Natalie Mahowald, professor of earth and atmospheric sciences.

UN climate report author: ambitious actions needed to slow global warming

In March 2017, Natalie Mahowald, professor of earth and atmospheric sciences and the Atkinson Center for a Sustainable Future’s faculty director for the environment, was selected by the United Nations’ Intergovernmental Panel on Climate Change (IPCC) as a lead author on the “Special Report on Global Warming of 1.5 degrees Celsius.”

The final report made international headlines when it was released Oct. 8. Among its key findings: scientific evidence is clear that human activities have caused 1 C of global warming since the late 1800s, and current trends suggest if the planet keeps warming at the same rate global warming will pass 1.5 C around 2040, with disastrous consequences for humans and ecosystems alike. (In Fahrenheit, a change of 1 C is 1.8 F and 1.5 C is 2.7 F.)

In this Q&A, Mahowald discusses her role in the report, its findings and proposed solutions, and the work everyone must do to limit global warming.

How would you describe your role in preparing the IPCC report?

My title is lead author, and I worked on Chapter One: Framing and Context. I was also asked to be an author on the Summary for Policymakers, which is actually line by line approved by governments. I was in South Korea for that process last week.

Ninety-one authors and review editors from 40 countries worked on the report. What does that kind of collaboration look like?

There’s 400 pages for the whole report if you look at it in a Word file. We each have our own section that we’re the lead on. We spent a lot of time talking to each other and making sure we’re reaching consistent assessments of the peer-reviewed literature. We included citations of 6,000 articles, so it’s a huge amount of work. This report was unique in the way it was so cross-disciplinary. That means everyone speaks a slightly different language. And yet we have to make sure we speak consistently across the whole report.

How does involving that many people shape the findings?

In a lot of ways, it’s really a consensus document. This is what we can all agree to. It goes through three rounds of expert reviews, and then the governments review it. That means the results are really in the middle of what the science suggests. They’re not the most alarmist, and they’re not the most skeptical.

How do you see countries working together to address issues raised in the report?

This report is also unique in that the governments called for its creation. It came out of the United Nations Framework Convention on Climate Change. The governments asked us to look at how we could limit global warming to 1.5 C, as well as a 2 C target (or 3.6 F), and what the differences would be. In previous reports, the scientists decided what the questions would be. But I think policymakers are better at figuring out what’s policy-relevant. Now we’ve passed it off to them to decide what to do with it.

Why is 1.5 C significant?

The Paris Agreement had looked at the impacts of reaching 2 C, but there are some countries that are very, very sensitive to temperature and at 2 C probably these countries will be under water. So these countries called for limiting warming to 1.5 C, and the rest of the countries backed them up. Even at 1.5 C, many of these countries will be highly threatened. It’s an existential threat. Many of the Pacific Island states, they’re small, they don’t have a lot of hills or high terrain, and they will be heavily impacted by any increase in temperature.

But there’s a lot of countries, including the United States, that are going to feel the sea-level rise under 1.5 C. A lot of Florida, for example, is extremely susceptible. And pretty much the whole eastern and western seaboards are going to be heavily impacted. Any country that has a coastline, really, will feel a sea-level rise. I can’t think of a place on the planet that won’t be impacted if we move to 1.5 C or 2 C. When the report was requested, we were at about 0.9 C. We are at 1 C right now. So it is possible to limit warming to 1.5 C, but we have to act extremely aggressively to do so.

How drastic are the transitions we need to make?

In some ways they’re incremental, and some are complete transformations. One way to think about it is, “Well, how did the world look 50 years ago? What kind of technology did we use, what kind of transportation, how interconnected was the world?” It was totally different. And in another 50 years it will be totally different. As we build new infrastructure, we’ll need to think about low-carbon emissions. Depending on how successful we are, we’ll still have to adapt to climate change, even if we limit warming to 1.5 C.

What are the critical areas that need to be addressed immediately?

There are a lot of different ways to limit warming to 1.5 C, but we can’t just choose one of these options. It’s much easier to reach a lower temperature target if we change our own behavior, if we conserve energy, if we think about where our food is sourced, if we reduce food waste. In addition, we need to convert to sustainable energy, without a doubt. Luckily there’s all these innovations in wind and solar, and now they’re cheaper than using fossil fuels.

A lot of ways we’re going to reduce our impacts actually help us now. For example, if we switch off of fossil fuels like coal or natural gas and move onto something like wind or solar, air quality will improve.

What technologies and methods are available to remove carbon dioxide from the atmosphere?

There are really easy, inexpensive things that make a ton of sense, like reforesting old forests that were cut down. We can also use agricultural soils to draw down more carbon dioxide, and that makes the land more fertile and enhances biodiversity, too.

In addition, there are new technologies being developed here at Cornell, as well as other places, that can potentially sequester carbon dioxide from the atmosphere to make plastics or new fuels.

Are these technological developments achievable in the given timeline?

Climate change is really a long-term problem, so we need to be moving relatively quickly to transition from dirty energy sources to cleaner, cheaper energy sources, like wind or solar, as well as sustainable agriculture, over the next 10 years. Then in 20 or 30 years, we want to have large-scale deployment of carbon dioxide removal technologies, if we can develop ones that make sense and aren’t environmentally damaging or impact food security. Sooner is better, but we’re not under the gun for all technologies.

What do you say to people who are daunted by the massive amount of change that needs to occur to keep global warming to 1.5 C?

I understand it is a really big problem. Who’s going to solve it? Well, everybody’s going to have to solve it. What an individual can do, and must do, is make individual changes in energy conservation, changes in diet, and think about reducing your impact. In addition, at the city level, the state level, the government level, within businesses, within nonprofits like Cornell, we all have to be thinking about how to reduce our carbon emissions and act in a way that is consistent with our low-carbon goals. We all have to be working together.

Are there any other big takeaways from the report?

I think it is important that some of the new studies within the report show a rise of 0.5 C – which doesn’t sound like very much – actually will be felt by humans and by ecosystems. It makes a statistically significant difference in extreme precipitation, in extreme heat events, in drought occurrences. It matters. We’ve already felt climate change, right now at 1 C, and at 1.5 C we’re going to be able to tell the difference. And between 1.5 C, and 2.0 C, we’ll be able to tell the difference.

It’s also important for people to understand the impacts from climate change only get worse as the temperature rises. So if somebody says to you, “Well, we’re not going to keep global warming to 1.5 C, so let’s just give up,” that’s not the right attitude. The right attitude is we should get as low a temperature as we possibly can, and that will make it much easier for humans and ecosystems to survive.

David Nutt is managing editor of the Atkinson Center.

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