Climate scientists have long argued that ancient air trapped in Antarctic ice is the smoking gun that links carbon dioxide to global warming.

Over the past 800,000 years or so the planet has gone through a series of ice ages interspersed with relatively warm periods (during which glaciers retreat back toward the poles) — and inevitably, these warm interludes happen when there’s more CO2 in the atmosphere.

The only tricky part of this argument is that the smoke seems to come before the gunshot.

It’s most apparent in the most recent warming period, which began about 19,000 years ago: the temperature seems to begin rising before CO2 concentrations increase.

Climate skeptics have argued that since effects don’t come before causes, the whole theory falls apart.

In fact, it’s not much of an argument, since even little bit of warming would release extra carbon dioxide into the air, leading to a feedback loop, causing even more warming.

But whatever feeble merit the skeptic argument might have had, a new study just published in Nature — one of two climate studies from that prestigious journal that we’re reporting on — pretty much demolishes it.

It’s the most comprehensive analysis ever done of carbon dioxide and temperature at the end of the last ice age, and it shows quite clearly that in most of the world, the thermometer began to shoot up only after the atmosphere was spiked with carbon dioxide.