Jerry Mitrovia was the winner of the Ottawa event of CIFAR's Next Big Question. Here is a summary of his presentation. The folliowing discussion took place at globeandmail.com/science on April 29.
What does the future hold for the planet?
12:01 Sasha Nagy: Welcome to the chat today. We have Harvard professor Jerry Mitrovica with us. He is here to discuss his CIFAR Next Big Question: "What does the future hold for the planet?" Thank you for joining us today. I know it is huge question, but can you briefly summarize your thesis before we take reader questions?
12:04 Jerry Mitrovica: There are many important questions facing society, but the "next" big question facing us is the future of our planet. Answering it will require technological advances and cultural shifts, but there is no doubt that we must act quickly to minimize the damage to our planet from climate change.
12:06 David from Toronto: I was a little surprised at how urgent you made this question sound in the audio clip on this site. Would you say you're optimistic or pessimistic about our chances to answer this question in the right way and the right time for it to do us some good?
12:09 Jerry Mitrovica: It depends on what aspect of the problem we are considering. There is no way, I think, to avoid a century of increasing sea levels - the ice sheets are clearly responding to the warming of the planet. But other potential problems - changes in ocean circulation and regional climate responses to that for example - may be minimized with timely action on emissions. But you are right - I do feel a sense of urgency. People must understand that there are tipping points in climate.
12:11 Comment From David from Toronto: What would a "tipping point" look like? Could humanity recover from something like that? Could the planet?
12:14 Jerry Mitrovica: Here's an example. Ice shelves encircle many parts of the West Antarctic. They are floating portions of ice that act to girdle the main ice sheet and keep it in place. The problem is that these shelves are being warmed both from below (the water) and above (the atmosphere) - and the thinning will reach a point where they will tip into collapse. In fact it has happened - the Larsen B ice shelf on the Antarctic Peninsula - a shelf the size of Manitoulin Island - collapsed in just a few weeks.
12:15 Comment From Tom: What are your suggestions for forcing the long-term costs into company risk and operations calculations in order to promote action on unsustainable practices? Free-market environmentalism? a systems-thinking approach?
12:19 Jerry Mitrovica: A difficult question for a physicist to answer, but a crucial question nonetheless. I just read a long article by Paul Krugman in the New York Times magazine from a few weeks ago. It was the first article that led me through the main issues around things like cap and trade, etc. I am not trying to evade the question in saying that I am only now beginning to formulate an opinion on this. Email me in a month or so and I will tell you where that is leading me.
12:20 Comment From Ainat: What will happen to ocean circulation if the ice sheets melt?
12:27 Jerry Mitrovica: Here is a major concern for scientists in the area of climate. Why are major cities in Europe like London and Paris warmer than cities like Toronto or Ottawa? The reason is that cold winds coming west to east over the north Atlantic are warmed when they cross warm ocean water that emerges just east of Europe. This ocean circulation is like a big conveyor belt (a common analogy used in textbooks) that brings warm deep waters up to the surface, and it includes things like the Gulf Stream. The problem is that if Greenland continues to melt, and that fresh water continues to enter the north Atlantic, the conveyor belt may weaken, and even stop. If that happens then Europe will enter a much colder climate because the winds will no longer be warmed. This will not take a couple of years, but it is a longer time scale (decades to century) concern. It is ironic in the sense that global warming will lead, in this scenario, to a dramatic cooling of temperatures in one region of the Earth.
12:28 Comment From Jack: Have you heard of James Lovelock's "Gaia Theory?" Do you think there might be self-regulating mechanisms in the biosphere that could correct for some of the changes we are seeing now?
12:32 Jerry Mitrovica: Yes, I have heard of the theory. Climate is a complex system and there are all sorts of connections between the solid Earth, oceans and atmosphere. Changes in one of these regions (or parts of the region) will impact others - scientists call this "feedback". But one should not think that all feedback mechanisms will help the climate stay stable (if you mean by "self-regulating" is "self repairing"). Some feedback will help, but others will in fact makes things worse. The net effect, in the view of most climate scientists (and data support this) is that the various feedbacks are leading the system down a one way street. The Larsenn B ice shelf I mentioned is gone - nothing in the climate system was able to stop it when the system was perturbed as much as it was.
