Shirshov Institute of Oceanology, Russian Academy of Sciences
Geophysical Center, Russian Academy of Sciences
Maykop State Technological University
Geophysical Center, Russian Academy of Sciences
Maykop State Technological University
S. Yu. Witte Moscow University
Russian Federation
Maikop State Technological University
National Research University of Electronic Technology
Shirshov Institute of Oceanology, Russian Academy of Sciences
Moscow, Russian Federation
Saint Petersburg State University
Russian State Hydrometeorological University
The Voeikov Main Geophysical Observatory
S. Yu. Witte Moscow University
UDC 55
CSCSTI 37.00
CSCSTI 38.00
Russian Classification of Professions by Education 05.00.00
Russian Library and Bibliographic Classification 26
Russian Trade and Bibliographic Classification 63
BISAC SCI SCIENCE
The paper’s aim is to study the impact of global and regional climate change on the state of the Caspian Sea. Determining the most probable climate scenarios for different coastal zones is an important step in predicting the change in the Caspian Sea level and developing plans for the region's adaptation to future climate change. This study assessed the Shared Socioeconomic Pathways (SSP) climate scenarios obtained using the CMIP6 global climate models (GCMs) by comparing the simulated data with actual measurements of surface air temperature (tas) at 72 weather stations in a 200-km buffer zone of the Caspian Sea. The analysis covered the period from 2015 to 2025. The research focuses on air temperature as the most reliably predicted parameter. The study used four main SSP scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5) calculated based on six climate models (AWI-CM-1-1-MR, CMCC-CM2-SR5, CNRM-CM6-1-HR, EC-Earth3, MPI-ESM1-2-HR and INM-CM5-0). The quality of the modeling was assessed using a number of indicators: mean error (ME), correlation coefficient (r), coefficient of determination (𝑅2), root mean square error (RMSE), Nash–Sutcliffe efficiency (NSE) and Kling–Gupta efficiency (KGE). The results showed a high degree of agreement between the models and observations for temperature, with correlation coefficients ranging from 0.85 to 0.96. However, systematic biases are observed (from −12.9 to +6.5 °C), with modeled data generally overestimated for lowland areas and underestimated for mountainous areas. The choice of the “best” SSP scenario varies depending on the metric used: based on RMSE and NSE, the most consistent with the actual mean temperature data (2015–2025) is the SSP5-8.5 scenario, while based on KGE, the SSP3-7.0 scenario better reproduces the variability and structure of the time series.
Caspian Sea, air temperature, weather stations, SSP, CMIP6, global climate models
1. Court R., Lattuada M., Shumeyko N., et al. Rapid decline of Caspian Sea level threatens ecosystem integrity, biodiversity protection, and human infrastructure // Communications Earth & Environment. — 2025. — Vol. 6, no. 1. — https://doi.org/10.1038/s43247-025-02212-5.
2. Eyring V., Bony S., Meehl G. A., et al. Overview of the Coupled Model Intercomparison Project Phase 6 (CMIP6) experimental design and organization // Geoscientific Model Development. — 2016. — Vol. 9, no. 5. — P. 1937– 1958. — https://doi.org/10.5194/gmd-9-1937-2016.
3. Gupta H. V., Kling H., Yilmaz K. K., et al. Decomposition of the mean squared error and NSE performance criteria: Implications for improving hydrological modelling // Journal of Hydrology. — 2009. — Vol. 377, no. 1/2. — P. 80– 91. — https://doi.org/10.1016/j.jhydrol.2009.08.003.
4. Hoseini S. M., Soltanpour M. and Zolfaghari M. R. Projected changes in Caspian sea level under CMIP6 climate change scenarios: probabilistic and deterministic approaches // Climate Dynamics. — 2025. — Vol. 63, no. 1. — https://doi.org/10.1007/s00382-024-07548-w.
5. IPCC. Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland. / ed. by H. Lee and J. Romero. — Geneva, Switzerland : Intergovernmental Panel on Climate Change (IPCC), 2023. — https://doi.org/10.59327/ipcc/ar6-9789291691647.
6. Kostianoy A. G., Malinin V. N. and Frolov A. V. Main Reasons for Changes in the Caspian Sea Level // Izvestiya, Atmospheric and Oceanic Physics. — 2025. — Vol. 61, S1. — S101–S115. — https://doi.org/10.1134/s0001433825701178.
7. Kostianoy A. G. and Pesic V. Advances in Environmental Monitoring of the Caspian Sea // Ecologica Montenegrina. — 2024. — Vol. 76. — P. 201–210. — https://doi.org/10.37828/em.2024.76.12.
8. Lavrova O. Yu., Ginzburg A. I., Kostianoy A. G., et al. Interannual variability of ice cover in the Caspian Sea // Journal of Hydrology X. — 2022. — Vol. 17. — P. 100145. — https://doi.org/10.1016/j.hydroa.2022.100145.
9. Nash J. E. and Sutcliffe J. V. River flow forecasting through conceptual models part I - A discussion of principles // Journal of Hydrology. — 1970. — Vol. 10, no. 3. — P. 282–290. — https://doi.org/10.1016/0022-1694(70)90255-6.
10. National Centers for Environmental Information (NCEI). — 2024. — URL: https://www.ncei.noaa.gov/ (visited on 08/26/2025).
11. O’Neill B. C., Tebaldi C., Vuuren D. P. van, et al. The Scenario Model Intercomparison Project (ScenarioMIP) for CMIP6 // Geoscientific Model Development. — 2016. — Vol. 9, no. 9. — P. 3461–3482. — https://doi.org/10.5194/gmd-9-3461-2016.
12. Raspisaniye Pogodi Ltd. Weather for 241 countries of the world. — 2004. — URL: https://rp5.ru/ (visited on 08/26/2025).
13. Riahi K., Vuuren D. P. van, Kriegler E., et al. The Shared Socioeconomic Pathways and their energy, land use, and greenhouse gas emissions implications: An overview // Global Environmental Change. — 2017. — Vol. 42. — P. 153– 168. — https://doi.org/10.1016/j.gloenvcha.2016.05.009.
14. Semenov S. M. and Gladilshchikova A. A. Scenarios of anthropogenic changes in the climate system in the 21st century // Fundamental and Applied Climatology. — 2022. — Vol. 8, no. 1. — P. 75–106. — https://doi.org/10.21513/2410-8758-2022-1-75-106. — (In Russian).
15. VNIIGMI-WDC. Main meteorological parameters (urgent data). — 2024. — URL: http://meteo.ru/data/basic-parameters/ (visited on 08/26/2025).
16. Zonn I. S., Kostianoy A. G., Kosarev A. N., et al. The Caspian Sea Encyclopedia. — Berlin, Heidelberg, New York : Springer Berlin Heidelberg, 2010. — https://doi.org/10.1007/978-3-642-11524-0.
