Posted by: Dr Churchill | March 1, 2012

Oceans turning to acid

All the greenhouse gases and the carbon CO2 that we put into the atmosphere stay there for a very long time…

Still as it descends, some of it is absorbed by vegetation and a whole lot is taken up by the oceans. In fact the vast majority of CO2 is sunk  in the oceans or absorbed by them. Now if the normal CO2 absorption rate of the oceans changes, then the rate of Carbon build-up in the atmosphere will also change, speeding up in turn the rate of global warming.

Classic Earth science suggests that the build-up of CO2 in our atmosphere increases as the impact of warming on ocean currents, particularly the global “conveyor belt” that begins in the North Atlantic takes effect.

Most oceanographers believe that as warming takes hold, and ice formation is reduced, these currents – which lock CO2 up in the depths – could slow down or carry less water, meaning that less CO2 is removed from the atmosphere.

This is a classic feedback loop because it intensifies the problem and the global warming. Because as the ocean water carries dissolved CO2 with it on a centuries-long journey across the ocean floor, when the current slows down and the CO2 absorption capacity of the ocean is reduced the CO2 builds up faster in the atmosphere further intensifying global warming and so on so forth, until life on earth becomes unsustainable.

Now we have another and greater problem still…

Humanity’s greenhouse gas emissions are acidifying the oceans at a faster rate than at any time in the last 300 million years. The sheer speed of change means we do not know how severe the consequences will be.

As well as warming the planet, carbon dioxide seeps into the oceans and forms carbonic acid. As a result the water becomes more acidic.

The pH is currently dropping by about 0.1 per century. This ocean acidification harms organisms such as corals that rely on dissolved carbonate to make their shells. It also disrupts behaviour in some animals.

Bärbel Hönisch of Columbia University in Palisades, New York, and colleagues used the chemical record preserved in rocks to gauge previous ocean acidification events.

The best match for current changes was the Palaeocene-Eocene thermal maximum of 55 million years ago, when vast amounts of methane were released into the atmosphere causing rapid global warming, ocean acidification, and mass extinction. But even then, it took at least 3000 years for ocean pH to drop by 0.5. “That is an order of magnitude slower than today,” Hönisch says.

The 300-million-year period that Hönisch and colleagues studied includes the biggest extinction of them all: the end-Permian extinction. This event, 252 million years ago, wiped out up to 96 per cent of marine species. But it probably had other causes.

Acidification is not the only threat to the oceans from greenhouse gases, says Nicolas Gruber of the Swiss Federal Institute of Technology Zurich in Switzerland. Marine life also faces a threat from rising water temperatures and from oceans with far less dissolved oxygen in them.

“We have to think about these effects co-occurring,” Gruber says. While we have information on the consequences of each individual factor, we have no idea what the combined effect will be.




Add to this the other feedback loops and we are royally screwed if we let things proceed as they are unchecked.

Add to this the other feedback loops and we are royally screwed if we let things proceed as they are unchecked.

And truth be told, the feedback loops are accelerating all the time too.

Because since the start of the 21st century, the rate of accumulation has accelerated. It is now at twice the 1990s level. Nobody is sure why. It is not because emissions have accelerated. It could be temporary natural variability. Or it could be that the forests and the oceans are losing their ability to absorb our CO2 pollution.

If so, then the global warming could shortly gather pace and increase it’s intensity.

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