Five steps to help keep science straight on global warming


Scientists struggle to hold the public’s interest in global warming, particularly in the media – can we do anything but keep stating the facts?

SOME WEEKS ago, a programme was broadcast on TV3 in which two distinguished scientists debated the issue of climate change with members of a new Irish political lobby group. I thought the panel discussion a good example of the difficulty of discussing complex scientific issues in a public forum.

The lobbyists were clear, passionate and articulate, stating their views as established facts, uncluttered by equivocation. (The first sentence uttered was “the Earth is not warming” and there were many other such statements). Faced with a blank rebuttal of what is now well-established science, the scientists struggled to communicate the problem of global climate change.

It’s hard to know how to counter such resistance to what is, despite many uncertainties, accepted scientific fact (think creationism). I suppose all scientists can do is to describe the evidence, as clearly as possible, and hope that the public and policy-makers can tell the difference between informed and random opinion. Here are the main facts one would hope to include in any discussion on the global climate:

1. Global warming

There are now multiple lines of evidence that suggest that, over the past 50 years, the average surface temperature of the Earth and its oceans has been steadily increasing. This temperature rise (about 0.75°C) may seem small compared with the normal background variation, but it represents a significant physical effect (the difference between the average surface temperature today and that of the last ice age is only a few degrees).

2. A natural cycle?

Climatologists have concluded that the warming cannot be attributed to a natural cycle. One reason is the rapidity of the temperature rise over a relatively short timeframe; another is that the stratosphere (the top of the atmosphere) is cooling. Obvious external causes, such as solar cycles or changes in solar activity, have been specifically ruled out.

3. The cause

Physicists have long known that the temperature of the Earth is regulated by certain gases in the atmosphere. These gases trap heat radiated from the warm Earth’s surface, stopping the globe from radiating all of its heat to space – the so-called “greenhouse effect”. Although greenhouse gases account for only a tiny percentage of the gases in the atmosphere, one can expect any change in their concentration to have a significant effect on climate. We now know that the burning of fossil fuels such as oil, coal and gas increases the concentration of greenhouse gases in the atmosphere. Indeed, direct measurements of the current concentration of atmospheric CO2 indicate that it is now almost 40 per cent higher than in pre-industrial times. Hence, most climate scientists believe that global warming is almost certainly caused by man-made greenhouse gases, a phenomenon known as the enhanced greenhouse effect. There are now multiple lines of evidence for this hypothesis.

4. Consequences

Studies of past climate cycles suggest that as time goes on, global warming will accelerate due to feedback effects. For example, the melting of large areas of ice at the poles will significantly impair the ability of the Earth to reflect heat, causing additional warming. Rising temperatures may also result in the release of methane from the permafrost and from deep sea vents, and there are many other such feedback loops.

For human populations, the main consequences of a warming Earth will be increasing desertification and drought in the hotter regions, with a concomitant increase in global sea level (this last because water expands when heated and because of glacier melt). The former could have a devastating effect on agriculture in the interior of many continents, while the latter could cause widespread and permanent flooding in low-lying countries such as Holland and Bangladesh.

5. The solution

We can certainly reduce the effect by replacing the use of fossil fuels with renewable energy technologies such as wind, wave and solar energy. However, this will not be easy as the Western standard of living is built on the cost-effectiveness of fossil fuels.

Most importantly, action to curb fossil fuel use will only be effective if it is global and it is hard to persuade developing countries to curb fossil-fuel use. So far, attempts to reach international agreement on binding targets for carbon emissions have failed.

All of the above is well-established science that is now accepted by almost the entire scientific community. However, much debate on the topic occurs in the media which does not always clearly distinguish between informed and random opinion. The result is a continuing confusion and lack of public engagement with climate change, a state of affairs that makes it very difficult for governments to put in place any sort of co-ordinated action.

Dr Cormac O’Raifeartaigh lectures in physics at Waterford Institute of Technology and is a visiting fellow at the Kennedy School of Government at Harvard University