In a groundbreaking study published in the National Science Review, researchers from Fudan University and their collaborators have illuminated the severe regional disparities in climate change impacts triggered by greenhouse gas (GHG) emissions. Their work reveals that despite the relatively uniform global distribution of GHGs, the resultant warming and dry-hot extremes are disproportionately severe in North America and Europe. These two regions are projected to undergo some of the most intense climate perturbations by the end of the 21st century if GHG emissions remain unchecked, creating unprecedented challenges to ecosystems and human societies alike.
The study projects that under a high-emission scenario (SSP5-8.5), summer surface air temperature (SAT) in North America and Europe will increase by approximately 3.7°C ± 0.7°C and 3.8°C ± 0.5°C respectively by 2060–2099, significantly outpacing the global average land warming of 2.7°C ± 0.4°C. This amplified warming is accompanied by an expansion of drought-prone areas—by nearly 46% in North America and 13% in Europe—signifying a pronounced intensification of extreme dry-hot conditions. The regional prominence of these trends starkly contrasts with the milder effects anticipated in other parts of the world.
This spatial heterogeneity of climate effects is fundamentally linked to local feedback mechanisms, chiefly the land–air “dry-hot” feedback. This feedback loop operates through reductions in soil moisture, which decrease evapotranspiration and cloud cover. Consequently, more solar radiation reaches the ground, enhancing sensible heat flux and boosting surface and atmospheric temperatures. These changes further increase potential evapotranspiration, intensifying soil dryness and reinforcing the cycle of heat and drought. This nonlinear amplification mechanism is shown to be markedly stronger in North America and Europe than elsewhere.
Quantitatively, enhanced land–air coupling accounts for roughly 23.0% ± 9.8% of the total surface warming in North America and 22.4% ± 10.5% in Europe. This is substantially higher than the contribution in other regions, estimated at 7.9% ± 4.5%. The expansion of dry zones attributable to enhanced land–air interaction is similarly disproportionate, with increases of 44.2% ± 18.7% in North America and 22.6% ± 12.6% in Europe, whereas other global regions experience a negligible 1.6% ± 2.1%. These numbers underscore the critical role of local land–air processes in exacerbating regional climate extremes.
An alarming ecological consequence of this intensified dry-hot feedback is its suppression of Gross Primary Productivity (GPP) in these regions. GPP, a key indicator of vegetation health and carbon uptake, is projected to decrease by 27.1 ± 20.1 g C·m⁻²·month⁻¹ in North America and by 28.8 ± 16.9 g C·m⁻²·month⁻¹ in Europe under continued high emissions. These reductions could offset the fertilization effect of elevated atmospheric CO₂ concentrations on plant growth, weakening the resilience and carbon sequestration capability of ecosystems, and thereby exacerbating risks of ecological degradation.
The physical underpinnings of the land–air feedback mechanism center on hydrological and energy flux dynamics. As soil moisture declines due to warming, less water is available for evapotranspiration, leading to reduced latent heat flux and diminished cloud formation. The resulting increase in solar radiation absorbed at the surface elevates sensible heat flux, warming the boundary layer above the land surface. This not only directly raises surface air temperatures but also increases atmospheric demand for moisture, escalating potential evapotranspiration and deepening soil moisture deficits—a loop that propagates and magnifies the dry-hot anomaly.
Critically, the research indicates that without the intensified land–air feedback mechanism, North America and Europe would no longer emerge as extreme hotspots of warming and drought in climate model simulations comparing high-emission to low-emission futures. This finding highlights land–air coupling as an indispensable factor driving these regional climate extremes, beyond direct radiative forcing by greenhouse gases alone. It also accentuates the necessity of accurate representation of land surface processes in climate modeling to understand and predict regional climate risks.
The implications of these results are profound for climate policy and mitigation strategies. The study emphasizes that aggressive mitigation efforts to curtail GHG emissions can significantly ameliorate the severity of dry-hot extremes in North America and Europe, providing critical regional climate benefits. Given these regions’ outsized roles in historical emissions and their scientific capacity for climate leadership, the researchers advocate for robust domestic emission reductions and sustained international cooperation to achieve carbon peaking and neutrality goals globally.
Moreover, the projected intensification of extreme dry-hot events poses multifaceted risks involving public health, agriculture, water resources, and ecosystem integrity. Increasing frequency and severity of heatwaves combined with flash droughts threaten to undermine food security, biodiversity, and human well-being. These findings underscore the urgency for adaptive strategies alongside mitigation, focusing on enhancing land management, water use efficiency, and resilience building in vulnerable landscapes.
The study’s rigorous experimental framework leverages multi-model ensembles under the Coupled Model Intercomparison Project Phase 6 (CMIP6) and compares two contrasting emission pathways: SSP5-8.5 representing an unchecked high-emission future and SSP1-2.6 representing ambitious mitigation. The use of comprehensive climate models enables robust quantification of regional climate impacts and the isolation of contributions from land–air coupling, providing confidence in the mechanistic interpretations and projections.
This pioneering research marks a significant advancement in the understanding of regional climate dynamics under global warming. By pinpointing intensified land–air coupling as the key driver of anomalous warming and aridification in North America and Europe, it bridges gaps between global forcing and regional extremes. It opens pathways for more targeted climate prediction and informs policy frameworks tailored to the unique vulnerabilities of temperate mid-latitude regions.
Led by Academician Renhe Zhang and Professor Zhiyan Zuo from Fudan University, along with first author Associate Professor Liang Qiao of Lanzhou University, the interdisciplinary team integrates atmospheric science, hydrology, and ecosystem modeling to unravel the complexities of dry-hot feedback intensification. Their collaborative approach underscores the critical interplay between foundational climate science and applied environmental management in confronting the pressing challenges of climate change.
As the world confronts the escalating threat of climate extremes, this study offers both a warning and a beacon. The stark contrast between possible futures under high-emission versus mitigation scenarios illustrates the power and necessity of immediate and ambitious climate action. It highlights the intricate interactions within the Earth system that exacerbate risks but also presents pathways to reduce vulnerability, fostering hope for resilient and sustainable regional climates and ecosystems.
Subject of Research: Climate dynamics and regional extremes driven by greenhouse gas emissions and land–air interactions.
Article Title: Intensified GHG Emissions Drive Extreme Dry-Hot Extremes in North America and Europe.
News Publication Date: Not explicitly provided; see original journal reference for publication date.
Web References: DOI: 10.1093/nsr/nwaf435
References: National Science Review; CMIP6 climate model ensemble data.
Image Credits: ©Science China Press
Keywords: greenhouse gas emissions, land–air feedback, extreme heat, drought, North America, Europe, regional climate extremes, Gross Primary Productivity, climate mitigation, soil moisture, evapotranspiration
