— Ch. 1 · The Reflective Shield —
Ice–albedo feedback.
~5 min read · Ch. 1 of 6
Ice reflects far more solar energy back into space than open water or any other land cover. This simple physical property drives a powerful climate change feedback loop on Earth and potentially on exoplanets. When higher temperatures decrease ice-covered area, the planet exposes more open water or land. The albedo decreases, so more solar energy is absorbed. This leads to more warming and greater loss of the reflective parts of the cryosphere. Conversely, cooler temperatures increase ice cover, which increases albedo and results in greater cooling. This makes further ice formation more likely. Since higher latitudes have the coolest temperatures, they are the most likely to have perennial snow cover. Widespread glaciers and ice caps can form up to and including potential ice sheets. Thus, ice-albedo feedback plays a powerful role in global climate change.
Energy Budget Models
In the 1950s, early climatologists such as Syukuro Manabe began making attempts to describe the role of ice cover in Earth's energy budget. By 1969, both USSR's Mikhail Ivanovich Budyko and the United States' William D. Sellers published papers presenting some of the first energy-balance climate models. These models demonstrated that the reflectivity of ice had a substantial impact on the Earth's climate. Changes to snow-ice cover in either direction could act as a powerful feedback. This process was soon recognized as a crucial part of climate modelling in a 1974 review. In 1975, the general circulation model used by Manabe and Richard T. Wetherald incorporated what it described as "snow cover feedback". Calculations of the feedback are also applied to paleoclimate studies, such as those of the Pleistocene period from roughly 2.6 million years ago to about 10 thousand years ago. Ice-albedo feedback continues to be included in subsequent models today.