Although the terms global warming and climate change are often used interchangeably, they apply to different phenomena. Climate change refers to changes in Earth’s temperature, humidity, air pressure, wind, clouds, and precipitation patterns over time. Global warming is a contributing factor to climate change and refers specifically to the effect of greenhouse gases on Earth’s average surface temperature. When discussing rising temperatures caused by greenhouse gases, global warming is an acceptable term. However, climate change is the more accurate term when describing other long-term changes to the planet’s weather patterns.
The term global warming first appeared in geochemist Wallace Broecker’s 1975 Sciencemagazine article, “Climatic Change: Are We on the Brink of a Pronounced Global Warming?” Scientists began studying the effect of greenhouse gases on Earth’s climate more than a century prior, however, as early as 1820. It was during this time that French scientist Joseph Fourier first discovered that Earth’s atmosphere functions to retain the sun’s heat. In the early 1900s, Serbian astrophysicist Milutin Milankovitch also identified the long-term climate effects of natural fluctuations in Earth’s orbit as well as the tilt and precession of its axis. Since then, scientists and policymakers have worked to better understand the workings of the atmosphere, as well as how to respond to challenges created by climate change.
Causes of Climate Change
Earth’s atmosphere contains various gases that act as a blanket to trap heat from the sun and prevent it from escaping back into space. This process is known as the greenhouse effect, and the gases are referred to as greenhouse gases. The main greenhouse gases that occur in nature are carbon dioxide, methane, and nitrous oxide. Without the greenhouse effect, the planet would be too cold to support life. Over time, the amount of greenhouse gases trapped in Earth’s atmosphere has increased significantly, causing worldwide temperatures to rise.
Natural processes on Earth constantly create and destroy greenhouse gases. The decay of plant and animal matter, for example, produces carbon dioxide, which plants then absorb during photosynthesis. This natural cycle keeps the level of carbon dioxide in the atmosphere fairly stable. Shifts in the planet’s crust and changes in ocean patterns impact weather, as do fluctuations in the sun’s output of radiation. Volcanic activity also affects the climate because eruptions discharge greenhouse gases and other pollutants into the atmosphere. Climate change scientists at the National Aeronautics and Space Administration (NASA) and other federal and international agencies recognize that these natural factors continue to play a role in climate change but contend that the impact of these factors alone does not explain the substantial rise in Earth’s temperature. Natural causes of climate change are referred to as naturogenic, while human-made causes of climate change are referred to as anthropogenic.
Earth’s vegetation releases and absorbs more than two hundred billion metric tons of carbon dioxide annually. Human activities, such as the burning of fossil fuels, add an extra seven billion metric tons per year. Over time, these additions have had a dramatic effect on the atmosphere. In the past 150 years, the concentration of carbon dioxide in the atmosphere has risen by more than 30 percent. Deforestation has also played a role in this increase by eliminating forests that would otherwise absorb tons of carbon dioxide.
Increased levels of other greenhouse gases such as nitrous oxide and methane have also resulted from human activities. Several agricultural and industrial activities, such as the use of certain fertilizers in agriculture, produce nitrous oxide. Methane emissions come from the production of fossil fuels, from landfills, and from livestock. These gases may cause even more harm than carbon dioxide, even though less of them exist, because they have a much greater effect per pound on Earth’s temperature. Methane, for example, is a greenhouse gas that is twenty-one times as potent as carbon dioxide. Beginning in October 2015, a methane gas leak from a California storage facility vented about five billion cubic feet of gas into the atmosphere. The leak took more than three months to seal and was finally capped on February 18, 2016. The incident constituted the largest accidental discharge of greenhouse gases in US history, releasing the equivalent of the yearly exhaust emissions from 572,000 automobiles.
Humans have created and released greenhouse gases that do not occur in nature. These include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). These gases, released during such industrial processes as aluminum production and electrical transmission, have thousands of times greater effect on the planet’s temperature than carbon dioxide.