Increase in carbon dioxide, however, is beneficial for several crops such as wheat, rice, legumes and oilseeds. Crops such as maize, jowar, bajra and sugarcane do not benefit from increased carbon dioxide.

Extreme weather events have their way of impacting the crops. A study conducted on onion crop in Maharashtra indicates that the crop failed in 1997 Rabi due to high temperatures in bulb formation stage and in 1998 Kharif due to Purple Blotch and Stemphylium Blight diseases which were induced by high rainfall.

It has also been observed that the apple belt is shifting upwards in the apple growing areas of Himachal Pradesh due to decreasing chilling hours and increasing temperature during November to March months. New areas of apple cultivation have appeared in Lahaul and Spitti and upper reaches of Kinnaur district of Himachal Pradesh.

The analysis of data for the period 1901 to 2005 indicates increase in the annual mean temperature by 0.50C. The long-term variation of the mean annual temperature of the country for the period 1875 to 2004 was in the order of 0.030C per decade while for the period 1971 to 2004 it was around 0.220C per decade indicating greater warming in the recent decades.

Analysis of long term (1952-2007) mean annual temperature trends of 47 locations spread across the country indicated increasing trend in the Central and Southern parts and North Eastern Region. Decreasing trend in temperature is observed in some parts of Gujarat, Konkan Region, North West parts of Madhya Pradesh and Eastern Rajasthan.

The 4th assessment report (2007) of Intergovernmental Panel on Climate Change (IPCC) had projected that the global food production potential could increase with increase in global average temperature upto three degrees, but temperature rise above three degrees could decrease the production of food grains. Modeling studies of ICAR have also predicted the likelihood of adverse effect of temperature rise on production and productivity of food grains, especially rice and wheat.