The world is getting hotter. 1998 was the hottest in one thousand years, and the nine hottest years on record have all been in the past two decades. Humankind's actions on a global scale have changed not just the landscape of the Earth, but the world's climate too. Increasingly sophisticated measurements of the world's climate and weather systems have provided a wealth of evidence that the Earth has been getting steadily warmer. Since the beginning of the industrial revolution, atmospheric concentrations of carbon dioxide have increased by a huge number.
Methane concentrations have more than doubled, and nitrous oxide concentrations have risen significantly as well. These increases have enhanced the heat-trapping capability of the earth s atmosphere.
Why are greenhouse gas concentrations increasing? Scientists generally believe that the combustion of fossil fuels and other human activities are the primary reason for the increased concentration of carbon dioxide. Plant respiration and the decomposition of organic matter release more CO2 than is released by human activities; but these releases have generally been in balance during the centuries leading up to the industrial revolution with carbon dioxide absorbed by terrestrial vegetation and the oceans.
Over the last several hundred years the release of carbon dioxide by human activities has increased. Energy burned to run cars and trucks, heat homes and businesses, and power factories is responsible for about 80% of society's carbon dioxide emissions, about 25% of U.S. methane emissions, and about 20% of global nitrous oxide emissions. (Sullivan 65) Increased agriculture, deforestation, landfills, industrial production, and mining also contribute a significant share of emissions.
In 1994, the United States emitted about one-fifth of total global greenhouse gases.
To understand this what global warming is we must first define it. The term, Global Warming, refers to an expected rise in global average temperature due to the continued emission of greenhouse gases produced by industry and agriculture, which trap heat in the atmosphere. Greenhouse gasses are termed so because they act like the glass in a greenhouse making the greenhouse warmer. The glass walls and roof of a greenhouse allow most of the sun's light in, but do not allow most of the heat to escape. This causes the temperature inside the greenhouse to be warmer than the outside. Likewise these gases in the atmosphere are transparent to sunlight, allowing the sunlight to warm the earth, but they also prevent heat from escaping into space, and thus they keep the earth warmer than it would be naturally.
A majority of this greenhouse effect is natural, and maintains the average temperature on the earth about 57-60 degrees Fahrenheit. This Greenhouse Effect is one of the earth's natural processes, without which the earth would be an icy 32.C colder! But, human activity is adding more CO2 to the atmosphere, possibly enhancing the greenhouse effect and potentially resulting in global warming. The burning of fossil fuels, like oil, coal and natural gases, are sources of energy that release CO2 into the atmosphere. CO2 is one of the primary greenhouse gases in the atmosphere, which actually traps outgoing heat and warms the earth. Scientists can measure the amount of CO2 in the earth's atmosphere and have discovered that amounts of the gas are increasing. With this increase in mind, there is the possibility that more CO2 will lead to an enhancement of the greenhouse effect. Other Greenhouse gasses include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Methane is released during the production and transport of coal, natural gas, and oil. Methane emissions also result from the decomposition of organic wastes in landfills, and at farms where there are livestock. Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of solid waste and fossil fuels. The idea that the earths average temperate is increasing over time is not a new one. The record of instrumental temperature measurements extend back to 19th century, provide on clear indication: The mean annual surface air temperatures of the earth have risen approximately 1.5 degrees since 1860. (Maxted 88) Many people think that it s not a big deal that the temperature is rising by that small an amount but it could develop into a huge problem in the future. Temperature increases will have significant impacts on human activities: where we can live, what food we can grow and how or where we can grow food, and where certain organisms can live, and thrive. Many crops that have certain temperatures that they can grow at and anything less or more will disrupt the whole crop and they will not be able to grow in that area any longer.
Temperature is one of the major issue when it comes to global warming. Global temperatures are rising. Observations collected over the last century suggest that the average land surface temperature has risen 0.45-0.6.C (0.8-1.0.F) in the last century. (Steinberg 23) The surface of the ocean has also been warming at a similar rate. Studies that combine land and sea measurements have also stated: global temperatures have warmed 0.3-0.6.C (0.5-1.0.F) in the last century. (Steinberg 23) About two-thirds of this warming took place between 1900 and 1940. Global temperatures declined slightly from the 1940s through the 1970s; but have risen more rapidly during the last 25 years than in the period before 1940. Although surface temperatures are rising, they are not rising uniformly. Nighttime low temperatures are rising on average about twice as rapidly as daytime highs. Urban areas are also warming at a more rapid rate than rural areas.
