Time Left to Critical Feedback/Loops: Annual Solar Geoengineering-PLUS, Pathways Towards Planetary Self-Cooling - Preprint

[Geoengineering News]

https://www.researchgate.net/profile/Alec-Feinberg/publication/392529593_Time_Left_to_Critical_FeedbackLoops_Annual_Solar_Geoengineering-PLUS_Pathways_Towards_Planetary_Self-Cooling/links/691e47b919b35058639b4e10/Time-Left-to-Critical-Feedback-Loops-Annual-Solar-Geoengineering-PLUS-Pathways-Towards-Planetary-Self-Cooling.pdf

Authors: Alec Feinberg

Abstract 

Global warming (GW) contributions from feedback and feedback loops are projected to increase from~ 54%(loops: 29%) in 2024 to~ 75%(loops: 56%) under faltering RCP pathways without Solar Geoengineering (SG). These projections indicate that meeting CO₂ reduction targets may be increasingly challenging. A critical threshold, RCPCritical, defined as the point where feedback loops contribute over 50% of GW, is projected between 2075 and 2125. Beyond this threshold, the potential for tipping points may make reversing GW trends overly difficult. Based on this timeframe, an average mitigation difficulty rate (MDR) of 1.33% per year is approximated, indicating that by 2100, the SRM area required to offset annual warming will reach roughly 100% of today’s baseline, potentially approaching an unsustained-mitigation threshold (USMT) in 75 years if anticipated potential tipping points are active. Current feedback levels may already be driving nonlinear warming trends. These estimates are supported by three key data points: a no-feedback baseline from 1870, an estimated equilibrium climate sensitivity (ECS) range of 3.1 C–4.3 C (potentially reached by 2082), and trends consistent with IPCC AR6 confidence range. In response, Annual Solar Geoengineering-PLUS pathways (ASG+ Ps) are proposed as supplemental measures, including Earth Brightening, Arctic Stratospheric Aerosol Injection (SAI), and feasible L1 sunshade systems, to reduce feedback amplification and extend mitigation timelines.

Source: ResearchGate