GREENHOUSE EFFECT

The greenhouse effect is the process by which absorption and emission of infrared radiation by gases in the atmosphere are purported to warm a planet's lower atmosphere and surface. It was proposed by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896. The question in terms of global warming is how the strength of the presumed greenhouse effect changes when human activity increases the concentrations of greenhouse gases in the atmosphere.

Naturally occurring greenhouse gases have a mean warming effect of about 33 °C (59 °F). The major greenhouse gases are water vapor, which causes about 36–70 percent of the greenhouse effect; carbon dioxide (CO₂), which causes 9–26 percent; methane (CH₄), which causes 4–9 percent; and ozone (O₃), which causes 3–7 percent. Clouds also affect the radiation balance, but they are composed of liquid water or ice and so have different effects on radiation from water vapor.

Human activity since the Industrial Revolution has increased the amount of greenhouse gases in the atmosphere, leading to increased radiative forcing from CO₂, methane, tropospheric ozone, CFCs and nitrous oxide. The concentrations of CO₂and methane have increased by 36% and 148% respectively since 1750. These levels are much higher than at any time during the last 650,000 years, the period for which reliable data has been extracted from ice cores. Less direct geological evidence indicates that CO₂ values higher than this were last seen about 20 million years ago. Fossil fuel burning has produced about three-quarters of the increase in CO₂ from human activity over the past 20 years. Most of the rest is due to land-use change, particularly deforestation.

CO₂ emissions are continuing to rise due to the burning of fossil fuels and land-use change. Estimates of changes in future emission levels of greenhouse gases have been made, and are called "emissions scenarios." The future level of emissions will depend on uncertain economic, sociological, technological, and natural developments. In most scenarios, emissions continue to rise over the century, while in a few, emissions are reduced. These emission scenarios, combined with carbon cycle modeling, have been used to produce estimates of how atmospheric concentrations of greenhouse gases will change in the future. Using the six IPCC SRES "marker" scenarios, models suggest that by the year 2100, the atmospheric concentration of CO₂ could range between 541 and 970 ppm. This is an increase of 90-250% above the concentration in the year 1750. Fossil fuel reserves are sufficient to reach these levels and continue emissions past 2100 if coal, tar sands or methane clathrates are extensively exploited.

The destruction of stratospheric ozone by chlorofluorocarbons is sometimes mentioned in relation to global warming. Although there are a few areas of linkage, the relationship between the two is not strong. Reduction of stratospheric ozone has a cooling influence, but substantial ozone depletion did not occur until the late 1970s. Ozone in the troposphere (the lowest part of the Earth's atmosphere) does contribute to surface warming. 

MONTHLY CO2 MEASUREMENTS

Recent atmospheric carbon dioxide (CO₂) increases. Monthly Co₂ measurements display seasonal oscillations in overall yearly uptrend; each year's maximum occurs during the Northern Hemisphere's late spring, and declines during its growing season as plants remove some atmospheric CO₂.

GREENHOUSE GASES

Greenhouse effect schematic showing energy flows between space, the atmosphere, and earth's surface. Energy exchanges are expressed in watts per square meter (W/m²).

EXTERNAL FORCINGS

External forcing refers to processes external to the climate system (though not necessarily external to Earth) that influence climate. Climate responds to several types of external forcing, such as radiative forcing due to changes in atmospheric composition (mainly greenhouse gas concentrations), changes in solar luminosity, volcanic eruptions, and variations in Earth's orbit around the Sun. Attribution of recent climate change focuses on the first three types of forcing. Orbital cycles vary slowly over tens of thousands of years and thus are too gradual to have caused the temperature changes observed in the past century.

TEMPERATURE CHANGES

Two millennia of mean surface temperatures according to different reconstructions, each smoothed on a decadal scale. The instrumental record and the unsmoothed annual value for 2004 are shown in black.

Evidence for warming of the climate system includes observed increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level. The most common measure of global warming is the trend in globally averaged temperature near the Earth's surface. Expressed as a linear trend, this temperature rose by 0.74 ± 0.18 °C over the period 1906–2005. The rate of warming over the last half of that period was almost doubles that for the period as a whole (0.13 ± 0.03 °C per decade, versus 0.07 °C ± 0.02 °C per decade). The urban heat island effect is estimated to account for about 0.002 °C of warming per decade since 1900. Temperatures in the lower troposphere have increased between 0.13 and 0.22 °C (0.22 and 0.4 °F) per decade since 1979, according to satellite temperature measurements. Temperature is believed to have been relatively stable over the one or two thousand years before 1850, with regionally varying fluctuations such as the Medieval Warm Period and the Little Ice Age.

