A recent article in Grist proposes that we aren't sufficiently afraid of climate change. The writer bases his claim on a paper in Nature Geoscience, which reports that global climate models do a lousy job of simulating abrupt climatic shifts, favoring slow-moving changes that they can more easily wrap their silicon-chip brains around. Because of this bias, the models have supposedly been misleading us into a false sense of complacency when we should instead be "way more terrified" of what may lie ahead. But speaking as a paleoclimatologist, this isn't really news, and I don't think we should freak out about it.
Paul Valdes, author of the aforementioned Nature Geoscience article, cites four examples from the deep past to illustrate what happens when a climate trend passes a "tipping point" that sets larger and faster changes in motion (and how badly most models handle it). He describes a super-greenhouse episode that toasted the world 56 million years ago, which I've written about previously, the rapid birth of the Sahara 5,500 years ago, gigantic gushes of icebergs into the North Atlantic ("Heinrich events") that messed with ice age ocean currents, and sudden jags in paleotemperature curves called Dansgaard-Oeschger events which are as yet unexplained.
Valdes concludes: "If the models are to be used for the prediction of potential future events of abrupt change, their ability to simulate such events needs to be firmly established—science is about evidence, not belief systems."
This isn't news. People like me, who reconstruct climatic history from lake sediments, ice cores, and such, have long bemoaned the inability of models to simulate certain aspects of climate properly. There's even some mild rivalry between our disciplines because of it. In fact, some of us recently published a critique of several models in Science because they failed to simulate an ancient drought precisely. But any such rivalry is strictly professional and mostly good-natured, and I've mingled with modelers over beers often enough to learn that they sometimes trash-talk my own group, too, calling us rock-jocks and technophobes.
Valdes, on the other hand, straddles both camps, routinely balancing models against climate history. His comments therefore carry extra weight, and I came away from his paper saying "right on!"
Sure, maybe his description of the Sahara desiccating in the blink of an eye is questionable. It's mainly based on the sudden appearance of fine desert grit in sediments off the coast of Africa, but other Saharan sites suggest a more gradual transition. And the primordial super-greenhouse probably developed over many centuries, hardly an instantaneous leap.
But the central point of Valdes' paper is sound. If you want to know as much as possible about what lies ahead, don't put all of your trust in one single information source. We paleo nerds can tell you a lot about what real climates have been like on a real Earth, but we can't manipulate history to address some important "what if" questions. Modelers hold that ground more firmly, though their simulations operate in artificial worlds; that's why we call them "models," as in model airplanes. Together, though, our strengths and weakness mesh well, and our combined efforts have long pointed to the possibility of abrupt climatic shifts heading our way.
And should our inability to know exactly what's coming at us make us weep and wail? That depends on who you are. One famous scientist told me that he exaggerated the dangers of climate change in his lectures because "if people aren't scared, they won't pay attention." This strategy has apparently worked well enough that one in three school kids surveyed back in 2009 were afraid that the Earth won't exist when they grow up, and half thought that the entire planet will soon become an unpleasant wasteland.
But most of the scientists I know favor truth over fiction, and most of my college students are refreshingly well-informed, hopeful, and eager to save the world. We think that the reality of climate change is serious enough that it doesn't need to be exaggerated in order to be taken seriously. The regrettable polarization of public discourse over our effects on climate largely reflects agendas other than the pursuit of good science, and obvious fear-mongering merely deepens that divide.
When faced with a crisis, some of us freeze in terror while others shift into high gear. "Sit and tremble" may be a good strategy for a camouflaged critter waiting in the underbrush for a predator to go away, but there's no place to hide when the whole planet is involved, and the threats posed by our carbon emissions won't go away for tens of thousands of years. For me, uncertainty about some details of future climate change is just one more reason to pay close attention to what's going on while also preparing for the unexpected. This is no time to freeze up and give up; there's so much at stake, and we've got so much work to do.
[Image: Flickr user mtsrs]
Curt Stager is an ecologist, paleoclimatologist, and science journalist with a Ph.D. in biology and geology from Duke University. His new book is DEEP FUTURE: The Next 100,000 Years of Life on Earth (St. Martin's Press, March 2011).