Greenhouse gases and air pollution
Greenhouse gases are atmospheric gases that allow sunlight to enter the Earth’s atmosphere while trapping some of the heat that radiates back into space. Human activities, particularly since the mid-19th century, have significantly increased concentrations of these gases, contributing to global warming and changes in climate patterns. By the 2020s, a scientific consensus emerged acknowledging that this rise in greenhouse gas emissions, driven by fossil fuel combustion, agriculture, and industrial processes, has led to an average increase in Earth's surface temperature of approximately 0.4 degrees Fahrenheit per decade since 1880.
The primary greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and fluorocarbons. While water vapor is the most abundant, human actions primarily influence the levels of carbon dioxide and methane. The international community has recognized the urgent need to address these emissions, leading to agreements such as the United Nations Framework on Climate Change, the Kyoto Protocol, and the Paris Agreement. Despite varying levels of commitment from different nations, as of 2023, 195 countries have signed the Paris Agreement, reflecting a growing global acknowledgment of climate change as a significant and pressing challenge. The ongoing aim is to implement effective policies that can mitigate the impacts of climate change in a timely manner.
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Greenhouse gases and air pollution
DEFINITION: Atmospheric gases that allow sunlight to reach the earth’s surface but at least partially block infrared from radiating back into space
By the 2020s, the global scientific community acknowledged that human activities are contributing to increased concentrations of greenhouse gases and thus to increases in the earth’s average surface temperature. This stood in contrast to previous decades where such consensus had yet to be reached.
According to 2023 data from the National Oceanic and Atmospheric Administration (NOAA), the temperature of the Earth has risen by an average of 0.4 degrees Fahrenheit (0.08 Celsius) every decade since 1880-, or two degrees Fahrenheit in total. Also, the ten warmest years on record have occurred from 2014 to 2023. Other sources attribute at least half of this temperature rise to the release of greenhouse gases into the atmosphere by human beings. Since greenhouse gases are transparent to visible light, sunlight passes through the atmosphere and warms the earth’s surface. The warmed surface radiates infrared into the sky, where greenhouse gases absorb infrared and radiate it again. About half of this escapes into space, and the remainder is directed down to Earth’s surface. Since the earth absorbs more energy than it radiates back into space, it heats up until the energies entering and leaving are equal. Balance is possible because a hotter Earth radiates with greater intensity and at shorter wavelengths where greenhouse gases allow more infrared to escape into space.
Water vapor strongly absorbs infrared of about 3 microns wavelength (3,000 nanometers), as well as carbon dioxide. An increase in carbon dioxide does not change the amount of energy passing out into space, as water vapor absorbs all the energy of that wavelength. Nonetheless, additional carbon dioxide would make a difference at 4.5 microns wavelength (4,500 nanometers) because water vapor does not absorb at that wavelength. This means that doubling the amount of carbon dioxide in the atmosphere does not necessarily double the effect of carbon dioxide. In fact, most climate scientists believe that increasing carbon dioxide will increase the surface temperature, which will cause more water to evaporate. More water vapor in the atmosphere should further warm Earth’s surface, but it will also cause more clouds to form that would reflect sunlight back into space. These additional clouds would help cool the earth. Under these competing processes, it is believed that temperature will increase until a new equilibrium is reached.
Earth’s Major Greenhouse Gases
Water vapor, carbon dioxide, methane, nitrous oxide, fluorocarbons, and ozone are the major greenhouse gases. The effect of a particular gas depends on which other gases are present, how much of the gas is present, and how likely a gas is to absorb infrared radiation.
Water vapor is the most important greenhouse gas, but human activities have no direct effect on the global average amount of water vapor, which is fixed mainly by evaporation from Earth’s oceans. Other greenhouse gases are significantly affected by human activities. Burning fossil fuels and in the Tropics increase the amount of carbon dioxide in the atmosphere. Rice paddy farming and the digestive processes of livestock produce large amounts of methane. Fertilizers used in farming produce nitrous oxide, and refrigeration systems and some manufacturing processes release chlorofluorocarbons, other perfluorocarbons, and sulfur hexafluoride.
Since the mid-nineteenth century, carbon dioxide in the air has increased from 280 parts per million to almost 380 parts per million. Normal carbon is carbon 12 (6 protons and 6 neutrons in the nucleus), but about 1 percent of carbon is carbon 13 (6 protons and 7 neutrons). Plants prefer carbon 12, so plant carbon (and fossil fuels from plants) has a smaller ratio of carbon 13 to carbon 12 than the atmosphere does. Analysis of air bubbles in ice cores shows that the ratio of carbon 13 to carbon 12 in the atmosphere has been decreasing since the mid-nineteenth century, presumably because of the increased burning of fossil fuels and the practice of setting fire to forests to clear land.
Politics
Demonstrating its acknowledgment that greenhouse gas emissions were a threat to the Earth's population, the United Nations Framework on Climate Change (UNFCC) was adopted on March, 21, 1994. Perhaps one of its most notable aspects was that the document acknowledged that human activities were causal in both increased emissions and its negative effects, such as the rise in global temperatures. Several years later, the follow-on Kyoto Protocol was ratified in December 1997, and went into effect in February 2005. Under the protocol, industrialized nations set goals for reductions. In the immediate years afterward, few nations were fully implementing the agreement. For example, in 2007 only Germany, Norway, France, and the United Kingdom were meeting their goals. Several nations that had been part of the former Soviet Union reduced emissions, in large part because their economies floundered. In 2015, the Kyoto Protocols were augmented by the Paris Agreement, which set national metrics for the reduction of greenhouse emissions. Since then, compliance with the UNFCC and Kyoto and Paris agreements have increased among international nations. A 2021 "Climate Scoreboard" placed the countries of the Europe Union as the most committed signatories to these agreements. This was based on a range of criteria, such as pledged reductions and moves toward carbon neutrality. The United States was ranked far below and was only slightly above a grouping of the least committed countries which included Russia, China, and Iran.
In December 2009, the US Environmental Protection Agency (EPA) released a finding that greenhouse gases threaten the public health and welfare of the American people. The United States signed the Kyoto protocol under the presidential administration of Bill Clinton, but the treaty was not sent to the Senate for ratification. The compliance of the United States has, since that time, been enacted through presidential executive action. This has resulted in the extent of American participation being varied by presidential administration. Seeing the Paris Agreements as flawed because it placed no limits on China, the world's largest source of emissions, or India, in 2017 under the presidential administration of Donald Trump, the United States suspended its implementation of the 2015 Paris Agreement. On January 20, 2021, the United States reversed its previous position as President Joe Biden signed an executive order mandating the United States rejoin the Paris Agreement. The next year, on August 17, 2022, the Inflation Reduction Act was signed into law. The Biden administration pledged $369 billion in new environmental funding, in part, to address rising global temperatures.
International efforts to reduce greenhouse gas emissions have encountered challenges since they first began to be proposed. Nonetheless, an area of success has been that the issue of climate change is now recognized as an existential issue throughout the global community. This was not always generally accepted. By 2023, 195 countries had become signatories to the Paris Agreement. Instead of addressing persistent doubts about whether climate change was actually occurring, the enduring challenge now is whether global implementation of policies can be implemented quickly enough to forestall life-altering climatic changes.
Bibliography
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