Norway spruce (Picea abies (L.) Karst.) is an ecologically and economically important conifer species that naturally dominates European boreal forests, the subalpine regions of the Alps, and the Carpathians. It is also widely planted beyond its native distribution area. In 2023, a significant spruce dieback was detected in the Carpathian Basin. To assess the extent of the damage, self-reported data were collected from citizens across Hungary about street, garden, and park spruce trees, covering all counties. A total of 4,081 spruce trees were reported in 2023, of which 2,422 (59.1

Examining continental ice layers accumulated before the nuclear era, when the artificial tritium component can be excluded, enables us to better understand the natural variation of cosmogenic tritium (3H). The extremely sensitive 3He-ingrowth method of 3H analysis allows us to determine low level tritium activities with high accuracy. Here we provide a detailed tritium profile of two shallow ice cores drilled in the European Alps and Greenland. A sensitive tritium profile of the top 33.7 m of the ice accumulation at Colle Gnifetti (Swiss-Italian Alps) is provided. The tritium concentrations of annual ice layers before 1953 vary between 0.050 and 0.145 TU with uncertainties of 0.0019 to 0.0048 TU. The tritium values reconstructed for the time of accumulation are varying between 4 and 10 TU. The long-term pattern of tritium in the ice (mainly before 1940) is in anti-correlation with the sunspot numbers. As the ice is not contaminated with artificial tritium, this change can be strongly attributed to the 11-year cycle of solar magnetic activity. This confirms the existing link between the Solar cycle and the cosmogenic tritium of precipitation [1]. On the contrary, in Greenland at the EGRIP camp, the signal of the solar cycle is hardly visible. The natural level of tritium at around 20 TU is disturbed by large spikes (>400 TU). These spikes seem to be randomly distributed in time. There are annual layers which are unaffected. The reason of the high tritium concentration might be the stratospheric moisture input as shown by Fourré et al. (2018) [2]. Stratospheric moisture can be also identified by its 17O-excess pattern. Here we provide the correlation of tritium and 17O, as a hint of the origin of excess tritium. On the other hand, the evaluation of the first results shows that the strength of the stratospheric intrusions qualified by tritium amount seems to be weakening over the last 100 years. [1] Palcsu, L., Morgenstern, U., Sültenfuss, J., Koltai, G., László, E., Temovski, M., Major, Z., Nagy, J.T., Papp, L., Varlam, C., Faurescu, I., Túri, M., Rinyu, L., Czuppon, G., Bottyán, E., Jull, A.J.T. Modulation of Cosmogenic Tritium in Meteoric Precipitation by the 11-year Cycle of Solar Magnetic Field Activity, Scientific Reports 8 (2018) 12813. [2] Fourré, E., Landais, A., Cauquoin, A., Jean-Baptiste, P., Lipenkov, V., Petit J.-R. Tritium Records to Trace Stratospheric Moisture Inputs in Antarctica. Journal of Geophysical Research: Atmospheres 123 (2018), 3009-3018.

A trícium régóta használt, hasznos nyomjelző izotóp a légköri transzport, a felszíni és a felszín alatti vizek, valamint a globális vízforgalom tanulmányozásához. Az elmúlt évtizedekben a tríciummérések alkalmazása jelentősen megnövekedett a vízkutatásban, hidrológiában, meteorológiában, oceanográfiában. A tanulmány célja, hogy bemutassa a trícium természetes és mesterséges forrásait és nyelőit, valamint kémiai-fizikai formáit a légkörben. Továbbá összefoglaljuk a csapadékban a trícium környezeti szintjét befolyásoló hatásokat: a hidrológiai ciklus különböző fizikai folyamatait, a csapadék mennyiségét, hígulását, a naptevékenységet, a szélességi és szárazföldi hatást. 1963 óta a nukleáris tesztekből származó magas tríciumkoncentráció a csapadékban jelentősen lecsökkent, majdnem elérve az egyensúlyi szintet. Emiatt a tríciumidősorokban azonosíthatók lettek a naptevékenység által kiváltott mintázatok, amelyeket a légköri folyamatok szintén befolyásolnak.

