Krishnan's Blog

Measurements of temperature taken by instruments all over the world, on land and at sea have revealed that during the 20 th century the Earth’s surface and lowest part of the atmosphere warmed up on average by about 0.6°C. During this period, man-made emissions of greenhouse gases , including carbon dioxide , methane and nitrous oxide have increased, largely as a result of the burning of fossil fuels for energy and transportation, and land use changes including deforestation for agriculture. In the last 20 years, concern has grown that these two phenomena are, at least in part, associated with each other. That is to say, global warming is now considered most probably to be due to the increases in greenhouse gas emissions and concurrent increases in atmospheric greenhouse gas concentrations , which have enhanced the Earth's natural greenhouse effect . Whilst other natural causes of climate change can cause global climate to change over similar periods of time, computer mod...

Climate change has potential risks for the British Isles. Most critical of these risks is an increase in frequency and intensity of extreme weather such as hot spells, drought and storms. Accompanying a projected rise in average surface temperature of between 0.9 and 2.4°C by 2050 will be the increased occurrence of hot, dry summers, particularly in the southeast. Mild wet winters are expected to occur more often by the middle of the 21 st century , especially in the northwest, but the chance of extreme winter freezing should diminish. Higher temperatures may reduce the water -holding capacity of soils and increase the likelihood of soil moisture deficits, particularly if precipitation does not increase as well. These changes would have a major effect on the types of crops , trees or other vegetation that the soils can support. The stability of building foundations and other structures, especially in central, eastern and southern England, where clay soils with a large shrink-swe...

Methane (CH 4 ) is a colourless, odourless non-toxic gas consisting of molecules of four hydrogen atoms and one carbon atom. Methane is combustible, and mixtures of about 5 to 15% in air are explosive. It is the main constituent of natural gas, a fossil fuel . It is released into the atmosphere when organic matter decomposes in environments lacking sufficient oxygen. Natural sources include wetlands, swamps and marshes, termites, and oceans. Man-made sources include the mining and burning of fossil fuels , digestive processes in ruminant animals such as cattle, rice paddies and the burying of waste in landfills. Most methane is broken down in the atmosphere by reacting with hydroxyl (OH) radicals. Like carbon dioxide , methane is a greenhouse gas whose molecules absorb heat trying to escape to space. Methane contributes to the Earth's natural greenhouse effect . Man-made emissions of methane are helping to enhance the greenhouse effect. Since the beginning of the Industrial Re...

Chlorofluorocarbons, commonly known as CFCs, are a group of man-made compounds containing chlorine, fluorine and carbon. They are not found anywhere in nature. The production of CFCs began in the 1930s for the purpose of refrigeration. Since then they have been extensively utilised as propellants in aerosols, as blowing agents in foam manufacture and in air conditioning. There are no removal processes or sinks for CFCs in the lowest part of the atmosphere called the troposphere. As a result they are transported up into the stratosphere, between 10 to 50 km above the Earth's surface, where they are broken down by ultraviolet (UV) radiation from the Sun, releasing free chlorine atoms which cause significant ozone depletion . Although the amounts of CFCs in the atmosphere are very small, measured in parts per trillion (million million), they do contribute significantly to the enhancement of the natural greenhouse effect , because they are very good at trapping heat. Molecule for mo...

Global warming will lead to an intensification of the global water or hydrological cycle through increases in surface temperature and rates of evaporation, and in some regions, increases in precipitation . Changes in the total amount of precipitation and its frequency and intensity directly affect the magnitude and timing of run-off and the intensity of floods and droughts. Such changes will have significant impacts on regional water resources. It is not certain how individual water catchment areas will respond to changing evaporation rates and precipitation. It is likely however, that currently dry regions will be more sensitive to changes in climate. Relatively small changes in temperature and precipitation could cause relatively large changes in run-off. Arid and semi-arid regions will therefore be particularly sensitive to reduced rainfall and to increased evaporation. An increase in the duration of dry spells will not necessarily lead to an increased likelihood of low river fl...

