The greenhouse effect refers to circumstances where the short wavelengths of visible light from the sun pass through a transparent medium and are absorbed, but the longer wavelengths of the infrared re-radiation from the heated objects are unable to pass through that medium. The trapping of the long wavelength radiation leads to more heating and a higher resultant temperature.
Besides the heating of an automobile by sunlight through the windshield and the namesake example of heating the greenhouse by sunlight passing through sealed, transparent windows, the roundhouse effect has been widely used to describe the trapping of excess heat by the rising concentration of carbon dioxide in the atmosphere. The carbon dioxide strongly absorbs infrared and does not allow as much Of it to escape into space. Solar radiation at the frequencies of visible light largely passes through the atmosphere to warm the planetary surface, which then emits this energy at the lower frequencies of infrared thermal radiation.
Infrared radiation is absorbed by greenhouse gases, which in turn re-radiate much of the energy to the surface and lower atmosphere. The mechanism is named after the effect of solar radiation passing through glass and warming a greenhouse, but the way it retains heat is fundamentally different as a greenhouse works by reducing airflow, isolating the warm air inside the structure so that heat is not lost by convection. If an ideal thermally conductive blackbody was the same distance from the Sun as the Earth is, it would have a temperature of about 5. 3 co.
However, since the Earth reflects about 30% of the incoming sunlight, this idealized planet’s effective temperature (the temperature of a blackbody that would emit the same amount of radiation) would be about -18 co. The surface imperative of this hypothetical planet is 33 co below Earth’s actual surface temperature of approximately 14 co. The mechanism that produces this difference between the actual surface temperature and the effective temperature is due to the atmosphere and is known as the greenhouse effect Earth’s natural greenhouse effect makes life as we know it possible.
However, human activities, primarily the burning Of fossil fuels and clearing of forests, have intensified the natural greenhouse effect, causing global warming. The Earth’s atmosphere and clouds absorb and emit infrared (IR) radiation (sometimes called “heat” radiation). This is the source of the Earth’s so-called “greenhouse effect”, which both makes the Earth’s surface warmer than it would otherwise be, and also allows the atmosphere to cool to outer space. The main greenhouse gases are water vapor, carbon dioxide, and methane.
Here we look as some of the everyday consequences of the greenhouse effect in action. Weather Requires the Greenhouse Effect Most people don’t realize that without the greenhouse effect, we would not have weather. Without greenhouse gases, the atmosphere would not be able to cool in response to heating from the solar-heated surface below. The atmosphere would warm to a vertically-uniform temperature, which would inhibit vertical air currents, which are ultimately what drive most of what we perceive as “weather” (clouds, precipitation, wind, etc. Instead, the different layers of the atmosphere absorbing and emitting IR radiation cause a desalination, with strong warming of the lower atmosphere, and strong cooling of the upper atmosphere. This drives vertical air currents, and causes weather. Nighttime Cooling Without the atmosphere emitting large amounts of IR radiation downward toward the surface, nighttime temperatures would be much cooler than we observe. For example, in deserts where there is little water vapor in the atmosphere (Earth’s main greenhouse gas) nights can become very cold.
Cloud Effects at Night Most people have experienced the warming effects of clouds at night, that is, cloudy nights tend to be warmer than clear nights. This is because the intensity of IR radiation emitted downward by clouds is greater than that of the clear atmosphere. The most dramatic example is a cold winter night when clear skies give way to increasing clouds. The resulting warming can cause a temperature increase of 10 or deg. F. Mechanism of Green House Effect The solar spectrum of electromagnetic waves includes energy packed heat generating waves called radiation waves.
As they lie beyond red color waves of visible spectrum, they are also called ‘infra-red rays’. These infrared rays lie in the wave length range of 700-900 mm. Two types of infrared rays can be identified – a shorter wavelength radiation rays (700 – 800 mm) and larger wave length radiation rays (800 – 900 mm). While both these types of radiation are received by earth from sun, longer wave length rays are absorbed by carbon dioxide, carbon monoxide in the air. But shorter Waves reach the surface.
