Two
competing theories for global warming and its effect on Earth’s changing
climate persist today. The first theory suggests that the driver for global
warming is the increasing amount of greenhouse gases dumped into the atmosphere
as a result of humanity’s burning of fossil fuels. The second theory posits
that the solar wind and its associated magnetic field alters the Earth’s cloud
cover and adjusts the atmosphere’s water vapor content, which leads to the
steady temperature rise known as global warming.
The
latter theory involves a stream of plasma, or high-energy charged particles,
propelled from the sun’s upper atmosphere. This stream of electrons and protons
escapes the gravitational pull of the sun and creates the solar wind. It varies
in speed from 190 to 500 mi. (306 to 805 km) per second and passes by Earth as
the sun rotates in space. The solar wind affects Earth’s magnetic field and, in
turn, is believed to have a major effect on climate change.
Opponents
to the greenhouse gas theory of global warming argue that increasing radiation
activity from the sun over the past 300 years has been the primary culprit—not
an increase of atmospheric carbon dioxide. Researchers believe that because the
doubling of the sun’s magnetic flux recorded in the 20th century had led to
increased sunspot activity as it follows its periodic 11-year cycle, the
ferocity of the solar wind and the overall brightness of the sun also
increased.
Proponents
of global warming who subscribe to increasing carbon dioxide emissions as the
cause of the problem avoid citing work done by NASA’s Goddard Institute for
Space Studies (GISS) or other scientific evidence offering credence to the
solar wind theory. Just like the greenhouse gas theory, the GISS climate model is
used to show that changes in the solar wind throughout the ages have varied
surface warming.
Climate
researchers determined that the sun has played a role in modulating the
atmosphere’s moisture content and its circulatory patterns, causing droughts in
ancient times. Backing up these computer-generated data are a number of natural
records that correlate with the model’s projections. Lake sediment analysis,
fire records, and tree-ring measurements from locations such as the Yucatan
Peninsula, Mexico, and Peru, illustrate that periods of drought occurred during
times of heightened solar output.
Increasing
solar wind produces more ozone in Earth’s upper atmosphere by breaking up
oxygen molecules
and heating the atmosphere. As a consequence, the circulation of the atmosphere
is affected right down to the surface, which in general warms and reinforces
existing rainfall patterns. Wet regions receive more rain, and dry the warmer
air temperature pulls more moisture out of the soil. Droughts become more
intense.
Although
such facts are rarely disputed, the scope of the influence of solar wind is
hotly debated. Some researchers state that the current period of global warming
cannot be caused by the changes in solar output alone. Other researchers
suggest that a double effect is in play, in which a more vigorous solar wind
increases the global temperature, which in turn causes the oceans to warm, as
made evident by melting sea ice.
Because
warm water absorbs less carbon dioxide, more of that greenhouse gas remains in
the atmosphere. The debate boils down to whether all, some, or none of the
burning of fossil fuels leads to global warming. Most scientists and the
popular media believe that human activity adds so much greenhouse gas to the
atmosphere that this round of global warming could be catastrophic to life on
Earth.
Solar-focused
satellites have been monitoring the sun since the 1970s. More recently, the
Solar and Heliospheric Observatory and the Wind and Advanced Composition
Explorer have kept their instruments trained on the sun to measure the sun’s
temperature, capture the ion content of the solar wind, and determine how the
solar wind is accelerated. Recently, the twin STEREO spacecraft were launched
to expand on and augment existing satellite measurements by tracking the sun
together and reporting on its solar behavior.
The
Solar Terrestrial Relations Observatory became operational in 2007 and will
provide researchers the first three-dimensional space forecasts associated with
solar activity. Whatever the conclusion as to the ultimate cause of global
warming, the “third rock from the sun” will play a big role. The question for
humanity is to determine which theory best describes global warming—greenhouse
gas emissions or solar wind influences—and to develop policies to mitigate the
effects on human civilizations.
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