Planet Earth Still Absorbing Half of our Greenhouse Gases
Planet Earth’s oceans, forests, and other assorted ecosystems are continuing to soak up approximately half the carbon dioxide we humans pump into the atmosphere every day, even as those emissions continue to increase, once again belying the very little knowledge we currently have of our planet.
“Globally, these carbon dioxide ‘sinks’ have roughly kept pace with emissions from human activities, continuing to draw about half of the emitted CO2 back out of the atmosphere. However, we do not expect this to continue indefinitely,” said NOAA’s Pieter Tans, a climate researcher with NOAA’s Earth System Research Laboratory in Boulder, Colo., and co-author of the study.
Scientists led by the University of Colorado’s Ashley Ballantyne analysed 50 years worth of global carbon dioxide measurements and found that the processes by which planet Earth’s oceans and other ecosystems absorb greenhouse gases are not yet at capacity.
Recent studies have suggested that natural sinks of carbon dioxide may be having trouble keeping up with the sheer level of carbon dioxide humans are pumping into the atmosphere. If that was in fact the case, we would expect to see a faster-than-normal rise in atmospheric carbon dioxide as the same levels of CO2 find no place to go.
That being said, however, Ballantyne and co. saw no such rise in carbon dioxide levels, estimating that the planet’s ecosystems continue to absorb approximately half of humanities carbon dioxide emissions from the atmosphere. Since emissions of CO2 have increased substantially since 1960, Ballantyne said, “Earth is taking up twice as much CO2 today as it was 50 years ago.”
The remaining percentage is accumulating in the atmosphere where it is pushing the planet’s temperature skyward.
This new global analysis makes it clear that scientists do not yet understand well enough the processes by which ecosystems of the world are removing CO2 from the atmosphere, or the relative importance of possible sinks: regrowing forests on different continents, for example, or changing absorption of carbon dioxide by various ocean regions.
“Since we don’t know why or where this process is happening, we cannot count on it,” Tans said. “We need to identify what’s going on here, so that we can improve our projections of future CO2 levels and how climate change will progress in the future.”
“The uptake of carbon dioxide by the oceans and by ecosystems is expected to slow down gradually,” Tans said. Oceans, for example, are already becoming more acidic as they absorb about a quarter of the carbon dioxide pumped into the air by human activities. “As the oceans acidify, we know it becomes harder to stuff even more CO2 into the oceans,” Tans said. “We just don’t see a letup, globally, yet.”
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