Filed under: 2.Cause of Global Warming
Cause of global warming
Almost 100% of the observed temperature increase over the last 50 years have been due to the increase in the atmosphere of greenhouse gas concentrations like water vapour, carbon dioxide (CO2), methane and ozone. Greenhouse gases are those gases that contribute to the greenhouse effect .The largest contributing source of greenhouse gas is the burning of fossil fuels leading to the emission of carbon dioxide. More than 80% of the worldwide energy demand is currently supplied by the fossil fuels coal, oil or gas. They are non-renewable as it took nature millions of years to generate this resources and yet, we are using them up within the next decade. It will be impossible to find alternative sources, which could replace fossil fuels in the short or medium term. The energy demand is simply too high.
Carbon Dioxide from Power Plants
In 2002 about 40% of U.S. carbon dioxide emissions stem from the burning of fossil fuels for the purpose of electricity generation. Coal accounts for 93 percent of the emissions from the electric utility industry.
Coal emits around 1.7 times as much carbon per unit of energy when burned as does natural gas and 1.25 times as much as oil. Natural gas gives off 50% of the carbon dioxide, the principal greenhouse gas, released by coal and 25% less carbon dioxide than oil, for the same amount of energy produced. Coal contains about 80 percent more carbon per unit of energy than gas does, and oil contains about 40 percent more. For the typical U.S. household, a metric ton of carbon equals about 10,000 miles of driving at 25 miles per gallon of gasoline or about one year of home heating using a natural gas-fired furnace or about four months of electricity from coal-fired generation.
Carbon Dioxide Emitted from Cars
About 33% of U.S carbon dioxide emissions comes from the burning of gasoline in internal-combustion engines of cars and light trucks (minivans, sport utility vehicles, pick-up trucks, and jeeps). Vehicles with poor gas mileage contribute the most to global warming. For example, according to the E.P.A’s 2000 Fuel Economy Guide, a new Dodge Durango sports utility vehicle (with a 5.9 liter engine) that gets 12 miles per gallon in the city will emit an estimated 800 pounds of carbon dioxide over a distance of 500 city miles. In other words for each gallon of gas a vehicle consumes, 19.6 pounds of carbon dioxide are emitted into the air. A new Honda Insight that gets 61 miles to the gallon will only emit about 161 pounds of carbon dioxide over the same distance of 500 city miles. Sports utility vehicles were built for rough terrain, off road driving in mountains and deserts. When they are used for city driving, they are so much overkill to the environment. If one has to have a large vehicle for their family, station wagons are an intelligent choice for city driving, especially since their price is about half that of a sports utility. Inasmuch as SUV’s have a narrow wheel base in respect to their higher silhouette, they are four times as likely as cars to rollover in an accident.
The United States is the largest consumer of oil, using 20.4 million barrels per day. In his debate with former Defense Secretary Dick Cheney, during the 2000 Presidential campaign, Senator Joseph Lieberman said, “If we can get 3 miles more per gallon from our cars, we’ll save 1 million barrels of oil a day, which is exactly what the (Arctic National Wildlife) Refuge at its best in Alaska would produce.”
If car manufacturers were to increase their fleets’ average gas mileage about 3 miles per gallon, this country could save a million barrels of oil every day, while US drivers would save $25 billion in fuel costs annually.
Carbon Dioxide from Airplanes
The UN’s Intergovernmental Panel on Climate Change estimates that aviation causes 3.5 percent of global warming, and that the figure could rise to 15 percent by 2050.
Carbon Dioxide from Buildings
Buildings structure account for about 12% of carbon dioxide emissions.
Methane
While carbon dioxide is the principal greenhouse gas, methane is second most important. According to the IPCC, Methane is more than 20 times as effective as CO2 at trapping heat in the atmosphere. Levels of atmospheric methane have risen 145% in the last 100 years. Methane is derived from sources such as rice paddies, bovine flatulence, bacteria in bogs and fossil fuel production. Most of the world’s rice, and all of the rice in the United States, is grown on flooded fields. When fields are flooded, anaerobic conditions develop and the organic matter in the soil decomposes, releasing CH4 to the atmosphere, primarily through the rice plants.
