Home >> Science & Nature >> Nature

Theories on Long-Term Climate Change

Most scientists accept that climate change is taking place on a planet-wide scale. The precise causes of climate change, however, are subject to much debate within the scientific community, with some holding the view that climate change is a man-made phenomenon while others believe it's a natural part of the Earth's cycle of heating and cooling. Meanwhile, a variety of theories have emerged to explain the various changes that can be seen taking place with climatic conditions throughout Earth.

A Manmade Phenomenon
- The most widely accepted theory of climate change is that burning fossil fuel for more than a century has resulted in greenhouse gases --- including carbon dioxide, water vapor, nitrous oxide and methane --- becoming released into the atmosphere. These gases trap the heat and light of the sun in the atmosphere. As a result, the overall temperature of the planet rises. Burning fossil fuels has increased significantly since the advent of the Industrial Revolution, and the volume of carbon dioxide in the atmosphere has increased by more than 25 percent since 1860.
The Sun
- Another theory of climate change involves the sun. The sun's magnetic field and the solar wind both serve to modulate how much high-energy cosmic radiation makes It to Earth. According to Danish physicist Henrik Svensmark, this theory's inventor, variations in the sun's magnetic activity and solar wind will affect the amount of cosmic rays that hit Earth, which in turn will affect the rate of low-level cloud formation. In a 2007 story in U.K. newspaper "The Telegraph," Svensmark described his theory that the planet is experiencing a period of low cloud cover caused by fewer cosmic rays entering the Earth's atmosphere. High solar activity, he noted, causes a decrease in cloud cover, which results in warmer temperatures, contributing to global warming.
Astronomical Theory
- The astronomical theory, also known as the Milankovitch theory, posits that slight variations in the Earth's tilt over tens of thousands of years have been responsible for previous heating and cooling periods on the planet. In this theory, devised by Serbian astronomer Milutin Milankovitch, tilts in the Earth as it rotates can result in more severe seasons, such as colder winters and hotter summers. Climate change is seen as a natural byproduct of this tilt, part of an ongoing long-term process that takes thousands of years.
Other Theories
- A number of other theories attempting to explain climate change have also been introduced, such as those detailed in Joseph L. Bast's book "Seven Theories of Climate Change." Among these: The bio-thermostat theory views the Earth as a "natural thermostat" that triggers automatic biological and chemical responses when carbon dioxide levels rise; another theory posits that humanity's impact on climate change isn't from greenhouse gas emissions but from clearing forests, irrigating deserts and counteracting nature by building cities; and another theory says a slowdown of ocean currents over the past 150 years has led to global temperature changes.

Nature