Fact No. 4. During the past several decades (and more), human technological advances have kept pace with, and in most cases exceeded the rate of climate change—no matter what the cause. For example, in major U.S. cities, where the thermal effects of urbanization are many times larger than the effects of any climate change, the population has become less sensitive to periods of extremely high temperature (heat waves). This is documented through declining heat wave mortality. In fact, today, many U.S. urban areas experience no increases in mortality during heat waves—a situation that was vastly different only 20 to 30 years ago.