Cooling Without Darkening — The Clear Shade: A Quantitative Note on PAR-Preserving, Near-Infrared-Selective Solar Radiation Management

Abstract

Most solar-radiation-management proposals are spectrally broad: they dim the light photosynthesis uses along with the light that merely heats. This note quantifies the alternative. For an illustrative 2.6 W/m² forcing offset, rejecting 2.1–2.3 percent of the 700–2500 nm near-infrared band alone delivers the required ~1.1 percent insolation trim with zero direct reduction of photosynthetically active radiation — the ideal filter leaves the visible sky untouched by construction. The note positions itself as an engineering-side companion to Seeley, Lutsko and Keith (2021), who demonstrated in idealized simulation that near-infrared-weighted shading preserves both temperature and rainfall; it credits the Angel (2006) and Szapudi (2023) sunshade lineage it would fly on, prices the radiation-pressure dividend of a transparent film, bounds the residual biology at order 0.1 K of leaf temperature, and states a falsifiable benchtop coupon specification. Every headline number is generated by the attached reference script, which self-checks against the Stefan–Boltzmann law before printing. Drafted and twice adversarially reviewed by independent AI referees; every accepted correction, and every declined one, is recorded on the page. Emission reduction remains primary; no deployment case is made.