NEED 01 SCIENTISTS 04 MORE CERTAINTY? Uncertainty is normal in We need to know when a scientific research but to policy decision is, and is not, makers, journalists and wider affected by whether we know society it sounds like something completely. This ‘unreliable’. Despite life telling idea is beginning to shape us otherwise, the assumption in the way that scientists and many debates is that we should policy makers use and expect certainty. communicate uncertainty. SO WHAT IS UNCERTAINTY PLAYING 02 FOR SCIENTISTS? 05 ON UNCERTAINTY There are different types of Uncertainty does not mean we uncertainty that are an ordinary know nothing, that evidence part of scientific research. These cannot be trusted, that anything can be addressed or taken into could turn out to be correct or account in several ways. that decisions can’t be made. PREDICTIONS DELVING 03 AND MODELS 06 DEEPER As numerical models can be Further resources on scientific used flexibly and updated as uncertainty, including blogs, knowledge changes, they are books and guides. routinely used in research that deals with high levels of uncertainty. These sometimes get a bad press, which misreads how and why they are used. 01 THOSE UNCERTAIN “…it becomes ever more obvious that none of them really has a clue” SCIENTISTS In the areas of research that are most often in the public eye, uncertainty has become a big point of misunderstanding (even conflict) “when distinguished between scientists and commentators. A scientists say it researcher presents his or her findings, the isn't actually proven…” radio interviewer (or the politician, journalist or official) asks: ‘can you be certain?’. The researcher has to answer truthfully 'no' and then defend their findings, for fear they will be interpreted as meaningless. In fact, they have provided important limits to the uncertainty. “you can't absolutely prove, Researchers use uncertainty to express how can you, that co2 is responsible confident they are about results, to indicate for global warming?” what scientists don’t yet know, or to characterise information that is by nature never black and white. But saying that something is ‘uncertain’ in everyday language has a negative connotation. When a researcher says ‘the predictions we made on “like with many neural the basis of our research have a margin of disorders and conditions uncertainty’, they mean they are very ..there is always uncertainty confident that the outcome will fall within the in their answers” predicted range. But a commentator is likely to understand from this ‘the piece of research is unreliable’. This is the type of disconnection we see in media reports of global warming, public health risks and earthquake prediction. 05 THOSE UNCERTAIN SCIENTISTS BUT WHY IS UNCERTAINTY SEEN TO UNDERMINE RESEARCH? Put crudely, scientists tend to think science is aspire to add something new to what we about things we don’t know fully. Journalists know. Uncertainty is what they are interested and politicians (and to a large extent, many in. Scientists design experiments or people) think it is about things we do know, data-gather to get new evidence which tests and they’re impatient with ‘maybe’s. models and theories in as minimally biased a way as possible – but there are limits on what The problem here is that not all scientific can be done, and simplifying assumptions that knowledge is the same, so treating it as have to be made. Research science is moved though it were is misleading. forwards by knowledge that is modified with new evidence – and most areas of research In the first place, there is rarely such thing as include some knowledge that is settled, and 100% certainty – and everything less than this some that is more uncertain. is uncertain. Scientific inquiry makes some (potentially imperfect) observations, then Across society, we don’t talk much about the makes predictions to test how widely the settled things we are confident of – the fact observed pattern holds true – from looking at that an antibiotic works, say. We talk about the how a molecule will behave in combating a interesting, newer issues – such as assessing disease to understanding the metabolisms of when antibiotic resistance might occur. dinosaurs. Most people know this to some extent. They know that there are varying risks The essential point is that new scientific in the things they do every day, and that knowledge usually includes greater perfect knowledge is rarely possible (most uncertainty and researchers often don’t know knowledge is not like a mathematical proof). how much of the picture it shows. It doesn’t But reports and commentaries like those mean scientists know nothing, and we should heading this section show that complete not be exasperated that it is less settled than certainty is still seen in society as the test of we want it to be. new knowledge. Secondly, new research needs to be looked at differently from settled science.