The Washington Post Sunday

The climate has changed before. It’s just a natural cycle.

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Last fall, when the first volume of the National Climate Assessment was released, White House spokesman Raj Shah responded that “the climate has changed and is always changing.” President Trump himself has embraced this position, claiming that the climate “will change back again.” This line is a popular one with people who dismiss climate change by maintainin­g that we’ve had ice ages before, as well as warm periods, and so the warming we’re seeing now is just what the Earth has always done.

But we can look at the natural factors that affect the climate. First, over the past few decades, energy from the sun has been going down, not up, so if changes in the sun’s energy drove our temperatur­e, we should be getting cooler, not warmer.

Others argue that we’re getting warmer because we’re recovering from the last ice age. But ice ages — and the warm periods in between — are caused by the Earth’s orbital cycles, and according to those cycles, the next event on our geologic calendar is another ice age, not more warming.

We can also rule out volcanoes, which do produce heat-trapping gases, but less than 1 percent of the CO2 that humans produce. And big eruptions, when they happen, cool the Earth instead of warming it. In other words, the climate change we’re experienci­ng now definitely isn’t natural.

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