The pollution we create on Earth by burning fossil fuels is harming our environment. When fossil fuels are burnt - forest fires, car exhaust gases, factory emissions and smoke from family chimneys - they release a gas called carbon dioxide into the atmosphere. It is collected in the atmosphere, trapped by the Sun’s heat energy. It is known as the greenhouse effect and is contributing to global warming.
Large tracts of forests worldwide are now being cleared. Some are already cleared for industrial or agricultural purposes. The remaining trees may not be enough to absorb the carbon dioxide in the atmosphere. The carbon dioxide is used by plants to manufacture food. It is also called a greenhouse gas. This kind of gas retains heat longer compared to other gases. Surface temperature rises as more trees and plants are cut or destroyed. The resulting high surface temperature due to the accumulation of the carbon dioxide is referred to as the greenhouse effect.
Carbon dioxide in the atmosphere acts like the glass in a greenhouse. It traps heat from the environment. It causes air temperature to rise. The glass of the greenhouse prevents warm air from escaping. The air temperature inside the greenhouse rises as a result. This would lead to global warming.
Moreover, global warming pertains to an increase of the temperature of the Earth’s atmosphere and oceans in these present days. During the 20th century, the atmospheric temperature of the earth increased 0.6 ± 0.2 °Celsius. The upsurge amounts of carbon dioxide and other greenhouse gases are the major causes of the component of warming. They are produced through the burning of agriculture, fossil fuels, and land clearing and may proceed to an upsurge in the greenhouse effect .
The intents of this paper are to:
What is global warming?
Global Warming is a term denoting the accelerated warming of the Earth’s surface due to anthropogenic (human activity-related) releases of greenhouse gases due to industrial activity and deforestation. Shown here are underbrush burns in a Brazilian rainforest. Slash and burn deforestation, used to clear land, releases carbon dioxide. The result is a greater concentration of carbon dioxide in the Earth’s atmosphere, which - many scientists believe - contributes to global warming.
The distribution of ozone in the atmosphere, published by NASA in 1994, is based on a multiplicity of digital data. Only small ozone concentrations (represented in blue) can be found close to the Antarctic ozone hole. (Note the error in the photograph which has the equator marked as "100" instead of "0".)
During its long history, the climate of the Earth has changed dramatically many times. But now changes are taking place that does not seem to be the result of natural processes. Scientists believe that these changes are a result of the way we live.
The Earth’s surface absorbs, or soaks up the Sun’s heat. Some of this heat then escapes back into space, but some of it is absorbed by gases such as carbon dioxide and water vapor in the atmosphere. In many ways, these gases behave like the glass in a greenhouse (Bellamy & Gifford, 1999). They trap some of the Sun’s heat and so help to keep the surface of the Earth warm. Without these gases, which are often called greenhouse gases; our Earth would be a much colder place. Many parts of the world would be too cold for people to live in.
Moreover, we are putting more and more carbon dioxide into the atmosphere by burning more and more fossil fuels (coal, oil, and natural gas), and by clearing huge areas of forest. Forests are especially important to us because trees, like other green plants, take carbon dioxide from the air when they make their food by the process called photosynthesis.
The earth’s energy balance.
