Carbon dioxide is removed from the atmosphere by natural processes at a rate that is roughly half of the current rate of emissions from human activities. Therefore, mitigation efforts that only stabilize global emissions will not reduce atmospheric concentrations of carbon dioxide, but will only limit their rate of increase. The same is true for other long-lived greenhouse gases.

This finding is from chapter 27 of Climate Change Impacts in the United States: The Third National Climate Assessment.

Process for developing key messages: Evaluation of literature by Coordinating Lead Authors

Description of evidence base: The message is a restatement of conclusions derived from the peer-reviewed literature over nearly the past 20 years (see Section 1 of chapter). Publications have documented the long lifetime of CO2 in the atmosphere, resulting in long time lags between action and reduction,4f2b13fe-2d6e-496f-a58e-8fd54225bd86 2e074f83-cc54-4c67-afdf-04484f5c464a a8b2d884-2bfb-4a5a-bfa4-a28bd4d68ca9 and Earth System Models have shown that stabilizing emissions will not immediately stabilize atmospheric concentrations, which will continue to increase.d534bf8b-1ec0-4dad-bf30-041e923780f6

New information and remaining uncertainties: There are several important uncertainties in the current carbon cycle, especially the overall size, location, and dynamics of the land-use sink4f2b13fe-2d6e-496f-a58e-8fd54225bd86 2e074f83-cc54-4c67-afdf-04484f5c464a and technological development and performance. Simulating future atmospheric concentrations of greenhouse gases requires both assumptions about economic activity, stringency of any greenhouse gas emissions control, and availability of technologies, as well as a number of assumptions about how the changing climate system affects both natural and anthropogenic sources.

Assessment of confidence based on evidence: Very High. Observations of changes in the concentrations of greenhouse gases are consistent with our understanding of the broad relationships between emissions and concentrations.

References :

• The Global Carbon Cycle (2e074f83)
• Long-Term Climate Commitments Projected with Climate–Carbon Cycle Models (d534bf8b)
• Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia (a8b2d884)
• Terrestrial ecosystems and the carbon cycle (4f2b13fe)