Decoupling is the idea that environmental impact per unit of economic growth is declining. If it were to decline fast enough, in theory, it would be possible for growth the continue indefinitely at the same time absolute impact is declining. This article tries to measure the rate this may or may not be happening, and concludes the long term trend is not even close to being on a path where we could turn the corner and see absolute impact stabilize, let alone decline.

While globally, CO2 emissions per unit of GDP are declining, the decoupling rate from 1995 to 2018 was only -1.8 percent annually. To achieve net zero by 2050, the rate would have to accelerate to -8.7 percent, assuming population and GDP growth projections as given, or by a factor of almost five.

Bruegel.org

This seems about right to me. The idea that we need to choose between “growth” and sustainability in the long term, of course, is logically flawed. If impacts continue to grow, there will come a point where the system breaks and human welfare is no longer able to increase.

There are a few flaws in the decoupling argument. “Growth”, as usually measured by GDP, is a measure of gross economic activity, which includes both benefits and costs to humanity. So in comparing impacts (costs) to GDP (sum of benefits and costs), you have an equation with too many unknowns, unless you can come up with some agreed-upon reasonable measure of costs. If you can do that, you would simply subtract costs from benefits to get net benefits, and figure out whether those are growing or not. They may or may not be growing right now. Even if they are, you need to consider whether they can continue to grow in the future, or whether the underlying system is eventually going to break and no longer be able to support further growth. You also need to consider risks of really bad things happening, as well as the odds of really good things like major technological breakthroughs happening. I would also point out that at the moment we are using carbon emissions as a proxy for sustainability more generally, but there is a lot more that should be considered in a holistic view of a sustainable long-term human-planet system.