WASHINGTON - The world is barreling down a path to heat up by four degrees at the end of the century if the global community fails to act on climate change, the World Bank said Sunday in a report.

Among the consequences are a cascade of cataclysmic changes that include extreme heat-waves, declining global food stocks and a sea-level rise affecting hundreds of millions of people, it warned.

All regions of the world would suffer - some more than others - but the Turn Down the Heat report finds that the poor will suffer the most.

The report is a snapshot of the latest climate science prepared for the World Bank by the Potsdam Institute for Climate Impact Research (PIK) and Climate Analytics.

"A four degrees warmer world can, and must be, avoided -- we need to hold warming below two degrees," said World Bank Group President Jim Yong Kim in the report.

"Climate change is one of the single biggest challenges facing development, and we need to assume the moral responsibility to take action on behalf of future generations, especially the poorest," it said.

The report said that the four degrees Celsius scenarios are potentially devastating: the inundation of coastal cities; increasing risks for food production potentially leading to higher malnutrition rates; many dry regions becoming dryer, wet regions wetter; unprecedented heat waves in many regions, especially in the tropics; substantially exacerbated water scarcity in many regions; increased intensity of tropical cyclones; and irreversible loss of biodiversity, including coral reef systems.

"The Earth system's responses to climate change appear to be nonlinear," said PIK Director, John Schellnhuber. "If we venture far beyond the two degrees guardrail, toward the four degrees line, the risk of crossing tipping points rises sharply. The only way to avoid this is to break the business-as-usual pattern of production and consumption."

The report, however, noted that a four degrees Celsius world is not inevitable and that with sustained policy action warming can still be held below two degrees Celsius, which is the goal adopted by the international community and one that already brings some serious damages and risks to the environment and human populations.

The World Bank Group's work on inclusive green growth has found that with more efficient and smarter use of energy and natural resources opportunities exist to drastically reduce the climate impact of development without slowing poverty alleviation or economic growth.