Global Challenges Facing Humanity

http://www.millennium-project.org/millennium/Global_Challenges/chall-01.html

The World Meteorological Organization reports that the amount of CO2 in the atmosphere reached a record levels in 2012, or 140% of the pre-industrial level of 280 parts per million. The daily average of atmospheric CO2 as measured in Hawaii surpassed 400 ppm on May 10, 2013. It was 391.03 ppm in October 2012; 388.92 ppm in October 2011; and 387.15 ppm in October 2010. According to NOAA, 2012 was the hottest year in the U.S. (coterminous 48 states) since record-keeping began in 1895, and the ninth warmest on record globally.

The total human-induced GHG emission is about 49.5 gigatons of CO2 equivalent per year. Nature absorbs about half of this annually, but that ability is diminishing. To achieve carbon cycle equilibrium, assuming nature’s absorption capacities remained the same, we would have to cut back to about 25 GtCO2e per year, which is deemed politically and economically unacceptable. The politically accepted target is a 2°C increase by 2100, requiring a reduction to around 44 GtCO2e by 2020. The business-as-usual scenario is an increase to about 56 GtCO2e by 2020. Oceans absorb atmospheric CO2 (about 25% of it today) and will continue absorbing human-generated CO2 for decades if not centuries, which increases acidity, affecting coral reefs and other sea life. Over the long term, increased CO2 in the atmosphere leads to a proliferation of microbes that emit hydrogen sulfide—a very poisonous gas.

There is also a growing fear that the target of not acceding 450 ppm of atmospheric CO2 is inadequate and should be lowered to 350 ppm, or else the momentum of climate change could grow beyond humanity’s ability to reverse it.

Climate change could be accelerated by dangerous feedbacks: melting ice/snow on tundras reflect less light and absorb more heat, releasing more methane, which in turn increases global warming and melts more tundra; warming ocean water releases methane hydrates from the seabed to the air, warming the atmosphere and melting more ice, which further warms the water to release more methane hydrates; the use of methane hydrates or otherwise disturbing deeper seabeds releases more methane to the atmosphere and accelerates global warming; Antarctic melting reflects less light, absorbs more heat, and increases melting; and the Greenland ice sheet (with 20% of the world’s ice) could eventually slide into the ocean.

Glaciers are melting, polar ice caps are thinning, and coral reefs are dying. Some 30% of fish stocks have already collapsed, and 21% of mammal species and 70% of plants are under threat. Oceans absorb 30 million tons of CO2 each day, increasing their acidity. The number of dead zones—areas with too little oxygen to support life—has doubled every decade since the 1960s.