New Book Explores Link Between Climate and Ocean Currents
Wallace Broecker is a climate scientist at Lamont-Doherty Earth Observatory who has helped shape our understanding of how the ocean moves heat around the globe, and how this so-called “great ocean conveyor” can switch the climate to a radically different state. Many scientists used to think that only periodic changes in earth’s orbit—so-called Milankovitch cycles– could change climate, over thousands of years, but Broecker has shown that ocean currents can influence climate in mere decades–and could do so again. He spoke with journalist Kim Martineau about his latest book, “The Great Ocean Conveyor: Discovering the Trigger for Abrupt Climate Change.”
How did abrupt climate change become such a buzz word?
In 1988, German scientist Hartmut Heinrich published a paper showing that melting glaciers in the North Atlantic had triggered global climate fluctuations. No one paid any attention. When the first ice core record in Greenland was presented there were just yawns. Everyone was looking for Milankovitch cycles. It was seen as a nuisance, and maybe just something strange going on in Greenland. Then there was the CO₂ record, and its link to the oceans. The ice core records in Greenland proved that change could happen quickly. By the mid-90s almost every paleoclimatologist was working on some aspect of abrupt climate change.
Are we in a period of abrupt climate change?
Not in the sense of the book. What I meant were changes in ocean circulation that caused a global cold spell 8,200 years ago, triggered by a massive release of fresh water from Canada into the Atlantic Ocean. Since then, we really haven’t experienced anything I would call abrupt climate change. Some people think that adding CO2 to the atmosphere will cause reorganizations, but we don’t know for sure.
This is your 10th book—is it the best?
I like it because it shows how science is done. On the back of the book, Kerry Emanuel [a meteorologist at Massachusetts Institute of Technology] calls it a detective thriller. Most science text books just state the facts and don’t go into the excitement and difficulty of figuring things out, partly because the science is new. Books usually lag 10 years behind what’s known. Already I can update this book and put in some interesting new things.
You mention in the book that you’re dyslexic. How has that influenced your research?
Normally, I look at a paper’s abstract and figures, and if I understand them I don’t bother to read anything else. I love lectures because listening to someone and having visuals behind them is the best way for me to absorb information. You can’t ask questions of a paper but at a lecture you can say I don’t understand that, I don’t agree. I don’t know if it’s the dyslexia, but I see how things fit. If you’re doing a picture puzzle and looking for a piece I’ll be the one to recognize when that piece shows up and where it goes.
What’s happening with the conveyor now?
There’s a long term program to study that—a set of instruments stretching from Spain to the Bahamas. But there is so much inter seasonal and inter annual noise that it may take 30 years to assess how it is changing. You have to average out all that stuff. A paper that claimed the conveyor was slowing down got a lot of publicity but that was premature.
Why is there a 16-foot terry cloth snake hanging outside your office?
I used to always talk about the angry climate beast and one day [Lamont scientist] Dorothy Peteet’s husband found that thing on the side of some Rockland County road. When I was away [Lamont scientist] George Kukla and Dorothy hung it up on wires in my old office. If you notice, there’s tape here and there to prevent the stuffing from pouring on the floor.
Why is the beast so angry?
During glacial times, when the climate was gently provoked, it did outrageous things, like me. I have a bad temper and unleash it every now and then. By adding CO₂ to the atmosphere, we’re giving the climate beast a really strong poke. We’re playing with a climate system that we really don’t understand all that well. Roger Revelle, one of the first scientists to study global warming, said that adding CO₂ to the atmosphere is man’s greatest geophysical experiment because it will change everything on the planet—agriculture, climate, ice cover, ocean circulation. But we don’t know to what degree. The details are murky.
What’s your next book?
I’m 78 years old. I’ve written almost 500 articles. I don’t need to write another book. I’m satisfied.