Current climate change models predict warming due to the greenhouse effect caused by increasingly large amounts of CO2 in the atmosphere, partly offset by cooling related to the presence of particles. CO2 and particles are both emitted as a result of human activity. However, the scale of this cooling effect has not been characterized with sufficient precision. As a result, there is uncertainty over the calculation of radiative forcing and the effect that human activity has on the climate. Because of this, it is difficult to obtain an empirical value for climate sensitivity based on available climate observations.
A study carried out by Norwegian, British and French researchers (LMD – CNRS-UPMC-ENS-École Polytechnique and LSCE – CEA-CNRS-UVSQ) , published online on February 23 in Nature Geoscience, shows that within the next 20 years the influence of CO2 on global warming will dominate radiative forcing.
"In the next few decades, we expect a reduction in aerosol concentrations in the atmosphere," explained Olivier Boucher, researcher at the CNRS Dynamic Meteorology Laboratory (LMD). "Their contribution to overall climate change will therefore decrease. This, in turn, will imply less uncertainty regarding the disruptive impact of human activity on the climate."
"In addition, the amount of CO2 emitted will continue to increase; we understand a great deal more about the effect of CO2 on the climate than we do about the effect of aerosols and other agents, such as ozone or surface albedo," explained François-Marie Bréon, researcher at the CEA Laboratory of Climate and Environmental Sciences (LSCE). "It is another factor that allows us to envisage more accurate quantification of the overall impact of human activity on the climate in the decades to come."
This will make climate sensitivity calculations much more precise, thus reducing the uncertainty of Transient Climate Response estimates by 50% by 2030, even without factoring in any improvement in scientific understanding of the climate.