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Aerosols on ice Part II

23 Jun 2021 | Science Notes

We told you last week about a remarkable study in which climate scientists led by Pengfei Liu of Harvard dug 250-year old ice out of the Antarctic ice cap and learned that the effects of greenhouse gases have been overstated and future warming will be less than expected. Be sure to read that item to understand how the work was done and how they came to that conclusion (which, we are pleasantly surprised to note, was published in a top journal, and received at least some media coverage, in the UK Daily Mail). Another remarkable finding of the Liu et al. study is that everything modelers thought about wildfire in the southern hemisphere (SH) was backwards. They used to think fire rates were low in the preindustrial period and rose alongside increasing settlement. The new data show they got it exactly wrong: “Between 1750 and the early part of the 20th century, [the data indicate] a relatively stable level of fire emissions in the SH, followed by a 30% decrease until about 1990.” Settlement drove wildfire down, rather than up. And wait, there’s more. You also get the Medieval Warm Period.

Remember all the hoo-hah two years ago because the Amazon was supposedly burning up and the “lungs of the Earth” were on fire? We debunked it at the time by showing that the fire rates weren’t even exceptional by modern standards. Yet now we know they also were low by comparison to the standards of centuries past. An interesting aside in the new paper reviews evidence from other paleoclimate studies that reconstructed wildfire back to 1000 AD. Liu et al. comment:

A general consensus of these other records is that the global fire emissions may have been relatively high early in the past millennium (1000 to 1500 CE), with a decreasing trend from the Medieval warm period (~1000 CE) to the Little Ice Age (LIA; 1600 to 1800 CE).

The Medieval Warm Period? The Little Ice Age? Weren’t these banished from discussion by Michael Mann and the IPCC long ago? Weren’t we told they were minor events confined to the northern hemisphere? Yet here they are turning up in wildfire records for the southern hemisphere. And being mentioned in a study that provides evidence to support the view that the climate is not as sensitive to greenhouse gases as had been assumed, a point we’ve made ourselves based on other lines of evidence.

A lot of people think the climate science disputes will be settled once the knuckle-dragging denier crowd abandon all resistance and embrace the climate alarmist movement. We prefer to believe that they will be settled when the data are collected and the studies are done and the evidence points to a clear conclusion.

For our part, we think we know what that conclusion will look like. But we will need a few more studies like one by Liu et al. before we can lace up for the victory lap.

One comment on “Aerosols on ice Part II”

  1. If fire activity during the Little Ice Age was greater relative to the Medieval Warm Period, wouldn't that indicate the level of fire activity increases during periods colder climate? If that is true, increased wildfire activity would indicate global cooling, not global warming.

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