The earth’s temperature is determined by the balance of energy entering and leaving the planet’s system. When sunlight hits the earth’s surface, it has two options: it can be reflected into space or absorbed. The world is warmed by incoming energy that is absorbed by the ground. After absorbing the energy, the planet releases part of it as heat into the atmosphere (also called infrared radiation). The planet is not warmed by solar radiation reflected in space.
Certain gases in the atmosphere absorb energy, slowing or stopping heat loss to space. “Greenhouse gases” are the term for these gases. They operate as a blanket, trapping heat and making the soil warmer than otherwise.
The “greenhouse effect,” is generally known as a natural and necessary process for life to exist. However, the recent accumulation of greenhouse gases in the atmosphere due to human activity has altered the earth’s climate, posing a threat to human health and welfare and ecosystems.
Important Greenhouse Gases
Human emissions of greenhouse gases have been responsible for most of the warming since 1950.
Human activities such as burning fossil fuels for heat and energy, clearing forests, fertilizing crops, storing trash in landfills, rearing livestock, and generating some industrial items contribute to greenhouse gas emissions.
The principal greenhouse gas responsible for modern climate change is carbon dioxide. Carbon dioxide is released into the atmosphere due to the combustion of fossil fuels, solid waste, trees, and other biological materials, as well as chemical reactions such as cement production. Animals’ and plants’ respiration, volcanic activity, and ocean-atmosphere exchange all absorb and emit carbon dioxide as part of the natural carbon cycle.
Both natural and human activity produces methane. Natural wetland, agricultural activities, and the extraction and transportation of fossil fuels, for example, all generate methane.
N2O (Nitrogen Oxide)
Agricultural practices and natural biological processes are the primary sources of nitrous oxide. Nitrous oxide is also produced by fossil fuel combustion and industrial activities.
Coolants, foaming agents, fire extinguishers, solvents, insecticides, and aerosol propellants contain chlorofluorocarbons, HCFCs, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride, together known as F-gases.
Greenhouse Gases from Other Sources
Ozone at Ground Level
In sunlight, a chemical reaction between nitrogen oxide and volatile organic compound emissions from automobiles, power plants, and other industrial and commercial sources produces ground-level ozone. Ground-level ozone is a pollutant that can cause respiratory problems and damage crops and ecosystems in addition to trapping heat.
Water vapor is another greenhouse gas that plays an important part in climatic feedback due to its propensity to trap heat. Warmer air holds more moisture than air that is cooler.
As greenhouse gas concentrations grow and global temperatures rise, the total amount of water vapor in the atmosphere rises, increasing the warming effect even further.
Aerosols in the atmosphere have the potential to influence climate. Aerosols are minuscule (solid or liquid) particles that, unlike bigger particles, remain suspended in the air for days to weeks rather than dropping to the ground. Although some aerosols come from natural sources such as volcanoes and marine plankton, human activities such as burning fossil fuels and biomass contribute to their emissions.
Aerosols, unlike greenhouse gases, have different climate effects depending on what they are made of and where they are emitted.
Aerosols can absorb or reflect sunlight depending on their color and other characteristics. Aerosols that reflect sunlight, such as volcanic ash or sulfur emissions from coal combustion, chill the atmosphere. Warming is caused by substances that absorb sunlight, such as black carbon (a component of soot).
In addition to direct absorption of incoming and reflected sunlight, black carbon can also absorb infrared radiation.
Black carbon can also be deposited on snow and ice, darkening the surface and speeding up the melting process by increasing the snow’s absorption of sunlight.
While reducing all aerosols can result in additional warmth, reducing black carbon emissions can help minimize global warming. Clouds can interact with warming and cooling aerosols, affecting their capacity to develop and evaporate and their reflectance and precipitation rates. Clouds can help with cooling and warming by reflecting sunlight and trapping outgoing heat.