CO2dubbling

CO2 doubling refers to the scenario in which atmospheric carbon dioxide concentration increases from pre-industrial levels of about 280 parts per million (ppm) to roughly 560 ppm. It is a standard benchmark in climate science used to study the sensitivity of the climate system to greenhouse gas forcing and to compare potential future changes.

A doubling of CO2 is associated with a radiative forcing of about 3.7 W/m², after accounting for well-mashed physics of the greenhouse effect. In climate models, this forcing tends to produce an equilibrium global mean surface warming in the range of about 1.5 to 4.5°C, with a commonly cited best estimate near 3°C. The exact amount depends on various feedbacks, including water vapor, clouds, ice albedo, and changes in natural emissions and sinks.

Current atmospheric CO2 is higher than pre-industrial levels but well below 560 ppm. As of the early 2020s, concentrations are around 410–420 ppm, about 1.5 times pre-industrial. Under mid- to high-emission scenarios, CO2 could reach 560 ppm within several decades to a couple of centuries, while strong mitigation could delay or prevent reaching that exact level.

Impacts associated with CO2 doubling include stronger global warming, shifts in precipitation patterns, more intense heat waves and extreme weather, sea-level rise, and ongoing ocean acidification. Ecosystems, agriculture, water resources, and infrastructure would face broader and longer-lasting stresses, though regional effects would vary.

The 2xCO2 scenario remains a central, simplified reference point in climate research, used to illustrate potential climate responses and guide policy discussions about emissions reductions and adaptation.