Scientists find that land and oceans absorb astonishingly stable carbon from the air
A new study suggests that the natural uptake of atmospheric carbon dioxide by land and oceans has been more efficient in the recent past than previously thought. The researchers came to this conclusion by mapping a new time series for global carbon emissions from deforestation – the missing link in understanding the global carbon cycle so far.
The study shows that carbon emissions from deforestation between the 1960s and 1980s were lower than assumed in previous studies. By combining the time series with other datasets, it shows that the uptake of carbon dioxide by nature has so far been less affected by climate change than thought.The study is Post today in scientific journals nature.
Smoke from forest fires in Bolivia and Brazil as seen by NASA’s MODIS satellite in 2010. (Image courtesy of NASA/Jeff Schmaltz)
To estimate carbon emissions from deforested regions in South America and Indonesia, scientists used ground-level air visibility measurements, which have been recorded along with temperature and precipitation data over decades. Smoke reduces visibility and can therefore be used to estimate deforestation in these areas. Consistent visibility records at airports and other locations go back much earlier than satellite data. “By linking them to deforestation and forest fires based on recent period satellite measurements, we were able to build a new time series of global deforestation carbon emissions and thereby elucidate the role of deforestation in the global climate system,” said co-principal principal. said author Margreet van Marle, a climate researcher at the Dutch research institute Deltares.
“These records are shared in real-time by weather services around the world and are fortunately archived. Before the advent of modern satellite records, we were able to use them as a proxy for fires,” said study co-author Robert Field of Columbia University.
Scientists have known since the 1970s that about half of our carbon emissions from burning fossil fuels and deforestation remain in the atmosphere. The other half is absorbed by sea and land. Whether this ratio has changed over the long term has been extensively studied, possibly because climate change has weakened the ability of vegetation and oceans to absorb carbon dioxide. This could lead to accelerated climate change as more carbon dioxide remains in the atmosphere. Previous studies have provided evidence for this, but researchers have struggled to draw firm conclusions, in part because emissions from deforestation have been a source of uncertainty.
The new time series shows that from the 1960s to the 1980s, emissions from deforestation were lower than earlier studies suggested. As a result, scientists believe that a larger portion of the total emissions remained in the atmosphere during that time. Over the entire 60-year time series, this means that the fraction of carbon that ends up entering the atmosphere is trending negatively—suggesting that nature’s uptake of carbon dioxide has kept pace with the rise in fossil fuel emissions, and may even become more severe over time. more efficient.
The reasons for this trend remain unclear, according to co-lead author Dave Van Ves of Vrije Universiteit Amsterdam. “It’s likely that some of the climate feedback loops we’re concerned about, such as permafrost thawing or more forest fires, have had an impact but are being offset by other mechanisms,” he said.
According to Guido van der Werf, a professor at Vrije Universiteit Amsterdam who established the study, it is currently difficult to draw firm conclusions about future climate change. “The main thing we can prove is that the worst nightmare scenario has not yet materialized,” he said. This, he said, was largely because the new insights were relevant to the 1960s, 1970s and 1980s. “Looking back over the past few decades, improvements in efficiency may have stalled,” he said.
The research was also carried out by scientists from the Woodwell Climate Research Centre and Wageningen University.
Adapted from a press release from Vrije Universiteit Amsterdam.
