Forecasting carbon-risk hotspots ahead of the extreme 2026 El Niño

The Earth breathes in carbon dioxide and exhales it back, a continuous exchange between the atmosphere and the living world. Plants pull the gas from the air to build their leaves and trunks, acting as a massive sponge that soaks up heat-trapping emissions. This natural process, known as the land carbon sink, is one of the planet's most vital defenses against rapid climate change. However, this sponge is not unbreakable. When the climate shifts dramatically, the balance can tip. In some years, the land stops absorbing carbon and starts releasing it, turning from a shield into a source of further warming. One of the most powerful drivers of these shifts is the El Niño phenomenon, a natural climate pattern that warms the tropical Pacific Ocean and sends ripples of drought and heat across the globe. When these ripples hit, they can dry out forests, stress trees, and ignite fires, causing the land to cough up the carbon it usually holds tight.

Scientists have long watched these events after they happen, measuring the damage to understand how the planet reacts. But as the climate warms, the stakes have risen, and the need to look ahead has become urgent. A team of researchers has now developed a way to see the future of this carbon balance before the worst of an El Niño event arrives. By combining advanced computer models of how vegetation grows with forecasts of upcoming weather, they have created an early-warning system for the land. This approach allows them to map out where the carbon sink is likely to weaken and where the risk of fire will spike, turning a reactive science into a proactive one.

The researchers focused their attention on a specific, powerful event forecasted for 2026. By mid-year, signs indicated that a super El Niño was forming, one that could rival the most intense events seen in recent decades. To understand what this would mean for the global carbon cycle, the team did not wait for the event to unfold. Instead, they took a set of 51 different weather forecasts for the second half of 2026, generated by the European Centre for Medium-Range Weather Forecasts. They fed these potential weather scenarios into two sophisticated computer models that simulate how plants and soils respond to temperature and rain. They also added a machine-learning tool designed to predict where fires would burn based on those same weather conditions. This allowed them to simulate the entire carbon cycle for the coming months, testing how the land would react to a range of possible futures.

The simulations revealed a clear and concerning trend. While the first half of 2026 showed a healthy land carbon sink, the second half is projected to weaken significantly. The models suggest that between July and December 2026, the global land sink could lose its ability to absorb about 0.23 petagrams of carbon, with a margin of error of plus or minus 0.21. To put this in perspective, a petagram is a billion metric tons, a scale of carbon loss that would be felt across the entire planet. The weakening is driven by two main forces: the land breathing out more carbon through natural respiration as it gets hotter, and a surge in carbon released by fires. While some cooler regions might see plants grow faster due to warmth, the tropical regions are expected to suffer, with the heat and dryness overwhelming the plants' ability to absorb carbon.

The danger is not spread evenly across the map; it concentrates in specific hotspots where the risk is highest. The researchers identified two primary regions of concern. The first is eastern South America, particularly Brazil. Here, the combination of drought and heat is expected to cause a significant drop in the land's ability to act as a carbon sink. The models show that nearly all of the weather scenarios agree on this outcome, pointing to a deepening crisis in the humid forests and savannas of the region. The second hotspot is Southeast Asia, specifically the peatlands of Indonesia, Papua New Guinea, and Malaysia. In this region, the threat is not just a weakening of the carbon sink, but an explosion in fire activity. The simulations suggest that the area burned by fire in these equatorial regions could be more than five times higher than the average for the same period in recent years.

The difference between these two regions highlights how the same climate event can hurt the planet in different ways. In South America, the carbon loss comes from the stress on living trees and the soil, which release carbon as they struggle to survive the dry heat. In Southeast Asia, the loss is driven by fire. The peatlands there are like sponges of ancient, carbon-rich plant matter that have been soaked in water for thousands of years. When the El Niño dries them out, they become highly flammable. Once ignited, these fires burn deep and hot, releasing vast amounts of stored carbon that would otherwise remain locked away. The researchers found that the risk of these fires is so high that it demands immediate attention, suggesting that managing water levels and preventing human-caused ignitions in these areas could be critical to limiting the damage.

What makes this study distinct is its ability to look forward rather than backward. Previous studies have analyzed El Niño events only after they have passed, offering lessons for the future but no warning for the present. This new framework bridges that gap, showing that it is possible to anticipate where the carbon cycle will break down months in advance. The team found that while the global average of carbon loss might look moderate, the local impacts could be severe. In fact, the simulations suggest that some areas could experience carbon losses even worse than those seen during the extreme El Niño events of 2015 and 2023. The uncertainty in the forecasts means that the exact magnitude of the loss is not guaranteed, but the direction is clear: the land is likely to release more carbon than it absorbs during the peak of this event.

The findings serve as a call to action for managers and policymakers. By knowing where the risks are concentrated, resources can be directed to the right places before the damage occurs. In Southeast Asia, this could mean reinforcing firebreaks and keeping peatlands wet. In South America, it could involve preparing for the stress on forests and the potential for increased fire risk in the coming months. The study does not claim to have solved the problem of climate change, nor does it promise to stop the El Niño. Instead, it offers a tool for resilience, transforming the way we understand the relationship between extreme weather and the carbon cycle. It suggests that with the right models and the right data, we can see the storm coming and prepare the ground before the first drop of rain falls.