Claim: Carbon-hungry plants impede growth rate of atmospheric CO2

Yet another excuse for the global warming pause — i.e., the plants did it.

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The media release is below.

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Study: Carbon-hungry plants impede growth rate of atmospheric CO2
Berkeley Lab-led research underscores need to protect vital ecosystems

DOE/LAWRENCE BERKELEY NATIONAL LABORATORY

New findings suggest the rate at which CO2 is accumulating in the atmosphere has plateaued in recent years because Earth’s vegetation is grabbing more carbon from the air than in previous decades.

That’s the conclusion of a new multi-institutional study led by a scientist from the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). It’s based on extensive ground and atmospheric observations of CO2, satellite measurements of vegetation, and computer modeling. The research is published online Nov. 8 in the journal Nature Communications.

To be clear, human activity continues to emit increasing amounts of carbon, and the atmospheric concentration of CO2, now at 400 parts per million (ppm), continues to rise. But the scientists found that between 2002 and 2014, the rate at which CO2 increased in the atmosphere held steady at about 1.9 ppm/year. In addition, the proportion of the CO2 emitted annually by human activity that remains in the atmosphere declined by about 20 percent. This slowdown can’t keep pace with emissions, so the overall amount of human-caused CO2 in the atmosphere increased, just not as quickly. And for that, new research suggests, we can thank plants.

“This highlights the need to identify and protect ecosystems where the carbon sink is growing rapidly,” says Trevor Keenan, a research scientist in Berkeley Lab’s Climate & Ecosystem Sciences Division and the corresponding author of the paper.

The scientists attribute the stalled CO2 growth rate to an uptick in land-based photosynthetic activity, fueled by rising CO2 levels from fossil fuel emissions. It’s a snowball effect: as CO2 levels rise in the atmosphere, photosynthetic activity flourishes and plants take in more carbon, sparking more plant growth, more photosynthesis, and more carbon uptake.

They also identified another player. Plant respiration, a process in which plants use oxygen and produce CO2, did not increase as quickly as photosynthesis in recent years. This is because plant respiration is sensitive to temperature, and it was affected by the recent slowdown in global warming that was observed most significantly over vegetated land. So, between 2002 and 2014, plants took in more CO2 through photosynthesis, but did not “exhale” more CO2 into the atmosphere through respiration.

“These changes decreased the amount of anthropogenic CO2 that stays in the atmosphere, and thus slowed the accumulation of atmospheric CO2,” says Keenan.

Their findings provide a possible answer to a climatic mystery. The growth rate of atmospheric CO2 climbed steadily during the latter half of the 20th century, from 0.75 ppm/year in 1959 to 1.86 ppm/year in 2002. But Keenan and colleagues discovered an inflection point last year when they analyzed the latest data from the Global Carbon Project, which quantifies carbon emissions and their sources annually. Since 2002, the growth rate has remained flat.

This pause is especially surprising because it has occurred as human activity pumps more and more carbon into the atmosphere. All that CO2 must be going somewhere, so the scientists suspected something about the carbon cycle has recently changed in a big way.

“We believed one of the planet’s main carbon sinks had unexpectedly strengthened. The question was: which one?” says Keenan.

The scientists ruled out oceans as a dominant cause because most computer models agree the amount of carbon taken in by oceans has increased steadily in recent years. That left terrestrial ecosystems, which undergo a large year-to-year variability in carbon uptake, and the two biggest influences on this variability are photosynthesis and plant respiration.

To study these influences, the scientists used ten “global dynamic vegetation models” that predict how the terrestrial carbon cycle changes over time.

They also used a model that incorporates satellite measurements of vegetation cover and plant activity to predict global photosynthesis and respiration rates. They validated the model by comparing its results with data from AmeriFlux and FLUXNET, which are networks of eddy-covariance research towers that measure ecosystem carbon, water, and energy fluxes in North and South America. Berkeley Lab manages AmeriFlux for the Department of Energy.

Model projections were generated using different scenarios of atmospheric CO2 level, temperature, soil moisture, and other processes. This enabled the researchers to evaluate the impacts of these processes on the planet’s terrestrial carbon cycle.