Accurate knowledge of the Ne isotopic composition of air is essential for planetary science. While the uncertainty of the noble gas isotopic composition of air has been drastically reduced to the level of similar to 0.1% in the last few years thanks to modern techniques, the most widely accepted value of the Ne-22/Ne-20 ratio of air (0.102 +/- 0.0008, Eberhardt et al., 1965) has an uncertainty of +/- 0.78% (1 sigma). Here we present the first multi-laboratory re-determination of the atmospheric Ne-22/Ne-20. An artificial, high purity mixture of Ne-20 and Ne-22 was prepared and the Ne-22/Ne-20 (0.11888 +/- 0.00001, 1 sigma) and Ne-20/Ne-22 (8.4118 +/- 0.0007, 1 sigma) determined gravimetrically. This gas was used to determine the mass fractionation of five mass spectrometers allowing the air Ne-22/Ne-20 to be determined (n = 234 analyses). Each laboratory sampled their own local air, used a different gas preparation system and analysis procedure as well as doing their own expansion of the high-pressure artificial Ne gas. Individual air Ne-22/Ne-20 determinations have uncertainties in the range of 0.01-0.08%. The overall reproducibility of the calculated Ne-22/Ne-20 of air between the laboratories shows no overdispersion with respect to the individual uncertainties. We report a global value for the atmospheric Ne-22/Ne-20 of 0.10196 +/- 0.00007 (0.07%, 1 sigma), equivalent of Ne-20/Ne-22 of 9.808 +/- 0.007. This is almost identical to the Eberhardt et al. (1965) value although its uncertainty shows a 12 times reduction. Our study did not verify any of the other previous determinations of atmospheric Ne-22/Ne-20. This highly accurate and precise atmospheric Ne-22/Ne-20 value provides a new reference for atmospheric Ne-21/Ne-20 determinations and we recalculate (Ne-21/Ne-20)(air) of five recent determinations. While this exercise resulted in no significant change to the absolute values, it gives more confidence with respect to the correctness of (Ne-21/Ne-20)(air). We suggest that the revised value for atmospheric Ne-22/Ne-20 be used routinely in all geoscience applications.

Radiocarbon-based age determination of wine samples has a great tradition worldwide, but most of the applied techniques, such as liquid scintillation counting and gas proportional counting analyses, have had large sample size requirements. However, accelerator mass spectrometry (AMS) based radiocarbon dating methods require much lower amount of carbon. Up to now, only a few available studies applied the AMS method to the dating of wine. We tested a preparation and measurement protocol for wine radiocarbon dating, not only for the ethanol fraction but for the distillation residue and submilliliter level preparation method of the wine sample without separation was also applied, using capillaries of the twenty wine samples from the Hungarian Tokaj wine region. The reliability of our method was verified by a comparison of wine time series with the Northern Hemisphere Zone 1 atmospheric C-14 data as a calibration curve. The measured C-14 values of the two different fractions, the ethanol and distillation residue, and the milliliter-sized non-separated samples also were in good agreement with each other, which shows both fractions could be used for radiocarbon dating of wine samples. Small sample size (similar to 10 mu L) wine radiocarbon dating does not destroy a significant part of a bottle of wine.