On receiving these Strong waves, the earth absorbs part of them and reflects back major part of it depending on its own capacity (black body effect). Such reflected radiation is usually in the form of long wave radiation. Major part of it may be trapped in the air, if its ICC concentration is high or obstruction in the form of dust, cloud is strong. An example of green house effect commonly experienced by all can be cited for easy understanding. Just prior to rainfall especially in early karri days, the climate is warm and dusty because of thick cloudy cover in air not allowing he earth’s reflected radiation to pass through.
The air gets heated up due to absorption of long range waves from both direct and reflected source. This phenomenon is called green house effect. In a global perspective it is relevant and a dynamic process as the composition of air is changing. The concept of reflection of waves from earth’s surface is an old natural phenomenon. But the trapping of radiation due to changed composition of air (which is dynamic in character) is an added man-made feature. Hence, the green house effect is due to man-made actions of changing the composition of air.
Greenhouse Gases Natural greenhouse gases emissions ICC (carbon dioxide) CHI (methane) NON (nitrous oxide) Anthropogenic I I H2O (water vapor) I CHIC (methane) I I ICC (carbon dioxide) 103 (ozone) I NINE (nitrous oxide) Table 1: natural and anthropogenic greenhouse gases Annual Greenhouse Gas Emission by Sector Global Warming Global warming is an average increase in the temperature of the atmosphere near the Earth’s surface and in the troposphere, which can contribute to changes in global climate patterns.
Global warming can occur from a variety of causes, both natural and human induced. In common usage, “global warming” often refers to the warming that can occur as a result of increased emissions of greenhouse gases from human activities. The origins of the term global warming are traced back to a 1 975 scientific paper titled, “Are we on the brink of a pronounced global warming? ” It was later made famous, and “stop global warming” became the slogan of a generation, after the testimony of NASA climate scientist James Hansen in front of the U. S. Senate in 1988.
Global warming refers to a slight but noticeable increase in temperature at the planetary scale. The results are not just merely warmer weather, but an erratic climate that if left unchecked could cause pervasive natural disasters and species extinction. The concern is that global warming is increasing. The greenhouse gas emissions that cause the warming trend are likely to continue into the future. The projection is that the warming will increase by six to ten degrees Fahrenheit by the end of the century. Effects of Global Warming Global warming affects many different facets of life on earth.
There will be winners and losers, even within a single region. But globally, the losses are expected to far outweigh the benefits. The regions that will get most severely affected are often the regions that emit the least green house gases. This is one of the challenges that policy makers face in finding fair international responses to the problem. Some Of the likely effects Of global warming include: Rise in Sea Level: It is a serious worry that rising sea levels from the melting of the polar ice caps could severely flood many countries.
A rise in sea levels of one meter, which many experts are predicting by the year 2100 (and some as soon as 2030), would flood 15 percent of Egypt, and 12 percent of Bangladesh. The Maldives in the Indian Ocean would almost completely disappear. Water Resources: Many of the major rivers in Europe and Asia emanate from the glaciers in the mountains. For example, the whole of the grain producing northern belt Of India is fed by rivers which originate from glaciers in the great Himalayas; electricity is also produced wherever the rivers are dammed.
Over the years it has been seen that because of global warming the glaciers are receding at an alarming rate, impacting the flow of the rivers, causing a reduction in production of food grain and electricity. Health and Disease: It is a known fact that people today are inflicted by many new diseases unheard of in the last century. Increase in ICC levels in the cities is the cause of pollution, and the effects of pollution are well documented. Global warming is also responsible for the introduction of some new diseases. Bacteria are known to be more effective and multiply much faster in warmer temperatures compared to cold temperatures.
The increase in temperature has led to increase in the microbes that cause diseases. Agriculture: It is said that should there be a few degree heating up of the earth it would have a potentially negative effect on the production of corn in North America, where most of the world’s food grain comes from. This would result in higher prices of food grain causing starvation in third world countries. On the other hand, it may so happen that colder regions further north would be able to grow crops that have never been cultivable before.
