It is through a natural cycle that the climate always undergoes change. Hence, climate is dynamic. Different activities of man have speeded up the process of climatic changes which are seen occurring in today‘s times. Scientists from all over the globe are conducting research to identify the exact reasons for changes in the climate. Evidence is being found from ice cores, tree rings, sediments from the sea and samples of pollen. It is in two categories that causes of climate change can be divided. Some are created by humans and the others are natural causes.
• Natural causes
• Man made causes
Natural Causes Of Climate Change
Various factors are responsible for a change in climate. While some of the changes are prominent, the others are meteorites, drifting of continents, comets, tilting of the earth’s axis, volcanoes and currents from the sea.
Drifting Of Continents
Continents like Africa and South America seem to fit into each other like puzzles of a jigsaw since they were joined around two million years back and were a common large mass. The Atlantic Ocean separates the two continents. Africa’s western coastline and South America’s coastline on the east have similar broad rock belts and animal and plant fossils.
Tropical plant fossils have been discovered in the Antarctica which indicates that it was first located close to the equator, in the past where there was lush vegetation, tropical climate and swamps. Drifting of land mass led to the formation of the continents millions of years ago. Physical changes in the features of the position of the landmass, water bodies and the landmass itself changed and in turn impacted the climate. Wind and flow of currents from the ocean changed after the landmass separation which in turn caused changes in climate. Even the Himalayan range has been rising since the Indian continent is gradually making a move towards landmass in Asia.
Tilting Of The Earth’s Axis
The earth's tilts to a 23.5 degree angle to the perpendicular plane of its path in the orbit. When its northern hemisphere tilts towards the sun, it is summer and the southern hemisphere which is away from the sun, experiences winter. No seasons would have been experienced, if there was no tilt. Winters are colder and summers warmer, when the tilt is more. Every century, the axis moves at the rate of just half a degree. It is not constant. Precession or change in the axis direction is one of the reasons for changes in climate.
Volcanoes
Huge volume of ash, sulfur dioxide, dust and water vapor, is thrown out on a volcanic eruption which influences patterns of climate. Tons of sulfur dioxide gas reaches the stratosphere, when major volcanic eruptions are caused. Rays of the sun are blocked from reaching the earth, which leads to cooling. Sulfuric acid droplets are formed when water and sulfur dioxide combine and remain aloft for many years. They prevent sun energy from reaching the ground which is otherwise received by the earth.
The aerosols move around a westerly or easterly direction around the globe rapidly. This movement is slow in the south and north. Hence after major volcanic eruptions, cooling is brought about for some years. In the Philippine Islands in April 1991 and in Western Europe and New England the volcanoes erupted in 1816 which has made the places cooler due to prevention of sun rays from reaching the ground.
Currents From The Sea
One of the major components for changes in climate is the ocean currents. Twice the amount of radiation from the sun is absorbed by oceans. Heat in vast amounts is moved by the ocean currents across the earth just as the atmosphere does. It is through the water channels that the heat gets transported. Current patterns in the ocean get driven by the winds that push the surface of the sea horizontally.
Some regions of the world are influenced by the ocean currents more as compared to others. For example the Humboldt currents influence the Peru coastline. Even in the Pacific Ocean, the El Nino affects global climatic conditions. North Atlantic is also influenced strongly by the ocean currents. Ocean currents slow down the direction or change the direction. Water escapes from the oceans in the form of water vapor, which shades the earth’s surface and in the process have a cooling effect on the earth. Hence this phenomenon has impacted climate over thousands of years and continues to do so.
Manmade Causes
Humans are also responsible for changes in climate. Industrial activities increased in the nineteenth century during the Industrial Revolution. The use of fossil fuels started. Jobs were created and people started migrating to urban areas from rural areas a trend that continues till date. Concretization has taken place by clearing vegetative areas. For consumption, construction, transportation and industrialization, natural resources like natural gas, oil and coal etc. are being extensively used.
Tons of wastage is being created each day. Incredible increase in population is also seen over the years. This has led to increase of greenhouse gases within the atmosphere. Emission of carbon dioxide besides nitrous oxide and methane from the various industries is also increasing. Release of carbon monoxide and nitrogen oxide do influence the atmosphere’s chemical cycle that destroy or produce greenhouse gases.
What Are Greenhouses And Their Various Sources?
In the atmosphere, the most important greenhouse gas is carbon dioxide. Due to its emission, changes have been caused in land usage, agriculture, deforestation, clearing of land and other kinds of activities. Methane gas is derived from domesticated sheep, dairy cows, horses, goats, camels and buffaloes. In the process of cud chewing, methane gas is produced. During the maturing and sowing seasons, the paddy and rice fields release methane gas when the fields get flooded. The soil lacks oxygen and becomes anaerobic when it gets covered with water. Methane gas is formed due to bacteria and decomposition of organisms in a flooded condition. The largest areas in the world that grow rice are India and China, as rice is the staple food here. Hence a large amount of methane gas release is seen in these regions.
From waste dumps and land filling areas too, methane gas is emitted. Carbon dioxide is emitted when waste is burnt or put into the incinerator. Gas leakage from pipelines, coal mining or drilling of oil also emits methane gas in large amounts. Fertilizer application has been linked to emission of large quantities of nitrous oxide. Tilling methods, and the kind of fertilizer used and when and how it is used are also attributed to this. Nitrogen is added to the soil by leguminous plants like pulses and beans.
Contribution By Humans In Their Daily Lives
Changes in climate are seen due to the ways of living adopted by humans. In the urban areas, the main power source used is electricity which is generated from the thermal power plants. Coal, an important fossil fuel is used in running the thermal power plants which in turn releases greenhouse gasses and pollutants in large amounts into the atmosphere. Goods and people are transported from one region to another by trucks, cars and buses which run on diesel and petrol. On diesel and petrol burning, large amounts of pollutants are released into the atmosphere. Damage is also caused due to plastic which continues to remain in the environments as waste for many years.
A lot of paper is used at offices and schools etc, which leads to cutting down and felling of trees to manufacture paper. Due to continuous deforestation and no large scale plantation of trees, the amount of carbon dioxide in the air has increased. Agricultural land is being used for the construction of houses which is gradually leading to a degradation of the ecological system. Rainforests are an important resource on earth, the evolution of which takes up to millions of years. They help in absorbing emissions of carbon dioxide and when deforestation takes place, this carbon dioxide absorption also gets reduced. Hence one of the main contributors for causing a change in climate is deforestation, which will have a devastating effect on earth.
Large quantities of fertilizers are being used for growth of high yielding crops which help in increasing output in agriculture. Due to this, nitrous oxide in large amounts is being released into the atmosphere, both from the industries that make the fertilizer and also from the fields where it is used. Many of the industries release chemical waste into rivers and seas which leads to pollution and gradual climatic changes on earth.
Manmade greenhouses are causing a change in the climate. This change is likely to accelerate over the years with increasing pollution in the environment. The energy sector too is responsible for this change. Seasons have been seeing a gradual change with rain showers during the summer season, sudden temperature changes etc. which affects vegetation and health of people in the long run. Ice in the polar region too is melting due to changes in temperature and global warming. The delicate ecosystem of this earth is gradually being affected by large scale human activities on earth.