Climate models may overestimate how much carbon trees release

Climate change research often paints a grim picture. Rising temperatures, vanishing forests, and escalating carbon dioxide (CO2) levels dominate headlines. But new research published in the journal Science offers a reason for cautious optimism.

An international team of scientists has uncovered findings that could change how we understand tree responses to warming temperatures.

Trees play a huge role in managing Earth’s CO2 levels. They absorb carbon during photosynthesis and release some of it back through respiration.

It has long been assumed that as the climate warms, tree respiration and the resulting CO2 emissions would sharply increase. That increase would then add more carbon to the atmosphere and fuel more warming.

This cycle, known as a positive climate feedback, has been a key concern for climate scientists. But according to a global study led by experts at Tsinghua University, trees may not release as much carbon as we once feared.

How trees release carbon

The study focuses on a specific type of carbon release: the respiration from tree stems. When trees grow, they use energy, and this process emits carbon dioxide. While photosynthesis captures CO2, respiration does the opposite.

Understanding this balance is essential to predicting how ecosystems respond to climate change.

Scientists have believed that warmer climates would naturally speed up respiration. That belief was based on short-term experiments, where researchers exposed plants to heat and recorded quick increases in CO2 emissions. These tests, though useful, do not reveal how trees behave over years or decades of warming.

“This is likely true, but this latest research reveals that carbon fluxes under warmer future climates will not increase as much as currently thought,” said Professor Ian Wright of Western Sydney University, co-author of the study.

How trees adapt to warming

To dig deeper, the team built a dataset of thousands of stem respiration measurements from hundreds of tree species. The trees came from all major climate zones: tropical, temperate, arid, and boreal.

The data included samples from Australian savannas, woodlands, and rainforests collected over the past decade by Professor Wright’s team.

This vast dataset allowed the researchers to test how tree respiration changes not just during sudden heat but over long periods. The results suggest that trees adapt to higher temperatures in ways that slow down CO2 release.

“Short-term, temperature-driven changes in plant respiration rates are measured in seconds, minutes and hours. Due to the quick-acting enzymatic processes in plant tissues, the changes in plant respiration are very fast, and predictable,” explained Professor Wright.

Trees release carbon differently

Professor Wright pointed out that long-term changes behave differently. Plants may quickly ramp up CO2 release in hot weather, but this response does not last forever.

“This contrasts with the long-term, temperature-driven changes in respiration rates that are measured in months, years and decades. Most global ecosystem models in the past have assumed that the same short-term behavior in plants also applies over a longer time period, but this is not the case,” said Professor Wright.

“We now know that thermal acclimation over long timescales will dampen the positive feedbacks between climate warming and carbon emissions from plants.”

Thermal acclimation refers to the process where plants adjust their internal systems to handle rising temperatures. This ability could be a hidden strength in forests worldwide.

Changing climate models for better

The research could ultimately reshape climate modeling. Existing global models often assume that tree respiration continues to rise sharply with temperature. That assumption might now be too simplistic. With better data on long-term plant responses, climate scientists can update their predictions.

The study’s lead authors, Dr. Han Wang and Han Zhang from Tsinghua University, noted that only recently has the global scientific community had enough consistent data to challenge the old assumptions.

The team’s research has caught the attention of top vegetation modelers. Professor Sandy Harrison from the University of Reading believes the implications are broad.

“These findings give scientists a new approach for assessing the degree to which ecosystems around the globe can slow the rate of warming,” said Professor Harrison.

Trees may naturally limit carbon emissions

The potential for trees to adjust and regulate their CO2 release adds a layer of resilience to Earth’s systems. Although humans continue to emit carbon at alarming rates, nature may not always respond in a way that intensifies the damage.

Professor Wright highlighted the practical importance of these results, especially in a world already experiencing frequent climate disruptions.

“We’re already seeing that play out both here in Australia and around the world. However, these new findings suggest that, to some extent, ecosystems globally will slow the trends in one key driver of these changes, elevated atmospheric CO2,” he said.

New data reshapes carbon forecasts

The research on trees and carbon brings cautious hope. It does not cancel out climate risks. However, it shows that ecosystems might absorb some shocks more gently than expected.

With new data, improved models, and a clearer picture of plant behavior, scientists can build better forecasts and solutions.

Nature’s processes are complex. Trees do not simply react, they adjust. This long-term adjustment could be one of the quiet forces helping the planet endure in the face of climate change.

Other institutions involved in the study include Imperial College London and University of California, Berkeley. For background on climate-carbon feedbacks, visit the IPCC Working Group I report.

The study is published in the journal Science.

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