The purpose of the Kyoto Treaty, also known as the Kyoto Protocol, is to reduce global warming by reduc- ing greenhouse gas emissions. Countries that ratify the Kyoto Treaty agree to reduce their greenhouse gas emissions to 5 percent below their 1990 level by the year 2012.
The treaty was first proposed in 1997. The Kyoto Treaty took effect on February 16, 2005, after ratification by Russia met the requirement that the treaty be ratified by countries accounting for at least 55 percent of global carbon emissions. As of September 2005 156 countries representing over 61 percent of global greenhouse gas emissions had signed the treaty; notable exceptions included the United States and Australia. Developing countries such as China and Russia are exempt from the requirement that they reduce greenhouse gas emissions.
Greenhouse gases contribute to global warming through what is known as the “greenhouse effect.” The analogy refers to a greenhouse used for gardening, in which sun rays are allowed to penetrate the glass walls and ceiling and warm the air within the greenhouse, and the warmed air is prevented from leaving the greenhouse by those same glass walls and ceiling. In the case of Earth, the planet is warmed by solar radiation which can penetrate Earth’s atmosphere, but a proportion of radiation reflected off the Earth cannot escape back through the atmosphere due to its different wavelength. Scientists estimate that without the greenhouse effect, the average surface temperature on Earth would be –18°C.
The Kyoto Treaty allows nations to engage in carbon emissions trading. This means that a signatory may increase their carbon emissions and remain within compliance by purchasing “credits” from countries that have decreased their emissions. Countries can also qualify for credits by engaging in clean energy programs and fostering forests and other natural systems referred to as “carbon sinks” because they remove carbon dioxide from the environment.
The current concern with greenhouse gases has to do with the increasing quantities of those gases, and the role they are believed to play in global warming, that is, an increase in the average temperature of the Earth’s surface and atmosphere. It is the consensus scientific opinion that global temperature has risen 0.4–0.8ºC since the late 19th century and that human activities are the cause of most of this change. Scientists who endorse the global warming hypothesis predict that the rise in temperature will continue to intensify with increasing industrial development and the resultant increase in greenhouse gas emissions. Predicted effects of continued global warming include a rise in sea level, leading to coastal flooding, extreme weather, and food shortages due to crop failures.
Not all scientists accept the global warming hypothesis, however. Alternative explanations include the argument that the increase in temperature has not been clearly established, that it is within the range of normal variation to be expected over time, or that it is due to the period when measurement began having been unusually cold. Others argue that although the global temperature does seem to be rising, there is no proof that the rise in temperature was caused by human activity.
See also environmental problems.