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acidificationThe world’s oceans are acidifying at an unprecedented rate, driven primarily by increasing carbon dioxide emissions. 

This week, the World Meteorological Organization released its annual Greenhouse Gas Bulletin, which traces the buildup of atmospheric carbon dioxide as well as other greenhouse gases (such as methane and nitrous oxide). The report found that carbon dioxide levels had surged between 2012 and 2013.

“The Greenhouse Gas Bulletin shows that, far from falling, the concentration of carbon dioxide in the atmosphere actually increased last year at the fastest rate for nearly 30 years,” said Michel Jarraud, secretary general of the WMO.

The concentration of CO2 in the planet’s Northern Hemisphere reached 400 parts per million in April, the highest it’s been in 800,000 years (or two glacial cycles).

“We know without any doubt that our climate is changing and our weather is becoming more extreme due to human activities such as the burning of fossil fuels,” said Jarraud.

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Source: World Meteorological Organization

This increase in carbon emissions is having a direct effect on the ocean, which absorbs over 25 percent of the planet’s carbon dioxide. The ocean processes CO2 by converting it into carbonic acid. Too much carbonic acid and the water will dissolve calcium carbonate in the water – the main ingredient in the shells of crabs, mollusks and other shellfish. Of late, the ocean is absorbing so much CO2 that the pH level of surface water has dropped from 8.18 to 8.07.

Numerically, it doesn’t seem like much, but researchers at the WMO say this change is unprecedented in the last 300 million years. It is already having a detrimental effect on sea life, leading to mass die offs in Alaska’s once fertile fisheries. And the news gets worse.

It appears that the ocean’s ability to absorb CO2 began to slow in 1980, and then again in 2000. According to a 2009 assessment by NASA’s Timothy Hall, “the fraction of anthropogenic CO2 emissions entering the ocean appears to be slowing, even while the absolute tonnage increases.” The slowdown, Hall writes, may be due to natural limits on the ocean’s ability to absorb carbon.

In other words, seawater is becoming so acidic that it is losing its ability to absorb more CO2. The WMO says that the ocean is now absorbing 70 percent of the carbon it absorbed in 1750, and by 2100 that capacity may decrease another 20 percent.

By the end of the century, if the oceans’ absorption rate is cut in half, that will drastically increase the effects of man-made global warming.

The map below is from the UN’s 2014 IPCC report. The dark blue areas show where pH levels are decreasing (resulting in faster acidification).

map

Click to embiggen

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