Some people argue against strong action on climate change with the following reasoning. “Whatever we do in this country makes no difference because China produces more than that in a week”. This line of thought is mistaken. There are two ways of thinking about the damage from CO2 emissions:
- Cumulative Damage: The damage from CO2 emissions is cumulative such that the costs of CO2 increases with additional CO2 emissions.
- Passing Thresholds: The damage from CO2 emissions stems from the risk that we pass tipping points, such as the melting of the Greenland ice sheet, or the burning of the Amazon rainforest.
On the Cumulative Damage view, the fact that China emits a lot more than the UK doesn’t matter for the question of whether the UK causes damage by emitting CO2. Regardless of whether China emits or not, the UK’s emissions still cause damage. When one thinks about small amounts of emissions, such as one person might produce, the cumulative damage view may look counterintuitive. But it is not really. If my personal emissions cause millions of people to die 0.000000001 second earlier, this amount of time spread across millions of people can be substantial and amount to years of life lost.
On the Passing Thresholds view, the UK’s emissions might not in fact cause us to pass a dangerous threshold, and so might not in fact do damage. However, we are uncertain about when we will pass climate thresholds. We don’t know what amount of emissions could cause the permafrost to melt, or the Greenland ice sheet to melt, or the Amazon to burn. If passing a threshold has some cost X, then the expected cost of our emissions is given by the probability that our emissions cause us to pass that threshold pc*X. So, on the Passing Thresholds view, our emissions do impose expected costs on society. It’s irrelevant that Chinese people are collectively pushing us much closer to the threshold than my personal emissions.