Estimates by NASA's Goddard Institute for Space Studies (GISS) and the National Climatic Data Center show that 2005 was the warmest year since reliable, widespread instrumental measurements became available in the late 1800s, exceeding the previous record set in 1998 by a few hundredths of a degree. Estimates prepared by the World Meteorological Organization and the Climatic Research Unit show 2005 as the second warmest year, behind 1998. Temperatures in 1998 were unusually warm because the strongest El Niño in the past century occurred during that year. Global temperature is subject to short-term fluctuations that overlay long term trends and can temporarily mask them. The relative stability in temperature from 2002 to 2009 is consistent with such an episode.

Temperature changes vary over the globe. Since 1979, land temperatures have increased about twice as fast as ocean temperatures (0.25 °C per decade against 0.13 °C per decade). Ocean temperatures increase more slowly than land temperatures because of the larger effective heat capacity of the oceans and because the ocean loses more heat by evaporation. The Northern Hemisphere warms faster than the Southern Hemisphere because it has more land and because it has extensive areas of seasonal snow and sea-ice cover subject to ice-albedo feedback. Although more greenhouse gases are emitted in the Northern than Southern Hemisphere this does not contribute to the difference in warming because the major greenhouse gases persist long enough to mix between hemispheres.

The thermal inertia of the oceans and slow responses of other indirect effects mean that climate can take centuries or longer to adjust to changes in forcing. Climate commitment studies indicate that even if greenhouse gases were stabilized at 2000 levels, a further warming of about 0.5 °C (0.9 °F) would still occur. 

GLOBAL WARMING- INTRO

Global warming is the increase in the average temperature of Earth's near-surface air and oceans since the mid-20th century and its projected continuation. According to the 2007 Fourth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC), global surface temperature increased 0.74 ± 0.18 °C(1.33 ± 0.32 °F) during the 20th century. Most of the observed temperature increase since the middle of the 20th century was caused by increasing concentrations of greenhouse gases, which results from human activity such as fossil fuel burning and deforestation.

Climate model projections summarized in the latest IPCC report indicate that the global surface temperature is likely to rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the 21st century. The uncertainty in this estimate arises from the use of models with differing sensitivity to greenhouse gas concentrations and the use of differing estimates of future greenhouse gas emissions. An increase in global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, probably including expansion of subtropical deserts. Warming is expected to be strongest in the Arctic and would be associated with continuing retreat of glaciers, permafrost and sea ice. Other likely effects include changes in the frequency and intensity of extreme weather events, species extinctions, and changes in agricultural yields. Warming and related changes will vary from region to region around the globe, though the nature of these regional variations is uncertain.

The scientific consensus is that anthropogenic global warming is occurring. Nevertheless, political and public debate continues. The Kyoto Protocol is aimed at stabilizing greenhouse gas concentration to prevent a "dangerous anthropogenic interference". As of November 2009, 187 states have signed and ratified the protocol. 

WORLD CLASSICAL TAMIL CONFERENCE, COIMBATORE 2010

World Classical Tamil Conference would be held in Coimbatore from 23rd Jun’10 to 27th Jun’10. 

‘CODISIA’ has been selected and announced as the venue of the world classical Tamil conference on 09th Nov’09. Tamil Internet Conference also is organized along the Tamil conference.
The chairman of the conference is Tamil Nadu CM.

The conference is organized by Tamil Nadu Govt. TN government spends crores of rupees for infrastructure development of Coimbatore. Tamil people from all over world are going to participate in the event. 

About Tamil
Tamil is spoken by Tamil people of India and SriLanka. It has official Status in Tamil Nadu, Pudhuchery, Srilanka and Malasiya. It is the first Indian language to be declared as classical language by Govt of India in 2004. 

