Climate change is the gradual change in a region’s weather. It spans from its origin through various geological periods to now. For example, it is a change from a sub-humid climate to a sub-arid climate.

The very slow, natural changes in the world’s climate over billions of years are called whole climate change. They occurred during different geologic epochs since the Earth’s origin. Current climate change is the most rapid climate shift. It is mainly due to human activity over the last 2,000 years. Due to various terrestrial and non-terrestrial reasons, the climate has changed in a short period of time. Various terrestrial and non-terrestrial causes of climate change are discussed below- Natural Causes, Geogenic Causes and Anthropogenic Causes

Natural Causes for Climate Change

• Solar radiation: Changes in its amount indicate climate shifts. The Sun is a variable star, and the amount of solar radiation decreases with time. Solar radiation varies for many reasons. They include changes in the atmosphere’s clarity, the Earth-Sun distance, and the energy radiated from the surface. Changes in the surface cover also play a role. A decrease in solar flares affects the thermal effect of sunlight. About 30 million years ago, the thermal output of sunlight decreased by about 40% compared to today, resulting in a cooler climate. According to scientist Simpson, Earth becomes warmer as solar radiation increases. It increases the water vapour-holding capacity of the air. Wind speed is very fast, and precipitation increases in the polar regions.
• Sunspots: Small black dots in the solar or sun’s bright halo are called sunspots. An increase in the number of these sunspots leads to an increase in surface enhancement, and a decrease in the number of sunspots shows the reverse. A sunspot cycle is, on average, 11 years. According to scientists, when the number of sunspots decreases, ozone in the stratosphere and the stratospheric temperature rise due to increased levels of gas and consequent absorption of UV rays. On the other hand, an increase in the number of sunspots increases the accumulation of ice particles and the intensity of storms.
• Precession: The equatorial position of the Earth’s axis changes every 10,500 years. In the Northern Hemisphere in January, the distance between the Sun and the Earth is the smallest (about 14.7 million km), which is known as the perihelion position. Earth receives relatively more solar energy during this time. On the other hand, on July 4, the distance between the Sun and the Earth is maximum (about 15 crores 20 lakhs), called Apasura. In this case, the Earth receives a relatively lesser amount of sunlight. This change in position with a time difference of about 10,500 years causes a difference in the amount of sunlight received, and this change in position is called positional ionization. Therefore, every 10,500 years, there is a winter season in the Northern Hemisphere of the Sun and a summer season in the following position. As a result, summers are hotter and winters cooler than at present, which accelerates climate change.
• Changes in Earth’s Orbit: The shape of Earth’s orbit around the Sun is not constant. Every 90,000 to 100,000 years, its shape changes from roughly circular to elongated elliptical. As a result, the distance between the Earth and the Sun changes in the winter and summer, and the amount of solar energy gained by the Earth increases, as does climate change. In a nearly circular orbit, the solar energy received by Earth increases by 0.014% compared to the present, increasing the temperature and ushering in the supernova. Again, in long elliptical orbits, it decreases to 0.17%, the vorticity is greatly reduced, and the cold age begins.
• Obliquity of the Earth’s axis: Earth’s axis is tilted at an angle of 66½° to the orbit when it revolves around the Sun. This angular position changes by 22°-25° every 45,000-50,000 years. As a result, the thermal effect of solar radiation also changes considerably. For example, if the tilt of the Earth’s axis is at maximum, the intensity of summer and winter is quite high, and on the other hand, if the tilt of the axis is at minimum, the intensity of summer and winter is also reduced.
• Eccentricity of the Earth’s orbit: The difference in distance between the Earth and the Sun affects the Earth’s climate over long periods. The orbit changes from circular to elliptical in about 98,000 years. Changes in solar heat gain due to changes in orbital shape also result in changes in solar heat gain. If the Earth’s orbit is elliptical, the amount of solar heat received decreases as the distance between the Sun and the Earth increases. Again, when the Earth’s orbit is circular, the amount of solar heat received increases as the distance is shorter.
• Cosmic events: extraterrestrial meteorites. When comets and planetary debris cover the Earth’s atmosphere, cooling is reduced, reducing the thermal effect of sunlight. Five to six million years ago, a remnant of the planet Earth hit the surface, and a large amount of dust was created and mixed with the atmosphere to cover the sun for several years. As a result, the Earth’s temperature decreased, and the Pleistocene Ice Age appeared.

