Scientists warn that we're pushing the climate toward something akin to the Pliocene Epoch between 2.6 million and 5.3 million years ago. At that time, sea level may have been about 30 meters (~100 feet) higher than today. Here's what that much sea level rise would do to New York City and surroundings. (Interactive sea level maps: Alex Tingle, flood.firetree.net. Animation: Tom Yulsman) From increasing heat, to melting snow and ice, and rising sea level, we've been getting a clearer picture of how Earth's climate is changing and where it is probably heading in the next hundred years. But what about beyond a century? One way to gain some insight into that question is to study past climates when atmospheric carbon dioxide and other greenhouse gases were as high or higher than they are today. And not surprisingly, that research paints a picture of considerably less ice and much higher sea level. But the past turns out to be an imperfect guide. That's because there is little in the past to compare with how fast and hard we're currently pushing the climate. "The fact is we are changing things fast, and we really don't know where we will end up and what the world will look like," says Bjørg Risebrobakken, a climate scientist at Uni Research in Bergen, Norway. This unsettling picture was my take-away from the science portion of the Arctic Frontiers conference in Tromsø, Norway last week, where Risebrobakken spoke about her research on climate change in the north. A very different picture emerged from the policy section of the conference, which featured a European prince, prime ministers, diplomats, high officials, oil industry executives, and analysts. To be sure, I didn't hear anyone deny the reality of significant human-caused climate change — a refreshing difference from those 49 Republican U.S. senators who did just that in a recent vote. But as in past years at the Arctic Frontiers conference, the main focus of the ministers, oil execs and others was on exploitation of the Arctic's resources and spurring economic development there, especially now that parts of the region are becoming more hospitable thanks to global warming. This paradoxical idea — rapid warming is opening a new Arctic frontier, which will lead to development of resources, which will only enhance warming — has been at the center of these Arctic Frontiers conferences for the past three years that I've attended. This year, I wondered whether it would change. And it did in some ways, with greater recognition that developing the Arctic's resources, including 22 percent of the world's undiscovered oil and natural gas reserves, could prove more challenging than boosters would like to admit. But by the end, I had to conclude that a large gulf still exists between what scientists are telling each other about their research on climate change, and the priorities of even relatively enlightened politicians and industry execs. This is, of course, completely understandable. Oil men are in the business of making shareholders happy by exploring for new resources. And politicians are elected to serve the relatively short-term interests of their constituents — first and foremost, providing them with security and economic opportunity. As obvious as this may be, it's still deeply unsettling. It suggests that despite efforts to bridge the gap between science and policy, our political and business institutions do not yet seem up to dealing with the significant changes we are making to a crucial planetary life support system — changes that will play out over a century and more, and which could hit us hard much sooner than that.
Heading for Terra Incognita
The Pliocene Epoch, between 2.6 million and 5.3 million years ago, is the best analogy we have (with one very important caveat, which will become clearer in a minute) for the kind of world we appear to be headed for. It featured carbon dioxide concentrations in the atmosphere that were even higher than today's (which now stand at about 400 parts per million — and are climbing fast). Temperatures during the Pliocene are estimated to have been about 3 to 4 degrees C warmer (5.4-7.2 degrees F) than in the 19th century, before humankind's emissions of CO2 and other greenhouse gases began heating things up. And sea level was much higher — perhaps about 30 meters, or ~100 feet, higher. The animation at the top of this post shows what that much sea level rise would do to the New York City area. And the next one shows the hypothetical impact on California:
Thirty meters of sea level rise would inundate a good portion of California's Central Valley. (Interactive sea level maps: Alex Tingle, flood.firetree.net. Animation: Tom Yulsman) Even if we were somehow able to cease pumping greenhouse gases into the atmosphere tomorrow, we'd still wind up with something at least roughly analogous to the Pliocene. That's because the greenhouse gases we've already added have probably already committed us to something akin to that geological epoch. As James White, director of the Institute of Arctic and Alpine Research at the University of Colorado, puts it:
We have enough greenhouse gases in the atmosphere already to turn us into the Pliocene. But there is inertia in the system. It takes decades to warm up a water planet like ours and centuries to raise the sea level. Also, it’s not going to be a smooth change. We know where we are headed – a Pliocene-like world — but getting there won’t be smooth. Change doesn’t happen the same way in every place. Some places change faster than others. Ours is a highly non–linear world.
(In the interest of full disclosure, White is my colleague here at the University of Colorado.) Risebrobakken emphasizes one very important caveat in comparing where we are headed to where the world has been during the Pliocene: The climate of that earlier epoch was more or less in equilibrium until cooling led to the beginning of glacial periods. That's not true of our climate today. With our ever-rising emissions of greenhouse gases, we are pushing on the current climate harder and harder. In this way, Risebrobakken says, "we don't really have an analogue for what we are doing." So even though the Pliocene gives us some general sense of the world to come, we may well be headed for terra incognita, climatologically speaking. I could understand why the politicians and oil men who attended the Arctic Frontiers conference might not put much stock in predictions of change that will play out on a timescale measured in centuries. Their focus is understandably decadal — at most. That said, I do wish they had paid more heed to what the scientists were saying at the same conference. Even if we are inevitably headed toward something Pliocene-like, the non-linear nature of the climate system could produce some nasty surprises along the way, surprises that we might still be able to mitigate. As renown earth scientist Wallace Broecker has famously put it
, "The climate system is an angry beast and we are poking it with sticks." If we keep poking, we'll do so at our peril.