Globally, carbonating cement materials are a large, overlooked and growing sink of CO2, which has offset 43% of the total process CO2 emissions (excluding those from related fossil energy inputs) from production of cement between 1930 and 2013.
Earth system models suggest significant weakening, even potential reversal, of the ocean and land carbon sinks under future negative emission scenarios. Weakening of natural carbon sinks will hinder the effectiveness of negative emissions technologies and therefore increase their required deployment to achieve a given climate stabilisation target.
In recent years, international trade has displaced radiative forcing related to aerosols such as black carbon, sulfate, nitrate and ammonium from developed, net-importing nations like the U.S. to emerging, net-exporting nations like China. We quantify this shift and discuss its policy implications.
Existing technologies, institutions, and behavioral norms together constrain the rate and magnitude of carbon emissions reductions in the coming decades. We review recent research on "carbon lock-in," the implications for decarbonization efforts, and propose a research agenda that can help bridge the gaps between science, knowledge and policy-making.
76 of the 77 (98.7%) scientists we surveyed had not encountered evidence of a secret, large-scale atmospheric spraying program, and said that purported evidence are more easily explained by well-understood physics and chemistry associated with aircraft contrails and atmospheric aerosols.