But for the greenhouse effect, life on Earth would not exist. The Sun emits radiation to the Earth. If we could imagine a flat surface at the top of the atmosphere, that radiation is about 340 watts per square metre (340 W/m-2). Just over 100 W/m-2 is reflected out again by atmospheric aerosols and clouds, and the Earth’s surface, leaving some 240 W/m-2 that heats up the surface of the Earth. The system must be in balance - energy “in” must equal energy “out” - so the Earth needs to re-radiate this amount back into the atmosphere. But the amount actually re-radiated depends on the Earth’s surface temperature: the hotter the surface is the more it will emit radiation. The outgoing radiation takes the form of “long wave” infrared thermal radiation. If the system balanced “naturally”, then the Earth’s surface would have a temperature of about –19° C (-66° F) since at this temperature 240 W/m-2 would be emitted (Cairncross, 2001). Obviously, something else must be happening because at such low average temperatures life would not exist. The Earth’s surface is very much warmer than this “natural” level (around 15° C/59° F) and hence far more radiation is emitted than the 240 W/m-2. What happens is that a lot of the Earth’s re-radiation bounces back to the Earth’s surface because it gets absorbed mainly by water vapor and carbon dioxide (CO2) in the atmosphere. Water vapor, CO2, and a few other minor gases act like a “blanket”. The balance is secured as follows:
Incoming solar radiation: + 340 W m-2
Reflected from clouds, the Earth’s surface, etc.: - 100 W m-2
Net incoming radiation absorbed by the Earth = + 240 W m-2
Outgoing radiation: - 420 W m-2
Greenhouse effect: + 180 W m-2
Net outgoing (thermal) radiation = - 240 W m-2
The way the system balances, then, is that the Earth’s surface warms up compared to what would happen if the Earth was not surrounded by a blanket of greenhouse gases.
The anthropogenic greenhouse effects.
The greenhouse effect refers to the way in which gases in the Earth’s atmosphere warm the Earth like the glass roof of a greenhouse - by letting sunlight in but keeping the reflected heat energy trapped inside. These naturally occurring gases, notably carbon dioxide and water vapor, are called greenhouse gases.
So far nothing is amiss. Indeed, the greenhouse effect is a good thing for life on Earth. The problem arises because humankind is adding to the effect by increasing the amounts of CO2 and a few other gases in the atmosphere, notably methane (CH4) and nitrous oxide (N2O). This results in the enhanced greenhouse effect, or “global warming”. Since the concentration of water vapor tends to be fixed (it is determined by the oceans) imagine what would happen if the atmospheric concentrations of CO2 were increased. The effect would be to increase the radiation bouncing back to the Earth and reducing the radiation leaving the top of the atmosphere. For a doubling of CO2 concentrations, the reducing atmospheric radiation would be about 4 W/m-2. But the system is now out of balance: 240 W/m-2 is coming in but 236 W/m-2 (240 W/m-2 minus 4 W/m-2) is going out. In order to balance, something must change, and what changes is the temperature of the Earth’s surface. Recall that if it increases, outward radiation will increase. This will happen until the 240:240 balance is restored. But while the balance is restored, the Earth has basically got hotter (Carwardine, 2002). For each doubling of CO2 concentration, the temperature increase is expected to be about 1.2° C. Various complicating factors intervene to enhance or reduce this figure. Water vapor might increase and this would make the enhanced greenhouse effect stronger still. Other factors of relevance are changes in cloud formation, changes in surface vegetation, the melting of the tundra (which would release methane), changes in ocean circulation, the cooling effects of sulphur aerosols, and so on. The end result is some uncertainty about projected climate change but an average temperature change of about 2° C by 2100 might be expected.
Where do the greenhouse gases come from? The fact that they come from economic activities that are so pervasive in the human society largely explains why global warming control is so complicated and so controversial. CO2 is emitted from the burning of fossil fuels so that most electricity production and most industrial activity contribute to global warming. Since gasoline, kerosene, and diesel are fossil fuels, they too contribute, which means that the entire transport sector is implicated. Methane is also emitted from fossil fuel burning, but also from gas pipeline leaks and from decomposing vegetation. Methane emissions are therefore associated with livestock and with rice growing (Cronin, 1999). Nitrous oxide comes from fossil burning and fertilizers. The burning of forests also contributes significantly to CO2 emissions.
The impact of global warming
The changes in average global surface temperature since the beginning of weather recordings in the mid-19th century are shown in this chart. It shows that since scientific recordings began, temperatures rose sharply to a high in the last two decades of the 20th century; they also rose sharply from about 1910 to the 1940s, although at a much lower average level than in the 1980s and 1990s.
