Global warming occurs when carbon dioxide (CO2) and other air pollutants and greenhouse gases collect in the atmosphere and absorb sunlight and solar radiation that have bounced off the earth’s surface. Normally, this radiation would escape into space—but these pollutants, which can last for years to centuries in the atmosphere, trap the heat and cause the planet to get hotter. That's what's known as the greenhouse effect.
There is global warming because of increased CO2 and Methane in the atmosphere. The CO2 is mostly from emissions from cars and such. The Methane is mostly from cows, meaning beef and dairy. This gets trapped in our atmosphere, letting heat warm the earth but it traps the heat. This leads to an increase in temperature.
The great increase in production of food grains (such as riceand wheat) due to the introduction of heigh- yielding varieties,to the use of pesticides,and to better management's techniques