Water Vapor in the Atmosphere
Increasing water vapor is the most prevalent and most powerful greenhouse gas on the planet, but its increasing presence is the result of warming caused by carbon dioxide, methane and other greenhouse gases. Water vapor holds onto two-thirds of the heat trapped by all the greenhouse gases. As the Earth heats up relative humidity is able to increase, allowing the planet’s atmosphere to hold more water vapor, causing even more warming, thus a positive feedback scenario. Because the air is warmer, the relative humidity can be higher (in essence, the air is able to ‘hold’ more water when its warmer), leading to more water vapor in the atmosphere, says the NCDC. There is much scientific uncertainty as to the degree this feedback loop causes increased warming, inasmuch as the water vapor also causes increased cloud formation, which in turn reflects heat back out into space.
Nitrous oxide
Another greenhouse gas is Nitrous oxide (N2O), a colourless, non-flammable gas with a sweetish odour, commonly known as “laughing gas”, and sometimes used as an anaesthetic. Nitrous oxide is naturally produced by oceans and rainforests. Man-made sources of nitrous oxide include nylon and nitric acid production, the use of fertilisers in agriculture, cars with catalytic converters and the burning of organic matter. Nitrous oxide is broken down in the atmosphere by chemical reactions that involve sunlight.
Deforestation
After carbon emissions caused by humans, deforestation is the second principle cause of atmospheric carbn dioxide. (Deforestation is responsible for 20-25% of all carbon emissions entering the atmosphere, by the burning and cutting of about 34 million acres of trees each year. We are losing millions of acres of rainforests each year, the equivalent in area to the size of Italy. The destroying of tropical forests alone is throwing hundreds of millions of tons of carbon dioxide into the atmosphere each year. We are also losing temperate forests. The temperate forests of the world account for an absorption rate of 2 billion tons of carbon annually. In the temperate forests of Siberia alone, the earth is losing 10 million acres per year.
In a December, 2005 study climate models at National Center for Atmospheric Research (NCAR) show that climate change may thaw the permafrost located in the top 10 feet of permafrost, releasing carbon dioxide into the atmosphere. “People have used models to study permafrost before, but not within a fully interactive climate system model,” says NCAR’s David Lawrence, the lead author. The coauthor is Andrew Slater of the University of Colorado’s National Snow and Ice Data Center. “Thawing permafrost could send considerable amounts of water to the oceans,” says Slater, who notes that runoff to the Arctic has increased about 7 percent since the 1930s. According to the NCAR press release (December 19, 2005 )permafrost may contain 30% of all the carbon found in soil worldwide. In areas to a depth of 11.2 feet climate models (assuming business as usual scenarios) show permafrost presently in an area of 4,000,000 square miles shrinking to 1,000,000 square miles by 2050 and 400,000 square miles by 2100. With a scenario of low emissions (assuming a high degree use of alternative energy sources and conservation) permafrost is still expected to shrink to 1.5 million miles by 2100………In a USA Today (December 26, 2005) interview David Lawrence says, “If that much near-surface permafrost thaws, it could release considerable amounts of greenhouse gases into the atmosphere, and that could amplify global warming,” …..”We could be underestimating the rate of global temperature increase.”
In a study reported in the journal Science June 16, 2006 researchers say that thawing permafrost may add to the buildup in atmospheric greenhouse gases significantly, stating that present climate models do not include releases of Siberian carbon dioxide from permafrost. Dr. Ted Schuur of the University of Florida traveled to Siberia and secured samples of permafrost soil up to 10 feet in length, maintaining it in a frozen state until arriving back in his laboratory, where the thawing soil was attacked by microbes, releasing carbon dioxide in the process. The frightening scenario that scientists, Sergey A. Zimov of the Russian Academy of Sciences, Ted Schuur and Stuart Chapin III of the University of Alaska, paint is one of hundreds of billions of tons of greenhouse gases entering an already destabilized atmosphere this century, spurring yet more warming in a positive feedback syndrome. Extend this scenario to Alaska, Canada and Scandinavia, where permafrost underlies much of these regions and there’s no other way to describe it. We’re in trouble.
