The world is "barreling down" a path to heat up by 4 degrees at the end of the century if the global community fails to act on climate change, triggering 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, according to a new scientific report commissioned by the World Bank.

Turn Down the Heat, a snapshot of the latest climate science prepared for the World Bank by the Potsdam Institute for Climate Impact Research (PIK) and Climate Analytics, says that the world is on a path to a 4 degree Celsius (4°C) warmer world by end of this century and that current greenhouse gas emissions pledges will not reduce this by much..

“A 4 degree warmer world can, and must be, avoided – we need to hold warming below 2 degrees,” said World Bank Group President Jim Yong Kim. “Lack of action on climate change threatens to make the world our children inherit a completely different world than we are living in today. 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.”

4°C scenarios are potentially devastating

The report says that the 4°C scenarios are potentially devastating: the inundation of coastal cities; increasing risks for food production potentially leading to higher under and 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.

 PIK Director, John Schellnhuber commented:

"The Earth system's responses to climate change appear to be non-linear. If we venture far beyond the 2 degrees guardrail, towards the 4 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."

Bank says "time is very short"

The report notes, however, that a 4°C world is not inevitable and that with sustained policy action warming can still be held below 2°C, which is the goal adopted by the international community – although even this one will already bring some serious damages and risks.

The World Bank President warned that time is now very short and that a global response equal to the scale of the climate problem was needed.

The World Bank Group’s work on inclusive green growth opportunities says that new initiatives could include:

• putting the more than US$ 1 trillion of fossil fuel and other harmful subsidies to better use
• introducing natural capital accounting into national accounts
• expanding both public and private expenditures on green infrastructure able to withstand extreme weather
• supporting carbon pricing and international and national emissions trading schemes
• and increasing energy efficiency – especially in buildings – and the share of renewable power produced.

Key findings include:

• Extreme heat waves, that without global warming would be expected to occur once in several hundred years, will be experienced during almost all summer months in many regions. The effects would not be evenly distributed. The largest warming would be exptected to occur over land and range from 4° C to 10° C. Increases of 6° C or more in average monthly summer temperatures would be expected in the Mediterranean, North Africa, Middle East and parts of the United States.
• Sea level-rise by 0.5 to 1 meter by 2100 is likely, with higher levels also possible.
• Agriculture, water resources, human health, biodiversity and ecosystem services are likely to be severely impacted. This could lead to large-scale displacement of populations and consequences for human security and economic and trade systems.

The report states that the science is unequivocal that humans are the cause of global warming, and major changes are already being observed. The global mean temperature has continued to increase and is now about 0.8°C above pre-industrial levels.

Last year, the Bank idoubled its financial lending that contributes to climate change adaptation. The Bank-administered US$7.2 billion Climate Investment Funds are now operating in 48 countries, leveraging an additional US$43 billion in clean investment.

Increasingly, the Bank is supporting action on the ground to finance the kind of projects that help the poor grow their way out of poverty, increase their resilience to climate change, and achieve emissions reductions.

Click here to download the Executive Summary