During the last few decades, concern has been growing internationally that increasing concentrations of greenhouse gases in the atmosphere will change our climate in ways detrimental to our social and economic well-being. Climate change or global warming means a gradual increase in the global average air temperature at the earth’s surface. Abundant data demonstrate that global climate has warmed during the past 150 years. The majority of scientists now believe that global warming is taking place, at a rate of around 0,3 deg. C per decade, and that it is caused by increases in the concentration of so-called “greenhouse gases” in the atmosphere. The most important single component of these greenhouse gas emissions is carbon dioxide (CO2). The major source of emissions of CO2 are power plants, automobiles, and industry. Combustion of fossil fuels contributes around 80 percent to total world-wide anthropogenic CO2 emissions.
Another source is global deforestation. Trees remove carbon dioxide from the air as they grow. When they are cut and burned that CO2 is released back into the atmosphere. Massive deforestation around the globe is releasing large amounts of CO2 and decreasing the forests’ ability to take CO2 from the atmosphere. The second major greenhouse gas is methane (CH4). It is a minor by-product of burning coal, and also comes from venting of natural gas (which is nearly pure methane). Different fossil fuels produce different amounts of CO2 per unit of energy released. Coal is largely carbon, and so most of its combustion products are CO2. Natural gas, which is methane, produces water as well as CO2 when it is burned, and so emits less CO2 per unit of energy than coal. Oil falls somewhere between gas and coal in terms of CO2 emissions, as it is made up of a mixture of hydrocarbons. The amount of CO2 produced per unit of energy from coal, oil and gas is in the approximate proportion of 2 to 1,5 to 1. This is one of the reasons why there is a move towards greater use of natural gas instead of coal or oil in power stations, despite the much greater abundance of coal.
HOW GLOBAL WARMING WORKS
The earth’s atmosphere is made up of several gases, which act as a “greenhouse”, trapping the sun’s rays as they are reflected from the earth’s surface. Without this mechanism, the earth would be too cold to sustain life as we know it. Since the industrial revolution, humans have been adding huge quantities of greenhouse gases, especially carbon dioxide (CO2) to the atmosphere. More greenhouse gases means that more heat is trapped, which causes global warming. By burning coal, oil and natural gas increases atmospheric concentrations of these gases. Over the past century, increases in industry, transportation, and electricity production have increased gas concentrations in the atmosphere faster than natural processes can remove them leading to human-caused warming of the globe.
Recently, alarming events that are consistent with scientific predictions about the effects of climate change have become more and more commonplace. The global average temperature has increased by about 0.5 deg. C and sea level has risen by about 30 centimeters in the past century. 1998 was the hottest year since accurate records began in the 1840s, and ten of the hottest years have occurred during the last 15 years.
Official confirmation of global climate change came in 1995, when the UN Intergovernmental Panel on Climate Change (IPCC), an officially appointed international panel of over 2,500 of the world’s leading scientific experts, found that “… the balance of the evidence suggests a human influence on the global climate.” It has been concluded that the temperature on this planet during this century has steadily risen with the higher concentration of carbon dioxide, at a rate in accordance with theoretical prediction and that this is an effect which would continue to raise the temperature for another 75 years even if carbon dioxide emission was stopped today.
The following are events which consistent with scientists predictions of the effects of global warming. The past two decades have witnessed a stream of new heat and precipitation records. Glaciers are melting around the world. There has been a 50 percent reduction in glacier ice in the European Alps since 1900. Alaska’s Columbia Glacier has retreated more than 12 kilometers in the last 16 years while temperatures there have increased. A huge section of an Antarctic ice shelf broke off. Some scientists think this may be the beginning of the end for the Larsen B ice shelf, which is about the size of Connecticut. Severe floods like the devastating Midwestern floods of 1993 and 1997 are becoming more common. Infectious diseases are moving into new areas. Corresponding with global warming, sea levels have risen, and climatic zones are shifting. All these changes exemplify the environmental impact of global climate change. Global warming and climate change pose a serious threat to the survival of many species and to the well-being of people around the world.
