Johannesburg — A new report released just days ahead of the UN climate change talks to be held in Doha, Qatar, paints an unnerving picture of a four-degree Celsius warmer world by the end of the century.
In such a scenario, there could a "new class of heatwaves" of magnitudes never experienced before, says the report entitled Turn Down the Heat, Why A Four Degrees Celsius Warmer World Must Be Avoided.
Current heat waves in sub-Saharan Africa and the Middle East even with temperatures consistently above 40 degrees Celsius, could seem like a pleasant prospect in a few decades.
A four-degree temperature rise by the end of the century could also trigger declining global food stocks and sea-level rises affecting hundreds of millions of people.
In such a scenario there would be no certainty that adaptation might be possible, says the report, a synthesis of the latest climate science prepared by the Potsdam Institute for Climate Impact Research (PIK) and German NGO Climate Analytics for the World Bank.
Taking steps to control global temperatures by reducing emissions of warming greenhouse gases is a key issue to be discussed at the Doha talks.
Signs of the rate at which the earth is warming are becoming more apparent, the report says. "The area of the Earth's land surface affected by drought has... likely increased substantially over the last 50 years, somewhat faster than projected by climate models."
The 2012 drought in the USA affected about 80 percent of agricultural land, making it the most severe drought since the 1950s, which recorded unprecedented temperatures, the report said.
Scientists have been warning countries to keep the global temperature increase below two-degrees by the turn of the century - otherwise we are headed towards a four-degree rise. Even a two-degree rise in global temperatures by the end of this century, which many predict will happen, would have a catastrophic effect: water stress in arid and semi-arid countries, more floods in low-lying coastal areas, coastal erosion in small island states, and the elimination of up to 30 percent of animal and plant species.
Projections for global temperature rises by the world authority on climate science, the Intergovernmental Panel on Climate Change (IPCC), show that if emissions of global greenhouse gases remain unchanged, a rise of 2.2 degrees is possible by 2050.
The PIK/Climate Analytics report says: "Current scientific evidence suggests that even with the current commitments and pledges fully implemented, there is roughly a 20 percent likelihood of exceeding 4°C by 2100, and a 10 percent chance of 4°C being exceeded as early as the 2070."
However, "warming would not stop there," says the report. "Because of the slow response of the climate system, the greenhouse gas emissions and concentrations that would lead to warming of 4°C by 2100 would actually commit the world to much higher warming, exceeding 6°C or more, in the long term, with several metres of sea-level rise ultimately associated with this warming."
"The Earth system's responses to climate change appear to be non-linear. If we venture far beyond the two-degrees guardrail, towards 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," said PIK Director John Schellnhuber in a statement.
The report is meant to "shock us into action," writes Jim Yong Kim, president of the World Bank in the foreword. "A 4°C world is likely to be one in which communities, cities and countries would experience severe disruptions, damage, and dislocation, with many of these risks spread unequally. It is likely that the poor will suffer most and the global community could become more fractured, and unequal than today."
Life as we currently know it could change considerably. Over the next 30-90 years southern Africa, the USA, southern Europe, Brazil, and Southeast Asia could see more frequent and intense droughts, says the report, citing new studies. By the turn of the century 43-50 percent of the global population will be living in water-scarce countries, compared to 28 percent today.
Countries in tropical South America, Central Africa, and all tropical islands in the Pacific "will see unprecedented extreme temperatures become the new norm in all months of the year," says the report. In fact, the coolest months in those countries now could become hotter than the current warmest months by the turn of the century.
Of the impacts projected for 31 developing countries, 10 cities account for two-thirds of the total exposure to extreme floods.
Here are some of the report's findings:
- Extreme heatwaves, which in the absence of global warming would be expected to occur once in several hundred years, will occur during almost all summer months in many regions. The effects would not be evenly distributed. The biggest jump in warming would be expected to occur over land (range from 4°C-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 USA.
- Sea level-rise by 0.5 to one metre by 2100 is likely, with higher levels also possible. Some of the most highly vulnerable cities are 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 affected. 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 Bank has urged countries to move towards greener economies, ease up on fossil fuels, and invest in infrastructure able to withstand extreme temperatures and other climatic shocks.
This report does not necessarily reflect the views of the United Nations.