In response to David Dilley’s letter of Aug. 8 claiming that the Milankovitch cycle explains our current global warming, the facts are that: The warmest point of the last (Milankovitch) cycle was around 10,000 years ago, at the peak of the Holocene.
Since then, there has been an overall cooling trend, consistent with a continuation of the natural cycle, and this cooling would continue for thousands of years into the future if all else remained the same.
But since 1750, however, the carbon dioxide content of the atmosphere has deviated from the natural cycle. Instead of decreasing, it has increased because of fossil-fuel burning.
Methane and nitrous oxide have also increased unnaturally because of agricultural practices and other factors.
The world has also warmed unnaturally. We are now deviating from the natural cycle.
The difference is that in the natural cycle, carbon dioxide lags behind the warming because it is mainly due to the Milankovitch cycles.
Now, carbon dioxide is leading the warming.
Current warming is clearly not a natural cycle.
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