Friday, March 15, 2013

Left Side of the Aisle #99 - Part 7

Global warming: scary graph

Something showed up recently that some climatologists - scientists who study climate - have called the scariest thing they've seen in a long time.

It was this graph.

Now, I know most everybody out there is being like count Floyd on SCTV going "ooh, scary." To understand what is so scary about this, we need to back up a little.

Back in 1999, a climatologist at Penn State University named Michael Mann published the results of a study he lead to create a record of temperatures for the northern hemisphere over the past roughly 1500 years. Obviously, records don't go back that far, in fact they only go back to about the 1880s, so he used proxies, which are types of physical evidence such as the thickness of tree rings, which can give at least a rough figure for earlier years.

The graph he produced became known as the "hockey stick" graph because of its superficial similarity to a hockey stick, with its fairly straight "shaft" ending with a sharply turned "blade," a  "blade" whose rise begins just about the time of the industrial revolution of the second half of the 1800s - that is, just about the time people started throwing greatly increased amounts of greenhouse gases into the atmosphere. The graph, the original "hockey stick" graph, was the one on the right.

The graph - and Dr. Mann's reputation - became targets for the nanny-nanny naysayers, who claimed that the entire case for human-caused global warming rested on this one graph - it didn't and doesn't, but never mind - and who set about trying to demolish it and Dr. Mann's reputation along with it. Unfortunately for them, several follow-on studies, by different combinations of researchers using different combinations of proxies, came to the same basic conclusion. When you combine them, the shaft gets kind of warped - but the blade, the rapid rise, is still there.

Okay, with that background, let's go back to the "ooh, scary" graph, which was published last week in the peer-reviewed scientific journal Science. If you notice on the right where it says "previous timeframe," that's the time that Mann and others covered, going back about 1500-2000 years. "BP" means "before present." This graph, using an additional method involving a chemical marker in fossilized ocean shells, reconstructs northern hemisphere temperatures going back over 11,000 years - about as long as there has been agriculture.

And what it shows is that we have lurched, skyrocketed, out of a several-thousand year cooling trend to the point where the northern hemisphere has warmed as much in the last 100 or so years as it had cooled in the previous 7000.

This rate of change is simply unprecedented. Shaun Marcott of Oregon State University, lead author on the study, said “We’ve never seen something this rapid.”

Now, let's be real here: The graph also indicates that at the beginning of the most recent cooling trend, about 7000 years ago, the northern hemisphere might have been about, almost, as warm as it is now. And the trough, the low point, of the earlier cool period, at the left end of the graph about 11,300 years ago, was about as cool as the trough of the more recent cooling trend. But here's the point and here's where the scary part comes in: That earlier low to that earlier high took 4000 years. We have warmed that much and more in little more than 100 years - and we are still getting warmer.

So the two points to make: Has it been this warm before anytime since the dawn of agriculture? Probably, at least almost. But the last time, plants, animals, people, society, had 4000 years to adjust and adapt. We basically have no time at all. And second, we are now facing climatic conditions which have not existed since before the advent of agriculture, that have not existed since before the time there were maybe a couple of million human beings on the entire planet, just a few of who, in the Fertile Crescent between the Tigris and Euphrates Rivers, were just starting to establish settled communities.

We are literally moving into unknown territory with the fate of tens of millions at stake. And yes, that is scary.


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