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Will the global atmospheric CO₂ concentration be in line with the pathway to limit warming to 2.0°C by mid-century, over the 2024 to 2027 period?

A Representative Concentration Pathway (RCP) is a greenhouse gas concentration trajectory adopted by the IPCC for its fifth Assessment Report (AR5) in 2014. These four pathways are prominently considered in IPPC climate modelling and research, which describe different climate futures, all of which are considered possible depending on how much greenhouse gases are emitted in the years to come.

The Representative Concentration Pathway (RCP) 8.5 corresponds to a high greenhouse gas emissions pathway compared to the scenario literature (IPCC 2008). The RCP8.5 is a so-called ‘baseline’ scenario that does not include any specific climate mitigation target. It combines assumptions about high population and relatively slow income growth with modest rates of technological change and energy intensity improvements, leading in the long term to high energy demand and GHG emissions in absence of climate change policies.

Pathway RCP4.5 limits mid-century (2046–2065) global mean temperature increase to 2.0°C with a likely range of 1.4°C to 2.6°C (95% confidence interval). Moreover, it limits end-of-century (2081–2100) global mean temperature increase to 3.7°C with a likely range of 2.6°C to 4.8°C (95% confidence interval) (IPPC, 2013).

Over the 2022 to 2025 period (inclusive), the RCP8.5 corresponds to an average of 426.63 parts-per-million (ppm) of global CO₂ atmospheric concentration per year (Meinshausen et al. 2011). Over the 2027 to 2030 period, it corresponds to and average of 440.01 ppm of global CO₂ atmospheric concentration per year (ibid.).

Will the average global CO₂ atmospheric concentration be less than 433.19 ppm over the 2024 to 2027 period (inclusive)?


This question resolves positively if the arithmetic mean of the annual mean CO₂ concentration over the 2024 to 2027 period (inclusive) is less than or equal to 433.19 ppm, as reported by Earth System Research Laboratory.



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