Geogenic Causes of Climate Change

• Eruption: Volcanic ash, including gases like CO2 and SO2, warms the atmosphere. Again, the eruptions in the coastal countries cause the sea water to rise, and events like El Niño change the climate. For example, the massive eruptions of the Krakatoa volcano in Indonesia in 1883 and the East Asian volcanoes in 1991-92 covered the atmosphere. As a result, the development of the world decreases.
• Continental drift: The German climatologist Alfred Wegener said, that during the Permian, the continents were a single landmass, Pangaea, at higher latitudes, south of their present location. They were surrounded by a single ocean, Panthalassa. Since the Mesozoic era, the breakup of Pangaea has occurred in different directions. Antarctica moved to the south, North and South America to the west, India and Australia to the northeast, and reached their present climates. As a result, Brazil, Argentina, India, Australia, and Antarctica have many traces of the high-latitude cold climate of the Southern Hemisphere.
• Sheet rifts: Reversible movement of sheets causes lava to be ejected and ocean currents to form. On the other hand, rift ridges caused by convergent movement of the sheets indicate changes in climate by affecting precipitation and wind.
• Mountain formation: It is the creation of tall ridges at convergent plate boundaries. Massive tectonic movements cause this. They block airflow and cool the air at high altitudes. The Earth is cooling. The land can store less heat and radiate more. The uplift of the Himalayas and Tibetan Plateau caused a cool, dry desert climate in western China and Central Asia. During the Pleistocene glaciation, four Ice Ages and four Upper Interglacials appeared in succession. This was due to the formation of high, widespread mountains, which raised the surface, and subsidence, which lowered it.
• Heat stored in ocean water: Changes in sea surface temperature cause long-lasting climate impacts. These include [i] sea level rise from climate change, which increases land elevation, and [ii] the slow warming and cooling of water due to its greater importance than air. Moreover, solar energy penetrates deep into sea water. As a result, ocean water stores a large amount of heat, which becomes a secondary energy alternative to solar energy to heat the atmosphere. [iii] Ocean currents transport heat stored in water, causing long-lasting changes in climate.
• Carbon dioxide theory: Since the Industrial Revolution, carbon dioxide in the atmosphere has increased by 0.5% annually due to fossil fuel burning and deforestation. Atmospheric CO₂ increased by 10% between 1860 and 1970. This gas, along with methane (CH4), nitrogen dioxide, and sulfur dioxide, has stored heat by absorbing the sun’s short-wave rays and blocking long-wave radiation. It also contains water vapour. This phenomenon is called the Greenhouse Effect. As a result, improvements have been increasing all over the world. This phenomenon is called land development. Global warming has increased the Earth’s temperature by about 0.5°-0.7°C over the past century. Again, land development will increase seawater evaporation and cloudiness due to increased CO₂. As a result, solar radiation reaching the Earth will be blocked, and the temperature will decrease naturally.

Anthropogenic Causes of Climate Change

Human activities have changed the atmosphere’s structure. They were inconsiderate. As a result, the greenhouse effect and globalization have caused rapid, lasting climate change. Human activities that are currently changing the Earth’s climate are:

• Industrialization: Since the Industrial Revolution, factories around the world have released various pollutants, including ash, smoke, and greenhouse gases, causing long-lasting and widespread climate change by depleting the ozone layer and increasing global temperatures.
• Combustion of Fossil Fuels: Indiscriminate burning of coal, natural gas, and mineral oil for thermal power generation, industrial plants, vehicles, and household use in the developed and developing countries of the world releases large amounts of CO2, CO, SO2, N2O, CH4, etc. into the air as greenhouse gases, heating the atmosphere at an alarming rate. Indirectly changing the climate.
• Vehicles: Emissions from diesel, petrol, and gasoline vehicles, including CO, CO2, N2O, and carbon particles, are causing severe climate change through land development and pollution.
• Deforestation: Since the mid-20th century, rapid population growth has destroyed 20 million hectares of forest each year for agriculture, industry, roads, and settlements. As a result, CO₂ absorption in the air has decreased. The average temperature of the Earth is increasing.
• Agriculture: The use of chemical fertilizers and pesticides in the cultivation of high-yielding crops increases N₂O, NH₄, and CH₄ gases. CH₄ is emitted from agricultural waste. These have made the greenhouse effect and climate change more dangerous.
• Urbanization: Population growth has led to rapid urbanization, leading to an unprecedented increase in the number of brick-and-concrete houses that trap heat and increase urban temperatures by destroying forests. Emissions of CO₂, CH₄, CFC, and N₂O from municipal organic waste decomposition, vehicles, and household appliances (refrigerators, AC) increase the greenhouse effect and heat. This city-centered climate is called a heat island.
• Thermal and Nuclear Power Generation: Coal, Diesel & During the generation of electricity by burning nuclear minerals, a large amount of heat, ash, smoke, CO2, N2O, NH4, SO2, and radioactive materials are released into the air, increasing the greenhouse effect and causing climate change.
• Nuclear Testing: Water-Land-Air Underground Nuclear Testing in World War II and the Post-Cold War Earth’s climate is being changed by heat and radioactive radiation emitted during inspections and nuclear explosions.
• Emissions of substances that deplete the ozone layer: the depletion of the ozone layer is caused by the emission of various pollutants, especially chlorofluorocarbons, and the increase in ultraviolet radiation causes climate change.