There are dissenting views on the causes and correct response to global warming, but few would bet against the mainstream scientists' case.
An overwhelming majority of scientists share a common view of climate change and what should be done about it. But a few hold other opinions. Should concerned non-scientists bet on the consensus, or on the dissenters?
The Climate Change Consensus
The “consensus view” is based mainly on the work of the Intergovernmental Panel on Climate Change (IPCC), a UN body set up in 1988, and underpins international negotiations within the framework of the Kyoto Protocol.
The basic propositions of the Kyoto “climate change consensus” are that:
• Average global temperatures are rising.
• The increases are largely due to increased levels of CO2 and other greenhouse gases in the atmosphere.
• Increased greenhouse gas levels are mainly the result of human actions;
• If they continue unchecked, present trends will lead to uncontrollable warming with dangerous and expensive consequences.
• Immediate steps to control and eventually reduce levels of greenhouse gas emissions may appear costly, but will be far less costly than allowing present trends to continue.
These points broadly represent the views of the vast majority of scientists who have worked in the field of climate change. Nevertheless everyone concerned acknowledges that the physical processes involved are highly complex and therefore notoriously difficult to model or predict accurately. So it should not be surprising that there are dissenting views on climate change.
Climate Change Skeptics
A few object in principle to having policy makers depend so heavily on the IPCC as a single source of scientific information. Some have written reports paid for by large corporations that may have a commercial interest in denying that climate change is happening. Others are habitual sceptics of mainstream scientific consensus and have taken minority views on other global issues, such as the effects of man-made chemicals on the ozone layer and the effects of passive smoking. And some raise legitimate, well-considered scientific concerns.
The skeptics’ arguments may be summarized as follows:
• The basic statistics that have been used to demonstrate temperature rises are unreliable, so temperatures are not really rising at all.
• If temperatures are rising, the contribution of greenhouse gas emissions from human activities is far less than the consensus claims; natural processes will eventually reverse the trend.
• Even if greenhouse gases are driving temperature rises, natural negative feedback mechanisms have not been accurately included in the climatologists’ models and could be strong enough to prevent continued, uncontrolled warming.
• Actions to control and reduce emissions are not likely to be effective and more attention should be given to strategies for adapting to rising temperature levels.
Climate Change and the Concerned Citizen
A few years ago the concerned layman might have been convinced by the first two arguments, but mounting evidence makes them an unlikely bet now.
Negative feedback – for example in the upper atmosphere warming might reduce levels of water vapour, itself a potent greenhouse gas – could limit temperature rises to manageable levels. But positive feedback processes could also be stronger than current science suggests. Questions over feedback mechanisms remain firmly within the realms of complex scientific debate and our gambling layman would be ill-advised to put his money on a benign outcome.
The last of the skeptics’ arguments deserves to be taken most seriously, not necessarily on scientific grounds but because of political considerations. Emissions levels are sure to continue increasing for many years in China, now acknowledged as the world’s largest source of greenhouse gases, as well as in other developing countries.
The Precautionary Principle
So even in the unlikely event that all the developed countries were to achieve their emissions reduction targets under the current Kyoto Protocol, increases in other parts of the world will probably more than compensate for the reductions and overall emissions levels will continue to rise for the foreseeable future.
With the stakes so high and in the face of such complex scientific questions and the occasional hidden agenda, the concerned citizen would do well to keep a sceptical eye on the evidence as it rolls in. Meanwhile there can be no better case for politicians and other decision makers and shapers of public opinion to adopt the precautionary principle: when in doubt, take the safer option.
