Solar Wind

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.