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Irreversible Does Not Mean Unavoidable

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  • Political Science


Irreversible does not mean unavoidable H. Damon Matthews1 and Susan Solomon2 1 Department of Geography, Planning and Environment, Concordia University [email protected] 2 Department of Earth, Atmospheric and Planetary Sciences, MIT [email protected] CO2 emissions cuts implemented today would affect the rate of future global warming immediately, without any lag from carbon-climate system inertia. There is a commonly held belief among both scientists and the general public that there is a delay between the CO2 emissions we put into the atmosphere, and the resulting climate change. As a consequence, there is a perception that current and near-future climate warming is pre-determined by past CO2 emissions, and by extension, that CO2 emissions reductions implemented now will not have any effect on the future rate of global warming for at least several decades. In this perspective, we argue that this conclusion is based on an incomplete interpretation of the inertia of the climate system. Considering the opposing effects of both physical climate and carbon cycle inertia, there is a compelling argument that the climate response to CO2 emissions cuts would not be delayed by lags in the climate system. Consequently, climate mitigation efforts implemented today would be of immediate importance for future global temperatures. This has important implications for climate policy: the potential for a rapid climate response to prompt CO2 emissions cuts opens the possibility that the climate benefits of emissions reductions would occur on the same timescale as the political decisions themselves. This question of how decreases in CO2 emissions would affect global temperatures has unfortunately been clouded in recent years in part by confusion regarding physical climate issues of ‘unrealized warming’ and irreversibility(1). The notion that there is unrealized warming or ‘warming in the pipeline’(2) if the concentrations of carbon dioxide (and other radiative forcing agents) were to remain fixed at current le

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