The next issue is to predict what would happen if these temperature changes were allowed to happen. The science of climate change impact assessment is very uncertain, not least because humans have the capacity to adapt to some of the expected changes. There are two stages to impact assessment: predicting what the consequences will be for ecosystem change and human health, and assessing how important those changes will be. The context of all this assessment is uncertainty, not least because the rate of change of temperature and the levels of temperature change together place some of the change outside human experience. That is, we have little idea how environments and humans will respond if the worst-case scenarios occur. An additional complication is that impacts will vary region by region, not just because of different susceptibilities but because there will be regional variations in temperature change, in precipitation, and in extreme events such as hurricanes (Davidson, 2000). Summer monsoons in Asia could become heavier, but summer rains in southern Europe could become less.
The kinds of impacts that would seem to be important are as follows. Sea levels will rise due to the thermal expansion of the oceans. Low-lying areas, such as the coastal regions of Bangladesh, and many small islands, could be seriously affected unless adequate sea defenses are built and maintained. Freshwater resources could be affected by saline intrusion as sea levels change. Existing dry land regions may become drier still, resulting in a greater likelihood of desertification. The agricultural output may change adversely in some regions, due to reduced rainfall, but may increase in other areas because CO2 also has a “fertilizing” effect on crops. While most of the work on impacts has been carried out in the agricultural sector, it is not clear that world food supply will be significantly affected: some regions will lose and some will gain. But the regions suffering losses may be some of the poorest in the world. In terms of human health there are similar ambivalent effects: if winter temperatures rise there may be fewer premature deaths due to winter cold (Durrell, 1999). But if summer temperatures also rise there may be added deaths from heat stress. The pattern of the world’s diseases may also change - diseases such as malaria, eradicated from Europe, could return to some areas. Perhaps the most important effects are the ones we know least about. Ecosystems change in response to climate change but, in general, past changes have occurred slowly as temperatures varied over long periods. A rise of 1 or 2° C in just a century is a very fast rate of temperature change, and some ecosystems may not be able to adjust. Even more speculative are the effects of extreme events: for example, the worsening of El Niño, and the potential effects on ocean currents and hence marine productivity.
Measuring the economic importance of global warming
How much does it all matter? Listing possible impacts is one thing; saying how important they are is another. Yet some idea of the collective magnitude of the impacts is essential because the measures needed to reduce rates of warming will not be cheap. Economic studies suggest a fairly uniform measure of damage of about 1 to 2 percent of the world’s entire economic output. But this is a figure relating to “2 x CO2”, that is, for a doubling of CO2 concentrations in the atmosphere. It is a benchmark widely used for economic and scientific analysis, but global warming will not stop there if unchecked, so the damages in the very far future could be very much higher. Another way of thinking about the economic scale of the damage is to translate it back into the economic damage done by the release of one additional tonne of carbon-equivalent now. This figure is probably around US$30 per tonne, but with a fairly wide range of uncertainty surrounding it. Since this is the extra damage incurred for the world as a whole from releasing one extra tonne of carbon-equivalent, it can be compared directly with the costs of reducing that tonne of carbon emission. As long as the cost of control is less than the damage done, it will pay the world as a whole to take action. This is the essence of the cost-benefit analysis approach to global warming policy.
As with virtually all aspects of the global warming debate, there are many complications. First, it seems likely that the costs of controlling carbon emissions now are fairly low for the first tranche of emissions, but as more and more reduction occurs it will become increasingly expensive to reduce emissions. Many of the economic models used to simulate policies estimate control costs of over US$100 per tonne of carbon, well above the damage figure and suggesting that it may not be economically justified to take drastic action to control global warming. Second, recent economic analyses have suggested that the incorporation of human adaptation into the calculations of damage would greatly reduce the damage figures, although there appear to be limited adaptation possibilities to some of the major ecosystem impacts. Third, and offsetting the argument about reduced damage, the control of CO2 emissions brings with it many other benefits. For example, CO2 emissions from the transport sector might be controlled by having more fuel-efficient cars and by traffic restraint programmes. This will bring with it benefits in the form of reduced conventional pollutants that harm human health, such as particulate matter, and traffic restraint will reduce congestion, noise, and perhaps accidents. Estimates of these ancillary benefits are very uncertain but may actually double the US$30 figure, so that it will pay to spend up to US$60 to reduce a tonne of carbon emissions in order to save US$30 of avoided global warming damage and to gain another US$30 of ancillary benefits. Fourth, failure to control global warming now simply shifts the problem forward on to future generations who are likely to face larger damage costs still. It can be argued that the current generation should incur costs now that are greater than the US$60 per tonne benefit figure in order to be fair to future generations (Simpson, 2001). Others disagree: why use valuable resources now to protect future generations who are likely to be richer anyway when the same resources could be used to reduce poverty now?
