Today is my birthday, and I’m sitting on a plane writing this entry. Yes, I’m busily contributing to the emissions problem, but this trip is well justified (trust me). And no, this entry will not be about carbon offsets or green travel. Instead it’s related to the birthday thing; I’ve been thinking about time. More specifically, I’ve been thinking about many of the things that I’ve seen so far in my life, compared to what my parents and grand-parents saw. I’m typing this little entry on my little laptop, certainly a device unknown to my parents at this age, but one that I would be reluctant to give up. But it’s shocking and saddening to recall stories that I was told of things that I am unlikely ever to see. My grandfather talked about manatees in Jamaica during his youth. I lived a good deal of my own childhood in Jamaica, but saw my first manatee only years later in Florida (I wonder how long they’ll last there?). My father, who was from Trinidad, would tell stories of the sky being clouded for days by thousands of birds on their annual migrations. I spent the other part of my youth in Trinidad; I never saw those migrations. My mother, Jamaican, now lives in Florida. She witnessed some of the great hurricanes that hit Jamaica in the mid-20th century, but cannot remember storm seasons ever as active or vicious as those of the past three years. I remember healthy coral reefs in the Caribbean. I also remember becoming aware of environmental complexities during the early days of the ozone problem (we solved that!). Twenty years ago I lived about 8 miles from the edge of the Florida Everglades. That same house is now about 15 miles from the new edge.
Two questions really bother me these days, so much so that I spend a good deal of my research time on them. First, are things really changing? Are the recent dry winters, warmer summers, the bleaching corals, the droughts, really the early heralds of a changing planet? How can we understand the time scales of environmental and ecological change? Second, which stories of lost stories will my daughter recall when she reaches this birthday? Well, whatever the answer, I hope that her trips are a little bit greener.
The term “tipping point” has entered the modern household vocabulary. It is being applied to a wide range of phenomena, ranging from social networks on the internet, to the spread of diseases, to climate change. These phenomena, from a technical scientific standpoint, are both different and the same. What I mean is that the underlying stories, causes and consequences are quite different, but they do share some intriguing mechanistic similarities. Let’s indulge in a little science for a moment. A tipping point is perhaps better understood as a surprise, that is, an incremental (or “smooth”) change in some input to a system at some point results in a sudden or discontinuous change in the state of the system. Let me demonstrate. Imagine that you have a small model boat with you in the bathtub. You roll the ship a wee bit to the left. When you release it, the boat promptly rights itself. You roll it again, but this time a little bit more to the left. Once again, the boat will right itself. You can continue to do this, with each time the boat righting itself. At some point, however, the little increase in roll will cause the boat to TIP over! The system, as we say, has entered a new stable state (much to the discomfort of the crew unfortunately).
Now why is all this relevant to climate change? A common hallmark of systems that exhibit tipping points, or surprises, is that they are complex; they tend to have many semi-independently interacting parts. These parts influence each other directly or indirectly, often amplifying or reinforcing perturbations or changes to the system. The amplifications, or positive feedbacks, can literally seem to blow a small change all out of proportion. A tipping point can be reached when these feedbacks cause the system to restructure itself, or unravel, to the point where the interactions are quite different, or the interactors are themselves changed. The tricky part, for us, is that complex systems are often very difficult to understand, and almost impossible to predict. Tipping points, surprises, catastrophes, etc. occur in these systems when external disturbances push the interactions to the point where internal dynamics and feedbacks take over control of the outcome. So does Earth’s climate have a tipping point? Will global warming result in gradual increases in temperature over the next century as predicted by IPCC models? Or will there be surprises along the way? Will ice sheets collapse instead of melting away with whimpers? I don’t know, but everything that I do know about complex systems tells me that we must be wary. If the ship that you are about to board is tossing about on the waves, and you’re not sure whether it can weather the storm, my best advice to you is to postpone your journey.
I’ll have a lot more to say about tipping points and complex systems in the next several postings. Stay tuned!