Over a cold beer at a conference in Vienna, I decided to stop flying so much. I was talking to Charlie, a friend with wild hair and even wilder ideas. He was describing his adventurous 15-hour train trip from his home northeast of London. I confessed I’d taken a boring flight from Copenhagen in under 2 hours.

“How do you make your life work without flying?” I asked.

“I decided to stop flying within Europe. It’s doable,” he replied.

Something clicked. I could do that too.

As a climate change scientist, I knew full well that each time I took a long plane trip, I was unleashing the equivalent of up to three tons of carbon dioxide into the atmosphere. I knew that this was more than I should be emitting in a whole year by 2050 if I want to do my share to meet global climate targets and avoid the worst impacts of dangerous climate change.

So I knew I was contributing to a ticking carbon bomb in the atmosphere that will change life as we know it. If humans don’t immediately start bending the emissions curve towards zero, my own research, for example, shows that climate change could devastate wheat yields in Australia and stress the wine industry in my home state of California.

Long-distance train travel is much more efficient than flying. Credit: Loco Steve Flickr (CC BY-SA 2.0)  

Leaning on the brass bar talking to Charlie, I felt it was time to face some uncomfortable truths about my personal contribution to this global problem.  

And I know I’m not alone. About half of global emissions from household consumption come from just 10 percent of the population, mostly in the developed world- a category that included me, and at least half of the residents of countries like Germany, the UK, and the US.

For years, friends and colleagues, students and cocktail-party acquaintances have asked me what they could do about climate change. Which personal choices would make the biggest difference?

I struggled to answer, overwhelmed by analysis paralysis and caveats.

But my colleague Seth Wynes and I have just published a study in Environmental Research Letters that provides some answers, focused on the power of personal actions that can make the biggest difference for the climate. We compiled 39 sources and put them in terms of their full life-cycle climate impact each year.

We found that individuals living in developed countries can take four fundamental steps that can significantly shrink their personal contribution to climate change. They are:

Step 1: Consider a plant-based diet

We found that switching to a meat-free diet for a year would cut the equivalent of 0.8 metric tons of carbon dioxide (CO2e)—about four times more effective for the climate than comprehensively recycling for a year. That savings is thanks to cutting methane emissions from livestock, as well as the greater efficiency of eating plants directly, rather than first feeding plants to animals. And because producing meat (especially beef) requires so much land, water, and other resources, eating plants is an enormous win for the environment overall. Research shows it’s also a win for health, reducing the incidence of Type II diabetes and some cancers.

 A plant-based diet reduces your personal carbon footprint. Credit: Toby Oxborrow Flickr (CC BY-SA 2.0)

Step 2: Travel overland

Finding ways to fly less can deliver a big win for the climate. Our study shows that skipping one transatlantic flight (say, a round trip from London to New York) saves an average of 1.6 tons of CO2e (and avoiding one long-haul plane trip, like London to Tokyo, can save nearly twice that). Consider that most people on Earth have never flown in an airplane, and most Americans probably didn’t fly in the last year. For frequent flyers, flying less is the first place to look to save tons of carbon.

Step 3: Live car-free

Finding a way to live car-free also produced big climate benefits in our analysis. Each year without a car saves 2.4 tons of CO2e—11 times more than recycling. Electric cars running on electricity grids today still produce about half the climate pollution of a gasoline car, and still require parking lots and highways. Going car-free is also a big benefit to your wallet, and can reduce obesity.

Step 4: Consider the next generation

Having a child is an enormous decision in every respect—personally, professionally, financially. Our research shows it is also by far the most crucial choice we make in terms of the climate. When accounting for the cumulative impact of future descendants at current emission rates, each additional child in a developed country represents a carbon legacy of  a stunning 58.6 tons per year. Put simply, in countries with high emissions rates, adding more people adds a lot more carbon to the atmosphere—and their children will add more still. This means that decarbonizing society overall could hugely reduce the climate impact of an additional child—making it up to 17 times less.

Credit: Amanda Montañez
Source: “The Climate Mitigation Gap: Education and Government Recommendations Miss the Most Effective Individual Actions,” by Seth Wynes and Kimberly Nicholas, in Environmental Research Letters, Vol. 12; July 12, 2017

Enabling kids to grow up in a safe climate is a huge incentive to reduce overall national emissions to sustainable levels, and has motivated some parents to reduce their household emissions as well. Meanwhile, recognizing that family size affects the climate can be one factor informing a complex and highly personal decision.

In my own life, I’m trying to take these findings to heart—and so far, the choices I’ve made have improved my quality of life.

After a long and confusing flirtation with eating less meat, four years ago I accepted a friend’s challenge to go vegan for a month. We cooked meals together and swapped recipes. It was surprisingly easy and fun. After that month, I returned to including cheese and eggs in my diet, but I haven’t missed the meat. I’ve seen benefits to both my health and grocery bills.

I’ve moved to the center of my small city and sold both (!) my cars, saving me thousands of dollars each year. Now, instead of hectic days where I would spend up to four hours commuting by car, often eating two meals behind the wheel, I bike to work and have time to cook tasty dinners at home with my fiancé (and we have romantic overland trips for holidays).

Since that beer with Charlie, I’ve let my elite air miles card expire, and reduced my flights by 80 percent. I now do the vast majority of my work travel by rail. Reducing my number of trips and focusing on quality instead of quantity has made me reconsider the value of my time and given me greater work-life balance. I save most of my flights to visit my family on the other side of the world, and even then, I’ve looked for ways to fly less, including incorporating a beautiful train trip across a snowy North America as part of a Christmas visit home.

Finally, my fiancé and I are still discussing what feels right for us on the question of starting a family. Obviously there are so many more factors at play beyond carbon in this huge life decision. But since we care so much about climate change, it’s one more reason we’re considering very carefully.

For me, turning my scientific knowledge into action was a little like falling in love. It was a switch that got flipped, and everything that has happened since has felt like puzzle pieces falling into place. It took setting a bold goal, over a beer, with a friend, to set me on the path. I still have further to go. But the journey has been a reminder that each one of us can contribute to tackling the climate challenge—and now we know where to start.

Kimberly Nicholas previously wrote Climate Change Will Alter the Taste of Wine for Scientific American