Oceans have slowed global warming for decades by soaking up at least a third of the carbon dioxide humans have been producing since the Industrial Revolution. The ocean may be asked to do even more now. To do that, its chemistry and biology would have to be changed to take in more carbon. Let us discuss some crucial ideas on climate change.
Climate simulations show that limiting warming by lowering carbon emissions alone is quickly becoming less possible, so this method should be considered. To stop the worst effects of climate change by 2100, scientists say we must actively pull carbon back out of the atmosphere on a scale that can only be done with the ocean’s help.
The Intergovernmental Panel on Climate Change says that this will cause the Earth to warm up by about 3.2 degrees Celsius by the end of the century compared to pre-industrial times. As of October 26, 2021, the world would still be about 2.7 degrees warmer if all countries kept their promises to cut emissions.
That’s more than the 1.5- to 2-degree goal set by the Paris Agreement, an international climate agreement signed by 195 countries in 2015. In fact, Earth’s average temperature is expected to rise above 1.5 degrees by the middle of the 2030s. As the temperature rises, the chance of terrible things happening goes up. These include deadly heat waves, stronger storms, and coastal towns flooded by melting ice and rising seas.
By the end of the century, technologies that take carbon out of the air might help chill things down again. Gabriella Kitch, a geochemist at the U.S. National Oceanic and Atmospheric Administration in Silver Spring, Md., says, “The latest IPCC report says that to meet the [Paris Agreement] climate goals, we need to use technologies that remove carbon dioxide.”
Carbon dioxide removal, or CDR, is still very new. It only removes about 2 billion metric tonnes of CO2 from the air every year. That’s a very small amount of the 37 billion metric tonnes of CO2 that people produce every year by using energy. Forests produce most of that CDR by planting new trees, letting old forests grow back, or better controlling the existing growth.
To stay on track with the Paris Agreement goals, the world must eliminate 10 to 15 billion metric tonnes of CO2 annually by 2050. That would add up to 400 billion to 1,000 billion metric tonnes of CO2 into the air by the end of the century. The exact amount depends on how quickly we reduce carbon output.
Kitch says that land-based CDR, like planting trees, restoring coastal ecosystems, and building facilities that take CO2 straight from the air, can help us get some of the way there. Kitch says that all of the carbon that would be taken in by land-based methods would add up to only 10 billion metric tonnes per year. She also says that these kinds of estimates need to make sure that there is enough land for food, water, and protecting biodiversity. “That gets us to the year 2050, but what about after that?”
The ocean steps in here. “One great thing about the ocean is how much it can hold,” says Kitch. The ocean can hold 19 times as much carbon as land.”
Increasing the ocean’s current carbon consumption can be done in a few simple ways: Boost the number of photosynthesizing organisms in the ocean, make the water more alkaline so it can take in more acidic CO2, and construct huge structures at sea that pull carbon straight out of the water.
But CDR in the big blue hasn’t been tried much. In this way, the ocean’s size is both good and bad. Because ocean water is complicated and always moving, it is very hard to keep track of changes in its makeup. Also, there isn’t a lot of background data for big parts of the ocean, which makes it hard to tell how well CDR is working. And the tools we have now for observing, like cameras, might be unable to handle the task.
People have been worried about the effects on the environment for a long time, but there isn’t much information about them. Critics point out that changes to the water quality in a certain area could affect whole ecosystems. For example, encouraging phytoplankton blooms could change the food webs in the area or even produce greenhouse gases. Animals in the area might be in danger if large amounts of rainwater are treated to get rid of carbon.
Time, though, is the hardest thing of all. Scientists are rushing to explore these uncharted waters as soon as possible, before the climate problem gets worse.
How getting rid of carbon dioxide could slow climate change:
Carbon dioxide can stay in the air for hundreds of years before plants take it up or make it part of the rocks’ chemical structure. However, those natural “sinks” for carbon are too slow to keep up with the release rate from burning fossil fuels and other human activities.
CDR is like “a time machine,” as David Ho, an oceanographer at the University of Hawaii at Manoa, wrote in Nature last year. Taking some CO2 out of the air would be like going back in time to a time when the amount of CO2 in the air was smaller.
Climeworks’ Orca plant is the world’s biggest direct air capture plant in Iceland. It can get rid of up to 4,000 metric tonnes of CO2 every year, which he thought might throw the clock back by about three seconds a year.
Peter de Menocal, president and head of the Woods Hole Oceanographic Institution in Massachusetts and a paleoclimatologist, says that planting 100 million trees worldwide would give people back about 33 minutes a year.
The ocean naturally produces about a quarter of the world’s carbon emissions annually. We’d have to turn the clock back about three months every year to do that.
The ocean has a huge amount of space to store carbon. For example, the amount of CO2 in the air was about 280 parts per million from 10,000 years ago until the start of the Industrial Revolution. But about 20,000 years ago, when the last ice age was at its worst, that level was only 180 ppm. During the ice age, the “missing” 100 ppm of CO2 was all stored in the ocean. This was partly because the ocean movement slowed down during this time.
