Abstract Active layer increase may contribute to greenhouse gas emissions, ecosystem change, and increased hazards. Here, we show the results of field measurements of active-layer thickness from 156 monitoring sites in Arctic, Antarctic and mountain permafrost regions. Active layer thickness increased significantly at 55% and 38% of sites in the Arctic and Antarctic regions, at more than 90% European mountain and high elevation Asian sites, and at sites in South America, demonstrating worldwide permafrost degradation during the first quarter of this century (2000–2024). The largest changes were observed in mountain regions where active layer doubled at several sites. The smallest changes were observed at sites with thick surficial organic horizons and high ground ice content. In continuous permafrost, sites generally exhibited smaller increases compared to sites in discontinuous permafrost. Regression analysis indicates Arctic active layer changes are attributable to increasing thawing degree-days, followed by increases in total rainfall. Other permafrost regions require more sites and longer time-series to draw conclusions regarding active layer change attribution.

Permafrost thaw affects the global carbon cycle and can significantly alter landscape morphology and associated processes of mass and energy transfer. An understudied aspect of thaw-affected permafrost landscapes is ubiquitous rivers connecting thermokarst lakes. These features of Arctic landscapes exhibit particularly high variability in water and energy transfer because, in lakes with larger water storage, excess water leads to comparatively small changes in water level and discharge, whereas in streams the channeled flow produces much larger fluctuations. Consequently, an equivalent absolute change in water level represents a much smaller relative change in lakes than in streams, resulting in a comparatively minor impact on overall heat content and energy transport. Such rivers thus provide an excellent field laboratory for analyzing how expected changes in meteorological forcing under climate change affect permafrost dynamics and carbon exchange within the land- and limnoscape. This paper presents a database from 2012 through 2022 for one such small stream connecting two thermokarst lakes. We instrumented two main stream cross sections with multiple subsurface thermistor chains to record temperature evolution from the land or water-land interface ( >= 5 cm depth) to soil depths of up to 5 m. The cross sections covered different topography and vegetation cover. One was located near the upper, and one in between the two thermokarst lakes. The main focus was set on the cross section midway between the two lakes (CS 9) due to the absence of a thermal imprint from the lake. Air, water, and ground temperatures, as well as physio-chemical river water and soil properties of the surrounding environment were measured continuously or during annual field campaigns and are provided as time-series or single tests. The data are organized in three main categories: atmosphere, water and ground, and are complemented by a GIS database including a digital surface model and an ortho-mosaic photo of the entire river valley to facilitate the search for measurements of interest. The database comes with a complete set of scripts to process any of the data, which are provided in CSV or other easily accessible standard file formats. Ultimately, the data can be used to develop models and validate numerical codes for improving the representation of permafrost processes in land surface and climate models where climate change induces significant changes in heat and mass transfer. All data and processing scripts are available through an online repository (10.5281/zenodo.14619854, ).

Global climate has undergone significant changes in the past 50-60 years. The transition from stable climate conditions to current warming has significantly influenced permafrost landscapes and infrastructure in cold regions. Arctic and Subarctic landscapes had distinct reactions to these changes. The objective of this study is to analyze the regional aspects of climate and permafrost changes in Yakutia's Arctic and subarctic regions from the past 50-60 years. Our analysis focused on climate change patterns during different periods, including cold period, pre-warming, and modern warming. We analyzed data on mean annual air temperature, thawing and freezing indices, and precipitation. During these periods, we determined the reaction's characteristics in various landscape regions. The most significant impact on permafrost began in the mid-2000s, as our observations confirmed. Global warming directly causes permafrost temperature to rise, the active layer to thicken, and cryogenic processes to develop. The conducted research provides the information needed to study the effects of global warming on permafrost and adapt socio-economic conditions in northern Yakutia.