The variability of the rainfall stable isotopic values (δ2Hp, δ18Op) in the Ecuadorian Amazon to the Andes presents a marked local “altitude” effect. At the same time, this complex orography creates diverse precipitation regimes (unimodal, bimodal, and three-modal) that make it difficult to establish a relationship with the local amount. Nevertheless, stations along these regions show a similar intra-annual isotopic variability, with lower values during MAM and ON. In contrast, higher values are found during DJF and JAS in a w-shaped pattern, suggesting a common regional controller. A monthly δ2Hp and δ18Op collection campaign was established in Central Ecuador (n = 30) to complement stations biased towards the northern and southern parts. Based on back trajectory analysis, the results demonstrated that moisture arrives from two primary sources: the Tropical North Atlantic (DJFM) and the Amazon Basin (JAS). Nevertheless, their convergence (AMJ and ON) is the crucial factor modulating the lowest isotopic values. Precisely, this convergence is stronger at the V-Index region (5° S–5° N, 65°–75° W), where the wind seasonality and reversal at low levels are enhanced, allowing the inter-hemispheric moisture flux transport (cross-equatorial flow). We propose that the amount of rainfall located at the V-Index region is a more robust approach for explaining the δ2Hp and δ18Op variability rather than the local amount.

The lack of delimitation between the South American Monsoon System (SAMS) and the Intertropical Convergence Zone (ITCZ) has led to problematic calibration of archives in paleoclimate studies, particularly in northern South America. We show for the first time recorded in a paleoclimate archive that the ITCZ is the primary controller of oxygen (δ18OTR) and carbon (δ13CTR) isotopes in Cedrela nebulosa tree-rings (1864–2018). In contrast, a monsoonal pattern is not observed at this latitude. Spatial correlations revealed that δ18OTR better reflects months of higher precipitation (Mar–Jun) in the western Amazon than local rainout processes at decadal time scale, owing to the strong convection in the basin at this time of the year. Similarly, this study identified cloud cover as a vital controller in sunshine duration, which influences the phenology of Cedrela nebulosa. We interpret the variability of the δ13CTR as an enhancement in the photosynthetic rate during light-increased months (Jul–Sep), strongly regulated by cloudiness reduction when the ITCZ rain band retreats to northwestern South America in austral winter. Overall, these results reveal that Cedrela nebulosa is well-adapted to wet environments, and its cellulose-based stable isotopic signals reflect the direct influence of the ITCZ excursions from austral autumn to winter (Mar–Sep) with minimal SAMS control.

We measured stable isotopes (δ 18 O and δ 13 C) in Sphagnum cellulose that was extracted from a long peat core drilled in the ombrotrophic Mohos peat bog, Ciomadul Mountain, Romania. The 10-m-long peat profile spans the period from 11,800 cal yr BP to present. The δ 18 O and δ 13 C data indicate there were several cooling events and warm periods in the area of the Mohos peat bog during the Holocene. The 8.2-ka cold event, however, was not detected using δ 18 O and δ 13 C values. Response of the peat bog to changing environmental conditions was inferred using data on organic matter accumulation, independent of the stable isotope results. All cool periods during the Holocene, whether of short or long duration, were identified as times of reduced organic matter accumulation rate. Similarly, dry periods were also correlated with reduced accumulation rates of organic matter.

A Correction to this paper has been published: https://doi.org/10.1038/s41467-021-21647-w

The methane emissions from the Hungarian Pannonian Basin are not well qualified, due to a lack of measurements of CH4 mole fraction and delta C-13(CH4) in the air. This study reports methane measurements in air samples from Hungary, placing them in the context of regional and global background data, to investigate the inputs to the methane burden in Central Europe. CH4 mole fraction and delta C-13(CH4) from the Hungarian tall tower station, Hegyhatsal, and additional data from Mace Head (Ireland) and Zeppelin (Svalbard) are used with back trajectory modeling to identify central European source areas and their seasonal variation between the summer vegetation and winter heating periods. Methane measurements in air masses sampled in the European interior, have significantly higher maxima and seasonal amplitudes than at the Mace Head and Zeppelin European background sites. The mean CH4 mole fraction value is about 80 ppb higher than the comparable marine background, and values above 2,000 ppb were frequently observed between February 2013 and December 2015. The mean delta C-13(CH4) value -47.5 +/- 0.3 parts per thousand (2 sigma) was comparable to values at all three monitoring sites, but specific pollution events were detected at Hegyhatsal. Concentration weighted trajectory modeling, meteorological parameters, stable carbon isotopic composition (delta C-13(CH4)), and Miller-Tans analysis show that the main factors influencing CH4 at the Hegyhatsal, apart from diurnal and seasonal changes in the planetary boundary layer, are emissions from residential heating and industrial CH4 emissions during the winter.

