Sustainability scientist Kevin Gurney has been studying climate change for 27 years. He has worked in academia, public policy, non-governmental organizations (NGOs) and think tanks, and is currently at Arizona State University in Tempe. He describes how he navigates the science–policy divide.

What convinced you to do a graduate degree?

As an undergraduate, I worked at the Lawrence Berkeley National Laboratory in California, taking spectroscopic measures of greenhouse gases. Working with wonderful mentors who were excited about the science was infectious. Later I did a master's in atmospheric science at the Massachusetts Institute of Technology in Cambridge and my focus shifted to chemistry and chlorofluorocarbons (CFCs) — greenhouse gases that also deplete Earth's ozone layer, and so have science and policy implications.

How did you become active in policy?

Regulation was ramping up to stop production of fully fluorinated CFCs, and industry was looking for alternatives. In 1986, I found that compounds called HCFCs, which contained less chlorine and thus caused less ozone depletion, still had the heat-trapping properties of CFCs. The policy implications were huge and there was so much misinformation. I was thinking, people need to know about this. I got more involved with policy at that point.

Why not go on immediately to pursue a PhD?

I wanted to work on the political implications first. In 1992, I started working with the Institute for Energy and Environmental Research in Takoma Park, Maryland. We sued the US Environmental Protection Agency to get it to regulate HCFCs, and we spread the word that HCFCs were not as environmentally friendly as manufacturers claimed. I also got involved in discussions on the Montreal Protocol, the treaty to regulate ozone-depleting chemicals. I realized how ineffectively science and policy interacted. I got a master's in public policy at the University of California, Berkeley, then a PhD in ecology at Colorado State University in Fort Collins. These days it is easier to get an interdisciplinary degree, but I tell my students that some degrees lack a rigorous science foundation. There is no substitute for a solid mathematics and physics background — it gives you credibility.

How did you move from CFCs to carbon?

I attended the negotiations in London and Copenhagen to amend the Montreal Protocol, laying out a plan to manage CFC phase-out. Once the treaty was set, I began to see that rising carbon dioxide levels were an interesting problem. I maintained a personal network of contacts in NGOs, and many organizations were shifting to carbon dioxide and climate research for exactly the same reasons I was — it was quickly gaining traction. NGOs, including the US branch of the conservation group WWF in Washington DC, paid for me to go to Kyoto Protocol negotiations, and I worked pro bono as a science consultant. I told the NGOs I was not going to give anyone just a line they wanted to hear. My PhD adviser let me take vacation to attend negotiations every four months.

What is climate-change negotiation like?

It is the most intense, pressure-filled world you can imagine. I was very involved with language in the Kyoto Protocol about the missing carbon sink — the carbon dioxide absorbed on land, which is not fully understood — and how to account for it. I learned a lot about law during my policy degree, which made me effective in crossing the divide between policy and science. You don't have to dumb down; you have to learn how legislators and policy-makers view science.

You won a Faculty Early Career Development award from the US National Science Foundation in 2009. How are you using it?

I'm doing a risky thing and getting involved with citizen science to use Google Earth to identify power plants (see Nature http://doi.org/nb3; 2013). Normally I would be too worried that it would fail to use funding dollars. But we have thousands of people involved and are adding hundreds of power plants to an emissions database that is part of NASA's pilot carbon-monitoring system. It is of interest to climate scientists, social scientists and policy-makers.