Heat vulnerability in big cities is important because of the increase in heat wave frequency and thermal stress that is identified by Urban Heat Island. Our study investigated intra-urban heat vulnerability in Moscow, which strongly influenced by historic context in urban planning, with a focus on local disparities. We considered the vulnerability framework in terms of “exposure,” “sensitivity,” and “adaptive capacity,” and adopted the concept of a 15-minute city to evaluate spatial patterns on example of 2021 heat waves. We used high-resolution meteorological data from the regional meteorological model COSMOCLM and calculated the Physiologically Equivalent Temperature (PET) to assess thermal stress and define exposure. The data from OSM and other open sources were used to assess sensitivity and adaptive capacity through the proximity of green spaces, cooling centers, healthcare, and premium service facilities. The PET varied from 25.3 °C in the outskirts to 30.2 °C in Moscow centre; however, variations in thermal stress did not have adverse effects on the spatial patterns of vulnerability. The vulnerability indicator in the east was six times higher than in more prosperous areas of the center, north and southwest, due to historical development, mainly the transformation from former industrial areas into residential areas.

By analyzing the last 50–60 years of climate changes in Arctic and Subarctic Yakutia, we have identified three distinct periods of climate development. The cold (1965–1987), pre-warming (1988–2004), and modern warming (2005–2023) periods are clearly identifiable. Yakutia’s Arctic and Subarctic regions have experienced mean annual air temperature increases of 2.5 °C and 2.2 °C, respectively, compared to the cold period. The thawing index rose by an average of 171–214 °C-days, while the freezing index dropped by an average of 564–702 °C-days. During the pre-warming period, all three characteristics show a minor increase in warmth. Global warming intensified between 2005 and 2023, resulting in elevated permafrost temperatures and a deeper active layer. Monitoring data from the Tiksi site show that warming has been increasing at different depths since the mid-2000s. As a result, the permafrost temperature increased by 1.7 °C at a depth of 10 m and by 1.1 °C at a depth of 30 m. Soil temperature measurements at meteorological stations and observations at CALM sites both confirm the warming of the permafrost. A permafrost–climatic zoning study was conducted in Arctic and Subarctic Yakutia. Analysis identified seven regions characterized by similar responses to modern global warming. These study results form the foundation for future research on global warming’s effects on permafrost and on how northern Yakutia’s environment and economy adapt to the changing climate.

This paper presents the results of 30 years of permafrost thermal monitoring in the Tiksi area in the eastern Russian Arctic. At a stone ridge site, the mean annual temperatures in the upper 30 m of the ground have increased by 1–2.4 °C compared to the first years of observations, with trends of °C/yr. At the same time, its change was uneven. In the last 20 years, the rate of increase has increased compared with the first decade of observations. At wet tundra sites in the foothill plain, the mean annual temperatures at the top of permafrost have increased by 2.4–2.6 °C between 2005 and 2022 at rates of 0.11–0.15 °C/yr, and the active layer thicknesses have increased at rates of 0.05–0.41 cm/yr.

Arctic regions are highly impacted by the global temperature rising and its consequences and influences on the thermo-hydro processes and their feedbacks. Theses processes are especially not very well understood in the context of river–permafrost interactions and permafrost degradation. This paper focuses on the thermal characterization of a river–valley system in a continuous permafrost area (Syrdakh, Yakutia, Eastern Siberia) that is subject to intense thawing, with major consequences on water resources and quality. We investigated this Yakutian area through two transects crossing the river using classical tools such as in–situ temperature measurements, direct active layer thickness estimations, unscrewed aerial vehicle (UAV) imagery, heat transfer numerical experiments, Ground-Penetrating Radar (GPR), and Electrical Resistivity Tomography (ERT). Of these two transects, one was closely investigated with a long-term temperature time series from 2012 to 2018, while both of them were surveyed by geophysical and UAV data acquisition in 2017 and 2018. Thermodynamical numerical simulations were run based on the long-term temperature series and are in agreement with river thermal influence on permafrost and active layer extensions retrieved from GPR and ERT profiles. An electrical resistivity-temperature relationship highlights the predominant role of water in such a complicated system and paves the way to coupled thermo-hydro-geophysical modeling for understanding permafrost–river system evolution.

