Dwyer 1 Jeffery D. Dwyer The causes and effects of Global Warming. Like many pioneer fields of study, there are uncertainties associated with the science of global warming. This does not imply that all things are equally uncertain. Some aspects of the science are based on well-known physical laws and documented trends, while other aspects range from 'near certainty' to 'big unknowns'. Scientists know for certain that human activities are changing the composition of Earth's atmosphere.
Increasing levels of greenhouse gases, like carbon dioxide (CO 2), in the atmosphere since pre-industrial times have been well documented. There is no doubt this atmospheric buildup of carbon dioxide and other greenhouse gases is largely the result of human activities. It's well accepted by scientists that greenhouse gases trap heat in the Earth's atmosphere and tend to warm the planet. By increasing the levels of greenhouse gases in the atmosphere, human activities are strengthening Earth's natural greenhouse effect.
The key greenhouse gases emitted by human activities remain in the atmosphere for periods ranging from decades to centuries. A warming trend of about 1. F has been recorded since the late 19 th century. Warming has occurred in both the northern and southern hemispheres, and over the oceans.
Confirmation of 20 th-century global warming is further substantiated by melting glaciers, Dwyer 2 decreased snow cover in the northern hemisphere and even warming below ground. Figuring out to what extent the human-induced accumulation of greenhouse gases since pre-industrial times is responsible for the global warming trend is not easy. This is because other factors, both natural and human, affect our planet's temperature. Scientific understanding of these other factors most notably natural climatic variations, changes in the sun's energy, and the cooling effect of pollutant aerosols remains incomplete. Nevertheless, the "Intergovernmental Panel on Climate Change" (IPCC) stated there was a "discernable" human influence on climate; and that the observed warming trend is "unlikely to be entirely natural in origin." IPCC also wrote, "Our ability to quantify the human influence on global climate is currently limited because the expected signal is still emerging from the noise of natural variability...
." (572) In short, scientists think rising levels of greenhouse gases in the atmosphere are contributing to global warming, as would be expected; but to what extent is difficult to determine at the present time. As atmospheric levels of greenhouse gases continue to rise, scientists estimate average global temperatures will continue to rise as a result. By how much and how fast remain uncertain. IPCC projects further global warming of 2-6. F by the year 2100. This range is primarily the result of uncertainties in the response of global climate to the buildup in greenhouse gases, as well as future greenhouse gas emission trends.
The IPCC states that even the low end of this warming projection "would probably be greater than any seen in the last 10, 000 years, but the actual annual to decadal changes would include considerable natural variability." (web) Scientists have identified that our health, agriculture, water resources, forests, wildlife Dwyer 3 and coastal areas are vulnerable to the changes that global warming may bring. But projecting what the exact impacts will be over the 21 st century remains very difficult. This is especially true when one asks how a local region will be affected. Scientists are more confident about their projections for large-scale areas (e. g.
, global temperature and precipitation change, average sea level rise) and less confident about the ones for small-scale areas (e. g. , local temperature and precipitation changes, altered weather patterns, soil moisture changes). This is largely because the computer models used to forecast global climate change are still ill-equipped to simulate how things may change at smaller scales. Some of the largest uncertainties are associated with events that pose the greatest risk to human societies. IPCC cautions, "Complex systems, such as the climate system, can respond in non-linear ways and produce surprises." (web) There is the possibility that a warmer world could lead to more frequent and intense storms, including hurricanes.
Preliminary evidence suggests that, once hurricanes do form, they will be stronger if the oceans are warmer due to global warming. However, the jury is still out whether or not hurricanes and other storms will become more frequent. More and more attention is being aimed at the possible link between El Nino events the periodic warming of the equatorial Pacific Ocean and global warming. Scientists are concerned that the accumulation of greenhouse gases could inject enough heat into Pacific waters such that El Nino events become more frequent and fierce. Here too, research has not advanced far enough to provide conclusive statements about how global warming will affect El Nino. Dwyer 4 Like many pioneer fields of research, the current state of global warming science can't always provide definitive answers to our questions.
There is certainty that human activities are rapidly adding greenhouse gases to the atmosphere, and that these gases tend to warm our planet. This is the basis for concern about global warming. The fundamental scientific uncertainties are these: How much more warming will occur How fast will this warming occur And what are the potential adverse and beneficial effects These uncertainties will be with us for some time, perhaps decades. Global warming poses real risks. The exact nature of these risks remains uncertain.
Ultimately, this is why we have to use our best judgement guided by the current state of science to determine what the most appropriate response to global warming should be. Some greenhouse gases occur naturally in the atmosphere, while others result from human activities. Naturally occuring greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Certain human activities, however, add to the levels of most of these naturally occurring gases: Carbon dioxide is released to the atmosphere when solid waste, fossil fuels (oil, natural gas, and coal), and wood and wood products are burned.
Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from the decomposition of organic wastes in municipal solid waste landfills, and the raising of livestock. Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of solid waste and fossil fuels. Methane traps over 21 times more heat per molecule than carbon dioxide, and nitrous oxide absorbs 270 times more heat per molecule than carbon dioxide.
Dwyer 5 Very powerful greenhouse gases that are not naturally occurring include hydro fluorocarbons (HFCs), per fluorocarbons (Pics), and sulfur hexafluoride (SF 6), which are generated in a variety of industrial processes. There are also several gases that do not have a direct global warming effect but indirectly affect terrestrial radiation absorption by influencing the formation and destruction of tropospheric and stratospheric ozone. These gases referred to as ozone precursors include carbon monoxide (CO), oxides of nitrogen (NOx), and non methane volatile organic compounds (NM VOCs). These are also referred to in the U. S. Clean Air Act as criteria pollutants.
In June of 1992, the United States signed the United Nations Framework Convention on Climate Change (UNFCCC). The objective of the UNFCCC is "to achieve stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system." (Article 2 of the Framework Convention on Climate Change published by the UNEP/WMO Information Unit on Climate Change. See web).