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Extreme Weather Events: Are they Influenced by Rising Atmospheric CO2?

4. Concluding Remarks

The public debate over the potential consequences of rising atmospheric CO2 on Earth's climate and biosphere has shifted over the years. First, the focus was squarely on temperature (global warming). Next came climate change, which shifted attention to multiple climatic indices that might be affected by the ongoing rise in the air's CO2 content. More recently, the debate has coalesced around concerns that rising CO2 might be impacting extreme weather, with many people claiming that the frequency and intensity of disaster-prone extreme weather events will increase. All too often, however, these latter claims have failed to stand up to scientific scrutiny, because they were made with little regard to following the principles of the scientific method.

As discussed in this report, key steps must be taken to ensure scientific legitimacy when making and testing claims about a possible CO2-induced influence on extreme weather events. Without following these steps, it is impossible to confirm any impact of CO2 on extreme weather over the past few decades. When such steps are followed, however, as illustrated by the large literature reviews herein, it is nearly impossible to not conclude that extreme weather events remain unaffected by CO2-induced global warming-at least in the manner projected by the models. Quite to the contrary, observational data often indicate just the opposite, that many types of extreme weather events have become less frequent and less severe as the air's temperature and CO2 concentration increased over the past half-century or more.

Those promoting the notion that floods, droughts, and/or storms are increasing because of CO2-induced global warming are ignoring the rigors of scientific inquiry and analysis. It is false to assert that these extreme weather events are getting worse; and it is wrong to assert that they will worsen in the future if carbon dioxide emissions are not reduced. The data simply do not support such claims.

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