The amount of sunlight that is reflected back into space is called the Earth’s albedo. This has some important implications for Earth’s climate.
A new paper published by the American Geophysical Union (AGU) finds, surprisingly, that the albedo of the northern and southern hemispheres is about equal even though the northern hemisphere is dominated by land and the southern hemisphere by ocean. There appears to be a “buffering effect” or a stabilizing feedback between atmosphere/ocean circulations, clouds and radiation. Climate models do not include this stabilizing feedback. This paper implies that cloud cover is a major forcing in controlling global temperature.
The full paper can be read at http://webster.eas.gatech.edu/Papers/albedo2015.pdf
Here is the abstract:
The fraction of the incoming solar energy scattered by Earth back to space is referred to as the planetary albedo. This reflected energy is a fundamental component of the Earth’s energy balance, and the processes that govern its magnitude, distribution, and variability shape Earth’s climate and climate change. We review our understanding of Earth’s albedo as it has progressed to the current time and provide a global perspective of our understanding of the processes that define it. Joint analyses of surface solar flux data that are a complicated mix of measurements and model calculations with top-of-atmosphere (TOA) flux measurements from current orbiting satellites yield a number of surprising results including (i) the Northern and Southern Hemispheres (NH, SH) reflect the same amount of sunlight within ~ 0.2Wm2. This symmetry is achieved by increased reflection from SH clouds offsetting precisely the greater reflection from the NH land masses. (ii) The albedo of Earth appears to be highly buffered on hemispheric and global scales as highlighted by both the hemispheric symmetry and a remarkably small interannual variability of reflected solar flux (~0.2% of the annual mean flux). We show how clouds provide the necessary degrees of freedom to modulate the Earth’s albedo setting the hemispheric symmetry. We also show that current climate models lack this same degree of hemispheric symmetry and regulation by clouds. The relevance of this hemispheric symmetry to the heat transport across the equator is discussed.
In their conclusion, the authors emphasize that “the cloudiness of the planet is the principal regulatory agent that maintains this symmetry with the increased energy reflected from SH clouds precisely balancing the larger reflections from NH land masses.”
The findings in this new paper corroborate previous research by Dr. Roy Spencer who shows small changes in cloud cover can have profound effects on global temperature and completely overwhelm any effects from carbon dioxide (See here, here, and here).
One other caveat about predicting future climate:
“In climate research and modeling, we should recognize that we are dealing with a coupled non-linear chaotic system, and therefore that the prediction of a specific future climate state is not possible.” — Final chapter, TAR 2000 (Third Assessment Report), IPCC (Intergovernmental Panel on Climate Change).