Beyond CO₂: How Ozone Is Heating the Planet Faster Than We Realize
The other greenhouse gas driving us beyond 3°C
A new paper, led by William J. Collins (University of Reading) and Fiona M. O’Connor (Met Office Hadley Centre), brings together an international team of scientists to look closely at ozone’s role in climate change. While most of the public conversation focuses on carbon dioxide, their findings show that ozone deserves more attention than it gets.
Ozone exists in two very different places in the atmosphere. Near the ground, tropospheric ozone is a pollutant, formed when sunlight reacts with methane and nitrogen oxides from cars, industry, and farming. High up in the stratosphere, ozone forms a protective shield that blocks harmful ultraviolet radiation.
Decades ago, global agreements phased out ozone-destroying chemicals like CFCs. That “saved” the ozone layer, but Collins and O’Connor show that the recovery of stratospheric ozone has a negative side: because ozone is a greenhouse gas, the recovery itself contributes to global warming. At the same time, human activity is driving up tropospheric ozone, which also heats the planet.
How Much Warming Are We Talking About?
Between now and 2050, ozone changes are expected to add roughly 0.2–0.25 °C of additional warming. That estimate is relative to today’s climate (not since pre-industrial times, but from about 2020 onward).
For comparison, rising carbon dioxide alone is projected to add about 0.5–0.7 °C over the same three decades in the IPCC’s central scenarios, and up to around 0.8–1.0 °C in its worst-case, high-emissions pathways. In other words, ozone won’t surpass CO₂, but it could deliver about a third to a half as much warming as CO₂ by mid-century. That makes it the second most important driver of near-term warming, ahead of methane and nitrous oxide.
Based on my observations, humanity has already warmed the planet by close to 1.5 °C compared with the pre-industrial era. By 2050, if current trends hold, we’re more likely to approach around 3.0 °C of total warming.
In high-emissions scenarios, the world could push well above 3 °C by 2050.
In those cases, ozone’s extra quarter-degree shoves the temperature change toward the upper end of the range. It is an overlooked accelerant.
The lesson here is not that we should regret fixing the ozone hole. Without that, we’d be facing other serious problems. But it does show how solving one environmental crisis can worsen another. The recovery of stratospheric ozone is now locked in, and continued growth in methane and other ozone-forming emissions only makes the problem worse. This is important because as the world considers so-called "solutions" to climate change (geoengineering, carbon capture, both of which so far are bullshit ) we should expect unintended consequences to emerge.
Read the full research report:
