Global Warming: Causes

The various causes related to Global Warming are as follows:

Climatic Change

• The causes of climate change are many. They can be grouped into astronomical and terrestrial causes. The astronomical causes are the changes in solar output associated with sunspot activities.
• Sunspots are dark and cooler patches on the sun which increase and decrease in a cyclical manner A decrease in sunspot numbers is associated with warm and drier conditions.
• The most important anthropogenic effect on the climate is the increasing trend in the concentration of greenhouse gases in the atmosphere which is likely to cause global warming.

Greenhouse Effect

• Due to the presence of greenhouse gases, the atmosphere is behaving like a greenhouse.
• The atmosphere also transmits the incoming solar radiation but absorbs the vast majority of long-wave radiation emitted upwards by the earth’s surface.
• The gases that absorb long-wave radiation are called greenhouse gases. The processes that warm the atmosphere are often collectively referred to as the greenhouse effect.

Greenhouse Gases(GHGs)

• The primary GHGs of concern today are carbon dioxide (CO2), Chlorofluorocarbons (CFCs), methane (CH4), nitrous oxide (N2O), and ozone (O3).
• Some other gases such as nitric oxide (NO) and carbon monoxide (CO) easily react with GHGs and affect their concentration in the atmosphere.
• The effectiveness of any given GHG molecule will depend on the magnitude of the increase in its concentration, its lifetime in the atmosphere, and the wavelength of radiation that it absorbs. The chlorofluorocarbons (CFCs) are highly effective.
• Ozone that absorbs ultraviolet radiation in the stratosphere is very effective in absorbing terrestrial radiation when it is present in the lower troposphere.
• Another important point to be noted is that the more time the GHG molecule remains in the atmosphere, the longer it will take for Earth’s atmospheric system to recover from any change brought about by the latter.

Presence of Carbon Dioxide

• The largest concentration of GHGs in the atmosphere is carbon dioxide. The emission of CO2 comes mainly from fossil fuel combustion (oil, gas, and coal). Forests and oceans are the sinks of carbon dioxide.
• Forests use CO2 in their growth. So, deforestation due to changes in land use, also increases the concentration of Co2. The time taken for atmospheric CO2 to adjust to changes in sources to sinks is 20-50 years.
• It is rising at about 0.5 percent annually. Doubling of concentration of CO2 over the pre-industrial level is used as an index for estimating the changes in climate in climatic models.

Chlorofluorocarbons

• Chlorofluorocarbons (CFCs) are products of human activity. Ozone occurs in the stratosphere where ultraviolet rays convert oxygen into ozone. Thus, ultraviolet rays do not reach the earth’s surface.
• The CFCs that drift into the stratosphere destroy the ozone. Large depletion of ozone occurs over Antarctica. The depletion of ozone concentration in the stratosphere is called the ozone hole.
• This allows the ultraviolet rays to pass through the troposphere.

Global warming is the long-term warming of the planet’s overall temperature. Though this warming trend has been going on for a long time, its pace has significantly increased in the last hundred years due to the burning of fossil fuels. As the human population has increased, so has the volume of fossil fuels burned.