A new study says 2 degrees Celsius warming may be unavoidable by 2100. When it comes to modeling climate change, researchers rely on the specification of plausible emissions scenarios to explore how climate will change over the coming century.
Using a standardized set of carbon dioxide and other greenhouse gas scenarios allows researchers from different modeling centers to compare results and allows more methodical assessment of uncertainty in the Intergovernmental Panel on Climate Change (IPCC) reports.
The set of emissions scenarios used in the past two IPCC reports were published in 2001 and need to be updated to take into account more recent socioeconomic modeling results.
In a new study, Arora et al. use a completely new set of scenarios, referred to as representative concentration pathways (RCPs). These will form the basis for new climate projections to be assessed in the IPCC’s Fifth Assessment Report (due out in 2014).
Using an upgraded Earth system model—which takes into account carbon dioxide and other greenhouse gases, aerosols, land use change, and the flow of carbon between the atmosphere and the underlying ocean and land surface—the researchers are able to calculate the carbon dioxide emissions compatible with each RCP and, in particular, the emissions reductions required to meet certain levels of global warming.
The authors find that even under the lowest concentration scenario, global average temperature increases exceed the 2 degrees Celsius (3.6 degrees Fahrenheit) limit agreed to by various governments in the Copenhagen accord. The researchers note that limiting warming to 2 degrees Celsius by 2100 will require global carbon dioxide emissions to be reduced to zero over the next 50 years, followed by measures to actively remove carbon dioxide from the atmosphere before the end of the century.
Source: Geophysical Research Letters, (GRL) paper 10.1029/2010GL046270, 2011
Title: "Carbon emission limits required to satisfy future representative concentration pathways of greenhouse gases"
Authors: V. K. Arora, J. F. Scinocca, G. J. Boer, G. M. Flato, V. V. Kharin, W. G. Lee, and W. J. Merryfield: Canadian Centre for Climate Modelling and Analysis, Environment Canada, University of Victoria, Victoria, British Columbia, Canada;
J. R. Christian: Canadian Centre for Climate Modelling and Analysis, Environment Canada, University of Victoria, Victoria, British Columbia, Canada and Fisheries; and Oceans Canada, Institute of Ocean Sciences, Sidney, British Columbia, Canada;
K. L. Denman: Canadian Centre for Climate Modelling and Analysis, Environment Canada, University of Victoria, Victoria, British Columbia, Canada; and VENUS, University of Victoria, Victoria, British Columbia, Canada.