Top Causes Affecting Climate: Natural and Man-Made

Climate Change brings significant changes in the global atmosphere which can further impact life on the earth. To understand this situation, we need to understand what are the factors which are responsible for climate change. In this article, we are going to discuss various factors including natural and man-made which are directly or indirectly responsible for climate change. This topic is very important for competitive exams like SSC, Banking, Railways, State PSC, etc.

 Climate Change: An Introduction:

• It is defined as long-term changes in temperature and weather patterns. These changes may be natural, for example, due to changes in the solar cycle. However, since the 19th century, human activity has been a major contributor to climate change, primarily through the burning of fossil fuels such as coal, oil, and gas.
  
• Burning fossil fuels releases greenhouse gases that wrap around the earth like a blanket, trapping the sun’s heat and increasing temperatures. Examples of greenhouse gas emissions that contribute to climate change are carbon dioxide and methane. These are caused, for example, by using gasoline to drive a car or by using coal to heat a building. 
  
• Deforestation can also contribute to the increase in carbon dioxide levels. Landfills are the main reason for methane emissions. Energy, industry, transportation, buildings, agriculture, and land use are the main sources of emissions.

Important Factors Affecting Climate Change:

1. Natural factors:

Many natural factors change the Earth’s climate. They affect climate over thousands to millions of years.

(a) Continental drift: The continents of today weren’t the same as they were 200 million years ago. They formed millions of years ago when continents began to move apart due to plate movement. This movement affected climate change by altering the physical properties and locations of land masses and the location of bodies of water, changing the order of ocean currents and winds.   The Himalayas are increasing by about one millimeter each year while the continent of India is moving towards the continent of Asia.

(b) Variations in the Earth’s orbit: The Earth’s orbit affects the seasonal distribution of sunlight reaching the surface. Slight changes in the Earth’s orbit can lead to different distributions around the world. Little change from average daylight. However, it has a significant impact on geographic and seasonal distribution. There are three types of orbital variations: variations in the eccentricity of the Earth, variations in the inclination of the Earth’s axis of rotation, and precession of the Earth’s axis.   Together these can cause Milankovitch cycles. This has a tremendous impact on climate and is known for its association with glacial and interglacial periods. Intergovernmental Panel on Climate Change results showed that Milankovitch cycles influenced ice formation behavior.

(c) Plate tectonics: Temperature changes in the Earth’s core forced mantle clouds and convection to adjust the tectonic plates, resulting in their rearrangement. This can affect global and regional climate and atmospheric patterns. The shape of the ocean is determined by the position of the continents. Therefore, the position of continents influences ocean patterns. The position of the oceans also plays an important role in controlling the global transport of heat and moisture, determining the Earth’s climate. A recent example of tectonic control of ocean circulation is the formation of the Isthmus of Panama about 5 million years ago, which prevented the direct mixing of the Atlantic and Pacific oceans. 

(d)Volcanism: When a volcano erupts, it releases gas and dust particles that partially block the sun’s rays. This can lead to cooler weather. The volcanic activity lasts only a few days, but the gas and ash released can last for a long time and affect the climate. Sulfur oxides released by volcanic activity combine with water to form tiny droplets of sulfuric acid. These droplets are so small that many can remain in the air for years. 

(e) Ocean currents: Ocean currents are one of the major components of the climate system. It is driven by horizontal winds that move water against the sea surface. Differences in water temperature affect the local climate.

2. Human factors:

Scientists have been studying the effects of human activity on climate change. Global warming, the long-term increase in the average temperature of the Earth’s climate system, is an important aspect of climate change. This is primarily an anthropogenic rise in the Earth’s surface temperature. The human-driven factors are:

(a) Greenhouse gases: Greenhouse gases absorb the sun’s thermal radiation. Since the industrial revolution began, greenhouse gas emissions into the atmosphere have increased exponentially. This resulted in greater absorption and retention of heat in the atmosphere. this is the reason behind the rise in temperature. Greenhouse gases do not absorb most of the solar radiation, but they do absorb most of the infrared radiation emitted by the earth’s surface.  

The principal greenhouse gases are:

• Water vapor (majority of greenhouse gases in the atmosphere, but less impact)
  
• Carbon dioxide released by natural and anthropogenic factors remains in the atmosphere longer, increasing its impact. CO2 concentrations have increased by 30% since the industrial revolution began. In addition to the industrial revolution, deforestation also contributes to CO increases.
  
• Chlorofluorocarbons used for industrial purposes, especially refrigerants and air conditioning, are man-made compounds that fall under the Montreal Protocol for their adverse effects on the ozone layer.   
  
• Methane is released from the decomposition of organic matter. It is more powerful than CO2 because it can absorb more heat.
  
• Nitrous oxide is produced in agriculture, especially in the production and use of organic fertilizers and in burning fossil fuels.

(b) Changes in land-use patterns: Half of the land-use change is said to have occurred during the industrial age. Most forests have been replaced by farmland cultivation and land grazing. Increased albedo (the reflectance of objects in space) in snowy high-altitude regions due to deforestation has led to the cooling of the planet’s surface. The lower the albedo, the more solar radiation is absorbed by the planet, increasing the temperature. A higher albedo and a more reflective Earth mean more radiation is reflected into space, cooling the Earth. Deforestation of tropical forests alters evapotranspiration rates (the amount of water vapor released into the atmosphere by evaporation and transpiration from trees), causes desertification, and affects soil moisture properties.  Satellite images show that clearing forest land for agriculture and irrigated agriculture in arid and semi-arid countries increases the absorption of solar energy and the amount of water that evaporates into the atmosphere. 

(c) Atmospheric aerosols: Atmospheric aerosols can: scatter and absorb solar and infrared radiation, altering the microphysical and chemical properties of clouds. Solar radiation cools the planet as it scatters. On the other hand, when aerosols absorb solar radiation, the temperature rises instead of the sunlight being absorbed by the Earth’s surface. Aerosols can be able to affect climate change directly by absorbing or reflecting solar radiation. You can also create indirect effects by changing cloud formation and properties. It can even be carried thousands of kilometers from its source by wind and atmospheric circulation. 

Aerosols are of 2 types: Natural aerosols and anthropogenic aerosols.

• Sources of natural aerosols include volcanic eruptions (which produce sulfate aerosols) and biogenic sources such as plankton (which can produce dimethyl sulfide).
  
• Anthropogenic aerosols include: Ammonia used in fertilizers or released by combustion of plants and other organic matter is a major source of nitrate aerosols. Burning coal and oil produces sulfur dioxide, which is the primary source of sulfate aerosols. The combustion of biomass can release a combination of organic droplets and soot particles. Industrial activities release various aerosols into the atmosphere. Vehicle exhaust can produce several pollutants that are either aerosols in nature or become aerosols through chemical reactions in the atmosphere. Aerosol concentrations in the northern hemisphere were found to be about three times higher than in the southern hemisphere. This means that the radioactivity concentration in the northern hemisphere is 50% higher than that in the southern hemisphere.