Speaking from Copenhagen, World Food Program Executive Director Josette Sheeran opened Wednesday's virtual conference, linking climate change to hunger.
"Today for the first time in history over a billion people on earth will go to bed hungry and one of the key factors is increasingly severe and erratic climate."
She said for many people around the world the reality of climate change is already being felt.
The World Food Program conference came on the third day of a major United Nations climate summit in Copenhagen, Denmark, where world leaders are trying to hash out an international agreement on how to fight climate change.
World Food Program representative Greg Barrow says climate change is already increasing malnutrition around the world.
"The World Food Program has witnessed for many years fluctuations in the global climate that have led to greater disasters and more frequent disasters affecting some of the poorest and hungriest people in the world."
He says climate change is leading to increased natural disaster, including flooding and drought.
"If you look at a region such as the Horn of Africa, we're seeing an increased frequency in droughts - long dry seasons where waterholes dry up, where crops wither, use to come maybe once every six to seven years. The frequency has been increasing in recent decades to the point where it's almost a chronic problem."
And he says it's the world's poorest who are worst hit.
"The poorest, the hungriest, the most vulnerable living in the least developed countries are perhaps living at the sharp end of climate change, whereas many people in developed countries are largely protected for the time being from these changes."
192 nations are meeting in Copenhagen until December 18th. They aim to come to an international agreement on how to cut greenhouse gas emissions to help stop the world from heating up.
Tensions have been high between rich and poor countries. Developing nations says rich countries should shoulder the responsibility for climate change and pay out billions of dollars in aid to help them adapt to climate change.