Extreme heat disrupts land's carbon absorption abilities

Extreme heat disrupts land's carbon absorption abilities
by Erica Marchand
Paris, France (SPX) Nov 18, 2024

A recent study supported by the European Space Agency (ESA) has revealed that the severe heatwaves of 2023, which led to widespread wildfires and intense droughts, significantly impaired the ability of land to absorb atmospheric carbon. This reduced absorption contributed to unprecedented increases in carbon dioxide levels, intensifying concerns about accelerated climate change impacts.

Data from the Mauna Loa Observatory in Hawaii indicated that atmospheric carbon concentrations surged by 86% in 2023 compared to 2022, marking a record high since monitoring began in 1958.

Although fossil fuel emissions increased by just 0.6%, the findings suggest that other elements, such as weakened carbon uptake by ecosystems, played a pivotal role in the sharp rise.

The ESA's Science for Society Near-Realtime Carbon Extremes project, along with the Climate Change Initiative RECCAP-2 project, enabled an international team of scientists to analyze satellite data and global vegetation models, providing a swift carbon budget report for 2023.

Ordinarily, land-based systems absorb around one-third of human-emitted carbon dioxide. However, according to research published in 'National Science Review', 2023 saw this capacity drop to just one-fifth of its typical level, representing the weakest land carbon sink performance in the past 20 years.

Analysis of the northern land carbon sink (blue line) and tropical land flux (green line) from 2015 - 2023 shows declines. Dynamic global vegetation models informed the solid line data, while NASA - JPL's Orbiting Carbon Observatory-2 data informed the dotted lines.

Philippe Ciais from France's Laboratory for Climate and Environmental Sciences stated, "Our research shows that 30% of this decline was driven by the extreme heat of 2023, which fuelled massive wildfires that devastated areas of Canadian forest and severe droughts across the Amazon rainforest.

"These conditions resulted in extensive vegetation loss, diminishing the land's carbon absorption capacity. Additionally, a strong El Nino contributed to this reduction, historically known to decrease carbon uptake in the Tropics."

The 2023 wildfires in Canada and Amazon droughts emitted carbon quantities nearly equal to North America's total fossil fuel emissions, underscoring the severe influence of climate change on natural carbon storage.

Long-term assessments show the Amazon's resilience is faltering, with some parts shifting from carbon absorption to net carbon emission sources.

The study suggests Earth's ecosystems may be nearing their absorption threshold, reducing their effectiveness in mitigating half of human-caused carbon emissions.

"Consequently, achieving safe global warming thresholds will necessitate more aggressive emission reductions than previously considered," Ciais emphasized.

The report also indicates that current climate models may not fully capture the swift impacts of extreme events, like droughts and fires, on carbon storage.

Stephen Plummer, ESA Earth Observation Applications Scientist, stressed, "Grasping the cascading effects of climate change on the carbon cycle is vital, and these ESA-supported projects underscore the value of Earth observation for rapid global impact assessments."

Clement Albergel, Acting Head of ESA's Actionable Climate Information Section, stated, "The findings are particularly concerning given the global challenge of limiting warming to 1.5 C, as outlined in the Paris Agreement."