This article provides a quantitative analysis of local climate-related factors that may influence the organization of large sport events in Moscow, Russia, and its graphic representation in form of CTIS (Climate-Tourism Information Scheme) with decade resolution for 1991-2021. The individual CTIS for two historical sport events with daily resolution were also done, and then compared to meteorological data recorded during two large sport events to assess the agreement between averaged and actual conditions, which was found to be good enough for CTIS to serve as basic evaluation method. The CTIS-difference with sport events in Moscow compared with cases of Doha and Tokyo seem to be more about identifying the time period with biggest thermal comfort frequencies, instead of looking for occurrences of heat stress conditions. According to 1980 Summer Olympics and 2018 FIFA World Cup events it can be noted that time period was planned satisfactorily.

Cold environment supports a large diversity of local climates. Among them, urban climates in northern cities stand out for their pronounced warm temperature anomaly known as the Urban Heat Island (UHI). UHI in northern cities has been already studies through satellite images and in-situ observations in the urban canopy layer (UCL). Yet, the vertical structure of the urban atmospheric boundary layer (UBL) has not been studied there. This work presents new observations of UBL in Nadym - a sub-Arctic Siberian city. During several intensive observing periods we run simultaneous registration of urban and rural meteorological parameters with unmanned drones, a microwave temperature profiler and a dense network of ground-based sensors. The data analysis reveals details of UHI development in the UCL and UBL, and links together horizontal urban-rural canopy-layer temperature differences, boundary layer stability, and UHI vertical extent. We show that during strong temperature inversions, UBL is less stratified than its rural counterpart, but it still remains very thin and limited in height by a few tens of meters. The observations disclose that the ground-based (50 m - 100 m above ground) temperature inversion is one of the strongest control factors for UHI in cold climate conditions in winter.

Recent evidence has shown that Arctic regions have warmed about twice as much as elsewhere on the planet over the last decades, and that high-latitude periglacial processes and hydrological systems are deeply impacted by rising temperatures. The study presents recent results concerning the fluvial dynamics of a large periglacial river, the Lena River. The Lena river drains a large basin (2.9 million km²) entirely occupied by permafrost (77% with a deep and continuous permafrost). We had previously demonstrated that in the Lena basin, the climate change induces important increase in the river water discharge, that destabilizes the fluvial bed. Here we focus on the fluvial islands dynamics by examining islands with permafrost and islands without permafrost, such comparison being considered as a good indicator of the sensitivity of the hydrosytem to climate change. Island changes are precisely examined: morphological parameters of about 100 islands are surveyed using a GIS on seven series of aerial photographs and satellite images of a 100 km-long reach, for the 1967 – 2017 period. Furthermore, data obtained on several monitored islands allow to analyze the control factors. Field surveys and monitoring of islands shows that within a zone of thick and continuous permafrost, the Lena floodplain is far from being thermally and geomorphologically homogenous: the floodplain rather consists of a juxtaposition of seasonally frozen islands and permanently frozen islands. First, the analysis demonstrates that the two types of islands present different dynamics in terms of erosion and sedimentation. A major change is observed for islands with permafrost at the beginning of the 21st century: they clearly underwent a stronger erosion for the last twenty years. During the same period, numerous small and non-frozen islands have been formed. Second, the morphological parameters are analyzed with respect to factors that play a major part: water discharge (duration of bar-full, bankfull and flood discharges, number and season of flood peaks…) and temperature of the river water and of the island ground. The submersion of islands during flooding do not deeply modify the thermal regime within the island ground. However, the duration of the discharge exceeding the bar-full level can induce a marked erosion of island bank, especially in summer. Thus, our study highlights the complexity of large river responses across Arctic periglacial environments.

