FEASIBILITY OF MIRROR ARRAYS TO ENHANCE EARTH’S ALBEDO

Earth’s climate-driven temperature increase has reduced ice extent, exposing lower albedo surfaces and initiating positive feedback in Earth’s energy budget and additional warming. We explore the potential for globally distributed arrays of mirrors to influence and reduce Earth’s energy budget by greatly enhancing albedo. This research specifically aims to quantify the ground cooling effect created by mirrors and determine the most effective placement of mirrors and for which land compositions.

To compare ground temperature cooling efficiencies, we monitored 10 cm-soil-depth temperatures for five plots in Plymouth, NH (43.78, -71.75), including a control plot (no mirrors), and plots with 6%, 11%, 16% and 29% mirror coverage, using 16 Type 105-EL thermocouple probes/plot, daisy-chained Temp120 Granite thermocouple modules and a CR1000X logger. We collected 10-minute-interval readings for these plots from Aug-Dec 2022. Soil temperatures in mirrored plots were significantly lower than the control plot, and this effect increased in daytime. The lowest mean soil temperature is at the 11% plot (16.0℃), 2.1 ℃ cooler than the control plot. The 6% is 17.1℃, 16% is 17.6℃, 29% is 16.8℃.

We also examine the intensity of within plot cooling by comparing the temperature of each center-most sensor to those at each plot’s perimeter. Surprisingly, the 6% plot has the greatest center-perimeter differential (1.0 ℃); otherwise, the differential decreases as mirror coverage increases. Overall, we find that the mirrors decrease ground temperature, but, for this latitude and season, the effect varies with soil moisture and peripheral shading by trees on a sub-hectare scale.

The ARCGIS National Land Cover Database (NLCD) provides information for assessing suitable mirror locations for developed land cover types in regions with similar latitude: open space, barren land, grassland, and hay. We compare the potential for mirror coverage in New Hampshire (NH) and South Dakota (SD). This area in NH, when normalized to the size of SD, is 6054 mi² while SD is 37,471 mi², largely because NH is more forested and mountainous. In conclusion, while flat grassland regions are most suitable for mirrors aimed at climate mitigation, even placement of a few mirrors in open fields of forested regions can significantly change ground temperatures.