Climate alarmists have long faced one uphill battle in public discourse: the very fact that they’re thought of as alarmists, embracing positions that, tested by empirical science, seem at the outer—and scary—edges of possibility.

What can make them seem moderate instead?

Nothing better than for one of the world’s most prominent science journals, Nature, to publish an article that is many times more extreme.

That’s what just happened September 26 when Nature published Carolyn Snyder’s “Evolution of global temperature over the past two million years,” the abstract of which concluded:

A comparison of the new temperature reconstruction with radiative forcing from greenhouse gases estimates an Earth system sensitivity of 9 degrees Celsius (range 7 to 13 degrees Celsius, 95 per cent credible interval) change in global average surface temperature per doubling of atmospheric carbon dioxide over millennium timescales. This result suggests that stabilization at today’s greenhouse gas levels may already commit Earth to an eventual total warming of 5 degrees Celsius (range 3 to 7 degrees Celsius, 95 per cent credible interval) over the next few millennia as ice sheets, vegetation and atmospheric dust continue to respond to global warming.

Whoa! A 9-degree C rise in global average temperature in response to doubled atmospheric carbon dioxide concentration! That’s double the high end of the IPCC’s estimated range (1.5 to 4.5C), which the IPCC says is quite unlikely!

The article makes all kinds of serious mistakes—so many, and so grievous, that even climate alarmist gatekeepers like Gavin Schmidt have blasted it.

But don’t write it off as unimportant. It plays a very important role in the global debate about global climate change. It stretches the boundary of discourse.

That is, it exemplifies the “Overton Window” in action. As Wikipedia defines it,

The Overton window, also known as the window of discourse, is the range of ideas the public will accept. …

Proponents of policies outside the window seek to persuade or educate the public in order to move and/or expand the window. Proponents of current policies, or similar ones, within the window seek to convince people that policies outside it should be deemed unacceptable.

After Overton’s death, others have examined the concept of adjusting the window by the deliberate promotion of ideas outside of it, or “outer fringe” ideas, with the intention of making less fringe ideas acceptable by comparison.

Snyder’s article moves the Overton Window of climate-change discussion way out beyond the previous boundary of extreme catastrophism. The consequence is making what previously sounded extreme sound moderate instead. Voila! Debate changed!