New Delhi, Aug 30 - Voicing concern over climate change, food shortage and poor monsoons, Bharatiya Janata Party (BJP) president Rajnath Singh Sunday wrote to Prime Minister Manmohan Singh that measures should be taken to improve the conditions.

'Climate change and its adverse effects on our people, agriculture and national economy are more than obvious. This year, nearly 250 districts have already been declared drought-affected. The foodgrain production may dip substantially, say by 10 per cent or so,' he said in his letter to the prime minister.

The BJP president said farmers, who constitute the bulk of the poor of the country, were hit the hardest.

The meteorological distresses have aggravated their problems and 'rendered them extremely vulnerable to the uncertainties of the climate change,' Rajnath Singh said.

'It is projected that mean annual temperature in India by the end of the 21st century will increase by three to six percent degrees and the rainfall by 15 to 40 per cent, but would be more erratic,' he added.

Singh said: 'Thus, the drought in kharif season (which will also affect water availability in the ensuing rabi) and high temperature in rabi season will respectively weaken rice and wheat economy - the two legs of food security and agrarian prosperity of the nation.