It will be interesting to see what climate deniers make of this headline: New Study Shows Climate Change Largely Irreversible. If it is—irreversible, that is—then a reasonable response might be, so then why exactly am I being asked to conserve energy and buy a hybrid car and pay more for wind power . . . when we’re toast anyway?

The study, published in the current Proceedings of the National Academy of Sciences, comes from one of the nation’s leading climatologists, Susan Solomon of the National Oceanic and Atmospheric Administration (who also co-chaired the working group on the physical basis of climate change for the 2007 assessment of the Intergovernmental Panel on Climate Change). Solomon and her colleagues conclude that there’s no going back: changes in global temperature, rainfall, and sea level will be essentially irreversible for more than 1,000 years after we completely stop releasing carbon dioxide and other greenhouse gases into the atmosphere.

“It has long been known that some of the carbon dioxide emitted by human activities stays in the atmosphere for thousands of years,” Solomon said. “But the new study advances the understanding of how this affects the climate system.” Short answer: not for the better.

Current levels of CO² have reached 385 parts per million. Solomon’s study examined what happens if it reaches 450 to 600 ppm before emissions are halted. Chief among the lasting effects: irreversible decreases in dry-season rainfall in southern Europe, northern Africa, southwestern North America, southern Africa and western Australia, with results “comparable to those of the ‘dust bowl’ era,” write the scientists. The calculations also foresee “inexorable sea level rise” of up to 3 feet if we peak at 600 ppm and just under 6 feet if we go all the way to 1000 ppm. When rainfall decreases for periods not of decades but of centuries, human water supplies will fall, wildfires will become more frequent, ecosystems will change beyond recognition and deserts will expand.

The reason the climate impacts last so long is the world’s oceans. They act like an immense heat sink to “keep temperatures almost constant for more than a thousand years,” said Solomon.

The scientists conclude like this: “It is sometimes imagined that slow processes such as climate changes pose small risks, based upon the assumption that a choice can always be made to quickly reduce emissions and thereby reverse any harm within a few years or decades. We have shown that this assumption is incorrect for carbon dioxide emissions . . . . Irreversible climate changes due to carbon dioxide emissions have already taken place, and future carbon dioxide emissions would imply further irreversible effects on the planet.”

So, returning to the question about how society acts when experts conclude there’s no going back, I imagine this will undercut efforts to reduce greenhouse emissions, and perhaps increase support for geoengineering schemes that suck CO² out of the air, as I discussed in 2007. What may well get lost is this: although some changes are locked in, how bad those changes are depends on how many more millions of tons of greenhouse gases we load into the atmosphere.

If you’re out of ideas for a conversation over family dinner tonight, try this (it works better if you have a four-legged pet): how do cats and dogs walk? That is, in what order do the four legs take steps?

If your family is like most of us—and “us” includes, somewhat appallingly, illustrators for veterinary anatomy books as well as toy designers and the curators who put together dioramas at natural history museums—they’ll get it wrong. According to a sobering little paper in the January 27 issue of Current Biology, both laymen and people who should know better get the walking gait of horses and other quadrupeds (something  Eadweard Muybridge documented and published in the 1880s; the Wikipedia entry has nice videos) wrong about half the time.

The study, led by Gábor Horváth and György Kriska of Eötvös University in Hungary, explains why model horses fall over so often. They’re typically depicted in stride, but the wrong stride; horses, dogs, cats et al. ambulate the way they do because it provides the greatest stability. If a quadruped walked any other way, it would tip over . . . as model horses tend to.

And now the answer: in all four-legged animals, the order is: left hind leg, left foreleg, right hind leg, right foreleg. Repeat. Any leg can take the first step, but once it does the sequence is that above.

Oh, and while illustrators and museums and toy designers mess up, Jurassic Park and The Lord of the Rings got the gaits of dinosaurs, elephants and fantasy beasts exactly right.