2015 年 10 巻 2 号 p. JTST0022
Global warming is one of the most serious problems faced by humans. One method to decrease the Earth's temperature is to reduce solar irradiation by dispersing nanoparticles in the atmosphere. Submicron-diameter particles or aerosols scatter solar irradiation, whereas they are transparent to long-wavelength infrared radiation emitted by the Earth. This phenomenon has received attention in the discussions of the nuclear winter, which is an uncontrolled cooling of the global temperature. The objective of the present work is to examine the first-order approximation of the feasibility of controlling the global temperature without reducing the emission of greenhouse gases. We propose the controlled dispersion of nanoparticles into the stratosphere at an altitude of 30 km. A precise analysis of the radiative properties of particles in the solar spectrum and IR regions is conducted, and radiative transfer through the stratosphere-dispersed nanoparticles is approximated using a one-dimensional single-scattering model. Several types of nanoparticles are considered. The optimum size of the nanoparticles determined using the model is 350-450 nm. The dispersion of nanoparticles with a total mass of 3×107 tons into the stratosphere will reduce 3% of the solar irradiation. The blockage can be maintained by launching 10-ton projectiles 19 times per day from 100 launch sites.