12:33 Comment From Carbon confused: Does carbon sequestration (like the under Bass Straights project in Australia) lead to possible failure resulting massive "burping" of the stored CO2. Given seizmic activity and tectonics, can we be reasonably assured that the earth won't fart and kill us all in some distant future if we spent 100 years sequestering carbon?
12:38 Jerry Mitrovica: People might be taken aback by the bluntness of your language, but your point is a valid concern. I do believe that carbon sequestration (essentially taking the carbon out of the atmosphere and storing it inside some stable part of the crust) is an important technology to be investigating. But, as you imply, many crustal regions are tectonically active and so this "stress" on the crust has to be very carefully considered when you decide where you might sequester the CO2. (By the way, the same issue is important when considering the storage of nuclear waste.) To make matters worse, you can be far away from the major tectonic boundaries and still be in a region of crust that is deforming and subject to earthquakes. So the problem is not as simple as avoiding obvious places like the San Andreas fault!
12:39 Comment From Magdalena: Given how interconnected these things are, could it mean, for instance, melting icecaps could affect tectonic activity? (This is a pet theory of my father's)
12:47 Jerry Mitrovica: A very subtle issue. I do not think the melting of ice on the Earth's surface will lead to any major increase in tectonic activity. But there may be some. There is plenty of nice work showing that Canada's ongoing crustal rebound after the ice cover during the last ice age disappeared (~10,000 years ago) has triggered earthquakes in Canada and parts of the US. Indeed there is consensus that these quakes are "post-glacial" in origin. Yet another reason to be careful about where you might store the CO2 - you wouldn't think that something as stable as the Canadian shield would be subject to earthquakes, but it is (though I must emphasize that these quakes are nowhere near as large as those that occur on plate boundaries).
12:48 Comment From duncan rutherford: When you and your colleagues hear about things like the iranian cleric who said that women dressing provocatively can cause earthquakes, do you find it funny, or is it frustrating?
12:54 Jerry Mitrovica: I do not think it is funny, nor do I feel frustrated. We live in a world informed by complex cultural issues, and the important thing is for scientists to push for their research results into the public domain. We have an important role in society - to provide information gained through rigorous scientific methods - that is part of the reason I agreed to do this online chat.
12:55 Comment From Phill: As an expert, what would you say is the single most effective thing we could do to slow down climate change?
1:05 Jerry Mitrovica: As a society I think we should be pushing governments toward coherent, organized international caps on future emissions. But in my view countries should begin to take action with or without that international consensus. It is no longer reasonable to say "we won't do it until they do it". It is important to show that substantive changes in emissions - driven by cultural shifts and technological innovation - are possible to realize in a cost effective way. Indeed, I think it is quite clear that innovation in this area will drive the economies of countries that are investing now (not leaving that investment until a time when the benefits become clear). But there is also one other thing we can do. We can vote for leadership that has vision - why is it that so many people are arguing that it is impossible to undo the damage to climate when as a society we have overcome equally onerous obstacles in the past. We need leadership.
1:07 Sasha Nagy: Jerry, that's about all the time we have today, thanks so much for your time and your great answers to the varied questions. Any closing comments? Also, perhaps you can tell us where your research will take you in the coming months, years.
Thanks again, and our apologies to those questions that we could not get to.
1:15 Jerry Mitrovica: I do think I will become more involved in public debates on these issues. As a scientist you aren't necessarily trained on the sound bites that seem to dominate the public discourse.
My future research will continue to focus on sea level changes - they are an elegant and precise indicator of climate change with far more information that people realize. For example, people who participated today may not know that when an ice sheet melts, sea level actually falls in the vicinity of that ice sheet - and rises by progressively larger amounts as you move further away. Using this geographic information, my colleagues and I are trying to unravel not only how much sea level is rising (in some average sense), but we are also trying to "fingerprint" where the meltwater is coming from. That's a topic for a future chat! Thanks for inviting me.