FUTURE IMPACTS OF CLIMATE CHANGE
The IPCC estimates that air temperatures will increase by another 1-3,5 deg. C, and sea levels may rise by up to 1 meter over the next 100 years. Changes of this magnitude will affect many aspects of our lives. Here are some of them :
Seas level will rise. Rising sea level will erode beaches and coastal wetlands destroying essential habitat and leaving coastal areas more prone to flooding. Just a 50 centimeters sea level rise would double the global population at risk from storm surges.
Food crop yields will be affected. A warmer climate will increase irrigation demands and the range of certain pests, but it will also extend the growing season for some areas. While some countries will find their food production increases with a warmer climate, the poorest countries that are already subject to hunger are likely to suffer significant decreases in food production.
More people will die from heat stress. Severe heat waves like the one that killed hundreds of people in Chicago in 1995 will become more frequent. Children and the elderly are most vulnerable to heat stress.
Tropical diseases will spread. Infectious diseases such as Malaria, Dengue fever, encephalitis, and cholera that are spread by mosquitoes and other disease-carrying organisms which thrive in warmer climates will be able to advance into new areas. This will lead to more incidents like malaria outbreaks in New Jersey and Dengue fever in Texas.
The water cycle will be disrupted. As the water cycle intensifies, some areas will experience more severe droughts, while others will have increased flooding. This variability will stress areas that are already prone to water quality and quantity problems.
Endangered species will suffer. Some of the most vulnerable plants, animals, and ecosystems will suffer major changes. Ten species at high risk from global warming are: Giant Panda, Polar Bear, Indian Tiger, Reindeer, Beluga Whale, Rockhopper Penguin, Snow Finch, Harlequin Frog, Monarch Butterfly, and Grizzly Bear.
Coral reefs will be harmed. Overheating of ocean waters, as a result of global warming, can lead to coral bleaching, which is a breakdown of the complex biological systems that corals have evolved in order to survive.
Another side effect of fossil fuels combustion and resulting emissions of pollutants is acid rain (or acid deposition). In the process of burning fossil fuels some of gases, in particular sulfur dioxide (SO2) and nitrogen oxides (NOx) are created. Although natural sources of sulfur oxides and nitrogen oxides do exist, more than 90% of the sulfur and 95% of the nitrogen emissions occurring in North America and Europe are of human origin. Once released into the atmosphere, they can be converted chemically into such secondary pollutants as nitric acid and sulfuric acid, both of which dissolve easily in water. The result is that any rain which follows is slightly acidic. The acidic water droplets can be carried long distances by prevailing winds, returning to Earth as acid rain, snow, or fog.
Natural factors such as volcanoes, swamps and decaying plant life all produce sulphur dioxide, one of the contributing gases to acid rain. These natural occurrences form some kind of acid rain. There are also some cases where acid rain may be produced naturally, which is also bad for the environment but occurs in much lower amounts and quantities than that of those found in urban areas. Between the 1950’s and the 1970’s the rain over Europe increased in acidity by approximately ten times. In the 1980’s however, acidity levels decreased, but although many countries have started to do something about pollution that causes acid rain, the problem is not going away.
Acid rain is often phrased as “acid precipitation”. On the pH scale, rain usually measures 5.6. Anything below this measurement is said to be acidified rainfall. The chemical equation for acid rain is as follows:
Acid rain =
SO2 (Sulfur dioxide) + NO (Nitrogen Oxide) + H2O (Water)
Water solutions vary in their degree of acidity. If pure water is defined as neutral, baking soda solutions are basic (alkaline) and household ammonia is very basic (very alkaline). On the other side of this scale there are ascending degrees of acidity; milk is slightly acidic, tomato juice is slightly more acidic, vinegar, lemon juice is still more acidic, and battery acid is extremely acidic. If there were no pollution at all, normal rainwater would fall on the acid side of this scale, not the alkaline side. Normal rainwater is less acidic than tomato juice, but more acidic than milk. What pollution does is cause the acidity of rain to increase. In some areas of the world, rain can be as acidic as vinegar or lemon juice.
