VATICAN CITY (CNS) -- Caritas Internationalis and other humanitarian organizations want world leaders to know that without bold action, global warming will have a disastrous effect on the world's poor and hungry.

Climate change is already undermining efforts to help the more than 1 billion people now suffering from lack of food, and without drastic measures to limit its effects, "the risk of hunger and malnutrition could increase by an unprecedented scale within the next decades," according to a Nov. 4 press release from Caritas Internationalis.

Caritas, the umbrella organization for 164 Catholic charities, said it has signed a joint statement addressed to environmental ministers and other officials who will participate in the U.N. Summit for Climate Change Dec. 7-18 in Copenhagen, Denmark. The message includes both dire warnings and practical suggestions for action.

The U.N. World Food Program and U.N. Food and Agriculture Organization, the World Health Organization, the International Federation of the Red Cross, Oxfam, World Vision and Save the Children are the other co-signers of the statement. In their message, the organizations stressed that it is the world's most vulnerable people, especially children, who will suffer the most from the effects of catastrophic climate change.

"Climate change will act as a multiplier of existing threats to food security," the joint statement read. "It will make natural disasters more frequent and intense, land and water more scarce and difficult to access, and increases in productivity even harder to achieve."

"The implications for people who are poor and already food insecure and malnourished are immense," the statement warned.

For example, the statement said, temperatures could increase 2-3 degrees Celsius (3.6-5.4 degrees Fahrenheit) in tropical and sub-tropical regions as early as 2020. This could cause a reduction in grassland productivity of 40 percent to 90 percent in arid and semi-arid regions and increase desertification in some areas of Africa, Asia and Latin America.

In the statement, the organizations advocated a plan of investment in the development of better and more sustainable food production systems, improved access to food and nutrition sources for populations at risk and enhanced social protection for the poor who cannot afford to feed themselves adequately.

Managing weather-related disasters, which typically affect underdeveloped countries most dramatically, is another priority if catastrophe is to be averted, the statement said.

The number of people affected by such disasters has more than tripled since the 1990s, the statement said. Climate change has been leading increasingly toward weather extremes marked by more storms, droughts and higher temperatures. In 2007 alone, more than 74 million people were victims of humanitarian crises originating from natural disasters, the statement said.

About 40 representatives from Caritas are expected to attend the summit.

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