While some adaptive measures are possible, limits to humans' ability to regulate heat will affect health and potentially cut global productivity in the warmest months by 40 per cent by 2100 . Body temperatures rising above 38 degrees impair physical and cognitive functions , while risks of organ damage, loss of consciousness and death increase sharpl y above 40.6 degrees, the draft report said. Farm crops and livestock will also struggle with thermal and water stress. Staple crops such as corn, rice, wheat and soybeans are assumed to face a temperature limit of 40-45 degrees , with temperature thresholds for key sowing stages near or below 35 degrees, the report said.
laundry list Positive feedbacks lead to runaway warming – multiple loops: 1. Permafrost carbon Klusinske, 3/11 – [Elizabeth, holds a Master of Science in Atmospheric & Oceanic Sciences, from the University of Wisconsin-Madison, Decoded Science, “Melting Permafrost in the Arctic: A Tale of Two Feedbacks”, 3/11/16, - tale-two-feedbacks/57919 , 7/20/16]JRO The permafrost carbon feedback is a positive biogeochemical feedback . The permafrost carbon feedback consists of the permafrost methane feedback, which is strongly positive , and the permafrost carbon dioxide feedback, which is weakly negative. The briefest explanation of the permafrost carbon feedback loop is this: Higher temperatures cause permafrost to melt. This melting releases carbon dioxide and methane. Releasing carbon dioxide and methane warm the climate further – which leads , in turn, to more melting. Permafrost is a layer of permanently frozen soil that exists in cold Arctic regions, including Alaska, northern Canada, and Siberia. Each summer, the top layer of the permafrost temporarily melts, forming small shallow depressions filled with meltwater and rain, known as “thaw ponds.” The seasonal cycle of freezing and superficial thawing is natural, but it has gone into hyper drive due to increasing temperatures causing excess melting in the past few decades , and the number of thaw ponds has increased dramatically as a result. This is where the permafrost carbon feedback loop comes into play. Carbon remains trapped in ground that is frozen, but melting and higher temperatures increase activity of microorganisms in soil. Soil microbes convert carbon to carbon dioxide (CO2) in dryer oxygen-rich environments, and to methane (CH4) in wetter oxygen-constrained environments (such as wetlands). Since wetlands and ponds are a source of methane (a greenhouse gas 27 times more potent than CO2), i ncreasing their number releases more methane into the atmosphere, leading to further warming, and yet more thaw ponds, in a repeating cycle. According to the study, rising air temperatures are the dominant factor in determining how much methane is currently emitted and will be emitted in the future . Since the northern permafrost region is warming almost twice as fast as the rest of the planet, methane emissions are already significant, and are projected to be between 2.5 and 2.9 times greater than
- Winter '16
- Jeff Hannan
- Climate Change, South China Sea