These are just a few of the philosophical and economic issues that continue to be aired in the global warming debate. Not surprisingly, views about the right course of action vary radically from those who see the damage to the future well-being of humankind as being little short of catastrophic, to those who believe that technology and adaptation will come to the rescue and that delaying serious action is the best policy.
The international response
These widely varying views also explain the differences of opinion about the adequacy of the actions already taken. It does not benefit any single nation to take action unless it can be assured others will act likewise. The disadvantages of being a “first mover” explain why the subject has to be dealt with at the international level, initially through the Framework Convention on Climate Change (FCCC) in 1992 in Rio de Janeiro, and subsequently at the Conference of Parties in Kyoto in 1997. The Kyoto Protocol, which emerged from the 1997 conference, is the first agreement under the FCCC with greenhouse gas emission reduction targets that will be binding in international law. The FCCC itself set voluntary targets for industrialized nations such that their CO2 emissions should be no higher in 2000 than they were in 1990. Developing countries argued that they had no responsibilities to cut emissions because the industrialized countries were the main emitters of greenhouse gases. Unsurprisingly, not many nations met their voluntary targets (see Environment Matters: Industry's Guide to the Issues, the Challenges and the Solutions, 1999). The Kyoto Protocol sought a 5.2 percent reduction in overall (carbon-equivalent) greenhouse gas emissions by about 2010 relative to 1990. This target applies collectively to industrialized economies only. Once again, developing countries have no mandatory targets. The target is differentiated between industrialized countries. The European Union (EU) as a whole must achieve an 8 per cent reduction, the United States 7 per cent, and Japan 6 per cent. Within the EU a separate agreement allocates the 8 per cent cut between member states.
How much of a breakthrough is the Kyoto Protocol? That there was any agreement at all is an achievement. After all, reducing greenhouse gases affects virtually all aspects of economic activity from electricity generation, industrial activity, agriculture, forestry, and transport. By calling for a change to a less carbon-intensive world, Kyoto signals the need for fundamental change in the way economic activity is organized. A second positive feature is that the agreement enables carbon trading to take place in order to help secure emission reduction targets. Carbon trading involves one country cutting emissions of CO2 (or another greenhouse gas) in another country. This has no deleterious environmental effect overall because a tonne of CO2 does the same amount of damage wherever it is emitted. But it is known that it is much cheaper to reduce emissions in, say, Eastern Europe than in the United States, so securing the reductions in Eastern Europe could save substantial sums of money for the US. Keeping these compliance costs down is crucial since the cost of meeting the Protocol targets are the biggest obstacle to the further international agreement (Turner & Kerry, ed. 1999). Under carbon trading, the United States would pay for the reductions but would secure the paper credit for the CO2 reductions, which it can then set its target. More sophisticated forms of trading are enabled under the Protocol as well.
Critics of the Kyoto Protocol point to the very slow pace of ratification and to the fact that even if the 2010 targets are met, very little happens to projected rates of global warming. The reason is that developing countries’ growth rates of emissions are very much higher than in the developed world. So far, developing countries have refused to adopt emission reduction targets. If they continue to refuse to do so, little will happen to change the rate of global warming. However, a more serious threat to the success of international climate cooperation came in early 2001 when President George W. Bush announced that the US would not implement the Kyoto Protocol. That the world’s greatest producer of greenhouse gases should review its climate change policy in this way was greeted with anger and frustration by governments and environmentalists worldwide, and meant that not enough big producers of greenhouse gases had signed up to bring the treaty into effect. This disappointment has been further exacerbated by the continuing refusal of Russia to ratify Kyoto, despite an initial enthusiasm to do so at the World Summit in Johannesburg in September 2002 (Johnston, 2003).
