The Greenhouse Effect is a naturally occurring phenomenon necessary to sustain life on earth. In a greenhouse, solar radiation passes through a mostly transparent piece of glass or plastic and warms the inside air, surface, and plants. As the temperature increases inside the greenhouse, the interior of the greenhouse radiates energy back to the outside and eventually a balance is reached.
The earth and its atmosphere simulates these greenhouse conditions. Short-wave radiation from the sun passes through the earth’s atmosphere. Some of this radiation is reflected back into space, some of it is absorbed by the atmosphere, and some of it makes it to the earth’s surface, where it is either reflected or absorbed. The earth, meanwhile, emits long-wave radiation toward space. Gases within the atmosphere absorb some of this long-wave radiation and re-radiate it back to the surface. It is because of this greenhouse-like function of the atmosphere that the average global temperature of the earth is 15°C (59°F). Without the atmosphere and these gases, the average global temperature would be a frigid -18°C (0°F), and life would not be possible on earth. These gases are called greenhouse gases and include carbon dioxide (CO2), water vapor (H2O), methane (CH4), nitrous oxide (N2O), chloroflourocarbons (CFCs), and ozone (O3).
The role of greenhouse gases in the atmosphere was first discovered during the 1800s (Kellogg, 1988). By 1896, Swedish scientist Svante Arrhenius was already calculating that the earth’s surface temperature would increase by 5-6°C (9–10.8°F) with a doubling or tripling of the atmospheric CO2 content, although he did not perceive that the greenhouse gas concentrations would increase so much in such a short period of time. Such predictions received relatively little notice until the 1950s. In 1957, Roger Revelle and Hans Suess, scientists at the Scripps Institution of Oceanography, said that by adding CO2 into the atmosphere humans were “now carrying out a large-scale geophysical experiment.” They also pointed out that the CO2 would remain within the atmosphere for a very long time because of how slowly it is absorbed by the oceans. Since then there has been a growing acknowledgment of the increasing concentrations of not only CO2 but also the other greenhouse gases and their potential impact on the global climate.
Public awareness of the Greenhouse Effect and the concern that the impact of increased emissions of CO2, CH4, N2O, and CFCs would raise global temperatures grew in the 1980s. During an intense drought and heat wave in 1988, the media and several scientists speculated that the drought and heat wave affecting much of the United States were evidence of climate change. In hindsight, the 1988 drought was likely within the range of normal climate variability, but the attention was focused on the Greenhouse Effect. Likewise, climate attribution researchers determined that the record-breaking warmth across much of the middle U.S. in March 2012 was much more extreme than climate change alone could explain.