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Vol. 38, No. 18 |
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3-4-2008 Ask the Expert, 3/6/08
Weather is what happens day to day in a particular locale and by definition is widely variable. Climate is weather as averaged over a span of years.
Some people have said the weather here and other places this winter is much colder than normal, so climate change/global warming isn’t occuring. Weather is not clearly connected to climate change. Hot or cold days by themselves are not clear indicators of climate change because weather is by definition variable and one day may be the warmest on record and several days later it may be the coldest on record for that date.
Climate change can only be seen by looking at patterns and seeing if there is a gradual change in one direction. For example, 11 of the last dozen years were the warmest in the historical instrumental record (1880-2008). This is unlikely if changes are truly random from year to year, the null result; the 12 warmest years should have been scattered, roughly one per decade over that 128 years of time.
Is there scientific consensus that human activity is contributing to climate change? The great majority of experts do believe that the human fingerprint is on our climate. However, we must bear in mind that science never can prove anything. Scientists observe nature and make inferences about how nature behaves. These inferences lead to models, ideas that lead to definite predictions that must either happen or not-if this model is right, then something specific will happen. If that thing that was predicted does happen, we do not learn very much, and we go on to make other predictions that can be tested. If that thing that was predicted does not happen, though, we learn a whole lot. Because the model failed, we must throw the failed model away. Many such models have been put forward to explain what is happening to Earth’s climate. The ones having no descriptive power have been abandoned. What’s left seems to work to describe what we see only if human impacts are present.
What is the consensus about our future climate? Earth of the future will be warmer. How much warmer is still not certain. The Intergovernmental Panel on Climate Change says the best estimate given a doubling of preindustrial CO2 is about 4 °F. This might not seem like much, but it is enough to cause major changes. There will be changes in agriculture and the native ranges of plants. “Winning” regions are more likely to be located toward the poles, and “losing” regions toward the equator. There may be consequences for people’s health as tropical diseases expand their ranges and heatwaves cause elderly people to die before their time. Most people live near coasts, and sea levels will rise, disrupting commerce and requiring expenditures to stave off flooding or abandonment of investment in real estate.
If the skeptics are right and the human race invests in prevention and mitigation, some money may be spent that would not have to be spent. If the skeptics are wrong and we do nothing, the consequences could be disastrous. Skeptics buy homeowner’s insurance just in case a catastrophe occurs. In the same way, the human race needs climate change insurance.
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