03/18/2010 05:12 am ET Updated May 25, 2011

The Maya Really Did Warn Us About Our Future (Unintentionally)

Roland Emmerich's enjoyably silly CG destruction-fetish flick '2012', featuring more ruined cities and panicked statesmen than any of his previous offerings, takes its cue from the cranky claim that the Maya calendar predicted the apocalypse, and we're now due. The premise is that the astronomers of the doomed medieval Central American civilization figured out that an alignment of the planets in the solar system on December 21st 2012 would somehow cause the sun to emit excessive radiation that would mess up Earth's core, in turn tearing up the ground we're standing on.

If I take time from your life now to point out that the Maya did not make such a claim, and that solar-system-wide planetary alignment would not so much as disturb your cable reception, I can only hope you will forgive me for insulting your intelligence so egregiously.

But as with many such fanciful claims, there is a real, actually interesting, story lurking in the background, brought to us by history and science. And it tells us something about our own possible future.

The Maya live on in Central America today, the term covering different communities in southern Mexico, Guatemala, Belize, El Salavador and western Honduras. Sadly, they are often grossly ill-treated peoples, long oppressed by ruling elites of European origin. But the great Maya civilisation that built some of the world's most impressive pyramids in highly populated cities and wrote in beautiful hieroglyphics from the 3rd to the 9th centuries AD disappeared long before the merciless Spanish conquest. Where millions once lived, Spanish armies would struggle to find enough food to steal from sparsely populated hamlets.

The ruins of their abandoned cities, given over to nature so soon after the height of their development have long presented an intriguing, romantic mystery since they were rediscovered by outsiders, John Stephens of the US and Frederick Catherwood from England in 1839. There are a number of competing theories of the principal cause -- from civil war to disease and foreign invasion to overuse of the soil. But another explanation that incorporates and expands on these, popularised by Jared Diamond in his book 'Collapse', is leading over the others -- and it's bad news.

Central America was never an easy place for a highly developed civilization to emerge, with its long dry season and unpredictable rains. The Maya required ingenuity and intense labor to keep the soil fertile, catch water in reservoirs and dig the canals and irrigation ditches that made the best use of it. The corn that made up much of their diet could not meet the nutritional needs of a marching army of an empire, but the Maya established flourishing city-state kingdoms that competed with each other for military and cultural pre-eminence. Surviving documents and monuments tout the achievements of self-obsessed kings and nobles, boasting of their conquests and the gory punishments meted out against the vanquished.

But 90 million miles away, their glories were undone. A pulse in solar activity with an average cycle of 1,500 years triggered climate change on Earth. Its impact was varied and seems to have primarily affected the North Atlantic region, unlike the artificial global warming we are experiencing today where temperatures rise steadily in every continent and ocean. But the lesser, natural, mediaeval warming was not without far-reaching consequences for people. Maya reservoirs could hold enough water to last 18 months without rain - but after the 8th century, this would not be enough. Evidence from sediment layers and pollen point to a history of drought, and in particular, three successive droughts between 800 and 950 AD, maybe decades long each.

Low-lying northern cities could access water from underground sources, but the southern cities, high up in the mountains depended on their reserves. Piecing together precisely what happened is not easy - but from 800 AD to 950 AD, the rule of the kings came to an end (perhaps at the hands of angry subjects), the calendar stopped and the Maya population fell between 90 and 99%.

The mega-drought theory for the Maya demise is not accepted by all archaeologists though it has been gaining ground. But while other causes have been suggested - such as the overuse of soil and warfare, the horrible possibility is that these were further consequences of regional climate change, the acts of increasingly desperate people. As Diamond suggests, "Like most leaders in human history, the Maya kings and noble did not heed long-term problems..." Faced with the greatest challenge to their rule, they recommitted to self-destructive habits of over-consumption, built greater monuments to themselves and killed each other over their dying land to the end. It is a warning to us.

The very existence of natural climate change is often brought up by global warming deniers as a feeble counter to the rock-solid science demonstrating man-made global warming, as though no climatologist had ever thought of it before. Even more curiously, they illustrate the history of natural climate change with cutesy anecdotes about wine-growing in a warmer northern England and ice fairs in London during colder times. The point being: climate change is natural ... and it's nothing to worry about! But the actual history of natural climate change is often of civilization-breaking havoc. And the medieval warming in the north Atlantic was weak stuff compared to the global warming our greenhouse gases are preparing for us, but was devastating nonetheless. Like the Maya, we face destructive forces that could be well beyond our capacity to adapt to. Their empty cities are a warning to us.

The major difference between the Maya in the 8th century and us now is that they had little ability to understand what was happening to them and even less to do anything about it. Our civilization, by contrast, knows what is happening and even at this late date has the ability to prevent catastrophe. What is in question is our willingness to act on what we know and demand the transformation the necessary transformation in the way we produce and use energy. Which is what you can do on December 12th, the day of the international climate conference in Copenhagen. It's not the day world ends, but it could be the day our governments didn't try to save it.