As the world warms, some extreme climate events, like the frequency of heat waves and very heavy precipitation, are expected to increase, but it remains uncertain whether or not to expect changes in the frequency of some other extremes. Moreover, it is important to note that it is not possible to link any particular weather or climate event definitively to global warming . The causal linkage, if any, between the frequency of extreme events and global warming only can be determined through statistical analyses of long- term data, because the natural climate system can produce weather and climate events that often appear to be uncharacteristic of the recent climate.