mediamattersforamerica:

Climate change is not that complicated! (h/t)

descentintotyranny:

The atmosphere has hit a grim milestone — and scientists say we’ll never go back ‘within our lifetimes’

June 13 2016

Scientists who measure and forecast the concentrations of greenhouse gases in the atmosphere said Monday that we may have passed a key turning point. Humans walking the Earth today will probably never live to see carbon dioxide concentrations in the atmosphere once again fall below a level of 400 parts per million (ppm), at least when measured at the iconic Mauna Loa Observatory in Hawaii, where the longest global record of Co2 has been compiled.

“Our forecast supports the suggestion that the Mauna Loa record will never again show CO2 concentrations below the symbolic 400 ppm within our lifetimes,” write the researchers, led by Richard Betts of the U.K. Met Office’s Hadley Center, in Nature Climate Change. The study was conducted with colleagues from the Hadley Centre and Ralph Keeling of the Scripps Institution of Oceanography in La Jolla, Calif.

Carbon dioxide concentrations in the pre-industrial atmosphere were around 280 parts per million. But concentrations began to rise with the early growth of industry and continually climbed throughout the 20th century, as documented by the famous Keeling curve, based on observations taken at Mauna Loa dating back to the late 1950s.

This record is referred to often as a “saw-toothed curve,” because every year, concentrations go up and down somewhat (because of the life cycles of plants across the globe, which draw in carbon dioxide through the process of photosynthesis). But nonetheless, the long-term trend is steadily upward because humans are putting more carbon dioxide into the atmosphere than plants and other natural “sinks” can pull back out again. 

Concentrations have crossed 400 parts per million on a temporary basis. It began as brief excursions, and last year the annual average concentration at Mauna Loa was more than 400 parts per million for the first time (it was 400.9). Nonetheless, during the course of the yearly cycle in carbon dioxide concentrations, there were still some parts of the year last year when they remained below that level. 

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