This acid rain can cause damage to plant life, in some cases seriously affecting the growth of forests, and can erode buildings and corrode metal objects. The primary component involved in corrosion is acid rain. It is estimated that the damage to metal buildings alone amounts to about 2 billion dollars yearly. The highest emissions of sulphur come from those sectors, which use the most energy and the highest sulphur-content fuels, that is solid fuels and high sulfur heavy fuel oil. Solid fuels are the most polluting fossil fuels locally and globally. These fuels range from hard coals to soft brown coals and lignite's, which have high proportion of combustion waste and pollutants such as sulfur, heavy metals, moisture and ash content.
One of the major problems with acid rain is that it gets carried from a mass acid rain producing area to areas that are usually not as badly affected. Tall chimneys that are built to ensure that the pollution that is produced by factories is taken away from nearby cities, puts the pollution into the atmosphere. When these particles get picked up by the moisture in the air, they form acids. As a result they become a part of the clouds. Then these clouds get carried off by wind, which means that when the rain falls it may be a long distance away from where the acidic particles were picked up from. An example of this would be Central and Eastern Europe and Scandinavia. Sweden suffer from acid rain because of huge sulphur emissions from Eastern European power plants with low emission standards and because of wind blowing the particles over to their country.
DAMAGE TO TREES AND SOIL
When acid rain falls, it can effect forests as well as lakes and rivers. In many countries around the world, trees are suffering greatly because of the results of acid rain. A lot of trees are losing their leaves and thinning at the top. Some trees are affected so severely that they are dying. To grow, trees need healthy soil to develop in. Acid rain is absorbed into the soil making it virtually impossible for these trees to survive. As a result of this, trees are more susceptible to viruses, fungi and insect pests and they are not able to fight them and they then die.
DESTRUCTION OF BUILDINGS
Acid rain can have a severe effect on buildings. Materials such as stone, stained glass, paintings and other objects can be damaged or even destroyed. It slowly, but gradually, eats away at the material until there is virtually nothing left. Building materials crumble away, metals are corroded, the color in paint is spoiled, leather is weakened and crusts form on the surface of glass. In certain parts of the world many famous and ancient buildings are been damaged by acid rain. St. Paul’s’ Cathedral in London is having it’s stone work eaten away by acid rain. In Rome the Michelangelo statue of “Marcus Aurelius” has been removed to protect it from air pollution.
ACID RAIN AND LAKES
Acid rain damages soil when it falls onto the ground. It also has a noticeable effect when it falls directly into or is washed into lakes. Most of the animal and plant life in clean lakes and rivers are unable to tolerate acid rain. They can be poisoned by substances that the acid washes out from the surrounding soil into the water. All over the world there are examples of plant life and animal life suffering a lot or even not surviving the effects of acid rain. For example, thousands of lakes in Scandinavia are without any kind of life, whether it be animal or plant. Over the past years they have received a lot of acid rain as a result of the wind blowing the particles into their country form places such as England, Scotland and Eastern Europe. Since the 1930’s and 40’s some Swedish lakes have increased acidic levels in their rain water by up to 1,000 times.
