New information about the link between atmospheric CO₂ and eventual global average warming bolsters the case for climate policy now
Read the full Risky Climate column at Bloomberg Green.
Is climate change scary because of “black swans”—the low-probability, high-impact tail risks that are, by definition, unlikely? Or is it about what’s well known, already quantified, and very likely to happen unless the world slams on the emissions brakes? And does the difference matter?
Headlines are typically driven by extremes: droughts, floods, fires, tropical cyclones, temperature records, and other nightmares both real today and projected to happen in the near and not-so-near future. It’s easy to see these headlines and want to appear “rational” by countering the “emotional” climate “alarmism.”
That reasoning has two fundamental flaws. First, even the most middle-of-the-road predictions of what’s likely in store are bad enough, pointing to the very real need to cut CO₂ emissions yesterday. Second, the low-probability, high-impact tail risks make action now even more desirable. Uncertainty is not our friend.
Last week saw the publication of a crucial new assessment on one of the most basic of climate science questions: the link between CO₂ in the atmosphere and eventual global average warming. For over 40 years, the answer to the question of how much temperatures increase when atmospheric CO₂ doubles has been a “likely” range of 1.5 to 4.5°C. The definition of what “likely” means has changed over the years. The range itself has barely budged, and not for a lack of trying.
This new assessment narrows the “likely” range to 2.6 to 3.9°C.
Good news, bad news. It’s good news because climate change just became significantly more predictable. After all, it’s the uncertainty itself that’s costly.
Continue reading at Bloomberg Green.