It might seem like an odd question since nobody seems willing to shut up about it. Some say there’s been nothing to rant about in about 20 years. But a new study based on tree rings in Central Asia comes to far more startling conclusion. The “hiatus” isn’t a recent phenomenon. Overall there’s been no warming in the region since… get ready for it… the 16th century. There was some in the 20th but it reversed. And these naughty researchers say it’s not about CO2, it’s about volcanoes and Mr. Sun. Commenting on it, Vijay Jayaraj of the Cornwall Alliance for the Stewardship of Creation says “Our understanding of the earth’s climate system is still in its infancy.”
There are all sorts of debates about temperature. Most people agree that there has been warming over the past three or four centuries, especially the past 150 years, though a lot of people don’t agree that a more or less continuous trend since 1860 suddenly acquired a new explanation in 1970. But they don’t agree nearly as much as you might suppose from reading the newspapers about exactly how much warming there’s been or how we know.
There are arguments about the Urban Heat Island effect including whether the problem is that thermometers tend to be in cities or where precisely they tend to be. There are arguments about the reliability of the historical sea surface temperature record. There are arguments about satellite measurements and how they relate to one another, to land surface readings and to ocean temperatures. And every once in a while someone throws a really radical idea into the discussion.
One of these is that solar cycles correlate with temperature over the last four centuries far better than CO2 does. Or even going back further using reconstructions rather than sunspot observations (and there are arguments about how consistent human sunspot observations have been). It’s exactly like science, with battles over hypotheses and data. And now we get a stunning challenge to the accepted history of the Earth’s temperature over five centuries or more (though not the first, as Michael Mann in particular tried to get rid of the Medieval Warm period 20 years ago, an attempt the IPCC first embraced and then largely rejected).
One thing is clear: The way to figure out whether Central Asia hasn’t seen warming since the Ming Dynasty is to look at evidence not to insult it.