How much higher is the global mean temperature compared to the level of the preindustrial era? Scientists put the increase at 0.8 degrees Centigrade — and climbing. The thinking of the international community has been to keep the warming below 2 degrees. In that way, the planet and its people would prevent more dangerous fallout from climate change.
Now comes the World Bank with an assessment by scientists at the Potsdam Institute echoing recent analyses that the rate of accumulating greenhouse gases and the commitments of countries to reduce them point to 3 degrees as more realistic. In addition, the study warns about a 20 percent likelihood of exceeding 4 degrees as early as the 2060s.
What would such an increase mean?
First, the study offers revealing context highlighting the magnitude of the difference. It notes that 4 degrees “approaches the difference between temperatures today and those of 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 degrees Centigrade to 7 degrees Centigrade lower.”
The study argues that a 4 degrees Centigrade world “would be one of unprecedented heat waves, severe drought and major floods in many regions. More probable would be episodes like the Russian heat wave of 2010, resulting in a death toll of 55,000, an annual crop failure of 25 percent, all economic losses totaling $15 billion. The study points to sea levels rising three feet or more by 2100. It explains that increasing acidification of the oceans would jeopardize coral reefs, reducing protection against coastal floods and storm surges, putting at grave risk habitats for many fish species.
No country would escape the impact. The World Bank emphasizes the vulnerability of many poorer nations, the most vulnerable cities in such countries as Mozambique, India, Bangladesh, Indonesia, Vietnam and the Philippines, in many places farmlands overwhelmed by rising seas. The study raises concerns about whether poorer nations have the tools and resources to adapt.
The study makes plain that for all of the analyses of climate change, too little has been done in weighing the impact of a 4 degrees Centigrade world. The scientific models reflect uncertainty about how the fallout would mount.
To be sure, much remains to be learned about climate change. Yet, what the World Bank assessment reinforces is the need to manage risk. The planet needs an insurance policy, taking steps to prevent the worst from happening, mobilizing sooner rather than later, to prevent the planet warming by 3 degrees or more.