The University of Arizona

Happy Halloween 7 Billion!

November 4, 2011
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How many of you noticed that the Earth’s human population hit seven billion on October 31, 2011? On Halloween - just a coincidence. We don’t really know the exact moment that we hit seven billion, but that’s the day we estimated that the Earth finally hit that mark. A good site to track population (and more) is the Worldometers site (http://www.worldometers.info/world-population/).

The Earth at Night on November 27, 2000. Photo from NASA (apod.nasa.gov/apod/ap001127.html)

Seven billion! When I was born over 50 years ago, there still weren’t even three billion people on Earth. We’ve more than doubled in my lifetime. Amazing! Any reason for concern?

Sure there should be reason for concern, but how much? When I talk to groups around the globe about climate change, there’s always a good chance that someone will ask about human population growth and isn’t that the problem we have to solve? Until recently, I never thought about it hard enough to say more than: yes, of course, the more people, the more fossil fuel burned, the more greenhouse gases emitted, the more climate change we’ll get. But, I’ve also liked to note that the real problem isn’t just population growth, it’s growth in per capita consumption. Everyone around the world wants to live like Americans, and I’m not sure the world can handle that without some innovation.

I decided that it would be good to get on top of the population issue; what I learned is both encouraging and discouraging.

First, the 20th century was probably the last century that will have a doubling (let alone a tripling) of population. Population growth is actually slowing as demographers said it would mainly because as societies (countries) become more developed, their population growth (excepting perhaps due to immigration) just about always goes down for well-understood reasons. Second, population is going to level off at 9 or 10 billion. It could go up more than that, but the demographers are pretty good at predicting this and based on their performance so far, I’m pretty confident that it’ll end up around 9 or 10 billion.

Third, developed countries consume much more energy per person than developing countries. That’s not good since more and more developed countries mean more and more fossil fuel burned, more pollution and more climate change. But, it turns out that the amount of energy needed for a unit of economic growth – termed “energy intensity” – is going down in the most developed countries like the U.S. And even better, the amount of carbon emitted per unit of economic growth – termed “carbon intensity” – is also going down in more developed countries.

Urban sprawl, Clark County, Nevada. Photo by Lynn Betts, Natural Resources Conservation Service, 2000. (photogallery.nrcs.usda.gov/Index.asp)

Therein lies the solution to sustaining 9-10 billion people on Earth, all striving to become more wealthy and bigger consumers. Think about it – this giant population of consumers is what will drive economic growth, lots of it. We don’t want to kill it, so we will need ways to drive energy and carbon intensity down, down, down, and to export that technology all over the planet. Sounds like lots of jobs and wealth to me, going to the countries that lead the market for low-carbon energy and efficiency technologies.

What am I talking about? Technologies that reduce our energy and carbon intensity are those that promote energy efficiency and low-carbon energy: solar energy, wind energy, ocean energy, geothermal energy, bioenergy, advanced nuclear perhaps. Many of the needed technologies are proven, and the prospects of 9-10 billion people all consuming more and more energy means the market for these technologies is becoming more of a sure bet. Add in the costs of climate change, air pollution, oil spills, huge exports of money for oil, wars to maintain the flow of oil, and the bet gets even better.

China and Europe are both placing money on this bet – big money. They are developing the low-carbon technologies that will drive the economic engine of the 21st century. These countries are investing heavily both in the private and public sectors. In America, the situation is more uncertain. If we place too many bets on fossil fuels, we could get our clocks cleaned when the world makes the inevitable decision to leave carbon-based fuels behind.

Nine to ten billion people are what make this inevitable.