Joseph Romm interviews Christopher Field

Joseph Romm: What would you say is the main cause of the climate change that we've been experiencing?

Christopher Field: The main cause of climate change is the release of carbon dioxide and other heat-trapping gases to the atmosphere as a consequence of human actions. Before the middle of the last century, most of those emissions came from cutting of forests and releasing the carbon in the trees to the atmosphere. Since then, it's mostly come from the combustion of fossil fuels: coal, oil, and natural gas.

Romm: And what sort of impacts are we seeing from climate change right now?

Field: We've already seen a wide range of impacts from climate change. The clearest ones are in shifts in the way ecological systems work--when spring arrives, when flowers bloom, when birds fledge. But we're beginning to see an increasingly serious number of impacts in the area of things like heat waves, in terms of outbursts from glacial dams and water availability. One of the most striking impacts that is really impacting where I live is that we've seen a dramatic decrease in the amount of snow pack that's available for providing California's many water users for water during the dry summer season.

Romm: So what do we risk if we take no significant action to reduce greenhouse gas emissions in the future? What kinds of impacts can we expect to see?

Field: Climate change can have impacts on a wide range of issues--human health through heat waves and infectious disease, agricultural productivity through direct temperature impacts on crops as well as effects of water availability, impacts on infrastructure through storm damage, and impacts on ecosystems and their ability to provide the goods and services that humans depend on. A wide range of potential impacts that degrade future opportunities for the human enterprise and for the natural enterprise.

Romm: During your remarks you mentioned this notion of tipping points. I'm just wondering if you'd comment on one or two of those tipping points and why we should worry about them.

Field: One of the areas of greatest concern in climate change is that we might reach a stage at which even reducing emissions to zero wouldn't allow us to stop the climate change trajectory. And among the kinds of tipping points that concern me the most and deserve to be the topic of intense research are the status of tropical rain forests and whether those could transition from being important sinks, taking carbon dioxide out of the atmosphere, into sources where they're releasing enough CO2 potentially to drive further global warming. And melting of permafrost, which you can think of as a big icebox storing vast quantities of frozen carbon that when thawed can rapidly decompose and enter the atmosphere potentially triggering a vicious cycle where the release of CO2 causes more warming which causes the release of more CO2.

Romm: And why are the reports issued by the Intergovernmental Panel on Climate Change important?

Field: The IPCC is a unique partnership between the scientific community and the world's governments. It's the most ambitious, thorough and successful science assessment there's ever been on any topic. And it provides a powerful way to get consistent overview of what is known and what isn't known about climate change and climate science.

Romm: Can we improve the IPCC process? And what would you suggest to do that?

Field: The IPCC process has been very successful in the past, but it can clearly be improved. The IPCC is run basically by volunteers who dedicate vast quantities of their time. And I think that most of the opportunities for improvement come in better educating volunteers about how to effectively contribute--making sure that all the topics are effectively covered, making sure that we engage the scientific community at the level that's necessary to ensure the high quality, absolutely air-free quality of the reports that I think the scientific community should demand and I think the world deserves.

Romm: And let me ask one last question. There are a lot of people out there who do not believe in the human-caused global warming. They think it's a hoax. What would you say to them? What do you say when you meet such people?

Field: You know, there are two important things people need to understand. The first is that within the scientific community, we have a lot of fingerprints for global warming, observations that are consistent with the hypothesis that climate change is caused by greenhouse gases released by humans, and not consistent with any of the alternative explanations, things like the heat content in the oceans, the way that the temperature of the atmosphere changes with elevation. None of these really depend on climate models, but provide a very high probability conclusion that it's human actions that have caused climate change.