Despite the setback of at least one developed nation refusing to adhere to the Kyoto Protocol, having some form of international agreement has produced some new initiatives in environmental policy elsewhere. A number of European countries have taxes on the carbon content of fuels - so-called carbon taxes - and there is a rapid growth in the various forms of carbon trading. There is a renewed focus on renewable energy because it is generally carbon-free, and on fuel-efficient transport (Jenner & Smith, 2002). In the longer term, the agreements could still spur the technological changes needed to bring about economies based more on hydrogen than carbon, and a generally more energy-efficient world. But it could go wrong. Reflecting on the human race, James Lovelock, author of Gaia: the Practical Science of Planetary Medicine (1991), remarks: “Intelligent we may be, but as social collectives, we behave churlishly and with ignorance.” Overcoming this human trait is fundamental to global warming control.
Reducing global warming
The results of global warming could be disastrous for many parts of the world. There are many things people can do now to slow down global warming. Insulating our homes, using less electricity and recycling rubbish, particularly glass, paper, and metals, will slow down the production of greenhouse gases. Walking or cycling instead of driving can have a big effect, as can traveling by train or bus, instead of by car.
On a more specialized level, we can reduce the quantities of fossil fuels we use by developing engines and heating systems that use fuel more efficiently. Governments can encourage the use of sources of power that do not burn fuel and release carbon dioxide. These include using wind, wave, tidal, hydroelectric and geothermal power.
Increasing amounts of several other greenhouse gases are also being released into the atmosphere, besides carbon dioxide and water vapor. They include methane, nitrous oxide, and substances called CFC, or chlorofluorocarbons. The methane comes from animal wastes, rotting rubbish heaps, rice paddy fields and oil and gas drilling rigs. Much of the nitrous oxide comes from car exhausts and chemical fertilizers, while the CFCs were used in the past in refrigerators, aerosol sprays and foam packaging.
As a result of all this extra pollution, our Earth is warming up. The problem began more than 100 years ago when people began to use fuels such as petrol and oil on a large scale. By 1990, average world temperatures had risen by about a half a degree Celsius. Many scientists now believe that the average global temperature will be at least 1 degree Celsius warmer by the year 2030.
A 1-degree rise in 40 years does not sound very much, but it is much faster than any climate change in the past 10,000 years.
Bellamy, D. and Gifford, J. 1999, Wilderness Britain?: a Greenprint for the Future. Sparkford: Oxford Illustrated. Popular work by leading biologist and environmental campaigner.
Cairncross, F. 2001, Costing the Earth: the Challenge for Governments, the Opportunities for Business. Boston, MA: Harvard Business School Press. Authoritative work by leading economic journalist, with bibliographies.
Carwardine, M. 2002, The WWF Environment Handbook. London: Macdonald Optima. Attractively illustrated handbook for the general reader.
Cronin, H. 1999, The Ant and the Peacock: Altruism and Sexual Selection from Darwin to Today. Cambridge: Cambridge University Press. Chapters 2, 3, 4 (pp. 7-110).
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Durrell, L. 1999, The State of the Ark. London: Bodley Head, Popular work, based on research by the International Union for Conservation of Nature and Natural Resources.
Environment Matters: Industry's Guide to the Issues, the Challenges, and the Solutions. London: World Petrochemicals Analysis1999-. Leading monthly journal.
Jenner, P. and Smith, C. 2002, The Environmental Business Handbook. London: Euromonitor. Handbook for business and industry.
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Simpson, St. 2001, The Times Guide to the Environment: a Comprehensive Handbook to Green Issues. London: Times. Authoritative and comprehensive; with bibliography.
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