Matvey Debolskiy

• Sathyanadh, Anusha; Esfandiari, Homa; Bourgeois, Timothée; Schwinger, Jörg; Bergman, Tommi & Partanen, Antti-Ilari [Show all 10 contributors for this article] (2026). Efficacy of individual and combined terrestrial and marine carbon dioxide removal. Environmental Research Letters. doi: 10.1088/1748-9326/ae2af5. Full text in Research Archive Show summary

  Abstract Limiting global temperature rise below 2°C requires significant reduction in greenhouse gas emissions and likely large-scale carbon dioxide removal (CDR). This study assesses the CO2 sequestration and efficacy of two CDR approaches, Bioenergy with Carbon Capture and Storage (BECCS) and Ocean Alkalinity Enhancement (OAE), applied individually and in combination. Using the Norwegian Earth System Model (NorESM2-LM), simulations were designed to ramp up deployment of BECCS and OAE, to an additional area of 5.2 million km² by 2100 for bioenergy feedstock for BECCS, and a CaO deployment rate of approximately 2.7 Gt/year for OAE within the exclusive economic zones of Europe, the United States and China. The combined land-ocean CDR simulation revealed a largely additive carbon removal effect. Over 2030-2100, OAE sequestered 7 ppm of CO 22 with an accumulated 82.3 Gt CaO, achieving a CDR effectiveness of 0.08 ppm (~ 0.17 PgC) per Gt CaO, while BECCS reduced 16 ppm of CO2, with CDR effectiveness of 3.1 ppm per million km² of bioenergy crops. Together, the carbon removal achieved by BECCS and OAE corresponds to anthropogenic CO₂ emissions of 5.4 Gt CO₂/year by 2100, slightly more than 60% of current global transport sector emissions. Notably, the efficiency of BECCS and OAE alone was unaffected by their concurrent deployment. Nevertheless, simulations revealed distinct non- linear interactions, such as declines in land and soil carbon sinks in the combined scenario. Furthermore, all simulations show negligible effects on the global annual mean temperature. These results highlight near-additive CDR responses even under net-negative emissions, but feedback on land and ocean carbon sinks must be considered when designing CDR portfolios. This study provides new insights into CDR portfolio design and Earth system feedback under an overshoot scenario, highlighting both their potential and the need for continued emissions cuts and supportive policies.

• Wall, Casey J.; Paynter, David; Qin, Yi; Debolskiy, Matvey; Duffy, Margaret L. & Michibata, Takuro [Show all 12 contributors for this article] (2025). Decomposing Cloud Radiative Feedbacks by Cloud-Top Phase. Journal of Climate. ISSN 0894-8755. 38(16), p. 4023–4043. doi: 10.1175/JCLI-D-24-0538.1. Full text in Research Archive Show summary

  Changes in cloud scattering properties and emissivity that arise from atmospheric warming cause substantial radiative feedbacks in model projections of anthropogenic climate change, and the relative importance of the underlying mechanisms is poorly understood. One leading hypothesis is that ice-to-liquid conversions cause clouds to optically thicken, producing a major negative feedback. We test this hypothesis by developing a method to decompose cloud radiative feedbacks by cloud-top phase. The method is applied to an ensemble of six state-of-the-art global climate models run with prescribed sea surface temperature. In these simulations, the global mean of the net cloud scattering and emissivity feedback from cloud-phase conversions ranges from −0.17 to −0.01 W m−2 K−1, while the overall net cloud feedback ranges from 0.02 to 0.91 W m−2 K−1. The multimodel mean of the cloud scattering and emissivity feedback from cloud-phase conversions is approximately 19% of the magnitude of the multimodel mean of the overall cloud feedback (−0.10 vs 0.52 W m−2 K−1). These results indicate that cloud-phase conversions cause a robust negative feedback by changing cloud scattering and emissivity, but this mechanism makes a modest contribution to the overall cloud feedback at the global scale. Significance Statement Climate warming changes Earth’s cloud properties, which then change the temperature further. One cloud-climate feedback mechanism involves the conversion of cloud ice particles to liquid droplets with warming. This makes clouds more opaque, causing them to reflect more solar radiation back to space. It is widely accepted that this mechanism dampens climate warming, but its importance relative to other feedback mechanisms has been unclear. This study develops a method to estimate the cloud opacity feedback from ice-to-liquid conversions in climate-model simulations. On average, cloud-opacity changes from phase conversions explain approximately 19% of the overall cloud–climate feedback in an ensemble of six climate models. This finding clarifies the importance of cloud-phase conversions in projections of anthropogenic climate change.