For more details,
http://www.ulakathamizhchemmozhi.org

Tamil University - www.tamiluniversity.ac.in
Tamil Virtual University - www.tamilvu.org
INFITT - www.infitt.org
Association of Tamil computing - www. kanithamizh.in

For more details, visit http://www.ulakathamizhchemmozhi.org

TUNDRA THAWING

Climate scientists also worry that permafrost in the Arctic tundra will thaw, releasing enormous amounts of CO₂ and methane gas into the atmosphere. According to Field, the most critical, short-term concern is the release of CO₂ from decaying organic matter that has been frozen for millennia. "The new estimate of the total amount of carbon that's frozen in permafrost soils is on the order of 1,000 billion tons," he said. "By comparison, the total amount of CO₂ that's been released in fossil fuel combustion since the beginning of the Industrial Revolution is around 350 billion tons. So the amount of carbon that's stored in these frozen soils is truly vast."

Much of the carbon is locked up in frozen plants that were buried under very cold conditions and have remained in deep freeze for 25,000 to 50,000 years, he added. "We know that the Arctic is warming faster than anyplace else," he said. "And there is clear evidence that these frozen plants are very susceptible to decomposition when the tundra thaws. So melting of permafrost is poised to be an even stronger foot on the accelerator pedal of atmospheric CO_2, with every increment of warming causing an increment of permafrost-melting that shoots an increment of CO₂ into the atmosphere, which in turn increases warming.

"There's a vicious-cycle component to both the tundra-thawing and the tropical forest feedbacks, but the IPCC fourth assessment didn't consider either of them in detail. That's basically because they weren't well understood at the time."

For the fifth assessment report, Field said that he and his IPCC colleagues will have access to new research that will allow them to do a better job of assessing the full range of possible climate outcomes. "What have we learned since the fourth assessment? We now know that, without effective action, climate change is going to be larger and more difficult to deal with than we thought. If you look at the set of things that we can do as a society, taking aggressive action on climate seems like one that has the best possibility of a win-win. It can stimulate the economy, allow us to address critical environmental problems, and insure that we leave a sustainable world for our children and grandchildren. Somehow we have to find a way to kick the process into high gear. We really have very little time."

FOREST-CARBON FEEDBACK

Of particular concern is the impact of global warming on the tropics. "Tropical forests are essentially inflammable," Field said. "You couldn't get a fire to burn there if you tried. But if they dry out just a little bit, the result can be very large and destructive wildfires."

According to several recent climate models, loss of tropical forests to wildfires, deforestation and other causes could increase atmospheric CO₂ concentrations from 10 to 100 parts per million by the end of the century. This would be a significant increase, given that the total concentration of CO₂ in the atmosphere is currently about 380 parts per million, the highest in 650,000 years.

"It is increasingly clear that as you produce a warmer world, lots of forested areas that had been acting as carbon sinks could be converted to carbon sources," Field said. "Essentially we could see a forest-carbon feedback that acts like a foot on the accelerator pedal for atmospheric CO₂. We don't exactly know how strong the feedback could be, but it's pretty clear that the warmer it gets, the more likely it is that degradation of tropical forests will increase the atmospheric CO₂."

The ocean is another vital reservoir for carbon storage. Recent studies show that global warming has altered wind patterns in the Southern Ocean, which in turn has reduced the ocean's capacity to soak up excess atmospheric CO₂. "As the Earth warms, it generates faster winds over the oceans surrounding Antarctica," Field explained. "These winds essentially blow the surface water out of the way, allowing water with higher concentrations of CO₂ to rise to the surface. This higher-CO₂water is closer to CO₂-saturated, so it takes up less carbon dioxide from the atmosphere."

NOBEL PRIZE

Established by the United Nations in 1988, the IPCC brings together hundreds of experts from around the world to assess the science and policy implications of climate change. In 2007, the IPCC and Al Gore were awarded the Nobel Peace Prize. Field was among 25 IPCC scientists who attended the award ceremony in Oslo, Norway.

Since 1990, the IPCC has published four comprehensive assessment reports on human-induced climate change. Field was a coordinating lead author of the fourth assessment, Climate Change 2007, which concluded that the Earth's temperature is likely to increase 2 to 11.5 degrees Fahrenheit (1.1 to 6.4 degrees Celsius) by 2100, depending on how many tons of greenhouse gases are released into the atmosphere in coming decades.

But recent climate studies suggest that the fourth assessment report underestimated the potential severity of global warming over the next 100 years. "We now have data showing that from 2000 to 2007, greenhouse gas emissions increased far more rapidly than we expected, primarily because developing countries, like China and India, saw a huge upsurge in electric power generation, almost all of it based on coal," Field said.

