Although scientists are uncertain of when some of the tipping points will occur, many say that it is extremely urgent that policies cut carbon emissions in the next 50 years; not doing so could trigger changes that are irreversible. Three “too close for comfort” tipping points are:
- complete coral bleaching which could damage world fisheries in three decades;
- serious sea level rise by the end of the century, taking tens of thousands of years to reverse;
- shutdown of the ocean current system that moderates temperatures in northern Europe, in as little as 200 years.
Princeton University geosciences and international affairs professor Michael Oppenheimer, who also advises the advocacy group Environmental Defense, said one of the greatest dangers is in the collapse of Greenland or West Antarctic ice sheets that consist of 20% of world’s fresh water. If either collapses, sea level would rise by 20 feet, flooding a third of Florida and Manhattan. Once lost, there would be no way to reverse it for thousands of years. A 1.8 degrees Fahrenheit rise would lead to serious coral bleaching. Many are worried about the collapse of Atlantic thermohaline circulation, a current bringing warm surface water to northern Europe as well as returning cold water from the south. According to Hans Joachim Schellnhuber, there is 50% chance that the current will collapse within 200 years.
Date: 29 January 2006