We have a winner! The #1 argument used by “skeptics” of climate science, according to the premier rebuttal site Skeptical Science, is this: “The climate has changed in earth’s past…so humans can’t be causing global warming now.”
It’s a logical fallacy, of course, like claiming that since forest fires occurred naturally in the past, before humans existed, so fires can’t be caused by arson.”
Or try this one: “People die natural deaths, so murder can be ruled out.” It doesn’t take Sherlock Holmes to see the illogic.
Over hundreds of millions of years, earth’s temperature pendulum has swung between extremes, from “Snowball Earth,” with a mile-high glacier covering New York and ice nearly to the equator, to “Hothouse Earth,” with palm trees growing in the Arctic. Over decades of research, scientist gradually unraveled the mystery, finding that these dramatic swings were likely triggered by small shifts in earth’s orbit — so-called Milankovic cycles — but then greatly multiplied by release of CO2 and other greenhouse gases.
But the more scientists learn about earth’s past, the less reassuring they find it. Currently, instead of an orbital trigger, human CO2 emissions are directly jumpstarting the warming cycle.
The bottom line, as Skeptical Science’s John Cook puts it: Our understanding of Earth’s past wild climate swings are “cause for concern, not complacency.”