According to resource specialists IPCC emission scenarios are biased towards exaggerated availability of fossil fuels reserves RCP 4.5 is the most probable baseline scenario (no climate policies) taking into account the exhaustible character of non-renewable fuels. Emissions in RCP 4.5 peak around 2040, then decline. RCP 4.5 is described by the IPCC as an intermediate scenario. Ī 2021 paper suggests that the most plausible projections of cumulative CO 2 emissions (having a 0.1% or 0.3% tolerance with historical accuracy) tend to suggest that RCP 3.4 (3.4 W/m^2, 2.0–2.4 degrees Celsius warming by 2100 according to study) is the most plausible pathway. As well as just providing another option a variant of RCP3.4 includes considerable removal of greenhouse gases from the atmosphere. RCP 3.4 represents an intermediate pathway between the "very stringent" RCP2.6 and less stringent mitigation efforts associated with RCP4.5. RCP 2.6 is likely to keep global temperature rise below 2 ☌ by 2100. For RCP 2.6, those negative emissions would be on average 2 Gigatons of CO 2 per year (GtCO 2/yr). Like all the other RCPs, RCP 2.6 requires negative CO 2 emissions (such as CO 2 absorption by trees). It also requires that methane emissions ( CH 4) go to approximately half the CH 4 levels of 2020, and that sulphur dioxide (SO2) emissions decline to approximately 10% of those of 1980–1990. Īccording to the IPCC, RCP 2.6 requires that carbon dioxide (CO 2) emissions start declining by 2020 and go to zero by 2100. RCP 1.9 is a pathway that limits global warming to below 1.5 ☌, the aspirational goal of the Paris Agreement. The RCP scenarios superseded the Special Report on Emissions Scenarios projections published in 2000 and were based on similar socio-economic models. The four RCPs are consistent with certain socio-economic assumptions but are being substituted with the shared socioeconomic pathways which are anticipated to provide flexible descriptions of possible futures within each RCP. The IPCC studies the carbon cycle separately, predicting higher ocean uptake of carbon corresponding to higher concentration pathways, but land carbon uptake is much more uncertain due to the combined effect of climate change and land use changes. Despite characterizing RCPs in terms of inputs, a key change from the 2007 to the 2014 IPCC report is that the RCPs ignore the carbon cycle by focusing on concentrations of greenhouse gases, not greenhouse gas inputs. The RCPs are consistent with a wide range of possible changes in future anthropogenic (i.e., human) GHG emissions, and aim to represent their atmospheric concentrations. Since AR5 the original pathways are being considered together with Shared Socioeconomic Pathways: as are new RCPs such as RCP1.9, RCP3.4 and RCP7. The RCPs – originally RCP2.6, RCP4.5, RCP6, and RCP8.5 – are labelled after a possible range of radiative forcing values in the year 2100 (2.6, 4.5, 6, and 8.5 W/m 2, respectively). The pathways describe different climate futures, all of which are considered possible depending on the volume of greenhouse gases (GHG) emitted in the years to come. Four pathways were used for climate modeling and research for the IPCC fifth Assessment Report (AR5) in 2014. Projections used in climate change modeling All forcing agents' atmospheric CO 2-equivalent concentrations (in parts-per-million-by-volume (ppmv)) according to the four RCPs used by the fifth IPCC Assessment Report to make predictionsĪ Representative Concentration Pathway ( RCP) is a greenhouse gas concentration (not emissions) trajectory adopted by the IPCC.
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