A change in global climate would be accompanied by shifts in climatic zones, thereby altering the suitability of a region for the growth of distinctive species. Trees in particular have long reproductive cycles, and many species may not be able to respond to the climatic changes quickly enough. A shift in climatic zones not only affects the vegetation but also affects the incidence of tree pests such as insects and diseases. These pests have less difficulty in migrating with their climatic zones than vegetation and may damage tree species with lower immunity. As well as the effects of temperature and precipitation variations, and changes to weather patterns, forest growth may also respond to increased atmospheric concentrations of carbon dioxide. Studies with immature forest plantations suggest that an increase in atmospheric carbon dioxide would be beneficial to tree growth. The elevated carbon dioxide concentrations enhance photosynthesis rates with increased utilisation of carb...

The Sun, which is the Earth's only external form of heat, emits solar radiation mainly in the form of shortwave visible and ultraviolet (UV) energy. As this radiation travels toward the Earth, 25% of it is absorbed by the atmosphere and 25% is reflected by the clouds back into space. The remaining radiation travels unimpeded to the Earth and heats its surface. The Earth releases a lot of energy it has received from the Sun back to space. However, the Earth is much cooler than the Sun, so the energy re-emitted from the Earth's surface is much weaker, in the form of invisible longwave infrared (IR) radiation, sometimes called heat. Greenhouse gases like water vapour, carbon dioxide , methane and nitrous oxide trap the infrared radiation released by the Earth's surface. The atmosphere acts like the glass in a greenhouse, allowing much of the shortwave solar radiation to travel through unimpeded, but trapping a lot of the longwave heat energy trying to escape back to space...

Conventional power stations burn coal, oil or gas to produce electricity. Road vehicles also burn fossil fuel in the form of petrol or diesel, products refined from oil. Coal, oil and gas are called fossil fuels because they form over millions of years through the decay, burial and compaction of rotting vegetation on land (coal), and marine organisms on the sea floor (oil and gas). Burning fossil fuels in this way releases carbon dioxide , a greenhouse gas , which enhances the natural greenhouse effect . Coal is a solid fuel formed over millions of years by the decay of land vegetation. Over time, successive layers become buried, compacted and heated, a process through which the deposits are turned into coal. Coal is widely used in the generation of electricity in power stations because it is a highly concentrated energy source. However, it is not a particularly "clean" fuel, releasing more sulphur dioxide than either oil or gas. Coal was the first fossil fuel to be exploit...

Climate is the most significant factor in determining plant growth and productivity. Without intervention to reduce emissions of greenhouse gases, global average surface temperature is projected to increase by about 0.2°C per decade during the 21st century. This rapid change in climate will have major implications for agriculture around the world. Crop growth is often limited by temperature. Temperatures during the 21st century are expected to increase more in the higher latitudes where shifts in vegetation will be greater. In Britain an increase in temperature of 1.5°C by 2050 is the equivalent of a decrease in altitude of approximately 200m. This is the same as a shift southward in latitude of 200-300 km. Such an increase in temperature would allow widespread maize cultivation across southern England to take place. In other regions however, a rise in temperature may not be so beneficial. Small increases in temperature would extend the range of temperature-limited pests. The European ...

Carbon dioxide (CO 2 ) is a colourless, odourless gas consisting of molecules of two oxygen atoms and one carbon atom. Carbon dioxide is produced when any form of carbon or almost any carbon compound is burned in an excess of oxygen. For example, it is released into the atmosphere during natural forest fires and the man-made combustion of fossil fuels . Other natural sources of carbon dioxide include volcanic eruptions, decay of dead plant and animal matter, evaporation from the oceans and respiration (breathing). Carbon dioxide is removed from the atmosphere by carbon dioxide "sinks". The main removal processes are absorption by seawater, and utilisation (for photosynthesis) by ocean-dwelling plankton and land-dwelling biomass, including forests and grasslands. Through Earth history the amount of carbon dioxide in the atmosphere has varied significantly. The Earth's early atmosphere was probably composed mostly of carbon dioxide. At that time, the natural greenhouse e...

