The study stressed that engineering approaches would only have a limited impact, and that efforts should continue to be focused on reducing CO2 emissions.

“(Governments) should make increased efforts toward mitigating and adapting to climate change and in particular agreeing to global emissions reductions of at least 50% on 1990 levels by 2050 and more thereafter,” the authors wrote.

But, they continued, there should be “further research and development” into geo-engineering options “to investigate whether low-risk methods can be made available if it becomes necessary to reduce the rate of warming this century”.

Injecting sea salt into the clouds could cool the planetOf the two basic geo-engineering approaches, the report concluded that those involving the removal of carbon dioxide were preferable, as they effectively return the climate system closer to its pre-industrial state.

But the authors found that many of these options were currently too expensive to implement widely.

This included “carbon capture and storage” methods, which require CO2 be captured directly from power plants and stored under the Earth’s surface.
Current proposed methods also work very slowly, taking many decades to remove enough carbon dioxide to significantly reduce the rate of temperature rise.

Of the carbon removal techniques assessed, three were considered to have most potential:
1. CO2 capture from ambient air: This would be the preferred method, as it effectively reverses the cause of climate change.
2. Enhanced weathering: This aims to enhance natural reactions of CO2 from the air with rocks and minerals. It was identified as a prospective longer-term option.
3. Land use and afforestation: The report found that land-use management could and should play a small but significant role in reducing the growth of atmospheric CO2 concentrations.

Read more about it here.