Humanity's effects on the global environment have grown more and more significant since becoming the dominant species on Earth. According to Smithsonian Magazine, many scientists refer to the current geological time period as "The Anthropocene Era," meaning "the new period of man." Never before in our planet's history have human activities had a greater impact on the environment. Many scientists and environmental groups believe that the most significant environmental issues today result from burning fossil fuels for energy, leading to land and water pollution, ecosystem damage and importantly, climate change.
Over the course of our planet's 4.5 billion year history, many types of organisms have lived and died. During the Carboniferous period, about 300 to 360 million years ago, land plants, multiple forms of aquatic life and giant insects flourished in an oxygen-rich environment. As these lifeforms died, they decomposed in vast quantities over eons, creating the numerous coal and petroleum deposits that are now extracted for fuel and burned to generate electricity and power vehicles.
When fossil fuels are burned, multiple chemicals and organic compounds are released into and generated by chemical reactions in the atmosphere. Some of these include mercury, sulfur oxides, methane, nitrogen oxides and most importantly, carbon dioxide. Mercury often falls back to the ground when released from burning coal, poisoning fish and threatening food chains, including human food supplies. Sulfur, nitrogen and volatile organic compounds react with oxygen and other naturally occurring gases in the atmosphere, contributing to the phenomenon of acid rain. Acid rain can seriously damage forests and contaminate soils, making them less suited to productive agriculture.
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The Greenhouse Effect
According to the U.S. Environmental Protection Agency, nitrogen oxides, methane, carbon dioxide and fluorinated gases are considered the primary greenhouse gases. High levels of these trap energy from the sun in the earth's lower atmosphere. This causes increasing average temperatures across the globe, greatly affecting climate patterns. Ice-cap and glacial melt, combined with thermal expansion of warming oceans, is predicted to cause significant sea-level rise by the end of the 21st century, flooding many low-lying coastal areas. Warming temperatures may also severely disrupt sensitive arctic ecosystems, contribute to increasing desertification and affect weather patterns that humans currently depend on for agriculture.
Controversy and Consensus
Although scientists do not fully understand all of the variables that are driving climate change and although there is still some controversy, there is increasing evidence that these changes are human induced. In its 2013 report, the Intergovernmental Panel on Climate Change declared 95 percent certainty that global warming since 1950 is man-made. The report also highlights the possible amount of global temperature increases over the next century and the probable effects on global climate patterns.