Climate change is not a new phenomenon. Change has
been a consistent feature of the earth's climate. Periods of relatively
cool temperatures caused the ice ages. For the past 10,000 years,
however, the earth has experienced the longest period of consistently
warm temperatures, since the beginning of life. That warm period almost
exactly matches the period over which modern agriculture has evolved.
For the first time in the history, climate appears to
be changing as a direct result of human activity. People have released
chlorofluorocarbons (CFCs) into the atmosphere, thereby degrading
stratospheric ozone and increasing biologically harmful ultraviolet (UV)
radiation that reaches the earth's surface. Through mining and
combustion of fossil fuels, deforestation, maintenance of livestock
nerds, and even through crop cultivation, people have released enormous
quantities of carbon dioxide (CO2), methane (CH4), and other
"greenhouse" gases into the atmosphere. Samples from ice cores
show that in past the fluctuations in global temperatures were strongly
correlated with concentrations of atmospheric CO2. Simulation models of
global atmospheric circulation predict that greenhouse gases will cause
a 2-8°C global temperature rise before the end of the 21st century.
International research organizations all over the
world and the United States Environmental Protection Agency (USEPA) are
cooperating to determine the effects of a likely global climate change
on crop production. Under such studies are: i) direct and indirect
effects of ultraviolet-B (UV-B) radiation on crop, and ii) the direct
and indirect effects of increased CO2 and temperature on different crop
Ultraviolet-B (UV-B) radiation damages leaf tissues
in crop seedlings. Leaves become stunted, stomata collapse, and
photosynthesis decreases. Some crop varieties appear to be better able
than others to withstand the adverse effects of UV radiation. Leaves of
tolerant varieties contain phenolic compounds, which are natural
chemicals that filter out harmful UV-B radiation before it can damage
sensitive tissues. Research is now in progress to predict possible
regional losses in crop productivity if UV-B radiation continues to
increase, and whether plant breeders can prevent those yield losses by
developing new varieties that tolerate UV radiation.
In addition to its adverse direct effects on crop
plants, UV-B may change the susceptibility and/or tolerance to disease.
Although, there is no evidence as of yet that susceptibility to blast is
affected by UV-B, it appears that the tolerance for blast decreases. In
other words, disease frequency is not increased by UV-B, but the effects
of disease on plant growth is enhanced by UV-B radiation.
Although, increasing atmospheric CO2 stimulates plant growth, the
beneficial effects on crop growth have been observed for levels only up
to 500 ppm. Some plant species respond positively to CO2 levels up to
1,000 ppm. Experts predict that atmospheric CO2 will surpass 650 ppm
before the end of the 21st century. Furthermore, the benefits of
increased CO2 would be lost if temperatures also rise. That is because
increased temperatures shortens the period over which crop grows.
Research is being conducted to identify means by which crop plants may
better benefit from increases in atmospheric CO2 while minimizing the
adverse effects of warmer temperatures.
Plant growth and development and primarily governed
by environmental conditions of the soil and climate of a country. The
success and failure of agricultural crop productivity is generally
related to the prevailing weather conditions. Weather plays an important
role from germination of seeds to the maturity of the crops.
Interestingly, the most important fact about climate is that it changes
on every scale of time and space, every year, decade, century and in
every region of the world.
The green revolution has made a tremendous conditions
to food production by prevailing weather condition but does not move
forward as per expectation. The changes in weather fluctuation have been
largely responsible for slowly down the production momentum of the green
revolution of early 1960. The earlier high yielding varieties of cereal
crops have become sensitive to weather vagaries and thus the yield of
such varieties have gone down substantially. The atmosphere is becoming
warmer day by day due to increase in pollutants such as CO2, CH4, CO,
SO2, SO4, nitrous oxides and particulate matters in the atmosphere. The
most important atmospheric pollutant is carbon dioxide (CO2) and its
content is increasing rapidly all over the world due to burning of
fossil fuels, coal, fire wood, etc.
The USA is the maximum producer of carbon dioxide. It
produces about 160 billion tons of CO2 annually, which is about 25 % of
the total CO2 produced in the world. Other main producers of CO2 are
China, India, Australia, Canada, Ukraine, Mexico, U.K., Brazil, France,
Spain, Germany, etc. The presence of CO2 in the atmosphere causes the
colossol warming of climate, and thus the change is rainfall pattern, a
process on which crops are highly dependent. Hill storms, flood, severe
winds blow and frosts are also expected under such conditions, which
ultimately affects the productivity of the crops 1n a country.
If the climate of any country becomes even more warm
and dry, the food production can be a tremendous problem. According to
the agricultural weather experts, the last 45 years were exceptionally
stable climatically, which have contributed towards the greatest food
expansion all over the world. Now the situations have been changed and
this is unlikely to continue in the future due to rapid environmental
degradation. However, agrometeorological informations can increase
agricultural yield in the country.