About 50 billion tons of carbon are estimated to be held in a frozen state in the tundra, and now the tundra is beginning to become a source of carbon dioxide. In the 1970′s University of California biologist Walter Oechel studied carbon dioxide emissions in the tundra, which until this time had been thought of as a carbon sink. Doing further tests in the 1980′s, Oechel discovered that this was no longer the case, that warming temperatures had changed the tundra to a net emitter of carbon dioxide. Says Oechel, ” We found to our great surprise that the tundra was already losing carbon dioxide to the atmosphere. So that by the start of these experiments, which was in 1982, the tundra had already warmed and dried enough, that its historic role as a carbon sink had reversed and changed. It was now losing carbon dioxide to the atmosphere. That was totally unexpected.”
The greenhouse effect
When sunlight reaches Earth’s surface some is absorbed and warms the earth and most of the rest is radiated back to the atmosphere at a longer wavelength than the sun light. Greenhouse gases in the atmosphere absorb some of these longer wavelengths before they are lost to space. The absorption of this longwave radiant energy warms the atmosphere. These greenhouse gases act like a mirror and reflect back to the Earth some of the heat energy that would otherwise be lost to space. The reflecting back of heat energy by the atmosphere is called the “greenhouse effect”.
The major natural greenhouse gases are water vapor, which causes about 36-70% of the greenhouse effect on Earth (not including clouds); carbon dioxide CO2, which causes 9-26%; methane, which causes 4-9%, and ozone, which causes 3-7%. It is not possible to state that a certain gas causes a certain percentage of the greenhouse effect, because the influences of the various gases are not additive. Other greenhouse gases include, but are not limited to, nitrous oxide, sulfur hexafluoride, hydrofluorocarbons, perfluorocarbons and chlorofluorocarbons.
Global warming causes by greenhouse effect
Greenhouse gases in the atmosphere (see above) act like a mirror and reflect back to the Earth a part of the heat radiation, which would otherwise be lost to space. The higher the concentration of green house gases like carbon dioxide in the atmosphere, the more heat energy is being reflected back to the Earth. The emission of carbon dioxide into the environment mainly from burning of fossil fuels (oil, gas, petrol, kerosene, etc.) has been increased dramatically over the past 50 years, see graph below.
Fig. 1: Cause for global warming: Carbon dioxide emissions in million tons per year over the last 200 years. (graph taken from http://www.globalwarmingart.com/wiki/Image:Global_Carbon_Emission_by_Type_png)
Fig. 2: Global warming cause: Concentration of carbon dioxide has dramatically increased in the last 50 years (Source: NOAA)
Fig 2: Trends for greenhouse gases: Carbon dioxide (CO2) and nitrous oxide (NOx) concentrations in the atmosphere are still increasing. For the other major greenhouse gases, the steady upward trend has been broken. (Graph taken from http://upload.wikimedia.org/wikipedia/en/b/bb/Major_greenhouse_gas_trends.png)
Fig 3: From which sectors do the major greenhouse gas emissions come from? The lower part of the picture shows the sources individually for the gases carbon dioxide, methane and nitrous oxide, respectively. (Graph from http://en.wikipedia.org/wiki/Image:Greenhouse_Gas_by_Sector.png)
The increase of greenhouse gas concentration (mainly carbon dioxide) led to a substantial warming of the earth and the sea, called global warming. In other words: The increase in the man-made emission of greenhouse gases is the cause for global warming. For the effects of global warming see below.
Conclusion:
Someone who respects Nature and regards mankind as a part of a larger whole would never dream about using up non-renewable resources in a short time nor would this person contaminate the environment with large amounts of pollution.
Global warming doesn’t primarily ask for a technical solution but for a different thinking and attitude. We must regain the true meaning of life . We incarnate to train those personality traits, which will finally lead to perpetual harmony with ourselves and with our environment as well as to inner calm and peace. This goal can only be reached with a respectful treatment of Nature.
By anonymous: The lesson from global warming is to base all decisions on deep respect and consideration for Nature. The true cause of global warming is our thoughtless attitude to Nature.
Leave a Comment so far
Leave a comment
