“It’s warming. It’s us. We’re sure. It’s bad. We can fix it.” Those were the words that Kimberly Nicholas, an associate professor of sustainability science at Lund University in Sweden, wrote on a poster she brought to her first climate change protest in that country in 2014. These words also echo throughout her new book Under the Sky We Make: How to be Human in a Warming World (G. P. Putnam’s Sons, 2021). Like many scientists, Nicholas had not thought of herself as an activist, and marching made her feel vulnerable. Then she read an article that made her think, “What if this was the thing that made the difference?”

Tipping points are a theme of the book. They include big climate domino effects, such as the collapse of the Amazon rain forest or the melting of the Greenland ice sheet. They also include social milestones—such as when Swedish teenagers started calling out celebrities for taking unnecessary flights after opera singer Malena Ernman, also known as climate activist Greta Thunberg’s mother, resolved to stop flying completely. Nicholas examines her own uncomfortable feelings and how she has used them to fuel her science, activism and personal carbon emissions goals. She has honed her philosophies through many conversations with friends who are dealing with their own moral dilemmas, such as whether to have a child (a carbon-intense prospect). She also lays out the five stages of radical climate acceptance—ignorance, avoidance, doom, all the feels and purpose—and gives advice about how readers can navigate each.

Scientific American spoke with Nicholas to explore that advice and how she came to use it herself.

[An edited transcript of the interview follows.]

A lot of your book focused on grief. Why did you feel you needed to cover that before you moved onto positive actions people can take?

It is natural and right to grieve when something we care about is harmed or lost. The facts alone do not automatically implement themselves into policies and behavior change. That has been helpful to me in being able to tolerate the difficulties of the current moment and all the overwhelming feelings of how far we are from a stable climate.

In your book, you lay out the five stages of radical climate acceptance: ignorance, avoidance, doom, all the feels and purpose. What would you say to people who are stuck in the avoidance or doom phases?

I’ve been there, and it sucks. So you have my sympathy. I think avoidance in particular is the worst, because not facing something takes so much energy.

I built my career, and even part of my identity, around frequent flying. I knew that flying was by far the worst thing that I was doing for the climate. I just avoided that fact until I couldn’t anymore. And then, over beers with my friend Charlie at a climate conference, I finally faced my frequent flying. Charlie had already stopped flying within Europe, so I asked him a lot of questions. I was not ready to entirely stay on the ground and give up flying, because I felt like it meant I would never see my family [in California] again. But I was able to do a lot more than I thought. Once I established a clear principle I chose to follow (I don’t fly within Europe), I actually felt relief. It led to the adventure of our transcontinental wedding by train across North America, which was such a wonderful celebration of quality time with people we love and of adventurous slow travel. Having those conversations and being able to face these uncomfortable feelings was the secret for me.

Why did you spend so much of your book focused on what individuals can do to decrease their carbon footprint even though we will ultimately require massive policy changes to get to zero emissions?

I wrote the book for friends. I wanted to make this connection between our own individual lives and the choices that we make every day: what we buy and how we travel and where we live. There’s a huge gap between trivializing individual action and putting all the burden of change only on individuals. There’s also a risk to glorifying only systemic action. We need both.

I had the privilege to be in the room when the Paris agreement was adopted, and I’ve been a part of policy processes. They’re necessary; they’re important. But they’re not sufficient to move 10 times faster on emissions reduction. We can’t have just top-down policies. We need citizens to be educated and understand what’s required of this moment. That’s the only way that citizens will support bold actions from politicians. And people will lead the way by showing that it’s possible to have a great life and very quickly reduce emissions. That’s the niche I’m trying to fill.

What are some of the differences in approach to climate change you noticed when you moved from California to Sweden? What ideas should the U.S. be replicating?

It’s much easier to get out of bed in the morning as a scientist in a place that has acknowledged biophysical reality. We can’t underestimate how much burnout scientists in the U.S. experience when they feel like they’re swimming upstream because of the 10 percent of Americans who don’t believe the fact that humans are warming the climate. This group is loud and influential, a lot of them are sitting in Congress, and one was previously in the White House. That makes a huge difference to what we can imagine as possible.

In Sweden, we have a climate goal to reduce emissions by 85 percent by 2045. We’re not anywhere near meeting it. The last time I checked, the only countries that were on track to limit warming to 1.5 degrees [Celsius] were Gambia and Morocco—quite small countries and historically low emitters. The major emitters need to get our butts in gear and actually start reducing about 10 times faster than we were pre-pandemic.

Decarbonizing the energy system is a critical first step. Sweden has been doing that for quite a while, which enables other changes that help keep fossil fuels in the ground. The next challenge for us here in Sweden is decarbonizing transport. That’s harder than decarbonizing energy because that also means planning cities so you don’t need a car. We need 15-minute neighborhoods—like in Paris, where you can have all your arts, culture, health, education, green space and everything else you need within walking or biking distance from your house.

What is the best future you can imagine for humanity?

Climate change is a huge problem, and we’re very far behind where we need to be. But I really believe that change can happen really fast. The novel New York 2140, by Kim Stanley Robinson, takes place after catastrophic climate change. Most of New York City is underwater, and people are bumbling along and making life happen anyway. In describing the book, Robinson basically said: “Oh, you know, once it was too late to avoid catastrophic warming, we got off those dirty, dangerous fuels really quickly. And it wasn’t that hard.” They reached a social tipping point.

That social tipping point is not a consensus. Research has shown that it only takes about 25 percent of people. We’re getting close to that, but it’s nail-biting because the alternative is these terrible climate and ecological tipping points that we definitely don’t want. So much hinges on this decade. The best future I can imagine for humanity is: we actually have cut emissions in half or more by 2030. Because that’s what’s necessary to leave open all the wonderful possibilities that we want.