When the G7 committed to a complete phase out of fossil fuels, I was optimistic about the implications. Coal, oil and gas—I suggested—were now operating on borrowed time. Others, however, were less excited. After all, a century-long phase out is hardly ambitious, and would almost certainly push us beyond the Earth's "carbon budget." And these critics make an important point:
A ton of carbon saved now is worth an awful lot more than a ton of carbon saved in 2045.
The fact is that global climate change is not primarily influenced by how much carbon dioxide and other greenhouse gases we emit in any given year, but rather the total amount and composition of greenhouse gases in the atmosphere. While this might sound like wonkish detail, it has very real world implications.
Scientists have mapped out a cost-effective path to 100 percent renewable energy for all US states by 2050. Let's assume, for a moment, that we are 100 percent guaranteed to meet that goal—meaning that US energy supply would be essentially emissions-free by 2050.
This would, of course, be a fantastic achievement—but just how fantastic it was would depend not just on how fast we reach the end goal, but on how fast we got from where we are today to 30 percent, 50 percent and 70 percent too. In other words, we'll have a much greater chance of avoiding catastrophic climate change if we make some of the biggest cuts now. Not only would we build momentum that makes the long-term goal more likely, but by cutting what we can now—getting the low hanging fruit first—we also buy more time to eliminate the hardest-to-eliminate greenhouse gas sources, like aviation emissions, for example.
For a powerful, visual illustration of this phenomenon, take a look at TrillionthTonne's emissions calculator—as our total emissions tick rapidly up, the percent at which we need to slash our emissions each year rises at a disconcerting pace.
So by all means, let's make ambitious long-term emissions reduction goals. But then let's get serious about moving toward those goals. In many ways, ambition is easier than incrementalism, both in terms of our end goal and the path we choose to get us there.