GLOBAL CLIMATE CHANGE
Climate is the consistent, long-term behavior of weather over time, including its variability; this contrasts with weather, which is the condition of the atmosphere at any given place and time. Global climate does not stay the same but fluctuates. Long-term influences on climate include the wobble of the earth as it rotates the variation of its tilt, and the shape of the earth’s orbit around the sun. These influences cause cycles that last tens and hundreds of thousands of years.
Other natural influences on climate change include plate tectonics, which build mountains; volcanic eruptions, whose gases and ash can cause temperatures to decline; and oceanic circulation patterns. Changes in the configuration of ocean basins, in sea surface temperatures, and in salinity and upwelling and down welling rates affect the formation of marine air masses and air temperature.
Until the industrial revolution began in the early 19th century, life forms on earth had coevolved with all of these natural influences, including naturally occurring pollutants like nitrogen oxides, carbon monoxide, hydrocarbons from plants and trees, and carbon dioxide. But when the age of industry began, something changed. Humans began to burn fossil fuels oil, coal, and natural gases at ever increasing rates, injecting additional amounts of pollutants into the atmosphere. These anthropogenic contaminants are forcing global climate to change faster than it would if these concentrations of pollutants were absent. The signs of global climate change are all around us.
Thousands of research scientists in an array of disciplines, including paleoclimatology, oceanography, geology, climatology, biology, biogeography, and ecology are amassing a huge body of research that documents evidence not only of wide scale climatic change but also of the effects of this change. Paleoclimatologists know from ice-core records that climate has abruptly shifted in the past. But whether global climate change is gradual or quick, there are many more human witnesses to it. Never before in the history of the planet have there been so many people. We are living in the fastest climate warming in the past 10,000 years, and there are 6.3 billion people to experience it. Some will benefit, but many will be harmed. Even if we were to stop all emissions of greenhouse gases now, the warming will continue, since greenhouse gases stay in the atmosphere for decades and centuries.
Green House Effect
The greenhouse effect is a naturally occurring process that aids in heating the Earth’s surface and atmosphere. The atmospheric gases change the energy balance of the planet by absorbing long wave radiation from the Earth’s surface. Without the greenhouse effect, life on this planet would probably not exist as the average temperature of the Earth would be a chilly -18°C, rather than the present 15°C.
Since 1750, methane concentrations in the atmosphere have increased by more than 140 %. Methane is produced in anaerobic environments by the action of methanogenic bacteria and by biomass burning. The major anaerobic environments that produce CH include wetlands, rice fields and enteric fermentation in the digestive system of cattle, sheep.
Since the Industrial Revolution, the level of nitrous oxide in the atmosphere has increased by 16%. Livestock & fertilizers are the largest source of atmospheric ammonia emission. Due to the long time it spends in the atmosphere, the Nitrous oxide that we release today will still be trapping heat well into the next century.
CFCs absorb infrared in wavelengths missed by carbon dioxide and water vapor in the lower troposphere. As radioactively active gases, CFCs enhance the greenhouse effect in the troposphere and are a cause of ozone depletion and slight cooling in the stratosphere. They diffuse up in the stratosphere, where they are destroyed by photolysis by solar radiation and by reaction with excited atomic oxygen.
Krypton 85 & other trace gases
Krypton 85 emitted from nuclear reactors reduces the electrical resistance of the atmosphere between the oceans & the ionosphere. This in turn affects the electrification of thunder & precipitation levels.
Other trace gases
Other trace gases include bromide compounds, carbon tetrafluoride, carbon tetrachloride & methyl chloride. It is estimated that increased presence of these gases may increase global surface t° up to 1.4 – 2.2°C.
Atmospheric measurements confirm that halogen source gases with long atmospheric lifetimes are well mixed in the troposphere and are present in the stratosphere. Increased UV radiation in the troposphere can result in increased amounts of photochemical smog. Photochemical smog is already a health hazard in many of the world’s largest cities. Photochemical smog is a mixture of primary and secondary pollutants that forms when some of the primary pollutants interact under the influence of sunlight. The resulting mix of more than 100 chemicals is dominated by ozone, a highly reactive gas that harms most living organisms. On a sunny day the smog builds up to peak levels by early afternoon, irritating people’s eyes and respiratory tracts. People with asthma and other respiratory problems, and healthy people who exercise outdoors between 11 a.m. and 4 p.m., are especially vulnerable.
The understanding of the impact of ozone depletion on climate change has been strengthened. There has been a global and annual-mean cooling of the stratosphere over the past two decades, which can be largely attributed to the observed stratospheric ozone depletion and increases in well-mixed greenhouse gases and water vapor. As has been noted in past assessments, cooling of the lower stratosphere leads to cooling of the Earth’s climate system.
Other atmospheric changes influence both the ozone layer and the climate system. Observations have provided stronger evidence for a widespread increase in stratospheric water vapor, which plays a role both in cooling the lower stratosphere and in depleting ozone through chemical interactions, thereby contributing to climate processes. Greenhouse gases exert some influence on ozone depletion. Further, surface ultraviolet radiation may be directly affected, both positively and negatively, by the effects of climate change (for example, changing cloudiness). Today, some scientists are predicting the stratospheric ozone layer will recover to 1980 ozone levels by the year 2050.
Albedo is the term used to describe the proportion of energy reflected and hence is a measure of the ability of the surface to reflect radiation. Land-use changes create differences in albedo which have important effects on the energy balance and water balance. Over grazing and deforestation affect temperature levels. Decrease in plant cover would lead to a decrease in the net incoming radiation and an increase in the radiative cooling of the air resulting in suppressed rainfall.
Global pollution trends
If car numbers keep increasing at the present rate, there will be more than a billion on the road by 2025. Today, motor vehicles put out 900 million tonnes of carbon dioxide a year – about 15 per cent of our total output. More vehicles will mean more global warming.
Also by 2025, two-thirds of the world’s people will live in cities, so traffic jams and pollution will loom large in most people’s lives. Worst of all will be the mega cities of Asia. Beijing, Shanghai and Kolkota will each be home to as many as 20 million people, Mumbai to 25 million.
Life in the country may not be much better. Asia is heading for a downpour of acid rain that will destroy forests and wither crops. The worst hit look like being Thailand, south-east China, north-east India and Korea, where economic growth is powered by fossil fuels rich in Sulphur.
Industrialized nations have reduced SO2 emissions. They have also cut production of CFCs and halons, the chemicals that destroy stratospheric ozone. But the ozone layer is not yet safe. Under the Montreal Protocol, developing nations have until 2010 to cut production. There is still a black market in CFCs, and halon production has increased in countries such as Brazil, India, Mexico and China.
Global climate change is likely to create uncertainties and instabilities. Most systems are complex and human agency is but one component of them. One big component in global climate change!
All over the world glaciers and ice caps are melting; sea levels are rising at record levels, increased/decreased precipitations and droughts in certain parts of the world. The average global temperatures have increased by 5°C in the past century.
The complexity of the climate system makes it difficult to predict some aspects of human-induced climate change. Historic records indicate global climate changes in the past without human involvement. The changes in the past occurred as a natural cycle. But today studies indicate that we are rushing towards that kind of global climate cataclysm. Will this lead to end of human race? That remains to be seen. Although God has given us dominion over nature, we need to respect her and be more environmentally friendly in our lifestyles.
Recently I saw the movie “The Day After Tomorrow”. The movie clearly depicted what we can expect when there is a global climate change. Although it is fictional, but the very thought of the consequences of climate change sent shivers down my spine. I guess it is time for mankind to wake up to the truth about global climate change.
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