This trend is likely to continue, he added, if more developing countries turn to coal and other carbon-intensive fuels to meet their energy needs. "If we're going to continue re-carbonizing the energy system, we're going to have big CO₂ emissions in the future," he said. "As a result, the impacts of climate change will probably be more serious and diverse than those described in the fourth assessment."

IPCC assessment reports are organized into three working groups. In September 2008, Field was elected co-chair of Working Group 2, which is charged with assessing the impacts of climate change on social, economic and natural systems. One of his major responsibilities is to oversee the writing and editing of the "Working Group 2 Report" for the IPCC fifth assessment, which will be published in 2014.

"In the fourth assessment, we looked at a very conservative range of climate outcomes," Field said. "The fifth assessment should include futures with a lot more warming."

CLIMATE CHANGE LIKELY TO BE MORE DEVASTATING THAN EXPERTS PREDICTED, WARNS TOP IPCC SCIENTIST

Without decisive action, global warming in the 21st century is likely to accelerate at a much faster pace and cause more environmental damage than predicted, according to a leading member of the Nobel Prize-winning Intergovernmental Panel on Climate Change.

IPCC scientist Chris Field of Stanford University and the Carnegie Institution for Science points to recent studies showing that, in a business-as-usual world, higher temperatures could ignite tropical forests and melt the Arctic tundra, releasing billions of tons of greenhouse gas that could raise global temperatures even more—a vicious cycle that could spiral out of control by the end of the century.

"There is a real risk that human-caused climate change will accelerate the release of carbon dioxide from forest and tundra ecosystems, which have been storing a lot of carbon for thousands of years," said Field, a professor of biology and of environmental Earth system science at Stanford, and a senior fellow at Stanford's Woods Institute for the Environment. "We don't want to cross a critical threshold where this massive release of carbon starts to run on autopilot."

Field will present his findings Feb. 14, at the annual meeting of the American Association for the Advancement of Science (AAAS) in Chicago during a symposium titled, "What Is New and Surprising since the IPCC Fourth Assessment?"

RAISE OF GLOBAL WARMING

Aerial view of a fire in the rainforest. Higher temperatures could ignite tropical forests and melt the Arctic tundra, releasing billions of tons of greenhouse gas that could raise global temperatures even more--a vicious cycle that could spiral out of control by the end of the century. 

COIMBATORE READY TO HOST FIRST WORLD CLASSICAL TAMIL CONFERENCE

World Classical Tamil

Coimbatore is all decked up to play host to the first the World Classical Tamil Conference beginning on Wednesday. The five day event is to be inaugurated by President Mrs Pratibha Devi Singh Patil. Thousands of Tamil scholars from across the world including, US, Switzerland, Finland, Singapore, and Malaysia are participating in the conference. A R Rahman has scored music for the theme song of the conference which has lyrics by Chief minister M.Karunanidhi.

Southern Railway has announced special trains for the benefit of people intending to visit Coimbatore for the conference, while the state government has declared a holiday for educational institutions to enable students participate in the event.

Deputy Chief Minister M.K. Stalin inaugurated the Semmozhi Kalaivizha, the cultural show organized as part of the World Classical Tamil Conference in Coimbatore last evening.

Chief Minister Mr M.Karunanidhi leaves for industrial city this morning and will visit the especially designed conference hall giving final touches for this mega event.

      In an interview to AIR, Chief Minister said that the conference assumes significance as it is being organized for the first time, after the language was accorded classical status. He invited people to gather in large numbers to make the five day event a grand success.

TANCET 2010 RESULT

Students can check their TANCET 2010 Results from the official website of Anna University. The direct link to TANCET 2010 Results –http://result.annauniv.edu/result.html. Stundents must enter their Application Number in order to fetch their TANCET 2010 Result.

Tamil Nadu Common Entrance Test (TANCET) is conducted every year by Anna University on behalf of Tamil Nadu Government for admission in the professional post-graduate programmes in various Government/Private universities/institutes in Tamil Nadu which include Anna University-Chennai, Anna University-Coimbatore, Anna University-Trichy, Anna University-Tirunelveli, Government and Government aided Institutes and Government Quota seats in private Institutes.

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NUMBER OF HUMANS WHO HAVE EVER LIVED

Estimates of "the total number of people who have ever lived" published in the 2000s range approximately from 100 to 115 billion (1 E11).