Although we are currently concerned about global warming caused by mankind's enhancement of the natural greenhouse effect through greenhouse gas pollution, the Earth's climate has fluctuated many times in the past in response to natural mechanisms of climate change. Such changes in global climate have also occurred over much longer time scales, from hundreds and thousands of years to millions and hundreds of millions of years. In fact the current global warming trend which began at the end of the 19 th century spans only a tiny fraction of the Earth's climatic history. Taking a longer perspective on climate variability can help us gain a better understanding of the global climate and of the evolution of the climate today and in the future. The overall state of the global climate is largely determined by balance between energy the Earth receives from the Sun and the heat which the Earth releases back to space, called the global energy balance. Many causes of climate ch...

One of the impacts which global warming may have on the surface of the Earth is to exacerbate the worldwide problem of desertification. A decrease in the total amount of rainfall in arid and semi-arid areas could increase the total area of drylands worldwide, and thus the total amount of land potentially at risk from desertification. Desertification was defined at the Rio Earth Summit in 1992 as "land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors including climatic variations and human activities". Desertification involves the depletion of vegetation and soils. Land degradation occurs all over the world, but it is only referred to as desertification when it takes place in drylands. This is because these areas are especially prone to more permanent damage as different areas of degraded land spread and merge together to form desert-like conditions. Global warming brought about by increasing greenhouse gas levels in the atmosphere is...

Everyone contributes to global emissions of greenhouse gases , but it is not only governments which can take action to reduce the threat of global warming. We all use energy for heating our homes, running electrical appliances, cooking food and driving our cars. Most of this energy comes from the burning of fossil fuels , such as oil, coal and gas, which release carbon dioxide , the main greenhouse gas, into the atmosphere. Despite uncertainties, the general scientific consensus is that increased levels of greenhouse gases as a result of mankind's activities are enhancing the Earth's natural greenhouse effect and causing global warming. Energy use is responsible for about 75% of man-made carbon dioxide emissions. Therefore, it is important to try to reduce our dependence on fossil fuels and reduce energy consumption. Energy used in the home can be saved by a number of measures, including draught proofing, insulation, and using energy efficient lighting and other household ...

During the 20 th century , the global climate has warmed by about 0.6°C, or about 0.06°C per decade. Computer models which simulate the effects on climate of increasing atmospheric greenhouse gas concentrations project that global average surface temperatures will rise by a further 3°C by the end of the 21 st century , or 0.3°C per decade. It is currently believed that most ecosystems can withstand at most a 0.1°C global temperature change per decade, before experiencing severe ecological stresses, leading in some cases to species extinction. A warming of even 2°C over the next 100 years would shift current climate zones in temperate regions of the world about 300 km towards higher latitudes, and vertically by 300 m. The composition and geographical distribution of unmanaged ecosystems will change as individual species respond to new conditions. At the same time, habitats will be degraded and fragmented by the combination of climate change, deforestation , desertification and ot...

Greenhouse gases are present in the atmosphere naturally, released by natural sources, or formed from secondary reactions taking place in the atmosphere. They include carbon dioxide , methane , nitrous oxide and ozone. In the last 200 years, mankind has been releasing substantial quantities of greenhouse gases into the atmosphere. These extra emissions are increasing greenhouse gas concentrations in the atmosphere, enhancing the natural greenhouse effect , which is believed to be causing global warming. While man-made greenhouse gases include carbon dioxide, methane and nitrous oxide, some like the CFCs are completely new to the atmosphere. Natural sources of carbon dioxide include the respiration (breathing) of animals and plants, and evaporation from the oceans. Together, these natural sources release about 150 billion tonnes of carbon dioxide each year, far outweighing the 7 billion tonnes of man-made emissions from fossil fuel burning, waste incineration, deforestation an...