Temperature increase will lead to precipitation changes the raising of sea level. Precipitation has increased by about 1 percent over the world's continents in the last century. Areas in higher latitudes are seeing more significant increases in rainfall, while in tropical areas rainfall has declined. In North America, precipitation has increased significantly. Precipitation in the United States has been increasing significantly in the last century, around five percent according to the National Oceanic and Atmospheric Administration (NOAA) Much of the increase in rainfall has been taking place between September and November. Rainfall is also tending to be more concentrated in heavy downpours, according to studies by UCLA. At the beginning of the 20th century, only 9 percent of the nation experienced a storm each year in which more than two inches of precipitation fell in a 24-hour period. In recent decades, such a severe storm has occurred each year over close to 11 percent of the nation. (Peiper 48)
According to reports also done by UCLA sea level has risen worldwide around 6-8 inches in the last century. Also approximately 1-2 inches of the rise has resulted from the melting of mountain glaciers. Another 2-7 cm has resulted from the expansion of ocean water that resulted from warmer ocean temperatures. The pumping of ground water and melting of the polar ice sheets may have also added water to the oceans. Many ecological consequences will ensue, among the most direct of which will be the melting of small glaciers and ice caps on land and the expansion of seawater as it warms. Both of these effects will cause global sea level to rise. This report discusses the impacts of that rise on selected coastlines and islands. Besides direct land loss due to rising sea levels, there are also many indirect effects on the world. These include erosion patterns and damage to coastal lands. Areas where there are deltas will be especially vulnerable since they are right next to the ocean and have to most interaction with the water. The average elevation of a delta is usually very low and therefore they have more interaction with the sea than other land formations. Affects of water rising can be felt for tens of kilometers inland sometimes even hundreds. Obviously this could cause serious problems for the environment. There are a few exceptions. Deltas in a closed in seas such as the Nile Delta are not as harshly affected as the others but they are still affected.
The next major issue dealing with global warming is the hole the ozone layer. Like I said at the beginning of the paper ozone is one of the greenhouse gasses and has a profound effect on the world. Ozone is a naturally occurring gas in the atmosphere, and is being depleted at an alarming rate. Ozone is constantly being produced and destroyed in a natural cycle. However, the overall amount of ozone is essentially stable. This balance can be thought of as a stream's depth at a particular location. Although individual water molecules are moving past the observer, the total depeth remains constant. Similarly, while ozone production and destruction are balanced, ozone levels remain stable. This was the situation until the past several decades.
Over 60 years ago, chlorofluorocarbons were invented in the United States, and they soon found many uses throughout the world in refrigeration, air conditioning, and other industrial processes. Due to scientific evidence that CFCs and other chemicals destroy ozone in the upper atmosphere, the United States, the country which has traditionally been the largest emitter of CFCs worldwide, is rapidly scaling back the use of these chemicals and phasing out their production. The ozone layer in the stratosphere protects life on earth from exposure to dangerous levels of ultraviolet light. It does so by filtering out harmful ultraviolet radiation from the sun. When CFCs and other ozone-degrading chemicals are emitted, they mix with the atmosphere and eventually rise to the stratosphere. There, the chlorine and the bromine they contain catalyze the destruction of ozone. This destruction is occurring at a more rapid rate than ozone can be created through natural processes.
The degradation of the ozone layer leads to higher levels of ultraviolet radiation reaching Earth's surface. This in turn can lead to a greater incidence of skin cancer, cataracts, and impaired immune systems, and is expected also to reduce crop yields, diminish the productivity of the oceans, and possibly to contribute to the decline of amphibious populations that is occurring around the world. The chemicals most responsible for the destruction of the ozone layer are chlorofluorocarbons, carbon tetrachloride, methyl bromide, methyl chloroform, and halons. Chlorofluorocarbons have long been widely used as coolants in refrigerators and air conditioners and as foaming agents, solvents, and aerosol propellants. Carbon tetrachloride and methyl chloroform are important industrial solvents. In the United States, carbon tetrachloride is now used almost entirely as a feedstock for the production of chlorofluorocarbons. Hydrogenated CFCs (HCFCs) have many of the same uses as CFCs and are increasingly employed as interim substitutes for CFCs. Halons have been used in fire extinguishers. Long predicted, the degradation of the ozone layer was dramatically confirmed when a large hole in the layer over Antarctica was reported in 1985. Smaller but significant stratospheric decreases have been seen over more populated regions of the Earth. Subsequent research established that industrial chemicals are responsible for the observed depletions of ozone over Antarctica and play a major role in global ozone losses. Chlorine and bromine are emitted to the atmosphere from both natural and human sources. These very stable human-made chemicals are not soluble in water and are not broken down chemically in the lower atmosphere. Thus they survive long enough to reach the stratosphere. The CFCs and carbon tetrachloride are relatively unreactive in the lower atmosphere (the troposphere) and move unscathed into the stratosphere where they are decomposed by intense sunlight, releasing chlorine to catalyze the destruction of ozone molecules. Certain ozone-depleting chemicals (HCFC-22 and methyl chloroform) are more reactive in the troposphere and deliver less of their initial chlorine load to the stratosphere. Halons also are generally reactive in the troposphere and deliver only a fraction of their initial load of bromine to the stratosphere, but bromine is 40 times more efficient at destroying ozone than chlorine. (
Gardener 76) Increasing attention is being focused on the ozone-depleting role of methyl bromide, which has three potentially major human sources (soil fumigation, biomass burning, and the exhaust of automobiles using leaded gasoline), in addition to a natural oceanic source.