• Duran, Brandon; Wall, Casey James; Lutsko, Nicholas; Michibata, Takuro; Ma, Po-Lun & Qin, Yi [Show all 9 contributors for this article] (2025). A new method for diagnosing effective radiative forcing from aerosol-cloud interactions in climate models. Atmospheric Chemistry and Physics (ACP). ISSN 1680-7316. 25(4), p. 2123–2146. doi: 10.5194/acp-25-2123-2025. Full text in Research Archive Show summary

  Aerosol–cloud interactions (ACIs) are a leading source of uncertainty in estimates of the historical effective radiative forcing (ERF). One reason for this uncertainty is the difficulty in estimating the ERF from aerosol–cloud interactions (ERFaci) in climate models, which typically requires multiple calls to the radiation code. Most commonly used methods also cannot disentangle the contributions from different processes to ERFaci. Here, we develop a new, computationally efficient method for estimating the shortwave (SW) ERFaci from liquid clouds using histograms of monthly averaged cloud fraction partitioned by cloud droplet effective radius (re) and liquid water path (LWP). Multiplying the histograms with SW cloud radiative kernels gives the total SW ERFaci from liquid clouds, which can be decomposed into contributions from the Twomey effect, LWP adjustments, and cloud fraction (CF) adjustments. We test the method with data from five CMIP6-era models, using the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite instrument simulator to generate the histograms. Our method gives similar total SW ERFaci estimates to other established methods in regions of prevalent liquid cloud and indicates that the Twomey effect, LWP adjustments, and CF adjustments have contributed −0.34 ± 0.23, −0.22 ± 0.13, and −0.09 ± 0.11 W m−2, respectively, to the effective radiative forcing of the climate since 1850 in the ensemble mean (95 % confidence). These results demonstrate that widespread adoption of a MODIS re–LWP joint histogram diagnostic would allow the SW ERFaci and its components to be quickly and accurately diagnosed from climate model outputs, a crucial step for reducing uncertainty in the historical ERF.

• Streletskiy, Dmitry A; Maslakov, Alexey; Grosse, Guido; Shiklomanov, Nikolay I; Farquharson, Louise & Zwieback, Simon [Show all 12 contributors for this article] (2025). Thawing permafrost is subsiding in the Northern Hemisphere—review and perspectives. Environmental Research Letters. 20(1). doi: 10.1088/1748-9326/ada2ff. Full text in Research Archive Show summary

  High-latitude and altitude cold regions are affected by climate warming and permafrost degradation. One of the major concerns associated with degrading permafrost is thaw subsidence (TS) due to melting of excess ground ice and associated thaw consolidation. Field observations, remote sensing, and numerical modeling are used to measure and estimate the extent and rates of TS across broad spatial and temporal scales. Our new data synthesis effort from diverse permafrost regions of North America and Eurasia, confirms widespread TS across the panarctic permafrost domain with rates of up to 2 cm yr−1 in the areas with low ice content and more than 3 cm yr−1 in regions with ice-rich permafrost. Areas with human activities or areas affected by wildfires exhibited higher subsidence rates. Our findings suggest that permafrost landscapes are undergoing geomorphic change that is impacting hydrology, ecosystems, and human infrastructure. The development of a systematic TS monitoring is urgently needed to deliver consistent and continuous exchange of data across different permafrost regions. Integration of coordinated field observations, remote sensing, and modeling of TS across a range of scales would contribute to better understanding of rapidly changing permafrost environments and resulting climate feedbacks.

