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

2.3. Non CO2-driven Impacts Must be Resolved and Removed

Anyone with limited knowledge of statistics knows that correlation among variables does not prove causation, and anyone with a limited understanding of weather and climate knows there are many factors that can cause extreme weather events. Natural forcings and factors operate across multiple timescales and varying spatial domains to cause extreme weather; and they have been doing it independent of the air's CO2 concentration for eons.

Consider, for example, the following analysis of extreme river levels and flows of the Nile River by Kondrashov et al. (2005). For their analysis, they applied advanced spectral methods to fill in data gaps and locate interannual and interdecadal periodicities in historical records of annual low- and high-water levels of the Nile River over the 1,300-year period A.D. 622 to 1922. In doing so, they found several statistically significant periodicities in the record, including cycles of 256, 64, 19, 12, 7, 4.2, and 2.2 years. With respect to the causes of these cycles, Kondrashov et al. say the 4.2- and 2.2-year oscillations are likely the product of El Niņo-Southern Oscillation variations. The 7-year cycle, on the other hand, is possibly related to North Atlantic influences, according to them, while the longer-period oscillations may be due to astronomical forcings.

In addition to revealing the stated periodicities, the results of Kondrashov et al.'s analysis and annual-scale resolution provide what they refer to as a "sharper and more reliable determination of climatic-regime transitions" for tropical east Africa, including documentation of fairly abrupt shifts in river flow at the beginning and end of the Medieval Warm Period, as well as for other periods throughout the record. These "fairly sharp shifts in the amplitude and period of the interannual and interdecadal modes over the last millennium-and-a-half," according to the researchers, "support concerns about the possible effect of climate shifts in the not-so-distant future."

Thus, those living near the Nile and who are dependent on it for their sustenance should be particularly concerned, for abrupt changes in flow rates and river levels have punctuated the river system for 1,300 years or more; and there is no reason why similar changes will not continue in the future, independent of any change in atmospheric CO2 concentration.

If and when the situation does change and the Nile flow rates and river levels experience extreme events, these natural periodicities would have to be accounted for and subtracted out before any attribution could properly be ascribed to rising CO2. The same is true for all indices of extreme weather. The burden of proof remains with the climate alarmists who must demonstrate that the influence of all other potential factors have been removed and ruled out as possible cause(s) of an extreme weather event increase before they can ascribe its rise to CO2. Unfortunately, many climate alarmists are not content to do this required work; and they therefore have no business making attribution claims that have not been properly vetted.

Furthermore, it is also important to note that results from one analysis in one location do not a global conclusion make. Similar trends from multiple locations around the globe are needed before a true assessment of the extreme weather hypothesis can be made. Fortunately, numerous such studies have been conducted according to the principles and steps outlined above; and they have been published in the peer-reviewed scientific literature, providing a fairly complete assessment of the entirety of the climate-alarmist hypothesis. The following section analyzes a significant portion of that literature, presenting a compelling refutation of the claim that CO2-induced global warming is increasing the frequency and severity of three key extreme weather phenomena.

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