We feel hot during summer and cold during winter. These are the different climatic conditions that we experience. The climate of a place is the average weather that it experiences over a period of time. The factors that determine the climate at a location are the rainfall, sunshine, wind, humidity, and temperature.
While changes in the weather may occur suddenly and noticeably, changes in the climate take a long time and are therefore less obvious. There have been changes in the earth's climate and all life forms adapted naturally to this change.
However, the last 150 - 200 years climate change has been taking place too rapidly and certain plant and animal species have found it hard to adapt. Human activities are said to be responsible for the speed at which this change has occurred.
The causes of climate change can be divided into two categories - Natural and man made
There are a number of natural factors responsible for climate change. Some of the important factors are continental drift, volcanoes, ocean currents and the earth's tilt.
The continents we see today were formed when the landmass began gradually drifting apart, millions of years back. This drift changed the position of water bodies of the landmass and the flow of ocean currents and winds. These changes affect the climate. This drift of the continents continues even today.
When a volcano erupts it throws out large volumes of sulphur dioxide (SO2), water vapour, dust, and ash into the atmosphere. Although the volcanic activity may last only a few days, yet the large volumes of gases and ash can influence climatic patterns for years. The gases and dust particles partially block the incoming rays of the sun, leading to cooling.
The earth is tilted at an angle of 23.5° to the perpendicular plane of its orbital path. Changes in the tilt of the earth affect the severity of the seasons. More tilt means warmer summers and colder winters; less tilt means cooler summers and milder winters.
The oceans are a major component of the climate system. They cover about 71% of the Earth. The oceans absorb the sun's radiation about twice as much as the atmosphere
The earth receives energy from the sun, which warms the earth’s surface. As this energy passes through the atmosphere, a certain percentage (about 30) gets scattered. Some part of this energy is reflected back into the atmosphere from the land and ocean surface. Certain gases in the atmosphere form a sort of blanket around the earth and absorb some of this energy. These gases like carbon dioxide, methane, and nitrous oxide, along with water vapour, comprise less than one per cent of the atmosphere. They are called 'greenhouse gases'. Just as the glass of the greenhouse prevents the radiation of excess energy, this ‘gas blanket’ absorbs some of the energy emitted by the earth and maintains keeps temperature levels. Hence it is named ‘greenhouse effect’.
The green house effect was first recognized by a French scientist, Jean-Baptiste Fourier. He pointed out the similarity in what happens in the atmosphere and in a greenhouse.The blanket of green house gases has been in place ever since the creation of the earth. However, as a result of increased human activities, more and more of these greenhouse gases are released into the atmosphere. This leads to the blanket becoming thicker and upsets the ‘natural greenhouse effect’.
Carbon dioxide is released when we burn such fuels as coal, oil, and natural gas. And, when we destroy forests, the carbon stored in the trees escapes as carbon dioxide into the atmosphere. Increasing agricultural activities, changes in land-use patterns, and other sources lead to rising levels of methane and nitrous oxide. Industrial processes also release artificial and new greenhouse gases like CFCs (chlorofluorocarbons), while automobile exhaust fumes lead to ozone generation. The resulting enhanced greenhouse effect is more commonly referred to as global warming or climate change.
How do we contribute to the green house gases?
Climate change is a threat to mankind. The earth's average surface temperature has increased by 0.3-0.6 0C since the end of the 19th century. Such increase in temperature may seem to be minimal to us but they can lead to a disaster as highlighted below.
The increasing population has resulted in increased demand for food. This results in pressure on natural resources. Climate change will affect agricultural yield directly because of alterations in temperature and rainfall, and indirectly through changes in soil quality, pests, and diseases. It is said that the yield of cereals is expected to decline in India. Extreme weather conditions such as high temperature, heavy rainfall, floods, droughts, etc. will also affect crop production.
A warmer climate will change rainfall patterns, lead to increased droughts and floods, cause melting of glaciers and polar ice sheets, and result in increased sea- level rise. An increase in the number of cyclones and hurricanes over the last few years has been attributed to changes in temperature.
Sea level rise
One of the outcome of climate change is the rising sea level. The heating of oceans, and melting of glaciers and polar ice sheets, is predicted to raise the average sea level by about half a metre over the next century. Sea-level rise could have a number of physical impacts on coastal areas, including loss of land due to inundation and erosion, increased flooding, and salt-water intrusion. These could adversely affect coastal agriculture, drinking water resources, fisheries, human settlements, and health.
Global warming will directly affect human health by increasing cases of heat-related mortality, dehydration, spread of infectious diseases, malnutrition, and damage to public health infrastructure.
Forests and wildlife
Plants and animals in the natural environment are very sensitive to changes in climate. If the rate of climate change continues to increase, extinction of various species of plants and animals could happen.
Source : Portal Content Team