The debate about global warming is about the outcome of a gamble. We are betting that the benefits of our industrial and agricultural activities - increasing standards of living for the rich and poor alike - will outweigh possible adverse consequences of an unfortunate by-product of our activities, an increase in the atmospheric concentration of greenhouse gases that could lead to global warming and global climate changes. Some experts are warning that we are making poor bets, that global warming has started and that disasters are imminent. Others assure us that the chances of global warming are so remote that the outcome of our wager will definitely be in our favor. The impasse is disquieting because the issue is of vital importance to each of us; it concerns the habitability of our planet. How long will it be before the experts resolve their differences? How long before it is imperative that we take action?
Some people are under the false impression that global warming is a theory that still has to be confirmed. They do not realize that scientists are in complete agreement that a continual rise in the atmospheric concentration of greenhouse gases will inevitably lead to global warming and global climate changes. The disagreements are about the timing and amplitude of the expected warming. It is as if we are in a raft, gliding smoothly down a river, towards dangerous rapids and possibly a waterfall, and are uncertain of the distance to the waterfall. If we know what that distance is then we can tackle the very difficult political matter of deciding on the appropriate time to get out of the water. Suppose, however, that the scientific results have uncertainties, that the scientists can do no better than estimate that we will arrive at the waterfall in thirty minutes, plus or minus ten minutes. Pessimists will then insist that we will arrive in 20 minutes or less, while optimists will state confidently that we won't be there for 40 minutes or more. Such disagreements usually result in the postponement of the political decision until more accurate scientific results are available -- everyone knows that scientists should be capable of precise predictions -- or until we are in sight of the waterfall. We recently had such an experience.
It is in our interest to limit the growth in the atmospheric concentration of greenhouse gases. it is wise to avoid comprehensive programs that decree a rigid course of action to reach a grand, final solution.It is better to take action, and to correct mistakes at an early stage before scarce resources have been wasted. We are courting a disaster and need to accept that uncertainties do not justify inaction.
Which of the following could replace whe word "imminent" in the text?