The interactions between living organisms and the chemistry of their aquatic habitats are extremely complex. If the number of one species or group of species changes in response to acidification, then the ecosystem of the entire water body is likely to be affected through the predator-prey relationships of the food web. At first, the effects of acid deposition may be almost imperceptible, but as acidity increases, more and more species of plants and animals decline or disappear. As the water pH approaches 6.0, crustaceans, insects, and some plankton species begin to disappear. As pH approaches 5.0, major changes in the makeup of the plankton community occur, less desirable species of mosses and plankton may begin to invade, and the progressive loss of some fish populations is likely, with the more highly valued species being generally the least tolerant of acidity. Below pH of 5.0, the water is largely devoid of fish, the bottom is covered with undecayed material, and the near shore areas may be dominated by mosses. Terrestrial animals dependent on aquatic ecosystems are also affected. Waterfowl, for example, depend on aquatic organisms for nourishment and nutrients. As these food sources are reduced or eliminated, the quality of habitat declines and the reproductive success of the birds is affected. Both natural vegetation and crops can be affected.
We eat food, drink water, and breathe air that has come in contact with acid deposition. Canadian and U.S. studies indicate that there is a link between this pollution and respirator problems in sensitive populations such as children and asthmatics. Acid rain also makes some toxic elements, such as aluminium, copper, and mercury more soluble. Acid deposition can increase the levels of these toxic metals in untreated drinking water supplies. High aluminium concentrations in soil can also prevent the uptake and use of nutrients by plants.
BAD AIR QUALITY
According to World Health Organization air quality guidelines for ozone limit values are frequently exceeded in most parts of developed countries. In the lower troposphere, close to the ground, ozone is a strong oxidant that at elevated concentrations is harmful to human health, materials and plants. In the upper troposphere, ozone is an important greenhouse gas and contributes greatly to the oxidation efficiency of the atmosphere.
Beside greenhouse gases, SO2 and NOx emissions that cause acid rain, emissions of particulate matter contribute to bad air quality. Fuel combustion is the most important source of anthropogenic nitrogen oxides, while fuel combustion and evaporative emissions from motor vehicles are the main sources of anthropogenic volatile organic compounds (VOCs). Motor vehicles account for a considerable fraction of the total emissions of nitrogen oxides and VOCs in Europe and North America. NOx emissions also contribute to the formation of tropospheric photochemical oxidants. Photochemical oxidants, especially ozone (O3), are among the most important trace gases in the atmosphere. Their distributions show signs of change due to increasing emissions of ozone precursors (nitrogen oxides, or VOCs, methane and carbon monoxide).
Smog over city.
Heavy metals like arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb) and zinc (Zn) are also released during fuel combustion. Lead pollution as the result of road traffic emissions have decreased markedly since early 80s due to increased consumption of unleaded gasoline and use of catalysts in cars. Nevertheless this sector remains the main source of lead in atmosphere.
Beside emissions of pollutants there are also some other impacts of fossil fuel combustion on local environment. Here microclimatic impacts like origination of fogs, less sunshine etc. are the results of large amounts of water vapour effluents from cooling towers of power plants.
Damage caused by the transport of oil is related to the pollution of the seas. Here as the scale of oil production has increased during the twentieth century, the quantity of oil transported around the world, most of it by the sea, has also increased. To cope with this increase, in a highly competitive market, the size of oil tankers has increased to the point where they are by far the largest commercial ships. Even in routine operation, this results in large quantities of oil being released into the seas. The tankers fill up with water as ballast for return journeys. When this is emptied, significant quantities of oil are released as well. Despite the fact that the transport of oil is generally a safe industry, the scale of it, and the size of tankers, means that when accidents do occur they have a large effect. Although the number of accidents is small in proportion to the number of tanker journeys, thousands of minor incidents involving oil spills from tankers, and oil storage facilities occur annually.
Between 1970 and 1985 there were 186 major oil spills each involving more than 1300 tonnes of oil. In 1989, the tanker Exxon Valdez ran aground off Alaska, releasing 39.000 tonnes of oil to form a slick covering 3.000 square kilometres and causing widespread environmental damage. People usually tend to think of the seas as a vast reservoir which can soak up limitless quantities of whatever we put into it. In fact, the scale of pollution from oil is such that clumps of floating oil are now common almost anywhere in the world’s oceans.