Fires are not unusual in Siberian forests, but the concern about this year’s blazes is their scale and their proximity to population centers. Siberia also saw massive fires last year, the year before, and the year before that. The most recent fires were preceded by temperatures upward of 14 degrees Fahrenheit warmer than the long-term average for the area. That fits within the pattern of what scientists expect as the global climate changes. As average temperatures rise, heat waves are becoming longer, more frequent, and more intense.