Representative Concentration Pathways (RCPs)

Representative Concentration Pathways (RCPs) are the latest approach to determining emission scenarios, outlining greenhouse gas concentrations that impact future climate modeling and research.

About Representative Concentration Pathways (RCPs):

• RCPs is the latest approach to determining emission scenarios.
• They outline concentrations of greenhouse gases that, by the year 2100, will lead to a specified increase in total radiative forcing compared to pre-industrial levels.
• They are a set of four greenhouse gas concentration trajectories used for climate modeling and research.
• They are used to capture assumptions within a set of scenarios, and the conditions of each scenario are used to model possible future climate evolution.
• They try to capture future trends, such as whether humans will continue to burn fossil fuels at an ever-increasing rate, or will they shift towards renewable energy.
• Four pathways: RCP8. 5, RCP6, RCP4. 5 and RCP2. 6 – the last is also referred to as RCP3-PD.
• The numbers represent the expected change in radiative forcing from the year 1750 to 2100.
  • For instance, RCP4.5 indicates an expected increase of 4.5 watts per square meter of radiative forcing between 1750 and 2100.
• The Intergovernmental Panel on Climate Change (IPCC) considers 1750 as the base year as it predates the Industrial Revolution and the radiative forcing was quite stable.
• A higher value of forcing means more concentration of greenhouse gases and other pollutants, which in turn, means higher global warming and a more pronounced impact of climate change.
• Scientists determined forcings and pathways by relying on the existing literature and synthesizing values from a broad spectrum of scientific and socioeconomic data.
  • This included factors such as population growth, GDP, air pollution, land use, and energy sources.
• RCPs are not forecasts or policy recommendations; rather, they are utilized to depict a wide range of potential climate outcomes.
• Policy makers can use RCPs to plan for the type of future they hope to help create.

What are the different RCP warming levels?

RCP2.6:

• It anticipates an additional radiative forcing of only 2.6 watts per square meter by the conclusion of the 21st Century.
• This represents the best-case scenario where greenhouse gas concentrations are significantly lowered, and stringent mitigation measures are implemented.
• RCP2.6 is also known as RCP3PD as emissions peak around 2050 and then decline.
• As a result, the global average temperature would increase by 1.6 degree Celsius compared to pre-industrial levels.

RCP4.5 and RCP6

• RCP4.5 and RCP6 represent intermediate scenarios.
• In RCP4.5, the global average temperature is projected to increase by 2.4 degrees Celsius, while in RCP6, it rises to 2.8 degrees Celsius above pre-industrial levels.

RCP8.5:

• The most severe scenario is RCP8.5, characterized by greenhouse gas and pollutant concentrations three times higher than the present.
• In this scenario, the temperature is projected to increase by 4.3 degrees Celsius by the year 2100.

What are emission scenarios?

• Emission scenarios are pathways that tell us about emissions of greenhouse gases and aerosol due to human activities over time.
• Scientists use these scenarios to feed into climate models, which then calculate things like future global temperatures or sea levels.

What is total radiative forcing?

• Total radiative forcing is the difference between the energy entering and leaving the Earth’s atmosphere.
• Presently, due to elevated levels of greenhouse gases and aerosols, more energy is entering the planet than leaving, contributing to global warming.
• Radiative forcing is quantified in watts per square meter.

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