However, it is a known fact that the availability of cultivable land decreases as you go north. Ecosystems: We are aware of the fact that the ecosystem of the world is fragile and delicately balanced. Any change brought about by global warming could result in disastrous consequences. Some of these the world has experienced in the last few decades by way of floods, droughts, frequent hurricanes, tornadoes, and severe cold waves. There have also been an increased number of forest fires in the recent past. There is, however, a very divergent view on global warming facts.
Many skeptics are of the view that global warming is a good and natural phenomenon. There are various benefits of global warming, and as per them it will increase humidity in tropical deserts, melting of snow bound areas will exult in vast tracks of land getting available for agriculture, the increase in carbon dioxide in the atmosphere will trigger plant growth. Another argument of global warming is that the earth has been gradually warming up through history, and nature will continue to adapt to these changes.
Despite the views of some skeptics mentioned above, there is a recorded negative impact of global warming. Due to the direct link between global warming and the greenhouse effect, the only way to turn the situation around is for everyone to do their bit to reduce the emission Of greenhouse gases. Reduction of use of fossil fuels, use of alternate sources of energy, restricting the emission of pollutants by industries, reducing forest degradation, eliminating the use of CIFS and planting more trees will help us overcome this seemingly insurmountable problem.
Some Important Facts about Global Warming 1 . While greenhouse effect pertains to increased concentration of gases within the atmosphere of earth, global warming is the average rise in temperature near the surface of the earth. 2. Global warming is a slow and consistent increase in temperature in the last 0 years, whereas greenhouse effect is faster in comparison 3. Greenhouse gases absorb infrared radiation and prevent it from escaping to space. 4. Carbon dioxide, methane, and nitrous oxide are very good at capturing energy at wavelengths that other compounds miss. . Average temperatures have climbed 1. 4 degrees Fahrenheit (0. 8 degree 6. Celsius) around the world since 1 880, much of this in recent decades, according to Anna’s Goddard Institute for Space Studies. 6. The rate of warming is increasing. The 20th century’s last two decades were the hottest in 400 years and possibly the warmest for several millennia, according to a number of climate studies. And the United Nations’ Intergovernmental panel on Climate Change (EPIC) reports that 11 of the past 12 years are among the dozen warmest since 1850. 7.
The Arctic is feeling the effects the most. Average temperatures in Alaska, western Canada, and eastern Russia have risen at twice the global average, according to the multinational Arctic Climate Impact Assessment report compiled between 2000 and 2004. 8. Arctic ice is rapidly disappearing, and the region may have its first completely ice or earlier. Polar bears and indigenous cultures are already offering from the sea-ice loss. 9. Glaciers and mountain snows are rapidly melting-?for example, Montana’s Glacier National Park now has only 27 glaciers, versus 150 in 1910.
In the Northern Hemisphere, thaws also come a week earlier in spring and freezes begin a week later. 10. Coral reefs, which are highly sensitive to small changes in water temperature, suffered the worst bleaching-?or die-off in response to stress-?ever recorded in 1998, with some areas seeing bleach rates of 70 percent. Experts expect these sorts of events to increase in frequency and intensity in the next 50 years as sea temperatures rise. 1 1 .
An upsurge in the amount of extreme weather events, such as wildfires, heat waves, and strong tropical storms, is also attributed in part to climate change by some experts. 12. Sea levels have risen between 4-8 inches worldwide during the last century, and experts predict they could rise as much 2 feet in the next 100 years. What Can We Do About Global Warming? We can’t realistically stop the rise of ICC in the near term, but we can slow it and therefore reduce the consequences that will occur.
More fuel-efficient ears, less frivolous driving, more use of mass transit, improved insulation to decrease the fuel burned to heat and cool our homes, more efficient appliances, use of fluorescent rather than incandescent light bulbs, and careful monitoring of home electricity usage (turn off the lights and TV when not using them) can reduce our energy needs. Conversion to alternatives like wind and solar power which don’t burn fossil fuels and emit ICC into the atmosphere. Planting large areas with trees will consume ICC as the trees grow, until the forests mature.