Taken together, the models zeroed in on rising CO2 levels as having the biggest impact on photosynthesis and plant respiration. The result is a boost in terrestrial carbon uptake, particularly in tropical and high-latitude ecosystems. Specifically, the models suggest rising CO2 levels caused terrestrial ecosystems to double the rate at which they take in carbon, from between one and two petagrams of carbon per year in the 1950s, to between two and four petagrams of carbon per year in the 2000s. For comparison, human activity emits between nine and ten petagrams of carbon per year (one petagram is one trillion kilograms).

The scientists conclude this increase in carbon uptake put the brakes on the growth rate of atmospheric CO2 between 2002 and 2014.

“Unfortunately, this increase is nowhere near enough to stop climate change,” says Keenan, adding that their results answer questions and pose new ones. “We’ve shown the increase in terrestrial carbon uptake is happening, and with a plausible explanation why. But we don’t know exactly where the carbon sink is increasing the most, how long this increase will last, or what it means for the future of Earth’s climate.”

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15 thoughts on “Claim: Carbon-hungry plants impede growth rate of atmospheric CO2”

  1. “This highlights the need to identify and protect ecosystems where the carbon sink is growing rapidly,” says Trevor Keenan

    Given that ecology is over 100 years old, one might have lived with the hope that all of these ecosystem thingys had already been identified. My hope has been dashed again.

  2. Unfortunately, this increase is nowhere near enough to stop climate change ???? and pray tell what is YOUR definition of climate change ?

  3. “The scientists ruled out oceans as a dominant cause because most computer models agree the amount of carbon taken in by oceans has increased steadily in recent years.” How did they do that? It seems to me that if the rate of photosynthesis in the oceans increased, the rate at which organic carbon sequestered on the ocean floor would increase as more of the little beasties would be dying and sinking each year. Did these scientists have some way of measuring the rate of carbon removal by that mechanism?

  4. Beauty is in the eye of the beholder.
    So the greening of Earth and more food for the third world are not a positive any more?
    I love that it was all done with “models”.

  5. The entire swamp will be self-draining if President Trump asks NASA to publicly answer the one question that will forever change society’s attitude toward science and religion, NASA, IS THE SUN A PULSAR?”

  6. It would appear they are measuring atmospheric CO2 levels with a resolution much finer than +/- 0.1 ppm. This amounts to precision finer than 0.1/400 = 0.00025% relative. I refuse to believe that atmosphere is so well mixed that such alleged precision is significant.

  7. Seems to me the reason CO2 is used in green houses is not for warmth but to make the plants grow better.
    Why wouldn’t plants grow more when CO2 levels are higher.
    However this is discounted by the AGW crowd.

  8. Funny, just been looking at this myself. Last peak was in 1998, which was the last El Nino, since then plateau in spite of “emissions” as per CDIAC rising by around 33% since that time. Cause and effect out of the window, where’s the missing CO2?

  9. I have a degree in plant science, and this is a bunch of nonsense. But is sure sounds good, I guess, as the AGW scientists desperately rationalize to support the tangled web of misinformation that they weave.

  10. NOW WAIT! I thought you told me the oceans ate my warming…?? So now it’s the plants? I getting a brain sprain trying to follow this.

  11. Nothing new here. I recall some researcher from the midwest last year looked at satellite images and noticed overall global increase in plant growth. We “deniers” have been saying for years that the photosynthesizing organisms of the planet would grow to the equilibrium point where they would eat up the CO2 at least as fast as the coal plants can belch it out. This “new finding” only supports the skeptics claims. This, and the recent discovery that world phytoplankton has increased tenfold over the last few decades in the face of alarmists predictions that the ocean’s plankton would be nearly extinct by now because of acidity. This study is very bad news for the climate hysteria crowd, though perhaps not nearly as bad as Tuesday’s election results. LOL

  12. The climate change scientists had it all figured out exactly just right.

    But once again nature (this time, plants and vegetation) messed things up. If all the natural forces would stop, our computer models might actually work.

  13. The irony of all this is that if the Dems government gets what it wants and taxes all the CO2, then we will NEVER get rid of those coal plants so long as the cash keeps rolling in. What will happen is that competing energy sources, like wind and solar, will either be taxed by the Left or found to be harmful to the environment (eg, kills birds) and eliminated and the government will declare that the coal tax is working and there hasn’t been any rise in temperature since it went into effect. You can then add CO2 belching smokestacks and automobiles to the list of things like cigarettes and, soon, high fructose corn syrup that the left complains is killing us and must be outlawed until they find out they can get cash flow out of it.

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