There was a chat program on the Irish channel TV3 last week that perfectly illustrated the difficulty of discussing complex scientific issues in a public forum (see last week’s post). It consisted of a tv panel debate on climate change, where two respected scientists and a member of Friends of the Earth debated climate issues with two members of a new Irish political lobby group. It quickly became clear that neither the Chair nor the lobbyists knew (or accepted) anything of the basic facts of climate science. Faced with a blank rebuttal of basic physics, the scientists had an uphill struggle tryng to communicate the issue of climate change.
I thought this a fairly typical example of the problems of such media discussions. The lobbyists were clear, passionate and articulate, stating their views as if they were established facts, uncluttered by equivocation. (The first sentence uttered was “the earth is not warming” and there were many other such statements). The scientists, by comparison, sounded rather uncertain and unclear. As so often, completely uninformed opinion, unweakened by any sort of balanced view, sounded much more convincing.
It’s very hard to know what to do when one encounters such resistance to basic science. I suppose all we can do is keep repeating the basics, as clearly as we can, and hope the public and politicians can discern the difference between established facts and random opinion. As an exercise, I decided to write down the main points I myself would hope to make during the course of such a debate. This is what I would like to have said:
1. GLOBAL WARMING
There are now multiple lines of evidence that show clearly that, over the last 50 years, the average surface temperature of the earth and its oceans has been steadily increasing. This rise (about 0.75 °C) may seem small compared with the normal background variation in day-to-day and seasonal temperatures. However, a gradual increase in average represents a significant physical effect; for example, the difference in the average global temperature of the last ice-age and the present is only a few degrees Celcius.
2. PART OF A NATURAL CYCLE?
Those who study past climate cycles have considered this question in great detail and their conclusion is that the temperature rise cannot be attributed to a natural cycle, for a number of reasons. The most obvious is the rate of change; the rise in average temperature we are seeing over the last few decades corresponds to a rise seen over thousands of years in past climate cycles. Obvious external causes, such as solar cycles or changes in solar activity, have been specifically ruled out (we are currently in a cooling part of the dominant solar cycle). Most tellingly, it has been discovered that while the lower atmosphere is steadily heating up, the top of the atmosphere (the stratosphere) is cooling down – an observation that strongly suggests a cause closer to home.
3. THE ENHANCED GREENHOUSE EFFECT
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 greenhouse effect). The ‘greenhouse gases’ only account for a tiny percentage of the atmosphere but they play a vital role in regulating the planet’s temperature. Hence global climate is highly sensitive to the concentration of greenhouse gases in the atmosphere and one can expect any change to this concentration to have a significant effect on climate. (The Irish scientist John Tyndall established that the most important greenhouse gases are water vapour, carbon dioxide and methane, while major gases such as oxygen and nitrogen do not block the earth’s heat).
We now know that, since the advent of the industrial revolution, mankind has been increasing the concentration of atmospheric greenhouse gases. In particular, the burning of fossil fuels such as oil, coal and gas all release extra CO2 into the atmosphere. Direct measurements of the CO2 content of the atmosphere have been made since the 1950s and there is no doubt that there has been a steady rise since measurements began; in general, it is estimated that the current concentration of CO2 in the atmosphere is over 35% higher than that of pre-industrial times. At first, it was thought that this extra CO2 would be absorbed by the oceans. Some of it is, and this causes its own problems. However, it is now known that much of the extra CO2 remains in the atmosphere.
Putting two and two together, scientists believe that the global warming we have observed in recent decades is almost certainly caused by man-made greenhouse gases released into the atmosphere, a phenomenon known as the enhanced greenhouse effect.There are now muliple lines of evidence for this hypothesis (not least direct satellite measurements of the heat radiated from earth into space that show an increasing dip in the region of the spectrum where CO2 absorbs).
4. THE FUTURE PROGNOSIS
Studies of past cycles suggest that as time goes on, the warming will accelerate because of feedback loops. For example, the melting of large areas of ice at the poles will significantly reduce the ability of the globe to reflect heat, causing additional warming. The oceans will lose their ability to absorb CO2 as they acidify, also causing further warming. Studies of past cycles also suggest that the rising temperature will itself lead directly to an increase in greenhouse gases such as CO2 and water vapour in the atmosphere, and eventually to the release of methane from deep sea vents and the permafrost.
For human populations, the main consequences of a warming earth will be increasing desertification and drought in the hotter regions, and an increase in sea level around the globe (the latter is because water expands when heated and because of glacier melt). The former could render large parts of Africa and Australia uninhabitable, while the latter could cause widespread and permanent flooding in low-lying countries such as Holland and Bangladesh (pop 55 and 25 million respectively).
5. THE SOLUTION?
We can certainly reduce the enhanced greenhouse effect by replacing the use of fossil fuels with renewable energy technologies such as wind, wave and solar energy that do not cause carbon emissions. Since there is a time lag associated with the effect, we need to do this as soon as possible. However, this is economically difficult 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 essential for their development. So far, attempts to reach international agreement on binding targets for carbon emissions have failed. Yet is estimated that China alone has coal deposits that if fully used, could tip us into irreversible climate change within one century.
All of the above is basic, well-established science that is accepted by almost the entire scientific community. However, much debate on the topic occurs in the media. This is simply a facet of a modern media that does not distinguish between informed and random opinion (not to mention vested interest). Uniquely among scientific theories, the theory of man-made global warming also faces great political resistance from conservatives who oppose regulation in almost any form. Lobbying by conservative interests can be heavily influential, in politics and in the media , particularly in the USA. The result is a continuing confusion and lack of public engagement with the issue, a state of affairs that is making it very difficult for world governments to put in place any sort of co-ordinated mitigating action.