Over the past twenty years the concept of “tipping points” has become more familiar to the public. Tipping points are critical thresholds at which small changes can lead to dramatic shifts in the state of the entire system. From a climate standpoint, the melting of Arctic sea ice is a simple example. As sea ice melts, less sunlight is reflected into space and more heat is absorbed by the ocean, further hindering the formation of sea ice and thereby leading to more warming. The positive feedback loop is leading toward ice-free summers in the Arctic, which will have dramatic implications for the Arctic ecosystem and knock-on effects for ocean circulation and weather patterns. The effects are already being observed, with Arctic sea ice extent trending sharply downward since the 1970s. Glaciers and icebergs in Antarctica. Photo credit: Mongabay Awareness of climate tipping points has grown in policy circles in recent years in no small part thanks to the work of climate scientist Tim Lenton, who serves as the director of the Global Systems Institute at Britain’s University of Exeter. In 2008 Lenton was the lead author of an influential Proceedings of the National Academy of Sciences (PNAS) paper that identified nine tipping points and ranked them by their near-term likelihood of occurring. These included: Arctic Sea-Ice; the Greenland Ice Sheet; the West Antarctic Ice Sheet; the Atlantic Thermohaline Circulation; the El Niño–Southern Oscillation (ENSO); the Indian Summer Monsoon; the Sahara/Sahel and West African Monsoon; the Amazon Rainforest; and the Boreal…This article was originally published on Mongabay Läs mer