The Equator Principles
June 5, 2022Environmentally Sound Management Principles
June 15, 2022
The Intergovernmental Panel on Climate Change (IPCC) published the 5th assessment report in 2014 which assesses projections of changes in the climate system using a hierarchy of climate models ranging from simple models, to intermediate and to complex comprehensive models. These models simulate changes based on a set of scenarios of anthropogenic forcing. The most recent set of scenarios from the Representative Concentration Pathways (RCPs) was used for the new climate model simulation carried out under the framework of the Coupled Model Inter-Comparison Project Phase 5 (CMIP5) of the world climate research programme regional downscaling methods. These provide climate information at smaller scales which are needed for many climate impacts studies such as the East African region including Uganda and Tanzania.
The RCPs describe four different 21st century pathways of greenhouse gas (GHG) emissions and atmospheric concentrations (see Van Vuuren et al, (2011)). The RCPs have been developed using Integrated Assessment Models (IAMs) as input to a wide range of climate model simulations to project their consequences for the climate system. Four RCPs were selected and defined by their total radiative forcing (cumulative measure of human emissions of GHGs from all sources expressed in watts per square meter) pathway and level by 2100 (note that these pathways are defined in terms of the concentration. The RCPs were chosen to represent a broad range of climate outcomes, based on a literature review, and are neither forecasts nor policy recommendations. The RCPs include a stringent mitigation scenario (RCP 2.6), two intermediate scenarios (RCP 4.5 and RCP 6.0) and one scenario with very high GHG emissions (RCP 8.5).
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RCP 8.5 – refers to the concentration of carbon that delivers global warming at an average of 8.5 watts per square meter (W/m2) across the planet in 2100. This is regarded as the high-emissions scenario, consistent with a future with no policy changes to reduce emissions and characterized by increasing GHG emissions that lead to high atmospheric GHG concentrations. It is aligned broadly with a Current Policies or Business-As-Usual Scenario.
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RCP 6.0 – refers to the concentration of carbon that delivers global warming at an average of 6.0 watts per square meter (W/m2) across the planet. This is a high-to-intermediate emissions scenario where GHG emissions peak at around 2060 - 2080 and then decline through the rest of the century.
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RCP 4.5 – refers to the concentration of carbon that delivers global warming at an average of 4.5 watts per square meter (W/m2) across the planet. This is an intermediate-emissions scenario, consistent with a future with relatively ambitious emissions reductions and GHG emissions increasing slightly before starting to decline around 2040 - 2060. Despite such relatively ambitious emissions reduction actions, RCP4.5 falls short of the 2°C limit/1.5°C aim agreed on in the Paris Agreement. It is aligned broadly with the GHG emissions profile that would result from implementation of the 2015 NDCs (out to 2030), followed rapidly by peaking and then reduction of global emissions by 50% by 2080.
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RCP 2.6 – peak in radiative forcing at ~ 3 W/m2 before 2100 and decline. This is representative of a scenario that aims to keep global warming likely below 2°C above pre-industrial temperatures (in line with the Paris Agreement’s stated 2°C limit/1.5°C aim). This RCP is consistent with ambitious reduction of GHG emissions, which would peak around 2020, then decline on a linear path and become net negative before 2100.[1]
While each single RCP is based on an internally consistent set of socioeconomic assumptions, the four RCPs together cannot be treated as a set with consistent internal socioeconomic logic. For example, RCP 8.5 cannot be used as a no-climate-policy socioeconomic reference scenario for the other RCPs because RCP 8.5’s socioeconomic, technology, and biophysical assumptions differ from those of the other RCPs.
the RCP 8.5 carbon emissions pathway is the most appropriate for conducting assessments of climate change impacts by 2050, as it is the closest approximation of both historical emissions and anticipated outcomes of current global climate policies, tracking within 1% of actual emissions. RCP 8.5 is also the best match out to mid-century under current and stated policies with still highly plausible levels of CO2 emissions in 2100.
This assertion is consistent with the TFCD (2017), which states that “for organizations wishing to understand their stressed exposure to plausible physical climate change risks in the time frame from now until mid-century, what is likely to be most helpful is to consider scenarios consistent with RCP 8.5 (which most closely reflects a business-as-usual pathway consistent with failure to properly implement NDCs)”.
