For example, during the same time period the global average yearly temperature has warmed, but at this location, for the month of July, the average temperature has cooled. This seemingly contradictory example illustrates the effect of your sample over time and space in determining climate trends. These are specific climate events that depart from the average in some significant way. F, under conditions of climatic warming, we would expect the frequency of such extreme days to increase. In other words, the probability that a given summer day would exceed 100 F would be higher under climatic warming than a stable climate.
Climatologists are concerned with more than temperature changes.
Changes in precipitation are also of critical importance. Precipitation patterns that deviate significantly from the average can result in droughts or floods. The Midwest floods of 1993 are a recent and devastating example of an extreme event. The average July precipitation pattern for the thirty-year period from 1961 to 1990 for the United States was very different from the average July precipitation recorded in 1993 as shown on the map below. Both climatic averages and the probability of climate extremes are, by definition, statistical measurements based on probabilities, not certainties.