Earth 2075—CO2 II. Targeting 0°C Global Warming, Ocean pH 8.2, and an Early Return to 280 ppm

In this second paper of CRT’s EARTH 2075—CO2 series, revised emissions targets take into account fossil fuel combustion and cement production trends, global change inertia, and developing countries’ future energy needs. Global CO2 emissions are currently ~10 GtC/yr. A 12 GtC/yr cap is recommended by 2023. A realistic schedule for subsequently reducing emissions is recommended—returning to 10.5 GtC/yr by 2030 and cutting to 6 GtC/yr by 2050, 3 GtC/yr by 2062, and 1 GtC/yr by 2078. Our forecasting model assumes developing countries (DC) would moderately burn fossil fuels through 2062 while today’s industrial nations compensate with high-impact atmospheric carbon capture, plus offsetting emissions reductions of their own—sufficient to cap global emissions by 2023 and enable the above-targeted reductions through 2062. Developing countries would begin or accelerate their emissions cuts in 2063. Our forecasting model projects emissions cap and reduction impact on the accumulated mixing ratio (ppm) for atmospheric CO2. Emissions cuts alone are no longer likely to prevent CO2 from reaching 450 ppm tipping levels. More drastic emergency intervention is required to forestall tipping level crossings and prevent disastrous future consequences, including ≥ 2°C warming accompanied by mega-drought, superstorms, partial polar ice collapse, and abrupt catastrophic sea rise. A new approach involving massively amplified safe capture of atmospheric CO2 at sea is proposed. This paper establishes open-ocean amplified capture targets and forecasts the beneficial impacts of meeting them. Recommended high impact targets for mid-ocean capture and sequestration of atmospheric CO2 include contingency for delays and energy to drive multi-stage (land/sea) amplified capture plus extra contingency to offset feedbacks, outgassing, and permafrost thaw-release, which the model didn’t anticipate. CRT recommends starting multi-stage short-cycle ocean-amplified carbon capture (OACC) in 2019 and ramping it up to net 10 GtC/yr average CO2 capture by 2025 across vast mid-latitude, mid-ocean expanses—far out at sea and well away from coastal waters—plus simultaneously compounding benefits of the 12 GtC/yr 2023 emissions cap and above-targeted post-2023 emissions reductions, culminating in 92 percent reduction by 2078. With the sum of OACC plus natural sinks matching capped emissions by 2023 and substantially exceeding reduced post-2023 emissions, accumulated atmospheric CO2 may be capped at ≤ 425 ppm by 2023 and reduced to 350 ppm by 2050, with an option to restore 280 ppm by 2075 and reduce twenty-first century warming to 0°C. High-impact ocean-amplified carbon capture (OACC) at the rate of 10 GtC/yr could enable DC emissions leniency and still turn 280 ppm atmospheric CO2, ∆T = 0°C, and ocean pH 8.2 into viable twenty-first century targets that can be met approximately 250 years earlier than with emissions reduction alone—if tropospheric aerosol pollution is concurrently reduced.

Fry R., Ison M., Chaudhuri S., Fry S., Klabunde K., Routh M., Fry G., Wroobel B., Hughes S., Hughes J. & Gower G., 2016. Earth 2075—CO2 II. Targeting 0°C Global Warming, Ocean pH 8.2, and an Early Return to 280 ppm. International Journal of Climate Change: Impacts & Responses 9(1):19-39. Article.

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