Global Warming

  Global Warming : Introduction

Global Warming is the increase of Earth's average surface temperature due to effect of greenhouse gases which have tendency to trap the outgoing long wave IR radiations that would otherwise escape from Earth.

Sequential Process of climate change

Natural Global Warming – volcanic eruptions etc

Anthropogenic Global Warming – increased fossil fuel consumption,  deforestation, landuse changes and industrialization

  Present CO2 levels and trend

Real time CO2 monitoring by NOAA-ESRL   

  GHG contribution in Global Warming

GHG contribution to global warming depends on three main factors:

Concentration or abundance

the amount of a particular gas in the air. Larger emissions of greenhouse gases lead to higher concentrations in the atmosphere. Greenhouse gas concentrations are generally measured in parts per million.                

How long do they stay in the atmosphere?

Each of these gases can remain in the atmosphere for different amounts of time, ranging from a few years to thousands of years. All of these gases remain in the atmosphere long enough to become well mixed.

How strongly do they impact global temperatures?

Some gases are more effective than others at making the planet warmer. Equal concentration of CO2 and methane is there in system, methane will cause more warming than CO2; its the meaning of how strong and effective the gas is in causing global warming. 


Example : Water vapours cause green house effect and warming, they are present in abundance means high concentration but life time is very less so it is not considered as a green house gas.




  Radiative Forcing

In layman’s terms, Radiative Forcing refers to an imbalance between incoming solar radiation and outgoing infrared radiation that causes the Earth’s radiative balance to stay away from its normal state

As per IPCC - Radiative forcing is a measure of how the energy balance of the Earth-atmosphere system is influenced when factors that affect climate are altered

Radiative Forcing is measured in Watts / m2

Positive forcing - factors that contribute to the warming of Earth’s surface

Negative forcing -  is exerted by factors that cool Earth’s surface

On average about 342 watts of solar radiation strike each square metre of Earth’s surface per year, and this quantity can in turn be related to a rise or fall in Earth’s surface temperature.

Average Radiative Forcing (1750 -2005 by IPCC)

CO2  - 1.66 W/m²

CH 4  - 0.48 W/m²

The total net anthropogenic Radiative Forcing estimated by IPCC is equal to an average value of 1.6 W/m² [0.6 to 2.4 W/m²]. This means a warming of the climate. More than 50% of radiative forcing is due to CO2

  Global Warming Potential (GWP)

GWP is a relative measure of how much heat a GHG traps in the atmosphere. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of CO2

A GWP is calculated over a specific time interval, commonly 20, 100 or 500 years. GWP is expressed as a factor of carbon dioxide (whose GWP is standardized to 1)

For example, the 20 year GWP of Methane is 21, which means that if the same mass of methane and carbon dioxide were introduced into the atmosphere, that methane will trap 21 times more heat than the carbon dioxide over the next 20 years

The substances subject to restrictions under the Kyoto Protocol either are rapidly increasing their concentrations in Earth’s Atmosphere or have a large GWP

The GWP depends on the following factors:

  • the absorption of infrared radiation by a given species
  • the spectral location of its absorbing wavelengths
  • The atmospheric lifetime of the species

  Impacts of Global Warming

Global Warming Impacts as per IPCC

IPCC is an intergovernmental panel jointly established by the World Meteorological Organization (WMO) and the United Nations Environmental Program (UNEP) in 1988, tasked with assessing human-induced climate change and its potential impact and global warming adaptation/mitigation

IPCC Assessment Reports - 1990, 1995, 2001, 2007, 2014

IPCC Assessment : In latest report the facts were established that major reason for Global Warming is anthropogenic and substancial reduction in CO2 is requird to reduce the impacts

  • CO2 concentration had increased from approximately 280 ppm in preindustrial times to 379 ppm in 2005, 1.4 times higher in 100 years resulting in 0.74 degree C increase in temperature
  • 3 – 6 C increase in annual mean temperature by year 2100
  • 15 – 40 % increase in rainfall with high regional variability
  • Warming more pronounced over north India



Major Impacts of Global Warming

Extreme events

  • Killer heat waves
  • Torrential rains and flooding
  • Drought
  • Forests and wildfires

Sea level rise and coastal flooding - average of 10 – 20 cm, ten times the average rate over the previous three thousand years

Snow, land ice and sea ice

  • Shrinking snow cover in mountains
  • Vanishing glaciers
  • Melting permafrost (the regions permanantly covered with snow) and damage to infrastructure (North America, Siberia, and the Himalayan/Tibetan region of Asia)

Ecological impacts

  • Damage to coral reefs (coral bleaching)
  • Shifting species ranges and yearly cycles (1,400 species, 6.1 m per decade upward in altitude and towards pole)
  • Declining arctic animals, polar beer

Outbreaks of vector-borne diseases

  • Higher temperatures accelerate the maturation of certain disease-causing agents and their vectors (Dengue mosquito 12 days to 7 day if temp increase from 30 to 32-350C, malaria, dengue fever, and yellow fever)
  • Heavy precipitation events and floods, can promote explosive growth in the populations of disease vectors


  India’s GHG Emissions; Mitigation & Adaptation

India’s per capita emission of 1.18 tonnes of CO2 equivalent in 2008 was nearly one-fourth of the corresponding global average of 4.38 tonnes

Planning Commission, Govt. of India

Climate Change - Mitigation

Enhanced action by countries for reducing greenhouse gas emissions



On June 30, 2008, Prime Minister Manmohan Singh released India’s first National Action Plan on Climate Change (NAPCC) outlining existing and future policies and programs addressing climate mitigation and adaptation.  The plan identifies eight core “national missions” running through 2017 and directs ministries to submit detailed implementation plans to the Prime Minister’s Council on Climate Change by December 2008

  • National Solar Mission
  • National Mission for Enhanced Energy Efficiency
  • National Mission on Sustainable Habitat
  • National Water Mission
  • National Mission for Sustaining the Himalayan Ecosystem
  • National Mission for a “Green India”
  • National Mission for Sustainable Agriculture
  • National Mission on Strategic Knowledge for Climate Change

Climate Change - Adaptation

Increasing the capacity to meet the consequences of climate change that has already taken place and is likely to continue to take place

Sectoral approach

Energy Sector – Renewable Energy i.e. Bioenergy, geothermal, solar, wind

Agriculture – draught prone varieties, reducing the use of chemical fertilizers

General Adaptation Strategies :

  • Landuse change and management
  • Solid Waste Management
  • Wastewater Treatment
  • Energy Audits
  • Climate Change knowledge Centers
  • Early warning and cyclone shelters
  • Disaster mitigation works
  • Health Surveillance
  • Increase water efficiency, bank loan, insurance to farmers
  • Joint Forest Management
  • Research Centers