Optimal Sunshade Configurations for Space-Based Geoengineering near the Sun-Earth L1 Point.

Joan-Pau Sánchez,Colin R Mcinnes,Franck Marchis

doi:10.1371/journal.pone.0136648

Joan-Pau Sánchez, Colin R Mcinnes + Show 1 more

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https://doi.org/10.1371/journal.pone.0136648

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Journal: PloS one	Publication Date: Aug 26, 2015
Citations: 20	License type: CC BY 4.0

Affiliation: University of Glasgow

Abstract

Within the context of anthropogenic climate change, but also considering the Earth’s natural climate variability, this paper explores the speculative possibility of large-scale active control of the Earth’s radiative forcing. In particular, the paper revisits the concept of deploying a large sunshade or occulting disk at a static position near the Sun-Earth L1 Lagrange equilibrium point. Among the solar radiation management methods that have been proposed thus far, space-based concepts are generally seen as the least timely, albeit also as one of the most efficient. Large occulting structures could potentially offset all of the global mean temperature increase due to greenhouse gas emissions. This paper investigates optimal configurations of orbiting occulting disks that not only offset a global temperature increase, but also mitigate regional differences such as latitudinal and seasonal difference of monthly mean temperature. A globally resolved energy balance model is used to provide insights into the coupling between the motion of the occulting disks and the Earth’s climate. This allows us to revise previous studies, but also, for the first time, to search for families of orbits that improve the efficiency of occulting disks at offsetting climate change on both global and regional scales. Although natural orbits exist near the L1 equilibrium point, their period does not match that required for geoengineering purposes, thus forced orbits were designed that require small changes to the disk attitude in order to control its motion. Finally, configurations of two occulting disks are presented which provide the same shading area as previously published studies, but achieve reductions of residual latitudinal and seasonal temperature changes.

Highlights

With the increasing recognition that climate change is happening, together with seemingly weak efforts to sufficiently reduce greenhouse gas (GHG) emissions to avoid dangerous climate change [1], a number of methods that seek to counteract the adverse climatic effects of GHG emissions have been proposed and investigated [2]
Later work [19], on the other hand, has shown that particular spatio-temporal shading patterns may potentially suppress some of these regional effects, such as warming at high latitudes, changes in tropical rain patterns or ice cover changes. Motivated by this prior work, this paper is aimed at investigating the possibility of designing new configurations of orbiting sunshades with the potential of containing the increase in global mean temperature, and residual regional anthropogenic climate change
It is clearly understood that by placing the occulting disk in-line with the Sun and the Earth, the maximum amount of shade is cast onto the Earth

Summary

Introduction

With the increasing recognition that climate change is happening, together with seemingly weak efforts to sufficiently reduce greenhouse gas (GHG) emissions to avoid dangerous climate change [1], a number of methods that seek to counteract the adverse climatic effects of GHG emissions have been proposed and investigated [2]. Research into these alternatives to PLOS ONE | DOI:10.1371/journal.pone.0136648. These deliberate interventions in the Earth’s climate system are generally known as geoengineering [4]

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