To meet the lower emissions scenario (B1) used in this assessment, global mitigation actions would need to limit global carbon dioxide emissions to a peak of around 44 billion tons per year within the next 25 years and decline thereafter. In 2011, global emissions were around 34 billion tons, and have been rising by about 0.9 billion tons per year for the past decade. Therefore, the world is on a path to exceed 44 billion tons per year within a decade.

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: A large number of emissions scenarios have been modeled, with a number of publications showing what would be required to limit CO2f15c9312-9b5a-412f-837d-d119e39407a6 bfd356e4-1e09-47b2-b618-218f59c7d5d3 6ac1aea5-6b76-46e1-822e-664cb3d11e9a d6ca431b-0c90-40e6-bb8d-47e5e293198a to any predetermined limit. At current concentrations and rate of rise, the emissions of CO2 would need to peak around 44 billion tons within the next 25 years in order to stabilize concentrations as in the B1 scenario. Given the rate of increase in recent years,da606b84-6d9a-4d7c-9bc0-73a22c1fca43 7b0489fe-3bdf-4744-ae47-f0e48d53a7d2 this limit is expected to be surpassed.49c48c84-0b97-49cd-a28e-70edc9cbda24

New information and remaining uncertainties: Uncertainties about the carbon cycle could affect these calculations, but the largest uncertainties are the assumptions made about the strength and cost of greenhouse gas emissions policies.

Assessment of confidence based on evidence: The confidence in the conclusion is high. This is a contingent conclusion, though – we do not have high confidence that the current emission rate will be sustained. However, we do have high confidence that if we do choose to limit concentrations as in the B1 scenario, emissions will need to peak soon and then decline.

References :

• SAP 2.1A. Scenarios of Greenhouse Gas Emissions and Atmospheric Concentrations (6ac1aea5)
• The representative concentration pathways: an overview (d6ca431b)
• Ten Years of Advancing Knowledge on the Global Carbon Cycle and its Management (da606b84)
• webpage Carbon Budget 2012: An Annual Update of the Global Carbon Budget and Trends (7b0489fe)
• RCP4.5: a pathway for stabilization of radiative forcing by 2100 (bfd356e4)
• International Energy Outlook 2011 (49c48c84)
• The next generation of scenarios for climate change research and assessment (f15c9312)