• Debolskiy, Matvey; Hock, Regine; Alexeev, Vladimir A. & Romanovsky, Vladimir E. (2023). Topographic controls of water balance response to air temperature increase in permafrost-affected watersheds. Frontiers in Earth Science. 11. doi: 10.3389/feart.2023.1288680. Full text in Research Archive Show summary

  Observed increases in runoff in permafrost regions have not only been associated with changes in air temperature and precipitation but also changes in hydrological pathways caused by permafrost thaw, however, the causes and detailed processes are still a matter of debate. In this study, we apply the physically-based hydrological model WaSIM to idealized small watersheds with permafrost to assess the response of total runoff and its components surface runoff, interflow, and baseflow to atmospheric warming. We use an idealized warming scenario defined by steady atmospheric warming (only in winter) over 100 years followed by 900 years of constant air temperatures leading to permafrost thaw. Sensitivity experiments include 12 watershed configurations with different assumptions on slope, profile curvature, and hydraulic conductivity. Results indicate that when subsurface conditions allow for faster lateral flow, at the end of the warming scenario the watersheds with steeper slopes or negative (convex) profile curvature, and thus larger unsaturated zones, experience delayed permafrost thaw due to decreased thermal conductivity and lower initial soil temperatures compared to watersheds with gentle slopes or positive (concave) curvature. However, in the long term, they exhibit a higher increase in annual runoff and baseflow (and subsequently winter runoff) than watersheds with lower hydraulic conductivity and/or more gentle terrain. Moreover, after the warming, for watersheds in which permeability at depth is lower than in near-surface soil, steeper slopes facilitate a significant reduction of the increase in baseflow (and winter runoff) and instead promote interflow generation compared to the watersheds with gentle slopes or lower near-surface permeability. For the watersheds with less permeable soil, a steeper slope facilitates a lesser decrease in interflow, and the increase in total runoff is delayed. In addition, water balance response to the warming has little sensitivity to profile curvature when hydraulic conductivity is low. On the other hand, in watersheds with high hydraulic conductivity, profile curvature can considerably alter water balance response to warming. Convex watersheds exhibit a larger (albeit delayed) increase in runoff and baseflow (and associated decrease in interflow generation) compared to those with zero or positive profile curvature.

• Steinert, Norman; Debolskiy, Matvey; Burke, Eleanor J.; García-Pereira, Félix & Lee, Hanna (2023). Evaluating permafrost definitions for global permafrost area estimates in CMIP6 climate models. Environmental Research Letters. 19(1). doi: 10.1088/1748-9326/ad10d7. Full text in Research Archive Show summary

  Global permafrost regions are undergoing significant changes due to global warming, whose assessments often rely on permafrost extent estimates derived from climate model simulations. These assessments employ a range of definitions for the presence of permafrost, leading to inconsistencies in the calculation of permafrost area. Here, we present permafrost area calculations using 10 different definitions for detecting permafrost presence based on either ground thermodynamics, soil hydrology, or air–ground coupling from an ensemble of 32 Earth system models. We find that variations between permafrost-presence definitions result in substantial differences of up to 18 million km2, where any given model could both over- or underestimate the present-day permafrost area. Ground-thermodynamic-based definitions are, on average, comparable with observations but are subject to a large inter-model spread. The associated uncertainty of permafrost area estimates is reduced in definitions based on ground–air coupling. However, their representation of permafrost area strongly depends on how each model represents the ground–air coupling processes. The definition-based spread in permafrost area can affect estimates of permafrost-related impacts and feedbacks, such as quantifying permafrost carbon changes. For instance, the definition spread in permafrost area estimates can lead to differences in simulated permafrost-area soil carbon changes of up to 28%. We therefore emphasize the importance of consistent and well-justified permafrost-presence definitions for robust projections and accurate assessments of permafrost from climate model outputs.

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• Zweigel, Robin Benjamin; Lee, Hanna; Debolskiy, Matvey & Westermann, Sebastian (2023). Simulating forest cover and terrain effects on ground hydrothermal regime in Mongolia and Siberia. Full text in Research Archive
• Zweigel, Robin Benjamin; Westermann, Sebastian; Lee, Hanna & Debolskiy, Matvey (2023). Simulating forest impact on ground thermal regime using the CryoGrid Community model – examples from Terelj, Mongolia. Full text in Research Archive
• Steinert, Norman; Schwinger, Jörg; Vrese, Philipp de; Asaadi, Ali; Debolskiy, Matvey & Lee, Hanna (2022). Arctic carbon cycle feedbacks under idealized overshoot scenarios. Full text in Research Archive

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