Best Effort Global Warming Trajectories

This is a "what if" tool for global warming policy makers. The policy contains just two parameters: the approximate number of (transition) years needed by the world to firmly decrease its annual carbon emissions, and the maximum annual emission reduction effort after that time, expressed in terms of Pacala–Socolow "wedges". Here "effort" is the additional emission reduction effort after all increases of future energy demands have already been stabilzed by carbon-free technologies. (So the Pacala–Socolow seven-wedge strategy is an immediate strategy of zero transitions/zero wedges for the next 50 years).
The purple curve is the world's annual carbon emission rate, the blue curve is the trajectory, and the black dashed line is the popular "doubling" target ceiling. All three curves share the same ordinate. The unit GtC stands for billions of metric tons of carbon.


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The world carbon cycle model is based on the one-tank model of Socolow–Lam: , where is time (years) offset from the start of the 21st century, is carbon in atmospheric in GtC (divide by 2.1 to get ppmv, parts per million by volume), is the annual emission rate (GtC/yr), and τ is CO2 atmospheric resident time. The value of is constrained to be always larger than times the number of wedges ("wedge" as defined by Pacala–Socolow), and the maximum effort is reached after t is larger than "transition years" (the approximate number of years needed by the world to make firmly negative). For more information, see [1]. For the Socolow–Lam paper, see [2].
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