This study compares three approaches to microclimate research by the example of Russian Arctic cities in winter conditions: (1) using high-resolution thermal images by the Landsat 8 satellite, (2) using low-resolution images of the MODIS imaging system, and (3) using direct measurements of the surface air temperature. The latter involves observations of automatic weather stations and temperature sensors of the Urban Heat Island Arctic Research Campaign (UHIARC) network and Roshydromet weather stations. Two methods for calculating the land surface temperature (LST) from Landsat 8 satellite images have been considered: the first method is based on the atmospheric correction of images using the MODTRAN radiation transfer model and tabulated emissivity values for different land cover types, and the second method uses no atmospheric correction. The study was performed for the cities of Apatity, Vorkuta, Salekhard, Nadym, and Novy Urengoy. The land surface temperatures calculated from Landsat 8 images without atmospheric correction have been shown to agree with MODIS data and observations better than the results obtained with atmospheric correction. This indicates an inaccuracy in the value of surface emissivity. For a number of cases, the spatial variation patterns of the land surface and air temperatures are closely related; here, both types of data are indicative of the effect of urban heat island with urban–rural temperature differences up to 4°C in the daytime. These results are fundamentally different from those obtained previously for lower latitudes, which indicates the prospects of using high-resolution satellite temperature data for mapping and further studies of the microclimate of Arctic cities in winter conditions.

The Pan-Eurasian Experiment (PEEX) Science Plan, released in 2015, addressed a need for a holistic system understanding and outlined the most urgent research needs for the rapidly changing Arctic-boreal region. Air quality in China, together with the long-range transport of atmospheric pollutants, was also indicated as one of the most crucial topics of the research agenda. These two geographical regions, the northern Eurasian Arctic-boreal region and China, especially the megacities in China, were identified as a “PEEX region”. It is also important to recognize that the PEEX geographical region is an area where science-based policy actions would have significant impacts on the global climate. This paper summarizes results obtained during the last 5 years in the northern Eurasian region, together with recent observations of the air quality in the urban environments in China, in the context of the PEEX programme. The main regions of interest are the Russian Arctic, northern Eurasian boreal forests (Siberia) and peatlands, and the megacities in China. We frame our analysis against research themes introduced in the PEEX Science Plan in 2015. We summarize recent progress towards an enhanced holistic understanding of the land–atmosphere–ocean systems feedbacks. We conclude that although the scientific knowledge in these regions has increased, the new results are in many cases insufficient, and there are still gaps in our understanding of large-scale climate–Earth surface interactions and feedbacks. This arises from limitations in research infrastructures, especially the lack of coordinated, continuous and comprehensive in situ observations of the study region as well as integrative data analyses, hindering a comprehensive system analysis. The fast-changing environment and ecosystem changes driven by climate change, socio-economic activities like the China Silk Road Initiative, and the global trends like urbanization further complicate such analyses. We recognize new topics with an increasing importance in the near future, especially “the enhancing biological sequestration capacity of greenhouse gases into forests and soils to mitigate climate change” and the “socio-economic development to tackle air quality issues”.

A novel satellite technique for air temperature mapping with a spatial resolution of similar to 100 m was proposed for the town of Apatity, the Kola Peninsula (Russia), taken as a case study. The main idea behind this novel technique is to find the statistical relationships between the land surface temperatures in each point of the study area, observed by multiple infrared thermal satellite imagery, and the time series of air temperatures recorded by World Meteorological Organization (WMO) weather station. Fourteen scenes of infrared thermal spectral band of the Landsat satellites for the period 2014-2019 were used, as well as the long-term time series of air temperature from the weather station and the results of air temperature observations carried out by the network of loggers. For calm weather conditions, according to the ground truth, the error of air temperature mapping was sigma = 1.5 degrees C, and the precision was estimated as delta = 1.0 degrees C. An analysis of the compiled air temperature map showed that, under polar night conditions, the air temperature on the hilltops was by 10-18 degrees C higher than in the lowlands. It was concluded that, for economic reasons, as well as for the reasons of population health protection in the Arctic, it would be advisable to plan the placement of new cities on the hills. Each of these new areas should be designed in a "semi-isolated" manner in order to minimize the time needed by the local people for crossing the lowlands between the nearby districts. A characteristic feature of modern megalopolises is their internal structure formed by the growing primary settlements that can be considered as nuclei interlinked by transportation routes. Thus, the new Arctic cities can be called "Arctic megalopolises" because of their internal structure that is specific to megalopolises.

