Page 17 - 全球气候变化及其影响Global Climate Change and Its Impacts-185×260

Chapter 1 Scientific Basis of Global Climate Change

Solar Cycle. During this period, the enhancement or weakening of magnetic field activity on
the solar surface leads to corresponding changes in solar radiation levels.
Research indicates that minor fluctuations in solar radiation intensity can trigger chain
reactions within Earth’s climate system. For instance, during solar maximum periods, Total
Solar Irradiance (TSI) may increase by about 0.1%. This seemingly insignificant variation
can sufficiently alter Earth’s energy balance, thereby affecting key climate factors such as
atmospheric circulation patterns, cloud distribution, and ocean temperatures. Additionally,
changes in ultraviolet radiation significantly influence stratospheric ozone concentration,
which further modifies atmospheric heating processes and consequently exerts indirect ef-
fects on climate.
In addition to the 11-year sunspot cycle, evidence suggests the existence of longer-term
solar activity variations, such as the approximately 200-year De Vries cycle and the 87-year
Gleissbergcycle (Gleissberg cycle). These long-term cycles are believed to be associated
with significant climatic events in Earth’s history. For instance, during the Little Ice Age
from the late 17th to early 18th century, solar activity was exceptionally low in a period
known as the Maunder Minimum, when sunspots nearly disappeared and Europe and North
America experienced unusually cold winters. Although solar radiation variations were not
the sole cause, they did contribute to intensifying the climatic cooling trend during that peri-
od to some extent.
It is noteworthy that although solar radiation variability is one of the important natural
driving factors for climate change, its influence is relatively small and gradual, insufficient
to explain the rapid warming phenomenon observed over the past few centuries. The current
global warming is primarily caused by greenhouse gas emissions from human activities.
However, studying solar radiation variability remains an indispensable part of understand-
ing the full picture of the climate system. It helps identify natural variability across different
timescales and provides foundational data support for developing more accurate climate
models.

II. Impact of Volcanic Activity

Volcanic activity, as a significant form of energy release from Earth’s interior, has long
been considered one of the natural drivers influencing global climate. Volcanic eruptions not
only release massive amounts of magma and volcanic ash but also emit substantial quantities
of particulate matter and gases into the atmosphere. These materials exert notable short-term
impacts on atmospheric composition and surface temperatures. The climatic influence of vol-
canic activity primarily manifests through its alteration of atmospheric components and the
resulting climatic effects.
The alteration of atmospheric composition by particulate matter and gases released
during volcanic eruptions is the primary pathway through which volcanic activity influences
climate. When a volcano erupts, vast amounts of volcanic ash and sulfide particles are eject-

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