Extreme Hot-Wet Weather Drove Record CO₂ Surge In 2024

By Pooja Toshniwal PahariaReviewed by Lauren HardakerApr 30 2026

Extreme weather didn’t just stress ecosystems in 2024; it flipped them from carbon sinks into sources, revealing a powerful climate feedback that could accelerate global warming. 

Study: Dramatic increase in ecosystem respiration causes record-breaking atmospheric CO2 growth rate in 2024. Image credit: Saulo Ferreira Angelo/Shutterstock.com

A new study published in Nature Communications explores the factors behind the unprecedented rise in global atmospheric carbon dioxide (CO₂) levels in 2024. Researchers integrated atmospheric inversion models with estimates of gross primary production and fire emissions. They found that a sharply weakened terrestrial carbon sink was the main driver, fueled by surging ecosystem respiration across grasslands and shrublands.

Compound hot–wet climatic conditions in many regions, alongside broader heterogeneous climate extremes, amplified this shift in 2024. The findings point to intensifying climate feedbacks, with higher temperatures accelerating carbon release from land ecosystems.

Climate Extremes Challenge Assumptions About Carbon Uptake

Advances in carbon cycle monitoring have improved understanding of the land–atmosphere carbon balance, but key uncertainties remain under extreme climate variability. Most research focuses on fossil fuel emissions or isolated El Niño events, while compound heat, rainfall extremes, and ecosystem responses remain poorly understood.

The record-breaking conditions in 2024, marked by simultaneous vegetation greening and regional browning, highlight these gaps and challenge assumptions about terrestrial carbon uptake. This shows how this year differs from prior events such as the 2015–16 El Niño and the 2023 carbon cycle anomalies.

Satellite And Inversion Models Uncover Global Carbon Flux Shifts

In this study, researchers examined the factors underlying the unusually high global atmospheric CO₂ growth rate reported for 2024. They integrated satellite observations, atmospheric inversion modeling, and carbon flux data. The team applied the Global Carbon Assimilation System version 2 (GCASv2) to derive monthly ocean and land fluxes at 1° × 1° resolution, using Orbiting Carbon Observatory-2 (OCO-2) satellite CO₂ retrievals. They constrained ocean fluxes using a global ocean carbon mapping product and drew on Global Carbon Project (GCP) datasets to estimate fossil fuel emissions.

The researchers carried out four inversion-based analyses of atmospheric carbon fluxes using different biosphere priors. These included the Boreal Ecosystem Productivity Simulator (BEPS) and the Carnegie–Ames–Stanford Approach coupled with the Global Fire Emissions Database version 4.1s (CASA-GFED4.1s). They also incorporated fire-related emissions data from the Global Fire Emissions Database (GFED4.1s) and the Global Fire Assimilation System (GFAS).

The team aggregated outputs to derive optimal flux estimates and quantified uncertainty using posterior spread and Monte Carlo simulations. Independent evaluation used marine boundary layer (MBL) CO₂ records and global background station observations.

The researchers integrated satellite-derived gross primary production (GPP) from solar-induced chlorophyll fluorescence and machine learning–based models, harmonizing all components on a consistent grid. They derived terrestrial ecosystem respiration (TER) as a key carbon budget component, estimated as a residual from net ecosystem exchange, GPP, and fire emissions, with fire emissions including CO₂ plus a fraction of CO and CH₄ contributions, enabling isolation of ecosystem carbon release dynamics.

For attribution analyses, the team used 2022 as a baseline to reduce legacy effects from earlier climate extremes. They examined anomalies in net ecosystem fluxes and TER across biomes, latitudinal bands, and regions defined by the Regional Carbon Cycle Assessment and Processes (RECCAP) project, using Moderate Resolution Imaging Spectroradiometer (MODIS) land cover data to assess spatial variability.

They also combined ERA5-Land climate reanalysis data, Gravity Recovery and Climate Experiment Follow-On (GRACE-FO)-based terrestrial water storage (TWS), and regression frameworks to quantify climate–carbon relationships. Flux tower observations from global eddy covariance (EC) networks validated TER estimates and ecosystem responses under hot-wet and hot-dry extremes.

Ecosystem Respiration Surge Overwhelms Gains In Plant Growth

The global CO₂ growth rate reached a record high in 2024, driven primarily by a weakened terrestrial carbon sink. This decline stemmed from a sharp rise in TER, especially in grasslands and shrublands under compound hot-wet conditions. Ecosystem respiration, rather than fossil fuel emissions or ocean uptake, dominated the anomaly in the global carbon balance.

Relative to 2022, global net carbon flux increased by 2.87 PgC/yr, reflecting reduced land carbon uptake. This shift indicates a significant weakening of sink strength. TER alone increased by 4.30 PgC/yr and outweighed gains in gross primary production, which rose by 2.28 PgC/yr, illustrating a key paradox where increased plant growth was insufficient to offset even larger respiration-driven carbon losses. Fire emissions added to carbon release but played a secondary role. The enhanced TER explained most of the global land sink reduction in 2024.

Spatially, shrub and grass ecosystems accounted for nearly half of the overall land carbon anomaly, followed by forests and croplands. Most regions, including Europe, North America, South America, Africa, and Asia, showed weakened land sinks. However, the dominant drivers varied regionally, with some areas influenced more by fire emissions or reduced plant productivity than by respiration alone.

Only limited high-latitude areas exhibited increased carbon uptake. Tropical ecosystems dominated the global anomaly signal, contributing roughly 1.4 PgC/yr of the total anomaly, with persistent reductions outweighing partial mid-latitude gains in spring.

Climate conditions strongly shaped these responses. Hot-dry environments reduced both plant productivity and respiration, while hot-wet conditions amplified both processes, with increasing respiration consistently exceeding productivity gains. This imbalance led to net carbon losses, particularly in tropical shrublands where heat and moisture extremes crossed identifiable thresholds.

Future Hot–Wet Events Could Intensify Carbon Release Cycles

The study identifies a sharp weakening of the global land carbon sink as the primary driver of the record CO₂ surge in 2024. It shows that terrestrial ecosystem respiration increases strongly with temperature and moisture, highlighting a potential positive feedback risk where future climate extremes, especially increasing compound hot–wet events, could further accelerate carbon release.

As climate extremes become more frequent, strengthening carbon sequestration and reducing emissions will be critical to limit this cycle and stabilize the climate system.

Download your PDF copy by clicking here.

Journal Reference

Dong, G., Jiang, F., Ju, W. et al. (2026). Dramatic increase in ecosystem respiration causes record-breaking atmospheric CO₂ growth rate in 2024. Nature Communications. DOI: 10.1038/s41467-026-72189-y. https://www.nature.com/articles/s41467-026-72189-y