But they caution against generalizing too much based upon the results.
"There are many quite different ecosystems in the world, and different ecosystems may show different responses of [the] carbon cycle to autumn warming," Piao noted.
"Further, more detailed studies are needed to quantify historical changes in [the] seasonal carbon cycle for each ecosystem."
Miller concurred.
"I think our current understanding of how earlier springs and/or later falls affect carbon uptake and release is quite weak," he said.
While scientists can accurately measure the "bottom line" levels of carbon entering the atmosphere, they don't fully understand all the variables that produce this result and how they change for different plant species and types of land.
"If we ever want to predict how climate change affects CO2 sources and sinks, we need to better understand how climate changes—including temperature, precipitation, soil moisture, and humidity—affect photosynthesis and respiration individually," Miller added.
But Piao's results do raise a disturbing possibility: We may no longer be able to count on plants and oceans to absorb 50 percent of our emissions as the planet continues to warm.
"It's possible that warming temperatures could help plants absorb more of our C02 emissions than they currently do, particularly if they somehow accelerate growth without also boosting decomposition," Miller allowed.
But, he stressed, models suggest that exactly the opposite will happen, and what he dubs the "50 percent discount" could be diminished.
"Most models predict that the land biosphere will start to lose carbon faster than it gains it."
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