Our oceans are turning sour


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Our oceans are becoming acidic 'at an unprecedented rate', warn scientists - and it's likely to get even worse.

By 2100, acidification could increase by as much as 170% and researchers say that CO2 emissions are to blame.

Atmospheric carbon dioxide (CO2) levels are rising as a result of human
activities, such as fossil fuel burning, and are increasing the acidity of
seawater. Historically, the ocean has absorbed approximately a quarter of all CO2 released into the atmosphere by humans since the start of the industrial revolution, resulting in a 26% increase in its acidity.

Latest research indicates the rate of change may be faster than at any time in the last 300 million years.

This is worrying enough, but what's concerning scientists even more is the way this interacts with other effects of global warming.

Carbon dioxide from the burning of coal, oil and gas has led to the oceans becoming warmer and research has shown that at different depths the oceans are moving less oxygen around because of the increased heat. Together, these effects amplify one another, leading to scientists describing the ocean's future prospects as "hot, sour and breathless."

The rate of change may be too fast for many species or populations to adapt through evolution, possibly leading to the loss of some 30% of ocean species by the end of this century.

Many organisms show adverse effects of this increased acidity, such as reduced ability to form and maintain shells and skeletons, as well as reduced survival, growth, abundance and larval development and changes in carbonate chemistry of the ocean may hamper or prevent coral reef growth within decades.

The effect of acidity is currently being most profoundly felt in the colder Arctic and Antarctic oceans, which hold more CO2 and are becoming acidic more rapidly than the rest of the world.

By 2020, researchers say that 10% of the Arctic will be inhospitable to species that build their shells from calcium carbonate - and it will be a hostile environment by 2100.

Some of the animals which will be affected are a key part of the food chain, so their loss could have a cascading impact.

Scientists warn that the only way to slow down the rate of acidification in the long term is by significant cuts in CO2 emissions. 

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