Can we steer the course of our changing climate?
Scott Doney says we’re already committed to some change.
What if, in your lifetime, the world suddenly got warmer? What if melting sea ice and glaciers caused sea level to rise, threatening low–lying cities? What if climate patterns across the globe shifted, with implications for humanity’s fresh water and food supplies? Scott Doney – a climate scientist – talked with Earth & Sky’s Eleanor Imster about how human behavior might change.
Imster: Do you think that the climate is changing so fast that we will need to adapt, or do we still have time to steer the course?
Doney: In the climate community, they talk about the amount of change that we’re already ‘committed to’. Given how much carbon dioxide we’ve emitted to the atmosphere, how much warming can we expect? How much sea level rise can we expect? We’ve already committed ourselves to a fairly substantial change in the ocean. And if I look around, it’s going to be very difficult for society to rapidly change the way it uses energy.
What I worry about is not so much the developed world, because I think the developed world has the opportunity to adapt. But I worry about the poorer countries, where they just don’t have the resources.
Imster: Scientists agree the Earth is warming. Is there a consensus in the scientific community about how this will affect Earth’s oceans?
Doney: Well, if you think about global warming, you can think about it in two ways. You can think about it as increasing air temperatures. How hot is it going to be in Dallas this summer? Or in twenty years?
But if you think about global warming as heat storage – as we add CO2, the planet is trapping heat – most of that heat is in the ocean, because the ocean is such an excellent reservoir. Water is a great storage container for heat. Global warming is actually ocean warming, because that’s where all the heat’s ending up.
Imster: What’s the impact of that heat storage?
Doney: There are some things that we know as a community fairly well. There are other things that are still open research questions.
Sea level rise has been fairly well documented, and it’s hard to argue the underlying physics. As the ocean warms, and as you have glacial melt, sea level is going to rise. Now, the exact magnitude of that depends not just on the physics of the ocean, but also what’s going to happen in the future. How much carbon dioxide’s going to be put in the atmosphere? Are we going to make changes to the way we manage the environment?
Similarly, all the models and the historical data suggest that there has been a warming of the upper oceans, and that that warming will continue into the future. The warming is more concentrated near the surface, but there is evidence of it going on at depth. The deeper water, the bottom water, down at 3,000 or 4,000 meters is more ambiguous.
For most of the physical climate impacts – sea level rise, global warming, sea ice melt – it’s really a matter of degree. How quickly is it going to happen? Not ‘is it going to happen?’ or ‘could it go the other way?’
Imster: So, it’s not whether the changes will happen, but how much and how quickly?
Doney: It’s the rate of change, and it’s the impact of that rate of change on natural ecosystems and human society. How quickly can we adapt to this changing climate?
With the observations we have now, we’re starting to get a pretty good idea about what’s happened over the last half of the 20th century. The question is, where are we going to be in the year 2100 or 2300? And that depends not just on the physics – what’s going on in the ocean or the atmosphere – but also on what we do as a society. Do we attempt to curb carbon dioxide emissions? Anytime you talk about the future, you have to say something both about your understanding of the climate system, but also some estimate of what people are going to do.
Predicting the future is a very tricky business, because as climate changes – and we’ve already seen this – people will change their behavior. And this brings in issues of economics and politics and social dynamics that make it a very complicated but interesting problem.
