Sometimes it takes a different perspective to grasp how the world is changing. Taking a birds-eye view (literally, from an airplane) over Tokyo, Sao Paulo, Mexico City, and New York City reveals some of the ways both the population is growing and evolving and how clean energy is (and isn’t) spreading. For example, giant warehouses and distribution centers congregate around most airports in the world. They have big, flat, ugly roofs staring up at the sun all day. In many cities, the last five-plus years have witnessed a rapid shift in what those roofs look like. Some are now covered in dirt (green roofs that can control temperatures inside very effectively), and a growing number are covered in more processed dirt — i.e., silicon in the form of solar photovoltaics. New York area and Tokyo seem to be making terrific progress here, while Sao Paulo and Mexico City are lagging.



Japan, Kanto Region, Tokyo Prefecture. JTB Photo/UIG/Getty Images

Over the course of a couple of weeks, I had the unique pleasure of flying into four of the most populated cities* in the world: Tokyo, Sao Paulo, Mexico City, and New York City. The metropolitan area of each of these mega-cities is home to more than 20 million people.

Besides realizing that my carbon footprint for this year would be particularly horrendous, two things occurred to me from my perch in the sky: 1) there are a lot of people out there and 2) you can get a sense of how well a region is embracing clean energy by just looking at rooftops.

People are everywhere. It’s obvious, but worth noticing periodically: there are a lot of people on the planet now. Like, a lot. Many of us know this intellectually, but we rarely feel it in our bones or contemplate the ramifications enough. And many believe that we humans are small relative to such a large planet — so, they ask, how could we possibly change the climate or overfish the vast oceans? But we’re not small anymore — not at all.

Now recognize that 2 billion more people will move to cities over the next generation. At the same time the global middle class will swell by about the same number. These 2 billion better-off humans will demand more energy, food, water, a TV, an air conditioner, lots of clothing, perhaps a car, and they’ll want to fly around on business and vacations. The draw on our shared resources is incredibly hard to picture, but we must try.

It’s at this point when we run into a problem. We humans are not good at understanding large numbers – it’s an identifiable “cognitive gap.” Grappling with a number like 7.5 billion — the number of us on the planet right now — is very, very hard.

So aside from literally flying over cities, I’ve created a mental exercise to help us envision this many people. Picture a large football stadium of 87,000 people. That’s more than two Fenway Parks. It’s a Yankee Stadium and a half. It’s bigger than MetLife Stadium, where the New York Giants play, and a bit smaller than London’s Wembley Stadium. Ok, now imagine all 87,000 people walking out of the stadium and spreading out over an unimaginably big parking lot — one with enough room that each person can enter a new stadium with 87,000 more people. Those 87,000 stadiums, each filled with 87,000 people, would hold all 7.5 billion of us.



Wembley Stadium, London, 1985. Photo by Dave Hogan/Hulton Archive/Getty Images

If you can even remotely imagine this, is it easier to see how we could overextend the limits of what even a planet as abundant as Earth can handle? Possibly.

This many people are of course a boon to business — lots of new customers and employees. But business does not escape the ramifications of the scale of the human enterprise, which brings incredible stress on the natural systems that feed (figuratively and literally) our human economy. In fact, business will be critical to finding the solutions to providing a quality of life for 9 or 10 billion people, all while enabling the planet to, you know, function.

We’ll need a new kind of economy, a circular one that radically reduces our draw on natural resources and, in particular, is powered by clean energy. Flying above many of these giant cities, I was able to see that new economy emerging.

The clean economy on the roof. One of the core solutions to our climate problem is moving to renewable energy. Looking down at cities from above gives you an interesting perspective on how we’re doing. You can see vast wind farms along ridgelines, of course, but I use one shorthand metric to gauge progress: how covered are the rooftops? (This quick measure of the clean economy is of course superficial, but it’s in the spirit of indicators like the so-called “Waffle House” metric: the U.S. Federal Emergency Management Agency (FEMA) looks at how fast these chain restaurants open after a natural disaster to gauge how well the area is recovering.)

Giant warehouses and distribution centers congregate around most airports in the world. They have big, flat, ugly roofs staring up at the sun all day. In many cities, the last five-plus years have witnessed a rapid shift in what those roofs look like. Some are now covered in dirt (green roofs that can control temperatures inside very effectively), and a growing number are covered in more processed dirt — i.e., silicon in the form of solar photovoltaics.



Sept 28, 2017, from high above Newark Liberty International Airport. Photo by Andrew Winston

By my little rule of thumb, I’d say the New York area and Tokyo are making terrific progress, while Sao Paulo and Mexico City are lagging. I took some pictures of my landing in Newark, New Jersey, and it was impressive (though it’s interesting to note the dichotomy of the huge solar arrays on the buildings on the right with the refinery tanks next door.)

It would be easy to write this off as just a developing vs. developed world situation, and that’s certainly part of it. But it’s as much about regional politics as anything. The difference in policy support for renewable energy, even between U.S. states, is vast. (I’ve also flown into Phoenix recently, and most giant rooftops are empty. It’s painful to see that lost opportunity to harvest roughly 300 days of sunshine per year.) So, it’s no surprise that different countries manage the issue differently. To get more context, I spoke to a friend who manages clean energy investments for a multinational in Sao Paulo. Apparently, unlike nearly everywhere else in the world, the cost of renewable energy is actually rising there. The problem, he said, is largely one of financing. The country’s corruption and budgetary woes are causing the financing options to shift from the government to private sector, and the latter isn’t providing as many guarantees or terms that are as favorable. That’s why I didn’t see many solar roofs at all.

At any rate, there’s no way to easily encapsulate the mix of financing, policy, and market demand that yields a robust market for clean energy — and certainly not from a snapshot from the sky. But given the growth of the global population and our ever-rising demand on natural resources, we better see more change in cities and landscapes soon. The sight of wind farms and solar fields near and in cities will have to keep rising. And if (or, better yet, when) it does, everyone looking down on that growth should feel better about how humanity manages its challenges.

* The definition of “most” and “city” in this phrase is surprisingly fluid. The Wikipedia page on the largest cities in the world uses three different definitions: City proper (population within administrative boundaries), Metropolitan area (the city and its main suburbs), and urban area (some more fuzzy boundary based on population density). By urban area, Tokyo, Sao Paulo, New York, and Mexico City are #1, #2, #6, and #11 in the world. By metro area, they’re #2, #9, #11 and #12. They’re all a bit further down the list for city proper. Perusing these lists is eye-opening. Guangzhou, China is the largest metro area with 44 million people!