≫ What is climate change?
- Climate Change is a periodic modification of Earth’s climate brought about due to the changes in the atmosphere as well as the interactions between the atmosphere and various other geological, chemical, biological and geographical factors within the Earth’s system.
- Climate change can make weather patterns less predictable. These unforeseen weather patterns can make it difficult to maintain and grow crops, making agriculture-dependent countries like India vulnerable.
- It is also causing damaging weather events like more frequent and intense hurricanes, floods, cyclones, flooding etc.
- Due to the rising temperature caused by climate change, the ice in the polar regions is melting at an accelerated rate, causing sea levels to rise. This is damaging the coastlines due to the increased flooding and erosion.
- The cause of the current rapid climate change is due to human activities and threatening the very survival of humankind.
≫ What are the factors that cause climate change?
Climate change is caused by natural factors as well as anthropogenic factors. However, anthropogenic factors create a higher impact on contemporary climate change.
≫ Natural Factors:
There are numerous natural factors that cause the Earth’s climate to change. They affect the climate over a period of thousands to millions of years.
(i) Continental Drift:
- The present-day continents were not the same prior to 200 million years.
- They have formed millions of years ago when the landmass began to drift apart due to plate displacement.
- This movement had an impact on climate change due to the change on the landmass’s physical features and position and the change in water bodies’ position like the change in the follow of ocean currents and winds.
- The drifting of the landmass is continued today. The Himalayan range is rising approximately 1 millimetre every year as the Indian landmass is moving towards the Asian landmass.
(ii) Variation of the Earth’s orbit:
- The Earth’s orbit has an impact on the sunlight’s seasonal distribution that is reaching the Earth’s surface.
- A slight change in the Earth’s orbit can lead to variation in distribution across the world.
- There are very few changes to the average sunshine. However, it causes a high impact on the geographical and seasonal distribution.
- There are three types of orbital variations – variations in Earth’s eccentricity, variations in the tilt angle of the Earth’s axis of rotation and precession of Earth’s axis.
- These together can cause Milankovitch cycles, which have a huge impact on climate and are well-known for their connection to the glacial and interglacial periods.
- The Intergovernmental Panel on Climate Change finding showed that the Milankovitch cycles had influenced the behaviour of ice formation
(iii) Plate tectonics:
- Due to the change in the temperature in the core of the Earth, the mantle plumes and convection currents forced the Earth’s Plates to adjust leading to the rearrangement of the Earth Plate.
- This can influence the global and local patterns of climate and atmosphere.
- The oceans’ geometry is determined by the continents’ position. Therefore, the position of the continents influences the pattern of the ocean.
- The location of the sea also plays a crucial role in controlling the transfer of heat and moisture across the globe and determines the global climate.
- The recent example of the tectonic control on ocean circulation is the formation of the Isthmus of Panama about 5 million years ago, leading to the prevention of direct mixing of the Atlantic and Pacific oceans.
(iv) Volcanic Activity:
- When a volcano erupts, it emits gases and dust particles, causing a partial block of the Sunrays. This can lead to the cooling of the weather.
- Though the volcanic activities last only for a few days, the gases and ashes released by it can last for a long period, leading to it influencing climate patterns.
- Sulphur oxide emitted by the volcanic activities can combine with water to form tiny droplets of sulphuric acid. These droplets are so small that many of them can stay in the air for several years.
(v) Ocean Currents:
- Ocean current is one of the major components of the climate system.
- It is driven by horizontal winds causing the movement of the water against the sea surface.
- The temperature differences of the water influence the climate of the region.
≫ Anthropogenic Factors:
Scientists, since the beginning of the 20th century, have studied the impact of climate change caused by human activities. Global warming, the long-term rise in the average temperature of the Earth’s climate system, is a major aspect of climate change. It is mainly a human-caused increase in global surface temperature. The anthropogenic factors causing climate change are as follows:
(i) Greenhouse Gases:
- The greenhouse gases absorb heat radiation from the sun. Following the initiation of the Industrial Revolution, the emission of greenhouse gases into the atmosphere has increased exponentially.
- This has led to more absorption and retaining the heat in the atmosphere. This resulted in an increase in Global Temperature.
- The greenhouse gases mostly do not absorb the solar radiation but absorb most of the infrared emitted by the Earth’s surface.
- The main greenhouse gases include
(i) water vapour (the majority of the GHG in the atmosphere but the impact is less)
- Carbon dioxide released due to natural and anthropogenic factors spends more time in the atmosphere, leading to an increase in its impact. There has been a 30% increase in the concentration of CO2 since the start of the industrial revolution. Apart from the industrial revolution, deforestation also contributes to the increase in the CO
- Chlorofluorocarbons, used for industrial purposes, especially in refrigerants and air conditioning, is a man-made compound regulated under the Montreal Protocol due to their adverse effects on the Ozone layers.
- Methane is released due to decomposition of organic matter. It is stronger than CO2 because of its capacity to absorb more heat.
- Nitrous oxide is produced by the agricultural sector, especially in the production and use of organic fertilizers and while burning fossil fuels.
(ii) Change in the land use pattern:
- Half of the land-use change is said to have happened during the industrial era.
- Most of the forests were replaced by agricultural cropping and grazing of lands.
- The increased albedo (reflectivity of an object in space) in the snow-covered high altitude regions due to deforestation led to the cooling of the planet’s surface. The lower the albedo, the more of the Sun’s radiation gets absorbed by the planet and the temperatures will rise. If the albedo is higher and the Earth is more reflective, the more of the radiation is returned to space, leading to the cooling of the planet.
- The tropical deforestation changes the evapotranspiration rates (the amount of water vapour put in the atmosphere through evaporation and transpiration from trees), causes desertification and affects soil moisture characteristics.
- From the satellite imagery, it is seen that the clearing of forest cover for agriculture and irrigated farming in arid and semi-arid lands can increase solar energy absorption and the amount of moisture evaporated into the atmosphere.
(iii) Atmospheric aerosols:
- Atmospheric aerosol can:
- scatter and absorb the solar and infrared radiation
- change microphysical and chemical properties of the clouds
- Solar radiation, when scattered, cools the planet. On the other hand, when the aerosols absorb solar radiation, it causes an increase in the temperature of the air instead of allowing the sunlight to be absorbed by the Earth’s surface.
- Aerosols can directly affect climate change by absorbing or reflecting solar radiation. They can also produce indirect effects by modifying the cloud’s formation and properties.
- They can even be transported thousands of kilometres away from its source through wind and upper-level circulation in the atmosphere.
- There are two types of aerosols – Natural aerosols and Anthropogenic aerosols.
- The sources of natural aerosols include volcanic eruptions (produces sulphate aerosols) and biogenic sources like planktons (can produce dimethyl sulphide).
- The anthropogenic aerosols include:
- The ammonia used for fertilizers or released by the burning of plants and other organic materials forms a major source for Nitrate aerosols.
- Burning of coal and oil produces sulphur dioxide that forms a major source of sulphate aerosols
- Burning of biomass can release a combination of organic droplets and soot particles.
- Industrial activities cause the release of wide-ranging aerosols into the atmosphere.
- Vehicle emissions can produce numerous pollutants that are aerosol from the beginning or becomes one due to chemical reactions in the atmosphere.
- It is found that the concentration of aerosols is about three times higher in the Northern Hemisphere than in the Southern Hemisphere, leading to Northern Hemisphere’s radiation concentration being 50% higher than that of the Southern Hemisphere.