Oceans Absorb a Third of Our CO2 – Will Climate Fears Evaporate?

A new study published in Science shows that 31% of human CO₂ emissions in the period from 1994 to 2007 was absorbed by the oceans. As such, nature has done more to reduce our carbon footprint than all climate treaties combined. This may significantly impact climate policies.

The Science

The ocean surface reacts chemically with CO₂ and creates carbonic acid (H₂CO₃), which is transported and diffused down into the ocean, where it stays for hundreds of years before it resurfaces and degasses into the atmosphere. Most of the world’s natural CO₂ is therefore stored in the oceans. They contain in the order of 50 times more than the entire atmosphere.

The Study

This mechanism has been known for a long time and is mostly understood.  A team of scientists led by Professor of Environmental Physics Dr. Nicolas Gruber at ETH Zürich wanted to measure and quantify this absorption, and data collected over a period of 13 years largely confirmed the models of oceanic sinks. The oceans are gobbling up our carbon emissions, and they will continue to do so until saturated.

A primary concern has been to come closer to finding the saturation limit, and Gruber explains that there are still no signs of reaching it: “Over the examined period, the global ocean continued to take up anthropogenic CO₂ at a rate that is congruent with the increase of atmospheric CO₂.”

Another concern was to quantify ocean acidification, which is postulated to affect ocean life negatively. "Our data has shown that this acidification reaches deep into the ocean's interior, extending in part to depths of more than 3000 m," Gruber says.

The Meaning

The study may be far better news than many feared. One early worry among scientists was that CO₂ absorbed by the oceans would be mostly trapped in the uppermost layer where most aquatic life exists. If that were the case, acidification could become a problem to organisms and could also mean that the water stopped absorbing our emissions, which would lead to a more rapid rise in the atmosphere instead.

However, measurements show that the recent anthropogenic carbonic acid has been transported to depths of more than 3000 meters, meaning that it will take a very long time before the oceans become saturated.

To put this in perspective, consider that, at the current rate, humans increase atmospheric carbon by about 0.5% annually. One-third of that goes into the ocean. Since the oceans contain roughly 50 atmospheres of CO₂, it would take us several hundred years to increase the oceanic carbon to 51 atmospheres, which is not particularly alarming.

Also, consider that around 120 million years ago, the atmospheric CO₂ level was four times higher than today and remained so for millions of years. It means that the oceans must have been far more acidic than today, and yet ancient aquatic organisms such as corals and sharks thrived and have survived to modern times.

The Politics

This should be considered good news but is highly unlikely to be presented as such, if reported at all. The study implies that we have far less to worry about than alarmists would have us believe. Our emissions are greening the earth, and the oceans are also gobbling up a big chunk of them, seemingly without an end in sight and without endangering aquatic life. What’s not to like about that?