This article is devoted to the study of the distribution of ground ice volumes in the upper layers of 5–10 m permafrost in the permafrost landscapes of Arctic Yakutia. Compilation of such a map will serve as a basis for assessing the vulnerability of permafrost to global warming, anthropogenic impact and forecasting the evolution of permafrost landscapes. The map was compiled using ArcGIS software, which supports attribute table mapping. The ground ice map of Arctic Yakutian permafrost landscapes shows that about 19% of the area is occupied by ultra ice-rich (above 0.6 in volumetric ice content) sediments. Very high ice volumes (0.4–0.6) are cover approximately 27%, moderate ice volumes (0.2–0.4)—25% of the area, and low ice volumes (less than 0.2)—about 29% of Arctic Yakutia.

Global climate changes give us the important task of obtaining information about the spatial distribution of bioclimatic comfort indicators at the global or continental level. One of the most applicable tools can be based on reanalysis data (meteorological gridded data with global coverage). This issue is fully relevant for the territory of Northern Eurasia with its diverse climates, rapid environmental changes, and often sparse network of in situ observations. In this paper, we present a conceptually new dataset for the most popular thermal comfort indices, namely heat index (HI), humidex (HUM), wind chill temperature, mean radiant temperature, physiologically equivalent temperature (PET) and Universal Thermal Comfort Index (UTCI) derived from ERA-Interim reanalysis hourly data for the territory of Northern Eurasia (the area limited by 40° N–80° N, 10° W–170° W). The dataset has horizontal resolution of 0.75° × 0.75° (up to 79 km), temporal resolution of 3 h, and covers the period from 1979 to 2018 (40 years), which corresponds to the standard of the World Meteorological Organization in determining the parameters of the modern climate. Time series of indices are supplemented with a set of 8092 pre-calculated statistical parameters characterizing climatology of the thermal stress conditions. We further present several examples of the North Eurasian Thermal Comfort Indices Dataset (NETCID) data application, including analysis of the spatial heterogeneity of thermal stress conditions, assessment of their changes and analysis of specific extreme events. Presented examples demonstrate a pronounced difference between considered indices and highlight the need of their accurate selection for applied tasks. In particular, for the whole study areas HI and HUM indices show much smaller thermal stress repeatability and weaker trends of its changes in comparison to PET and UTCI indices. NETCID is available for free download at https://doi.org/10.6084/m9.figshare.12629861 .

The phylloplane is an integrated part of green infrastructure which interacts with plant health. Taxonomic characterization of the phylloplane with the aim to link it to ecosystem functioning under anthropogenic pressure is not sufficient because only active microorganisms drive biochemical processes. Activity of the phylloplane remains largely overlooked. We aimed to study the interactions among the biological characteristics of the phylloplane: taxonomic diversity, functional diversity and activity, and the pollution grade. Leaves of Betula pendula were sampled in Moscow at increasing distances from the road. For determination of phylloplane activity and functional diversity, a MicroResp tool was utilized. Taxonomic diversity of the phylloplane was assessed with a combination of microorganism cultivation and molecular techniques. Increase of anthropogenic load resulted in higher microbial respiration and lower DNA amount, which could be viewed as relative inefficiency of phylloplane functioning in comparison to less contaminated areas. Taxonomic diversity declined with road vicinity, similar to the functional diversity pattern. The content of Zn in leaf dust better explained the variation in phylloplane activity and the amount of DNA. Functional diversity was linked to variation in nutrient content. The fraction of pathogenic fungi of the phylloplane was not correlated with any of the studied elements, while it was significantly high at the roadsides. The bacterial classes Gammaproteobacteria and Cytophagia, as well as the Dothideomycetes class of fungi, are exposed to the maximal effect of distance from the highway. This study demonstrated the sensitivity of the phylloplane to road vicinity, which combines the effects of contaminants (mainly Zn according to this study) and potential stressful air microclimatic conditions (e.g., low relative air humidity, high temperature, and UV level). Microbial activity and taxonomic diversity of the phylloplane could be considered as an additional tool for bioindication.