Tritium has been long recognized as a useful tracer for the study of atmospheric transport, ocean circulation, and the global water cycle. In addition, the application of tritium measurements in various fields has grown significantly in the last few decades. Since 1963, the atmospheric test-ban treaty, bomb tritium concentrations in precipitation have significantly declined. Therefore, in the last two decades, global tritium concentration of precipitation (including anthropogenic and natural sources) has almost reached a steady-state level. The aim of this study is to estimate the temporal variation of the natural tritium concentration of precipitation during the past decades. To do this, we use a backward predicting time-series model that exploits the correlation between precipitation tritium concentration and the secondary neutron flux in the atmosphere. The measured tritium time series of 21 Northern and two Southern Hemispheric stations are used, while neutron monitor (NM) data, which are widely compared to the production rate of cosmogenic isotopes in the atmosphere, is used as an external variable for the model. Backward predicting SARIMAX statistical models are fit on the period 2001–2018 and provide estimates of the natural precipitation tritium levels for the bomb peak period 1960–2000. Evaluation of backward estimations on the 1990–2000 test period yields RMSE measures between 0.5 and 4.6 TU for four of the 23 investigated stations, pointing out locations where the neutron flux is a good predictor of the precipitation tritium concentration.

In this study, we focus on the relationship between the water vapor source region and the isotopic composition of the precipitation. The change of isotope characteristics of precipitation depends on the moisture source region. Long-term stable isotope (δ18O, δ2H ) measurements of precipitation were performed in Debrecen, Hungary, between 2001 and 2014. The long-term isotope time series and trajectory modeling are suitable for determining moisture source regions. Backward trajectory analysis was carried out using the Lagrangian Raptor model based on ERA5 atmospheric data. Hourly backward trajectories were calculated for Debrecen for the days with precipitation in the period between 2001-2014. Based on the study three source regions were identified. Of these, 60% represented the Carpathian Basin, which is where most of the moisture evaporated from near the surface. The remaining 40% of the northwest and southwest were represented by moisture source regions. This means that the isotopic composition of precipitation significantly determines the local and continental effects, i.e. the moisture evaporated from the continental surface contributes significantly to the spatial and temporal variation of the precipitation isotope composition.

This paper describes the relation of noble gas temperature (NGT) and mean annual air (MAAT) and soil (MAST) temperature through studying water samples and meteorological data from six Hungarian regions. Alluvial plains, hilly and mountainous regions were studied to investigate the effects of geomorphological, hydrogeological and micro-climatic conditions. Water samples were collected from springs and wells fed from different aquifers. Comparing NGTs derived from these water samples with the MAAT and MAST values of the given region, we identified differences between the sampled areas. In case of the Geresd Hills, Mezőföld, Danube-Tisza Interfluves and Nyírség, the NGTs (13.0 ± 0.9 °C, 12.1 ± 1.1 °C, 12.1 ± 0.6 °C and 12.7 ± 1.6 °C, respectively) generally reflect MAST, however in karstic Bükk Mts. (6.8 ± 0.6 °C) and Mecsek Mts. (10.7 ± 1.9 °C) they are closer to MAAT. Consequently, it can be concluded that the direct relationship between noble gas temperature and mean annual air temperature is not always as well-defined as it is often assumed. It is shown that MAAT and MAST should be distinguished, especially when using NGT as a paleoclimate proxy.

