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| These smokestacks emit a large amount of greenhouse gases |
Approximately 50% of the total CO2 emissions from human activities since the industrial revolution have dissolved into the world’s oceans, negatively affecting marine life.
This is the conclusion of two new international studies. In the first study, scientists focused on the amount of CO2 stored in the oceans. They discovered that the world’s oceans act as a massive reservoir absorbing greenhouse gases. According to them, this process of removing CO2 from the Earth’s atmosphere has slowed global warming.
However, in the related second study, scientists indicated that this “reservoir effect” is currently changing the chemical properties of the oceans. This change has slowed the growth of phytoplankton, corals, and other invertebrate species—the most fundamental factors in the ocean food chain. The impacts on marine life could be very serious.
The Disappearance of CO2
Geophysicist Christopher Sabine, from the U.S. National Oceanic and Atmospheric Administration, stated, “The oceans are serving humanity by removing CO2 from the atmosphere. The problem is that this assistance has consequences for the ecological and biological structure of the oceans.” Sabine is a co-author of both studies.
As a greenhouse gas, CO2 traps solar heat in the Earth’s atmosphere. It is the largest contributor to global warming. Since fossil fuels began to be heavily used around 1800, the concentration of CO2 in the atmosphere has risen from about 280mg/l to 380mg/l. Today’s atmospheric CO2 levels are approximately 50% of what scientists had predicted, based on estimates that humans contribute 244 billion tons of CO2 into the atmosphere each year. According to Sabine, half of the remaining CO2 emissions are absorbed by the oceans or terrestrial plants.
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| Cement factory on the Volga River, Russia. |
For a long time, scientists have suspected that the oceans are a massive CO2 reservoir. Estimates of how CO2 is accumulating in the world’s oceans have been based on computer models or other indirect methods. However, in the new study, scientists collected direct samples of dissolved CO2 levels in the oceans worldwide throughout the 1990s. Data was collected from 9,600 points around the world during 95 separate research voyages. This was an effort by two international groups: the World Ocean Circulation Experiment (WOCE) and the Joint Global Ocean Flux Study (JGOFS).
Using this data, Sabine and researchers from the U.S., Europe, Australia, South Korea, Japan, and other countries completed the most comprehensive survey of oceanic chemical structure. Results showed that the oceans absorbed 48% of the total CO2 emissions from fossil fuel combustion and cement production from 1800 to 1994. This provides an answer to the question that has puzzled scientists before: Where has half of the CO2 that scientists estimate humans have emitted into the atmosphere gone?
Taro Takahashi, a geochemist at Columbia University, noted that this answer is important for two reasons: first, it helps us understand the Earth’s natural carbon cycle; second, it forms a solid strategy for managing CO2 emissions. Sabine, the lead author of the first study, stated that besides the atmosphere, the world’s oceans are the only large reservoir for the CO2 emitted by humans over the past two centuries. He pointed out that most previous studies have only focused on the amount of CO2 that plants have absorbed in recent decades.
The Impact of the Oceans
According to the research by Sabine and colleagues, the amount of CO2 that the oceans have absorbed is currently only one-third of what they could potentially hold. They warned that, as a result, global warming may accelerate.
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| Don’t let the oceans “burst”. |
In the second study, scientists found that although the oceans are helping to mitigate global warming, the dissolved CO2 within them is having harmful effects on marine life. Richard Feely, a marine chemist at the U.S. National Oceanic and Atmospheric Administration, led the second study. He stated, “Because CO2 is an acidic gas, the pH at the ocean’s surface is decreasing. The pH is a measure of acidity in solutions.”
If predictions made by Feely’s team are correct, the surface of the oceans, where we find most marine life, could soon be more acidic than it has been in the past five million years. The increase in acidity makes it difficult for shell-forming animals and some algae to accumulate carbonate ions from seawater to form their calcium carbonate shells. Corals, some mollusks, tiny single-celled organisms (foraminifera), and coccolithophores could be affected. Many of these species form crucial links in the marine food chain.
Past studies have shown that if atmospheric CO2 levels reach 700-800mg/l by the end of this century, shell-forming organisms could decline by 25-45%. And the scientific community has yet to predict the consequences of reduced shell-forming species on the food chain at this time.
Minh Sơn (According to National Geographic)
