GREEN HOUSE EFFECT

The greenhouse effect is the process of absorption and emission of infrared radiation by the gases in the atmosphere which tends to warm earth’s atmosphere and surface. It was first investigated by Svante Arrhenius in 1896 and was firstly proposed by Joseph Fourier in 1824.

Human activity since the industrial revolution has increased the amount of green house gases in the atmosphere. It was recorded that the concentration of CO₂ and methane have increased by 36% and 148% respectively since 1750. These are the highest level that are ever recorded during the last 65000 years. Three quarters of the increase in the amount of carbon dioxide is produced by fossil fuel burning while the rest is due to deforestation.

Human activities are being continued on the earth. Therefore, carbon dioxide emissions are also continuing to rise due to continue human activities like burning of fossil fuel and deforestation.Emission scenarios have been made to estimate the changes in emission level of green house gases in the future. The future level of emissions will depend on uncertain economic, sociological, technological, and natural developments.

In most scenarios, it is found that emissions continue to increase over the century while in some these emissions are reduced. These emission scenarios combined with carbon cycle have been used to predict how the concentration 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.^[46] This is an increase of 90-250% above the concentration in the year 1750.

How the green house effect occurs

To understand green house effect, first we need to know how the temperature is regulated on earth. The earth absorbs heat energy that comes to the earth from the sun. Generally, these are the rays having shorter wavelength. To maintain a steady temperature on the earth, the earth too reflects or radiates the energy back to the atmosphere. During this process, shorter wavelength rays that came to earth returns back with longer wavelength. There are some of the gases in the atmosphere like carbon dioxide, methane which do not allow the longer wavelength rays to pass through them. They act as blankets over the surface and help in warming up the earth.
Therefore, global temperature is maintained on the earth with nearly 30ºC warm, providing a suitable condition for the survival of human beings. This is named as green house effect as the glass in a green house also possesses the similar features to the atmosphere. It has been really advantageous in the agricultural field because using this method, non- seasoned crops can be grown at any time and the crops will not need to be specified to a certain area.
Even the beneficial thing can sometimes have a negative impact. Similarly, due to the rapid increase of the green house gases, it has proven to be threatening as the temperature of earth is being rapidly increased and human beings and other living organisms are being more prone to the effect of climate change.
Human activities such as burning of fossils fuels (coal, oil and gas) and emission of gases from the vehicles have increases the amount of carbon dioxide and methane in the atmosphere. These gases lead to increased global warming.


It is of great concern that we are more likely to experience change in terms of extreme weather such as floods, droughts and storms due to natural variability in climate. It is thought that these hazards will be more intense with the global warming.

CLIMATE VARIABILITY IN PAST AND ITS EFFECTS

If we look at the past evidences, it is found out that over the past century a lot of climate variability or the climate change has occurred due to volcanic eruptions, fluctuation in the solar energy, and other natural variations. Then, since 1970s there is rampant increase in the green house gases because of human activities. The record shows that 1990 has been warm in terms of global average temperature. 1998 was the warmest year and more specifically; first eight months of 1998 were the warmest of those months on the record.

If human does not control the activities that may lead to global warming and the concentration of carbon dioxide increases by twice its value, then most probably, the temperature of the earth increases by 2.5 ºC. It may seem to be less, but it is actually the annual increase in temperature of earth. This 2.5ºC rise represents about half an ‘ice-age’ in terms of climate change and it is obviously the rapid change.
If we look at the past evidences, it is found out that over the past century a lot of climate variability or the climate change has occurred due to volcanic eruptions, fluctuation in the solar energy, and other natural variations. Then, since 1970s there is rampant increase in the green house gases because of human activities. The record shows that 1990 has been warm in terms of global average temperature. 1998 was the warmest year and more specifically; first eight months of 1998 were the warmest of those months on the record.

If human does not control the activities that may lead to global warming and the concentration of carbon dioxide increases by twice its value, then most probably, the temperature of the earth increases by 2.5 ºC. It may seem to be less, but it is actually the annual increase in temperature of earth. This 2.5ºC rise represents about half an ‘ice-age’ in terms of climate change and it is obviously the rapid change.

GREEN HOUSE GASES

Green house gases are carbon dioxide, methane, chlorofluoro carbons. Naturally occurring green house gases have a warming effect of about 33 °C. Water vapour, which is one of the green house gases causes about 36-70 percent of green house effect, methane causes 4-9 percent green house effect and ozone causes 3-7 percent of green house effect. Clouds are also responsible for the green house effect.

Role of greenhouse effect on global warming

Green house effect is obviously an important phenomena in human life as it has made the life on the earth possible. Without it, the earth won’t be warm enough for human survival. However, due to the excessive release of the green house gases, the earth is heating up so fast that green house gases that were once thought of as essential have been fearful enough to cause global warming on the earth. During this era, it has been the most debated issue. The earth is rapidly drowning into the great ocean of global warming. It has threatened whole life on earth. Droughts, hurricanes, floods, changes in sea level and islands and inhabitants disappearing have been common nowadays and these are all due to global warming.

How the global warming occurs and its effects

GLOBAL WARMING

Climate change is the fluctuation in the climate condition that may range for a long period of time from decades to millions of years. It may be limited to a small area or may even cover the whole earth. It is generally referred to as Global Warming.

HUMAN CAUSES
• Human uses fossils fuels excessively to generate power. Excessive use of the fossils fuel results in the rapid emission of green house gases. Carbon dioxide is one of the major gas that is emitted and is responsible for the global warming.
• Besides this, there are CFC gases that come out from house equipments like refrigerator and ACs and these gases too help in increasing the temperature of earth.
• Human emits carbon dioxide through different ways. Nevertheless, there are seas which absorb these gases. But the problem is that these oceans absorb green house gases very slowly. So, there is great probability of rapid increase of global warming.
• Deforestation in large scale has lower the number of trees to absorb carbon dioxide for photosynthesis and this is also one of the human cause of global warming.
• Cultivation of paddy in the fields also adds methane in the atmosphere.
• The release of nitrous oxide from agriculture and manufacturing activities traps three hundred times more heat than carbon dioxide. it has been recorded that the level of nitrous oxide has been rapidly increased since the pre industrial era.

NATURAL CAUSES OF GLOBAL WARMING
Human causes are not the sole cause of increasing issue of global warming. Many natural causes have been found out to be responsible for global warming by the scientists. They include:
• Continental drift and mountain formation
• Changes in the orbit of the earth
• Volcanic eruption
• Solar variability
• Fluctuation in solar energy.

EFFECT OF GLOBAL WARMING ON NEPAL

The major effect of it in Nepal is poor crop yield. Nepal; is an agricultural nation where most of the people depends on yielding of crops for their survival. Due to the global warming and the extreme temperature, people out her hae to face water shortages, and poor crop yield.Farmers say that changing climate patter has greatly affected the crop yielding leaving them unable to feed themselves and getting into debt.

Nepal is observing an unpredictable climate pattern. Sometimes there is an intense rainfall while in other times there is drought. There are drier winters and delayed monsoons. These changes have great impact on the melting of the Himalayan glaciers. This effect could be seen beyond Nepal as well.

Not only the environment is affected by the climate change, but also humans are affected and this effect has been more concentrated on the women. Climate change has resulted into drought in most of the places and has forced women to travel farther to fetch water and also they need to take responsibility to feed their family since the male members migrate seasonally in search of jobs.

Nepal is one of the world’s poorest nations, with 31% of its 28 million-population living below the poverty line. It has one of the lowest emissions records in the world – just 0.025% of total global greenhouse gas emissions.