Climate change and evolution

Jan 24th 2011, 14:31 by M.S.

OUR topics this morning are global warming, evolution and feathers. Let's start with the warming. Despite a frenzied last-minute drive involving snowstorms in Europe and the eastern United States, planet Earth failed to save itself from another last-place finish in 2010: once again, it was the least cold year on record. The World Meteorological Organization announced its findinglast week that global mean temperatures for the year were 0.53°C above the 1961-1990 mean, 0.01°C warmer than 2005 and 0.02°C above 1998. With the comparison having a margin of uncertainty of 0.09°C, the three years are considered tied for the hottest year on record. That followed results the previous week from NOAA, which found 2010 and 2005 tied as the hottest years ever, and NASA, which found the same thing. (They both think 1998 was a bit colder.)

By itself, as we always say, one hot year doesn't prove anything. The fact that every one of the twelve hottest years on record has come since 1997 is a little harder to wave away. 2010 was also the wettest year ever, corresponding to the expectation that higher heat means more water vapour. More countries set national high-temperature recordsin 2010 than ever before, including the biggest one, Russia. Arctic sea ice in December was at its lowest level ever, temperatures across a broad swathe of northern Canada have been 20° C higher than normalfor the past month, the record temperatures are coming despite the lowest levels of solar activityin a century and a La Nina effect that should be making Canada colder rather than warmer, and so on. It is of course possible that global warming plateaued this year; it's also possible that it plateaued this morning. One can always hope! For now, though, this is the basic shape of things:

The George Will "global warming has ended" momentshows up as that little dip towards the end, before it returns to trend. So, what effect will the new data have on that meme? Quite possibly none. People who tried to cast doubt on global warming in 2009 based on a few years one could isolate so that they didn't show a discernible trend will now no doubt respond that a couple of very hot years don't prove anything. Which underlines how often the conclusions one draws from data are determined by a combination of the hypotheses you're framing, and at what point you start looking.

This brings me to the feathers. In this month's National Geographic, Carl Zimmer sums uprecent paleontological progress in figuring out when and how feathers evolved, and how they fit into the relationship between dinosaurs and birds. Apparently there have been tons of new feather-bearing fossils unearthed over the past 15 years, and scientists can now use microscopic analysis and knowledge of how modern feathers work to actually figure out what color some of the feathers on these dinosaurs were. It's pretty clear that the development of feathers came long before they had anything to do with flight, but it's still not so clear whether feathered dinosaurs evolved into birds or whether they (and feathered proto-crocodiles!) shared a common feathered ancestor. Anyway, towards the beginning of the article comes this:

The origin of this wonderful mechanism is one of evolution's most durable mysteries. In 1861, just two years after Darwin published Origin of Species, quarry workers in Germany unearthed spectacular fossils of a crow-size bird, dubbed Archaeopteryx, that lived about 150 million years ago. It had feathers and other traits of living birds but also vestiges of a reptilian past, such as teeth in its mouth, claws on its wings, and a long, bony tail. Like fossils of whales with legs,Archaeopteryx seemed to capture a moment in a critical evolutionary metamorphosis. "It is a grand case for me," Darwin confided to a friend.

Think about how that must have looked to contemporaries. Darwin publishes his theory that species develop through evolution from other species. Okay, many people think, wild idea, but can one species really change so deeply over time that it becomes a different species? Wolves into dogs, sure, but fish into lizards and so forth? Then, two years later, a fossil is discovered that suggests dinosaurs evolving into birds. To first have a theory presented that suggests these outlandish transformations, and then to have an example turn up that perfectly describes the theory's most improbable consequences, with no possibility of prior knowledge—this is an extremely convincing sequence of evidence.

But if you grew up, say, 150 years after "The Origin of Species" was published, you didn't experience that remarkable sequence of evidence. You get the theory of evolution and the fossil background presented at the same time. So if you want to be an evolution sceptic, the fossil record just becomes another set of data you can poke holes in, along with the theory. After all, nobody understands what function feathers served before they were used for flight. If they were for mating displays, why did they turn out to be perfect for aerodynamics? How come nothing has feathers anymore that doesn't fly, or isn't descended from something that did? Darwin's theory can't explain it! And so on.

Now, back to global warming. For me, or anyone older, the thesis that rising global temperature data were due to a greenhouse effect produced by industrial emissions of CO2 and other gases, and that this might lead to environmental disaster, was something we first encountered as a mind-bending idea being thrown around by scientists in the mid-1980s. The first time we heard a scientist authoritatively state that the evidence was in, and that global warming was real, was when James Hansen said it while presenting his researchto Congress in 1988. That was a daring claim for Mr Hansen to make at that point. It was daring because it was very clearly falsifiable. If, after 1988, global temperatures had stopped rising, or had started to exhibit a lot of volatility—if there had been a decade-long cooling episode, such as the world saw in the late 1930s and 40s—then Mr Hansen would have been discredited. But that didn't happen. Instead, for a decade and a half after Mr Hansen made the call, global mean temperatures kept going up and up. They bounced around a bit in the mid-2000s, and have now resumed rising again.

For people my age or older who were paying attention over the past couple of decades, that really ought to be convincing. But for people who just joined the conversation when "An Inconvenient Truth" came out, things are different. For them, the evidence of global warming was presented at the same time as the theory. And so they're susceptible to people trying to poke holes in the data or the theory. The temperature rise from 1998-2008 isn't statistically significant, tree ring data is unreliable, and so forth. Give them another two decades, and they'll probably come around. Unfortunately, by that time an enormous amount of damage will already have been done.

As to why George Will buys this stuff, I have no explanation. Maybe, in the internet age, we're all effectively getting our memories wiped every week or two, and it's as if we don't remember the sequence of events; everything is presented simultaneously. Or maybe we selectively wipe our own memories of the sequence of events when they threaten to prove inconvenient to our interests or our ideological predispositions
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