An estimate of the total number of people who have ever lived was prepared by Carl Haub of the Population Reference Bureau in 1995 and subsequently updated in 2002; the updated figure was approximately 106 billion. Haub characterized this figure as an estimate that required "selecting population sizes for different points from antiquity to the present and applying assumed birth rates to each period". Given an estimated global population of 6.2 billion in 2002, it could be inferred that about 6% of all people who had ever existed were alive in 2002.

In the 1970s it was a popular belief that 75% of all the people who had ever lived were alive in the 1970s, which would have put the total number of people who ever lived as of the 1970s as less than the number of people alive today. This view was eventually debunked.

The number is difficult to estimate for the following reasons:

§                     The set of specific characteristics that define a human is a matter of definition, and it is open to debate which members of early Homo sapiens and earlier or related species of Homo to include. See in this regard also Sorties paradox. Even if the scientific community reached wide consensus regarding which characteristics distinguished human beings, it would be nearly impossible to pinpoint the time of their first appearance to even the nearest millennium because the fossil record is simply too sparse. However, the limited size of population in early times compared to its recent size makes this source of uncertainty of limited importance.

§                     Robust statistical data only exist for the last two or three centuries. Until the late 18th century, few governments had ever performed an accurate census. In many early attempts, such as Ancient Egypt and in the Persian Empire the focus was on counting merely a subset of the people for purposes of taxation or military service. All claims of population sizes preceding the 18th century are estimates, and thus the margin of error for the total number of humans who have ever lived should be in the billions, or even tens of billions of people.

A critical item for the estimation is life expectancy. Using a figure of twenty years and the population estimates above, one can compute about fifty-eight billion. Using a figure of forty yields half of that. Life expectancy varies greatly when taking into account children who died within the first year of birth, a number very difficult to estimate for earlier times. Haub states that "life expectancy at birth probably averaged only about ten years for most of human history". His estimates for infant mortality suggest that around 40% of those who have ever lived did not survive beyond one year.

FORECASTS OF SCARCITY

In 1798 Thomas Malthus incorrectly predicted that population growth would out-run food supply by the mid 19th century. In 1968, Paul R. Ehrlich reprised this argument in The Population Bomb, predicting famine in the 1970s and 1980s. The dire predictions of Ehrlich and other neo-Malthusians were vigorously challenged by a number of economists, notably Julian Lincoln Simon. Agricultural research already under way, such as the green revolution, led to dramatic improvements in crop yields. Food production has kept pace with population growth, but Malthusians point out the green revolution relies heavily on petroleum-based fertilizers, and that many crops have become so genetically uniform that a crop failure would be very widespread. Food prices in the early 21st century are rising sharply on a global scale, and causing serious malnutrition to spread widely.

From 1950 to 1984, as the Green Revolution transformed agriculture around the world, grain production increased by over 250%. The world population has grown by about four billion since the beginning of the Green Revolution and most believe that, without the Revolution, there would be greater famine and malnutrition than the UN presently documents (approximately 850 million people suffering from chronic malnutrition in 2005). The energy for the Green Revolution was provided by fossil fuels in the form of fertilizers (natural gas), pesticides (oil), and hydrocarbon-fueled irrigation.

The peaking of world oil production (Peak oil) may test Malthus and Ehrlich critics. As of May 2008, the price of grain has been pushed up by increased farming for use in bio fuels, world oil prices at over $140 per barrel ($880/m³), global population growth, climate change, loss of agricultural land to residential and industrial development, and growing consumer demand in China and India. Food riots have recently occurred in some countries across the world. However, oil prices have fallen sharply since then, and they have remained below $100/barrel since September 2008. Resource demands are expected to ease as population growth declines, but it is unclear whether rising living standards in developing countries will once again create resource shortages.

Growing populations, falling energy sources and food shortages will create the "perfect storm" by 2030, the UK government chief scientist has warned. He said food reserves are at a fifty-year low but the world will require 50% more energy, food and water by 2030. The world will have to produce 70% more food by 2050 to feed a projected extra 2.3 billion people and as incomes rise, the United Nations' Food and Agriculture Organization (FAO) said.

The observed figures for 2007 show an actual increase in absolute numbers of undernourished people in the world, 923 million in 2007 versus 832 million in 1995; the more recent FAO estimates point out to an even more dramatic increase, to 1.02 billion in 2009.