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Chapter 1 Scientific Basis of Global Climate Change

Chapter 1 Scientific Basis of Global Climate
Change

Section 1 Components and Functions of the Climate
System

I. Earth’s Energy Balance

Earth’s energy balance is one of the central concepts in the climate system, describing
how the planet maintains its thermal equilibrium through the absorption and reflection of
solar radiation. Solar radiation serves as the primary energy source for Earth, with an inten-
sity of approximately 1361 watts per square meter outside the atmosphere. However, due to
Earth’s rotation and revolution, significant variations exist in solar radiation received across
different regions. This energy balance is primarily achieved through two processes: absorp-
tion and reflection.
The Earth’s surface and atmosphere absorb most solar radiation, particularly visible and
near-infrared radiation. Surface absorption occurs mainly over land and oceans, with oceans
storing substantial heat due to their immense heat capacity. Atmospheric gases like carbon
dioxide, water vapor, and methane regulate Earth’s temperature by absorbing both solar ra-
diation and long-wave radiation emitted from the surface. This absorption process maintains
temperatures within ranges suitable for sustaining life in both the Earth’s surface and atmo-
sphere.
Earth regulates its energy balance by reflecting a portion of solar radiation. This reflec-
tion primarily occurs through clouds, ice/snow-covered regions, and aerosol particles in the
atmosphere. Clouds serve as the primary contributors to Earth’s solar radiation reflection,
with their reflectivity (cloud albedo) depending on cloud type, thickness, and coverage. Ice/
snow-covered areas like polar regions and high mountains exhibit high reflectivity (known
as albedo), significantly reducing solar radiation absorption and lowering local temperatures.
Aerosol particles in the atmosphere, such as dust and sulfate, also reflect partial solar radia-
tion, influencing Earth’s energy balance.
Earth’s energy balance is not only influenced by solar radiation but also regulated by
internal geothermal heat. The planet’s internal heat primarily originates from radioactive
element decay in the crust and mantle, as well as residual heat from planetary formation.
This internal heat is released to the surface through volcanic activity, geothermal heat flow,
and tectonic plate movements, exerting a certain degree of impact on Earth’s climate sys-
tem. However, compared to solar radiation, the contribution of Earth’s internal heat remains
relatively minor. Nevertheless, under specific circumstances such as volcanic eruptions, its

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