Turn Down the Heat: Why a 4°C Warmer World Must be Avoided
This report provides a snapshot prepared for the World Bank by the Potsdam Institute for Climate Impact Research (PIK) and Climate Analytics of likely impacts and risks that would be associated with a 4° Celsius warming within this century. It is a rigorous attempt to outline a range of risks, focusing on developing countries and especially the poor.
Washington, 27 November 2012: The report, reviewed by some of the world’s top scientists, is being released ahead of the next comprehensive studies by the Intergovernmental Panel on Climate Change (IPCC) in 2013/14, and follows the Bank’s own Strategic Framework for Development and Climate Change in 2008 and the World Development Report on climate change in 2010. "Turn Down the Heat" combines a synthesis of recent scientific literature with new analysis of likely impacts and risks, focusing on developing countries. It chronicles already observed climate change and impacts, such as heat waves and other extreme events, and offers projections for the 21st century for droughts, heat waves, sea level rise, food, water, ecosystems and human health.
The report says today’s climate could warm from the current global mean temperature of 0.8°C above pre-industrial levels, to as high as 4°C by 2100, even if countries fulfill current emissions-reduction pledges. Furthermore it states 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.
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 and one that already brings some serious damages and risks to the environment and human populations.
Turn Down The Heat: Why a 4°C Warmer World Must be Avoided summarizes a range of the direct and indirect climatic consequences under the current global path for greenhouse gas emissions.
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. Some of the most highly vulnerable cities are located in Mozambique, Madagascar, Mexico, Venezuela, India, Bangladesh, Indonesia, the Philippines and Vietnam.
The most vulnerable regions are in the tropics, sub-tropics and towards the poles, where multiple impacts are likely to come together.
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.
Many small islands may not be able to sustain their populations.
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. While a global warming of 0.8°C may not seem large, the report notes that many climate change impacts have already started to emerge, and the shift from 0.8°C to 2.0°C warming or beyond will pose much larger challenges. But a global mean temperature increase of 4°C approaches the known historic level of change for the planet, which harks back to the last ice age when much of central Europe and the northern United States were covered with kilometers of ice and global mean temperatures were about 4.5°C to 7°C lower. And this contemporary human-induced climate change, the report notes, is occurring over a century, not millennia.
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. "While every country will take a different pathway to greener growth and balance their own need for energy access with energy sustainability, every country has green growth opportunities to exploit,” said Rachel Kyte, World Bank Vice President for Sustainable Development. Those 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 and urban public transport systems designed to minimize carbon emission and maximize access to jobs and services; supporting carbon pricing and international and national emissions trading schemes; and increasing energy efficiency – especially in buildings – and the share of renewable power produced. "This report reinforces the reality that today’s climate volatility affects everything we do,” Kyte said. "We will redouble our efforts to build adaptive capacity and resilience, as well as find solutions to the climate challenge.”
You can download the report here