Sadly, global warming has become politicized. Putting all the data together is not easy. However, there are ways of approaching the matter objectively. In the end, the conclusions each of us draw will depend on our different perceptions of risks and who will bear the brunt of the consequences.
I received training in radiation safety. Thinking about risks associated with use of potentially hazardous materials and equipment has become second nature to me. There are several overarching principles.
First, usually there are benefits associated with things that are hazardous. Consequently, we are faced with making risk-versus-benefit analysis of the activities that expose us to the hazard.
Then the actions we take to protect ourselves must be in proportion to the harm that could come should the hazard be unleashed.
Finally, efforts we make to reduce risk should be proportionate to the chance the risk will manifest itself.
There is a natural tension between these propositions. Not everyone will have the same perceptions of either the risks or benefits.
One must further ask if resources exist to affect the risk or mitigate the consequences of an event should it happen. Also, are the costs of marshalling those resources more onerous than letting things proceed unchecked?
The problem is especially difficult if the consequences of the risk are huge and the perceived probability of its becoming real is small. The magnitude of consequences and the seemingly remote risks are beyond the usual realm of experiences. How then does one determine an appropriate response?
This is not unlike trying to multiply a number approaching zero with a number approaching infinity? A thought experiment might help.
Suppose it is conceded the risk of a certain bad thing happening is not zero, but is very small. Let's say, for the sake of the argument, the risk is only 1 in 100,000 over the next 10 years. The risk is not zero, but very small.
Let's also say that, should the bad thing happen, it would be catastrophic, but not necessarily devastate everything. The event would be huge, but not infinitely large. It is hard to measure the magnitude of a catastrophic event. Again, for the sake of this discussion, suppose it results in the death of 500 million people.
A further difficulty comes, of course, from the impossibility of measuring the heartache and suffering from loss of life. This is the "approaching infinity" factor. Somewhat more tractable are estimating the impact on devastated economies, diminished quality of life and displacement of populations.
These factors are all relevant to the debate over global warming. Let's start with what we know.
There have been many times in the history of the Earth when temperatures have been much warmer or much colder than they are today. Without question, those extreme fluctuations have been catastrophic to whatever organisms existed at the time.
So, though we can only estimate the consequences of large climatic changes, it is beyond question they would radically change life as we know it. The consequences are huge.
What is the probability human activity contributes to global warming?
Without a doubt, huge quantities of carbon (the central chemical element in greenhouse gases) are contained in oil, coal and natural gas deposits. This carbon was removed from the atmosphere (when the planet was much warmer!) over a very long period several hundred million years ago. Its reintroduction to the atmosphere from burning fossil fuels will contribute greenhouse gases.
Greenhouse gases are easily shown to inhibit radiant energy from escaping into space. Abundant evidence, from independent sources, shows the Earth's history marked by warm periods. These are associated with natural events, including volcanic eruptions, that spewed greenhouse gases into the atmosphere.
Scientists can estimate the amount of gases introduced into the atmosphere by both natural and man-made processes. They also understand natural mechanisms for removing greenhouse gases. However, these removal processes are either extremely slow or only remove carbon for a short time.
Measurements of greenhouse gas concentrations show a steady increase. The increase is strongly correlated with the onset of the industrial revolution and its heavy dependence on burning fossil fuels.
It would seem the impact of humans on global warming is well established. But suppose, hypothetically, global warming is primarily driven by other, underappreciated, natural phenomena? Prudence dictates that if human activity is exacerbating the situation, given the consequences, we should do what we can to minimize the effect.
This is especially so when alternatives are available or within reach. Fossil fuel resources are limited, inevitably requiring us to develop alternatives. Good resource management would reserve fossil material for non-fuel purposes such as the manufacture of plastics.
The risk-benefit analysis becomes skewed when the benefits of burning fossil fuels go primarily to the current population, while the consequences are shuffled to our children. It is the classic pay-me-now-or-pay-me-later situation. Either we adjust now and pay for the cost of reducing fossil fuel use, or have our children suffer from our irresponsibility.
Steve Luckstead is a medical physicist in the radiation oncology department at St. Mary Medical Center. He can be reached at firstname.lastname@example.org.