Forests cover around a quarter to a third of the total land surface of the Earth. The reduction in area of this valuable environmental, social and economic resource through deforestation has the potential to cause problems on a global scale. Climate models have demonstrated a clear link between deforestation and climate change. Deforestation is the process of changing land use from forestry to a non-forest use. Western Europe has already lost over 99% of its primary forest. Today, deforestation programmes focus on the major rainforests of the tropics. In the 1980s global deforestation was estimated at 17 to 20 million hectares per year, equivalent to the size of Britain. Current tropical tree planting programmes are not keeping pace with this rate of deforestation. Countries in these areas are often under-developed and striving for improved economies. Deforestation for wood and agricultural land can provide numerous economic benefits, but can have damaging environmental impacts on ...

The Cooum River , is the famous river which ends in the city of Chennai (formerly Madras) in India on the Bay of Bengal . The river almost bisects the city. The name of Cooum appears to be derived from Tamil Literature. The word "coovalan" denotes a person who is well versed in the science of ground water, well water and stagnant water. It is also considered to be the shortest classified river draining into the Bay of Bengal and is only about 65 km long. Its source is in a place by the same name 'Koovam' in Tiruvallur district adjoining Chennai district. History Cooum is presently a river spoiled by filth and pollution and the water quality is considered to be highly toxic and completely non-potable. As early as thirty years ago recreational boats were available for leisure boating. The Annual tourism exhibition used to take tourists in the waterways until 1985. Ancient documents from the nearby temples states 'reaching salvation' on having a dip in Cooum...

If you test positive, the sooner you take steps to protect your health, the better. Early medical treatment, a healthy lifestyle and a positive attitude can help you stay well. Prompt medical care may delay the onset of AIDS and prevent some life-threatening conditions. It is important to know that a positive HIV test should always be confirmed, to be sure that it is a true positive. If your test result is positive, there are a number of important steps you can take immediately to protect your health: See a doctor, even if you don't feel sick. Try to find a doctor who has experience treating HIV. There are now many new drugs to treat HIV infection. There are important tests, immunizations and drug treatments that can help you maintain good health. It is never too early to start thinking about treatment possibilities. Have a tuberculosis (TB) test done. You may be infected with TB and not know it. Undetected TB can cause serious illness. TB can be treated successfully if detected e...

"With electronic items high on Christmas shopping lists, a new report is calling on the government to ensure that manufacturers collect and recycle unwanted computers and mobile phones to protect environmental and human health. "This is the motherboard of all problems. Federal and state governments must act to stop the dumping of millions of electronic items in landfill each year," says Jeff Angel, director of the Total Environment Centre (TEC), an independent Australian green organisation. In a report released earlier this month titled ‘Tipping Point: Australia's E-Waste Crisis', the TEC says that by the end of 2008, in excess of 168 million items of electronic waste -- known as e-waste -- will either be in landfills or on their way to be buried in the ground. The problem with this method of disposal, says the TEC's resource conservation campaigner, Jane Castle, is the hazardous legacy that e-waste can create. "There are toxic materials that are leached...

E-waste is a popular, informal name for electronic products nearing the end of their "useful life." Computers, televisions, VCRs, stereos, copiers, and fax machines are common electronic products. Many of these products can be reused, refurbished, or recycled. Unfortunately, electronic discards is one of the fastest growing segments of our nation's waste stream. With the passage of the Electronic Waste Recycling Act of 2003 , certain portions of the electronic waste stream are defined and the systems to recover and recycle them will be administratively regulated beyond the universal waste rules that now apply to material handling. Please review the CIWMB's efforts to implement the Act for more information. In addition, some researchers estimate that nearly 75 percent of old electronics are in storage, in part because of the uncertai...