Some of these arguments for action are applications of what is often called the Precautionary Principle, one of the basic principles that was included in the Rio Declaration at the Earth Summit in June 1992 (see box below). A similar statement is contained in Article 3 of the Framework Convention on Climate Change (see box on pages 291-2 in Chapter 10).
We often apply the Precautionary Principle in our day-to-day living. We take out insurance policies to cover the possibility of accidents or losses; we carry out precautionary maintenance on housing or on vehicles; and we readily accept that in medicine prevention is better than cure. In all these actions we weigh up the cost of insurance or other precautions against the possible damage and conclude that the investment is worthwhile. The arguments are similar as the Precautionary Principle is applied to the problem of global warming.
In taking out an insurance policy we often have in mind the possibility of the unexpected. In fact, when selling their policies, insurance companies often trade on our fear of the unlikely or the unknown, especially of the more devastating possibilities. Although covering ourselves for the most unlikely happenings is not our main reason for taking out the insurance, our peace of mind is considerably increased if the policy includes these improbable events. In a similar way, in arguing for action concerning global warming, some have strongly emphasised the need to guard against the possibility of surprises (see examples in Table 7.4). They point out that, because of positive feedbacks that are not yet well understood (see Chapter 3), the increase of some greenhouse gases could be much larger than is currently predicted. They also point to the evidence that rapid changes of climate have occurred in the past (Figures 4.5 and 4.6) possibly because of dramatic changes in ocean circulation; they could presumably occur again.
The risk posed by such possibilities is impossible to assess. It is, however, salutary to call attention to the discovery of the ozone 'hole' over Antarctica in 1985. Scientific experts in the chemistry of the ozone layer were completely taken by surprise by that discovery. In the years since its discovery, the 'hole' has substantially increased in depth. Resulting from this knowledge, international action to ban ozone-depleting chemicals has progressed much more rapidly. Ozone levels are beginning to recover - full recovery will take about a century. The lesson for us here is that the climate system may be more vulnerable to disturbance than we have often thought it to be. When it comes to future climate change, it would not be prudent to ignore the possibility of surprises.
However, in weighing the action that needs to be taken with regard to future climate change, although the possibility of surprises should be kept in mind, that possibility must not be allowed to feature as the main argument for action. Much stronger in the argument for precautionary action is the realisation that significant anthropogenic climate change is not an unlikely possibility but a near certainty; it is no change of climate that is unlikely. The uncertainties that mainly have to be weighed lie in the magnitude of the change and the details of its regional distribution.
An argument that is sometimes advanced for doing nothing now is that by the time action is really necessary, more technical options will be available. By acting now, we might foreclose their use. Any action taken now must, of course, take into account the possibility of helpful technical developments. But the argument also works the other way. The thinking and the activity generated by considering appropriate actions now and by planning for more action later will itself be likely to stimulate the sort of technical innovation that will be required.
While speaking of technical options, I should briefly mention possible options to counteract global warming by the artificial modification of the environment (sometimes referred to as geoengineering).11 The suggestion of iron fertilisation of the oceans was mentioned in Chapter 3. Other proposals have concentrated on techniques that might reduce the amount of sunlight absorbed by the Earth, for instance, the installation of mirrors in space to cool the Earth by reflecting sunlight away from it; the addition of dust to the upper atmosphere to provide a similar cooling effect and the alteration of cloud amount and type by adding cloud condensation nuclei to the atmosphere.12 None of these however has been demonstrated to be either feasible or effective, nor would any of them make any difference to the problem of increasing acidity of the oceans due to increasing carbon dioxide. Further, they suffer from the serious problem that none of them would exactly counterbalance the effect of increasing greenhouse gases. As has been shown, the climate system is far from simple. The results of any attempt at large-scale climate modification could not be perfectly predicted and might not be what is desired. With the present state of knowledge, extreme caution must be exercised when considering implementation of proposals for the introduction of artificial climate modification.
The conclusion from this section - and the last one - is that to 'wait and see' would be an inadequate and irresponsible response to what we know. That was recognised over 15 years ago by the FCCC signed in Rio (see box on pages 291-2 in Chapter 10) in 1992 and has often been reiterated since. Just what the required action should be is the subject of the next chapter.
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