Trees soak up around 30 percent of the carbon emissions from the burning of fossil fuels. That being said, they are Earth's greatest allies in fighting climate change and global warming.
For several decades, cold-climate forests in the Northern hemisphere have become even more effective in absorbing carbon as carbon dioxide levels and temperatures continue to rise.
However, a new study by the researchers from the University of Michigan gave a clearer picture of what is happening in the northern region and cast an uncertainty whether these forests or ecosystems will continue to absorb carbon dioxide as they become drier and hotter over time.
Siberian Forests Absorb Less Carbon
The researchers published their study in PNAS on Monday, August 17. The study reveals that Siberian forests are absorbing less carbon dioxide, increasing their contribution to the annual global carbon flux, compared to other forests in the same latitude.
Their study is the first to quantify how the seasonal cycle of carbon dioxide in the atmosphere is affected by the carbon emitted from a specific region during the annual carbon flux. Technically, Earth inhales carbon during spring and summer when trees and plants grow and photosynthesize. The planet exhales carbon dioxide during winter when vegetation is not present.
This information gives experts a picture of how productive forests in different regions can be and the amount of carbon they can absorb from the atmosphere. For instance, forests in similar latitudes such as those in North America may not have the same levels of carbon uptake.
Researchers noted that changes in the annual seasonal carbon flux have increased over the past decades. The intensity of flux in the Northern hemisphere has gone up 30 to 50 percent since the 1960s, which suggests that a widespread ecological changed happened.
But it is difficult to pinpoint the cause for the increase since previous studies have focused on fluxes happening in a global-scale or the hemisphere.
Brendan Rogers of Woodwell Climate Research Center said that there is a simple narrative that warmer temperatures fuel plant photosynthesis across high latitudes. Although that is true, experts have found different responses across regions.
"Siberia has been greening, strengthening its carbon sink and driving increases in seasonal CO2 exchange, but Arctic-boreal North America is showing much more browning under worsening stresses like fires, pests, and droughts," Rogers said.
He added that carbon budgets and models should include forests in Alaska and Canada as they are not usually included in models, and soon they might turn from a carbon sink into becoming a source.
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Carbon Dioxide Models
The researchers used the data from the National Oceanic and Atmospheric Administration of the measurement of atmospheric carbon dioxide for the past decades. They used a computer model and worked backward to quantify the carbon emissions in each region that matched the actual observations.
They tagged carbon emissions from each region with different colors: red for Siberia, blue for North America, and green for the lower latitudes. The method allowed them to classify areas responsible for the increase in the seasonal cycle.
NOAA has been tracking the seasonal cycle since 1976 at Barrow Observatory in Alaska.
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