Global warming is the term used to describe a gradual increase in the average temperature of the earth’s atmosphere and its oceans, a change that is believed to be permanently changing the earth’s climate.

Among the greenhouse gases, CO2 is the predominant gas leading to global warming as it traps long wave radiation and emits it back to the earth surface. Global warming is nothing but heating of surface atmosphere due to emission of greenhouse gases, thereby increasing global atmospheric temperature over a long period of time. Such changes in surface air temperature and consequent adverse impact on rainfall over a long period of time are known as climate change. If these parameters show year-to-year variations or cyclic trends, it is known as climate variability.

Global Warming Impacts

• Rising seas :- inundation of fresh water marshlands (the everglades), low-lying cities and islands with seawater. • Changes in rainfall patterns—droughts and fires in some areas, flooding in other areas.

• Increased likelihood of extreme events—such as flooding, hurricanes etc.

• Melting of the ice caps—loss of habitat near the poles. Polar bears are now ice to be greatly endangered by the shortening of their feeding season due to dwindling ce packs.

• Melting glaciers—significant melting of old glaciers is already observed.

• Widespread vanishing of animal populations—following widespread habitat loss.

• Spread of disease—migration of diseases such as malaria to new, now warmer, regions.

Bleaching of coral reefs due to warming seas and acidification due e t o carbonice wwarming formation—one third of coral reefs now appear to have been severely damaged ama gdby seas.

• Loss of Plankton due to warming seas—the enormous (900 mile long) Aleutian island ecosystems of orcas (killer whales), sea lions, sea otters, sea urchins, kelp beds, and fish populations, appears to have collapsed due to loss of plankton, leading to loss of sea lions, leading orcas to eat too many sea otters, leading to urchin explosions, leading to loss of kelp beds and their associated fish populations. 


Impact of climate change on agriculture will be one of the major deciding factors influencing the future food security of mankind on the earth. Agriculture is not only sensitive to climate change but also one of the major drivers for climate change.

over a period of time and adjusting the management practices towards achieving better harvest are challenges to the growth of agricultural sector as a whole. The climate sensitivity of agriculture is uncertain, as there is regional variation in rainfall, temperature, crops and cropping systems soils and management practices. The inter-annual variations in temperature and precipitation were much higher than the predicted changes in temperature and precipitation. The crop losses may increase if the predicted climate change increases the climate variability.

Different crops respond differently as the global warming will have a complex impact. The tropics are more dependent on agriculture as 75 per cent of world population lives in tropics and two thirds of these people’s main occupation is agriculture.

With low levels of technology, wide range of pests, diseases and weeds, land degradation, unequal land distribution and rapid population growth, any impact on tropical agriculture will affect their livelihood. Rice, wheat, maize, sorghum, soybean and barley are the six major crops in the world grown in 40 per cent cropped area, and contribute to 55 per cent of non-meat calories and over 70 per cent of animal feed. Consequently, any effect on these crops would adversely affect the food security. Projected changes, positive and negative impact of climate change on crops arc depicted below.



  • • Warmer temperatures
  • • Drier of wetter conditions
  • • Increased frequency of extreme climatic conditions
  • • Enhanced atmospheric CO2
  • • Changing market conditions


  • Increased productivity from warmer temperatures
  • Possibility of growing new crops
  • Longer growing season
  • Increased productivity from enhanced CO
  • Accelerated maturation rates
  • Decreased moisture stress


  • Increased insect infestations
  • Crop damage from extreme heat
  • Planning problems due to less reliable forecasts
  • Increased soil erosion
  • Increased weed growth and disease outbreaks
  • Decreased herbicide and pesticide efficacy
  • Increased moisture stress and droughts

The net impact on crops is uncertain and depends largely on the adaptation measures undertaken


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