In through the tap, out through the plughole

MAINSTREAM SCIENCE has shown that the world is warming, almost certainly because of human-induced emissions of warming gases to the atmosphere, principally carbon dioxide.

But science communication has failed to convince the general public and many policymakers that they should take global warming seriously. Dire warnings about its catastrophic effects are regularly issued to encourage action, but they have backfired. A different means of communicating the message is required. John Sterman assessed where we stand in Climate Change (vol 108, pp811-826; 2012).

It seems intuitively plausible that asking people to act now to forestall catastrophic effects of climate change – widespread flooding of coastal regions, and so on – on our children and on their children would be an effective technique to elicit action and support from the general public. But, surprisingly, this tactic has increased doubts in people’s minds that greenhouse-gas emissions from human activities cause global warming. Forty-eight per cent of Americans now believe that global warming is exaggerated, up from 31 per cent in 1997, and opinion on global warming is informed more by ideology than by science: 68 per cent of Democrats but only 33 per cent of Republicans believe that human emissions mainly cause global warming.

People innately believe that the world is fundamentally fair and stable, and they protect this belief when it is pointed out that future generations might unjustly suffer because of our “climate sins”, by ignoring reality and allowing events to unfold without interference. This hypothesis has been shown to hold true in recent psychological research (M Feinberg and R Willer, Psychological Science, vol 22, p34; 2011).

Another problem is the ineffective way in which the scientific evidence for climate change is communicated to policymakers and the public.

Scientific investigation of climate change is mainly carried out by the Intergovernmental Panel on Climate Change (IPCC), an international body of expert meteorologists, climatologists and others. IPCC issues large reports every few years, each accompanied by a “simplified” summary for policymakers. But even in this the level of scientific language is too complex for the general reader: it is pitched at postgraduate level.

Climate is a complex dynamic phenomenon. To understand it properly you need to have a grasp of nonlinearity, feedback, tipping points, stocks and flows, and more. The average person’s mental models do not easily accommodate these concepts, however: we tend to think in a straight-line, near-term, linear way. Nonlinear change occurs in climate models. Try this exercise in appreciating nonlinearity. If I give you a very large sheet of paper, 0.1 mm thick, and ask you to double it over and to continue this doubling 42 times, how thick will the 42-times doubled sheet be? Use your intuitive judgment: will it be 1m, 1km or 100km thick? Put down this article and give your answer before you read it in the next sentence. After 42 doublings the paper would be 440,000km thick: more than the distance from Earth to the moon.

The principle of accumulation must be grasped to understand climate change. Carbon-dioxide concentration in the atmosphere is determined by the balance between the processes that add CO2 (including human-induced emissions) and those that remove CO2 from the air (oceans and biomass). The analogy of a bathtub with water pouring in from a tap and leaving through an open plughole explains the situation. The water level in the bath will rise or fall depending on the rates at which water enters and leaves the bath. Many people think that carbon-dioxide levels would stabilise if we stabilised human emissions of CO2 at current levels. But, in that event, atmospheric carbon-dioxide levels would continue to rise, because the current rate of emission is greater than the rate at which water – in reality, CO2 – is leaving through the plughole.

It was never going to be easy to persuade people to make sacrifices now in order to prevent bad consequences in the distant future. We should remember how long it took to legislate for the use of car seat belts and childhood vaccinations despite the scientific evidence documenting their efficacy. But the right thing was done in the end.

So we must continue to explain the science of climate change to the general public but use effective language in doing so, including use of analogies such as the bathtub. And we must stop trying to scare people into action. Convince people of the facts and they will be easily persuaded to do the right thing.

William Reville is emeritus professor of biochemistry and public awareness of science officer at University College Cork; understandingscience.ucc.ie