From WeatherQuestions.com
Many people believe that we should act now on global warming, as a sort of "insurance policy", just in case it ends up being a serious threat. For instance, there has been quite a bit of buzz lately about a YouTube video in which an Oregon high school teacher, Greg Craven, uses logic to convince viewers that the only responsible course of action on global warming is to act as if it is manmade and catastrophic. In other words, the potential risk of doing nothing is so high that we must act, no matter what the science says.
Unfortunately, as in all exercises of logic (as well as of scientific investigation), your conclusions are only as good as your assumptions. The bad assumptions that Mr. Craven makes that end up invalidating his conclusions are these:
1. That there are actions we can take now that will greatly alleviate the global warming problem if it is manmade, and
2. That the cost of those actions to the world will, at worst, be only economic.
Both of these assumptions are false. Humanity's need for energy is so vast that, until a new energy technology is developed, fossil fuels will continue to dominate our energy mix. The only way to substantially reduce the risk of catastrophic manmade warming in the near-term (the next 20-30 years) would be to bring the daily activities of mankind to a virtual standstill.
Using Mr. Craven's logic, I could argue that people should stop eating because, no matter how small the risk, people can (and do) die from choking on food. Paraphrasing Mr. Craven, not eating is the only responsible course of action to prevent choking to death. The only problem with this, of course, is that we would all die of starvation if we quit eating.
While this is admittedly an extreme example, in the case of reducing mankind's greenhouse gas emissions it is much closer to the truth than what Mr. Craven portrays. People tend to forget that every decision we make in life, whether we know it or not, involves weighing risks against benefits. Mr. Craven incorrectly assumes that the benefits of immediate action on global warming will outweigh the risks.