Worldwide monitoring has shown that stratospheric ozone has been decreasing for the past two decades or more. The average loss across the globe totaled about 5 percent since the mid-1960s, with losses of about 10 percent in the winter and spring and a 5 percent loss in the summer and autumn over North America, Europe, and Australia. Since the late 1970s, an ozone hole has formed over Antarctica each austral spring (September/October), in which up to 60 percent of the total ozone is depleted. Record low global ozone levels were recorded in 1992 and 1993. (Halmann 15) As expected from the increasing use of CFC substitutes, observations from several sites have revealed rising concentrations of these compounds in the atmosphere. These substitutes have short troposphere lifetimes, which tend to reduce their impact on stratospheric ozone as compared to CFCs and halons. However, some are potent greenhouse gases. The link between a decrease in stratospheric ozone and an increase in surface ultraviolet (UV) radiation at the Earth's surface has been strengthened during the last several years by simultaneous measurements of total ozone and UV radiation in Antarctica and the southern part of South America during the period of the seasonal ozone "hole." The measurements show that when total ozone decreases, UV increases. Furthermore, elevated surface UV levels in mid-to-high latitudes were observed in the Northern Hemisphere in 1992 and 1993, corresponding to the low ozone levels of those years. However, the lack of long-term monitoring of surface UV levels and uncertainties introduced by clouds and ground-level pollutants have precluded the unequivocal identification of a long-term trend in surface UV radiation.
Another problem dealing with global warming is that many people are misinformed about the implications of adding excess carbon dioxide into the atmosphere. There are many myths out there concerning global warming. It is a myth that Carbon dioxide (CO2) is removed from the atmosphere fairly quickly, so if global warming turns out to be a problem, society can wait until after consequences occur to reduce greenhouse gas emissions. But in truth, CO2, which is emitted largely by combustion of fossil fuels, is the most important human-made greenhouse gas. If emissions of CO2 were halted today, it would take more than a century for the atmospheric level of CO2 to approach its preindustrial level. Also a small amount of around 15% of all CO2 already emitted would remain airborne for thousands of years, causing warming for a long lond time. In addition, the slow warming of the ocean creates a lag between emissions and their full effect on temperature. In other words, the consequences of past emissions are not yet entirely apparent. Human activities contribute only 4% of CO2 emissions, the rest comes from natural sources like decaying vegetation and forest fires started by lightning. Another myth is that the human contribution is too small to have a significant effect on climate, particularly since the oceans absorb most of the extra CO2 emissions. In truth Before human beings began to affect the level of CO2 in the atmosphere, natural processes that remove CO2 nearly exactly balanced the natural emissions of CO2. As a result, the amount of CO2 in the atmosphere had changed very little for thousands of years. The additional source of CO2 from human activities like burning coal and oil for energy has thrown the system out of balance. Although the oceans and forests absorb about half the CO2 emitted by industry, the rest builds up in the atmosphere. As a result, CO2 levels are now one-third higher than in pre-industrial times. Similar changes of CO2 occurred naturally long ago, and they were generally accompanied by large shifts in global average temperature.
Today, action is occurring at every level to reduce, to avoid, and to better understand the risks associated with climate change. Many cities and states across the country have prepared greenhouse gas inventories, and many are actively pursuing programs and policies that will result in greenhouse gas emission reductions.
At the national level, the U.S. Global Change Research Program (USGCRP) coordinates the world's most extensive research effort on climate change. In addition, the Clinton Administration is actively engaging the private sector, states, and localities in partnerships based on a win-win philosophy and aimed at addressing the challenge of global warming while, at the same time, strengthening the economy.
At the global level, countries around the world have expressed a need for strengthening international responses to the risks of climate change. The U.S. is working to strengthen international action and broaden participation under the auspices of the Framework Convention on Climate Change. We must team up with other countries all over the world and see what a world combined can do about this very serious situation that we face.
Lastly, this environmental crisis we face is the product of a crisis of perception; we as a species can't see that our actions will have tremendous effects. Industrial societies typically have a history of shallow ecological, reactive policy-making as opposed to deep ecological pro-active planning. With this tradition, how can we realistically expect to survive in the years to come? Yes, perhaps we will survive this threat, seeing as we have so many resources, but what will the quality of life be like? And what of less advantaged nations who may not survive at all the prospects of future generations being born into a world affected by human-induced warming seem probable unless we act pro-actively as an International community to examine how we contribute to global warming on an individual basis. The future of earth's climate is in the hands of humans. It seems to be that the human influence on the earth's natural balance will only lead to our destruction. With simple measures we, as inhabitants of this planet, can not seal our fate in rising temperatures, but rather we must change our views completely. We have to stop thinking of the natural world as something that we can exploit, and start thinking of it as something that is crucial to our very existence. We must take responsibility for our home. We have but one Earth, one chance.