Carbon emission limits required to satisfy future representative concentration pathways of greenhouse gases

Abstract

[1] The response of the second-generation Canadian earth system model (CanESM2) to historical and future natural and anthropogenic forcing is assessed using the newly-developed representative concentration pathways (RCPs) of greenhouse gases (GHGs) and aerosols. Allowable emissions required to achieve the future atmospheric CO 2 concentration pathways, are reported for the RCP 2.6, 4.5 and 8.5 scenarios. For the historical 1850-2005 period, cumulative land plus ocean carbon uptake and, consequently, cumulative diagnosed emissions compare well with observation-based estimates. The simulated historical carbon uptake is somewhat weaker for the ocean and stronger for the land relative to their observation-based estimates. The simulated historical warming of 0.9°C compares well with the observation-based estimate of 0.76 ± 0.19°C. The RCP 2.6, 4.5 and 8.5 scenarios respectively yield warmings of 1.4, 2.3, and 4.9°C and cumulative diagnosed fossil fuel emissions of 182, 643 and 1617 Pg C over the 2006-2100 period. The simulated warming of 2.3°C over the 1850-2100 period in the RCP 2.6 scenario, with the lowest concentration of GHGs, is slightly larger than the 2°C warming target set to avoid dangerous climate change by the 2009 UN Copenhagen Accord. The results of this study suggest that limiting warming to roughly 2°C by the end of this century is unlikely since it requires an immediate ramp down of emissions followed by ongoing carbon sequestration in the second half of this century.

Dependence of Present and Future European Temperature Extremes on the Location of Atmospheric Blocking

“…For further information on the CanESM2 model and the construction of the 50‐member large ensemble, see Arora et al. (2011) and Fyfe et al (2017). …”

Interactions between land use change and carbon cycle feedbacks

“…Most analyses of the climate-carbon feedback have been undertaken using idealized Earth system simulations without land use change [Arora et al, 2011;Friedlingstein et al, 2006Friedlingstein et al, , 2003]. Yet both the climate-carbon feedback and LULCC are simultaneously evolving, raising questions about which set of mechanisms has a larger impact on the terrestrial carbon budget as well as possible interactions.…”

“…Compatible fossil fuel emissions are calculated for each future scenario by allowing for a given atmospheric CO 2 concentration pathway (here the RCP8.5) and the ocean and land carbon fluxes calculated from CESM [e.g., Arora et al, 2011]. Following previous studies [Arora et al, 2013;Friedlingstein et al, 2003], we calculate the gain in the carbon-climate system using the differences between compatible fossil fuel emissions calculated in the simulations with CO 2 and other constituents impacting the climate (E coupled ) and with no anthropogenic impact on the climate (E no anthro ):…”

Evaluation of CMIP5 models over the northern North Atlantic in the context of forthcoming paleoclimatic reconstructions

“…Land surface interactions are parameterized using a soil-canopy model (Kowalczyk et al 1994). As described in detail in Arora et al (2011), CanESM2 evolved from the first generation CanESM1. It is composed of atmosphere, ocean, sea ice and carbon cycle models.…”