Recent evidence has shown that Arctic regions have warmed about twice as much as elsewhere on the planet over the last few decades, and that high-latitude permafrost-periglacial processes and hydrological systems are notably responsive to rising temperatures. The aim of this paper is to report on the thermal regime of islands located along the Lena River floodplain, upstream of the city of Yakutsk (eastern Siberia). Four islands were monitored using waterproof dataloggers and continuous monitoring of frozen soil in contact with ice breakup of the Lena River. For each of these islands, we measured: (a) ground surface temperature, air and frozen soil temperatures at different depths; and (b) submersion duration during the flood. Our results show that within a zone of thick and continuous permafrost, the Lena floodplain is notably heterogeneous, with a combination of permanently and seasonally frozen islands. The ice breakups seem to have a negligible impact on the ground thermal regime. Our study confirms that relatively young (<30 years old) islands, composed of fine sand material, appear less prone to permafrost formation compared to older islands with ice-rich silty material.

The problems of climate change, high-impact weather phenomena and human thermal comfort in urban areas nowadays receives more and more attention not only from urban scientific community, but also from professionals in related fields as well as from general public. Today, publicly available weather-focused web services and applications experience rapid development and expansion. However, such services focused on urban climate are very rare and have limited usability. In this presentation, we share our experience in development of web-mapping application for urban climate monitoring & research for Moscow megacity in Russia. We aim to develop the web-application which provides observation-based evidence about current and historical weather conditions and human thermal comfort in Moscow region. Such application could be a valuable tool not only for urban climate researchers, but also for citizens planning their outdoor activity, weather and climate enthusiasts, weather-focused media, popularization of science, school and university education, etc. Previously, we have developed a prototype of such web-mapping application, which collects and maps observations at official weather stations and crowdsourced observations at Netatmo citizen weather stations (Varentsov et al., 2020). Application backend includes software for automated data collection, PostgreSQL database, data preprocessing tools (quality control for Netatmo data, spatial interpolation, simple model for on-the-fly calculations of Universal Thermal Climate Index representing human thermal comfort), GIS-server Geoserver for showing raster data. The application frontend is based on the OpenLayers web mapping library. The database is accessed by using the supplementary Node.js server application. Current stage of development includes several new tasks. Firstly, we plan to increase the timespan of historical data available in the application by 2005-2022. Secondly, we plan to develop interactive tools for data analysis, including time series plots and temporal averaging. Finally, we plan to supplement the application by the catalogue of illustrative weather events, such as cases with intense urban heat island, extreme precipitation, and dangerous thermal stress, and to provide popular description of such cases. The recent version of web-application under development is available at http://carto.geogr.msu.ru/mosclim2/. Acknowledgements: Development of web-application was supported by Russian Geographic Society under grant No. 03/2021-Р. Selection of intense precipitation cases for catalogue of illustrative weather events was supported by the grant of President of Russian Federation for young PhD scientists No. МК-5988.2021.1.5. Data analysis performed by Mikhail Varentsov was also funded by Non-commercial Foundation for the Advancement of Science and Education INTELLECT. Reference: Varentsov M. I., Samsonov T. E., Kargashin P. E., Korosteleva P. A., Varentsov A. I., Perkhurova A. A., & Konstantinov P. I. (2020). Citizen weather stations data for monitoring applications and urban climate research: an example of Moscow megacity. IOP Conference Series: Earth and Environmental Science, 611(1), 012055. https://doi.org/10.1088/1755-1315/611/1/012055