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By Tim Lucas

It was a report on climate change, but it caused an earthquake.

When the United Nations’ Intergovernmental Panel on Climate Change (IPCC) released its “Special Report on Global Warming of 1.5°C” in October 2018, its findings shocked scientists and policymakers worldwide.

The report presented hard new evidence—based on more than 6,000 independent studies—that the impacts of climate change will be much worse than expected and will occur far sooner, unless governments phase out fossil fuels and transition to a carbon-neutral world economy at a speed and scale that has “no documented historic precedent.”

Climatologist Drew Shindell, Nicholas Professor of Earth Science, was a coordinating lead author of the report. His groundbreaking research and widely cited expertise on the human health impacts and other social costs of global warming helped shape the panel’s findings and guide its policy recommendations.

In the days following the report’s release, he appeared in nearly 1,000 newspapers and newscasts worldwide, parsing the science and laying out the policy options for avoiding the worst of the damage if Earth’s atmosphere warms more than 1.5°C above pre-industrial levels.The report shows that we are already fast approaching widespread irreversible damage, the consequences of which include extended droughts, crop failures, more severe storms, flooding and fires, and global economic and human health impacts.

51���� Environment recently sat down with Shindell to learn more about his experience helping draft the IPCC Report, and what its main takeaways are.

Question: Give us an idea of the scope and volume of work that went into preparing the IPCC report.

Answer: Ninety one authors worked for 18 months to write it. We reviewed more than 6,000 studies and discussed and debated nearly every finding in each of them. There were six meetings, most of which lasted at least a week. As co-lead author of one of the report’s five chapters, I also collaborated on a nearly daily basis with the other 12 authors in my chapter, and worked fairly regularly with many of the authors from the other chapters to coordinate what we were doing.

After our draft went out for review, we had to respond in writing to each and every one of the roughly 42,000 comments the report generated, which included thousands of comments on my chapter alone. It was a huge undertaking, involving countless hours of work and lots of late nights and weekends.

Question: In your opinion, what is the report’s main takeaway?

Answer: I think we make it crystal clear that we are essentially out of time. We need to start drastically decarbonizing immediately to stay below the 1.5°C threshold, and even if we start now it’ll be very challenging. We have to phase out fossil fuels, improve land management and reduce emissions of other gases like methane to have any chance of avoiding the damages that occur with warming greater than 1.5°C above pre-industrial levels.

The fact that we already are getting so close to 1.5°C allowed us to draw much stronger conclusions than in prior reports—especially about the speed and type of mitigations needed to stay below that target.

Question: What do we need to do to prevent the worst-case scenario?

Answer: Governments immediately need to commit to not building any more coal-fired power plants, and to phasing out most of the existing ones and replacing them with renewables by 2030. That’s very fast, of course, but we have delayed so long we really can’t wait any longer.

More than half of our electricity worldwide needs to come from renewables by 2030, and we need to cut our use of coal by nearly three-quarters by then. Wealthy countries need to generate a far larger fraction of their electricity from solar, wind and other green sources.

By that same 2030 deadline, we also must switch largely to electric vehicles for transportation, improve energy efficiency in buildings and industry, reduce deforestation, and decrease consumer demand for energy and greenhouse-gas intensive foods, especially cattle products.

Question: Communicating the report’s findings required a delicate balancing act between recognizing the dismal truth, based on the numbers, and still giving people hope. How difficult was that?

Answer: We struggled quite a lot with it. Technically, doing what we need to do to stay below 1.5oC is feasible. Economically, it’s feasible as much of the money needed for the green-energy transition will come from redirecting planned spending on fossil fuels. But politically, it’s not feasible without a big change of values.

There is still a possibility, but it’s hard to see nations, especially ours, stepping up to address this challenge adequately in the nearterm. But I am very hopeful that the action being taken by states, cities, companies and others, along with the progress being made at the national level in some countries, will make a big difference in just how bad things get. That’s my message of optimism—most of the world is moving in the right direction, even if not quickly enough.

Question: The report includes an assessment of the social costs of climate change, giving it broader scope than past IPCC reports. Why did you and your co-authors feel this was necessary?

Answer: We were specifically charged by the nations of the world to report our findings in the context of sustainable development. This was a recognition that there are a lot of other social and environmental challenges that not only interact with climate change but may sometimes be higher priorities.

This broader context allowed us to present strong evidence that carefully designed mitigation policies can lead to enormous benefits for sustainable development and human health, in addition to helping the climate. That dovetails with my own research, which shows that reducing emissions now will prevent millions of premature deaths due to air pollution in coming years. I was particularly pleased that the report used a study from my research group to quantify these dramatic public health benefits.

Showing these large, tangible benefits—which also include lower energy costs over the long term, enhanced biodiversity, enhanced food security and preventing more severe storms and flooding—is very important for helping policymakers see the multiple benefits of cutting emissions, and getting more of the public on board for taking action.