Don temperatures swing naturally?
Of course, but as far as we can tell this can’t explain recent behavior. We are rapidly learning more about past changes from examination of geologic evidence, which is probably the most exciting field in climate science today. Some changes have been huge: 55 million years ago the north pole was as warm as Florida today, while 20 thousand years ago, much of North America was under miles of ice. The really warm climates all occurred long before the advent of upright primates, but prehistoric humans made it through some pretty cold times. Since the dawn of agriculture, climate has been relativey boring. Science is a process of testing hypotheses against evidence. Many scientists, using different methods, have tested the hypothesis that the recent warming is also a natural shift. Every analysis has yielded the same answer— “no”—the warming since 1970 has been too widespread and too rapid. A few scientists still reserve judgment on this, but no model has been able to explain the warming na
