For 800,000 years before the twentieth century, carbon dioxide levels in Earth’s atmosphere never exceeded 300 parts per million. In March 2015, the monthly average went above 400 ppm for the first time.  Source: climate.gov

GR:  Emissions appear to be increasing despite all that’s been said.

From the article:  “In addition to the cascade of climate impacts from this global warming—rising sea level, more extreme rain events, insect pest population explosions, increasing coral bleaching—the extra carbon dioxide is also changing the pH of the ocean.  Carbon dioxide is mildly acidic when it dissolves in water (think of your favorite carbonated beverage). The ocean’s rising acidity has harmed oysters and other marine creatures by weakening their shells.”