A three-year-long methane mole fraction and d13CCH4 measurement campaign was performed at the Hungarian tall tower station, Hegyhátsál, between 2013-2016. The results were compared with that of two NOAA atmospheric monitoring sites Mace Head and Zeppelin to determine the continental methane excess and the relative isotopic shift. The data then were used for bac trajectory analyses to identify potential methane source regions in Europe coupled with d13CCH4 results. The Hungarian station can be separated from the coastal and polar areas based on the mole fraction results having higher maxima and seasonal amplitude, but the d13CCH4 results match well with the NOAA stations’ results. Our study shows that although the local, regional anthropogenic and natural sources are major influences, more distant regions can also influence the measured CH4 level and d13CCH4 signal in the Pannonian Basin.

Climate change is one of the most important issues of anthropogenic activities. The increasing drought conditions can cause water shortage and heat waves and can influence the agricultural production or the water supply of cities. The Carpathian region is also affected by this phenomenon; thus, we aimed at identifying the tendencies between 1960 and 2010 applying the CarpatClim (CC) database. We calculated the trends for each grid point of CC, plotted the results on maps, and applied statistical analysis on annual and seasonal level. We revealed that monthly average temperature, maximum temperature and evapotranspiration had similar patterns and had positive trends in all seasons except autumn. Precipitation also had a positive trend, but it had negative values in winter. The geospatial analysis disclosed an increasing trend from West to East and from north to west. A simple binary approach (value of 1 above the upper quartile in case of temperature and evapotranspiration, value of 1 below the lower quartile; 0 for the rest of the data) helped to identify the most sensitive areas where all the involved climatic variables exceeded the threshold: Western Hungary and Eastern Croatia. Results can help to prepare possible mitigation strategies to climate change and both landowners and planners can draw the conclusions.

ABSTRACT Deciduous tree leaf and grass samples were collected in Debrecen, the second largest city in Hungary. The aim of the study was to determine the rate of fossil fuel-derived carbon in urban vegetation. At the locations sampled, C3 and C4 plants close to roads were collected in September 2017. In total, 82 tree and grass leaf samples were gathered at 36 different sampling points all over the city of Debrecen. The radiocarbon (14C) results of the samples were compared to the local urban background atmospheric 14CO2 data to determine the percentage of the fossil fuel-derived carbon in the plants. Based on our results, the average fossil carbon content in the tree and grass leaf samples were 0.9 ± 1.2% and 2.5 ± 2.5%, respectively. The highest fossil carbon content was 9.6 ± 0.6% in a grass and 4.7 ± 0.7% in a tree leaf sample. It appears that the negative fossil carbon content results obtained at urban sampling areas reflect modern carbon emission, where radiocarbon content is higher than the corresponding local background, presumably due burning of recent wood containing bomb 14C in the suburbs as well as other possible sources such as litter decomposition or soil CO2 emission.

Understanding climate change and revealing its future paths on a local level is a great challenge for the future. Beside the expanding sets of available climatic data, satellite images provide a valuable source of information. In our study we aimed to reveal whether satellite data are an appropriate way to identify global trends, given their shorter available time range. We used the CARPATCLIM (CC) database (1961–2010) and the MODIS NDVI images (2000–2016) and evaluated the time period covered by both (2000–2010). We performed a regression analysis between the NDVI and CC variables, and a time series analysis for the 1961–2008 and 2000–2008 periods at all data points. The results justified the belief that maximum temperature (TMAX), potential evapotranspiration and aridity all have a strong correlation with the NDVI; furthermore, the short period trend of TMAX can be described with a functional connection with its long period trend. Consequently, TMAX is an appropriate tool as an explanatory variable for NDVI spatial and temporal variance. Spatial pattern analysis revealed that with regression coefficients, macro-regions reflected topography (plains, hills and mountains), while in the case of time series regression slopes, it justified a decreasing trend from western areas (Transdanubia) to eastern ones (The Great Hungarian Plain). This is an important consideration for future agricultural and land use planning; i.e. that western areas have to allow for greater effects of climate change.

Correspondence Péter Salavec, Unit of Aviation Meteorology, Department of Forecasting, Hungarian Meteorological Service, 15, Szabadság st., Tolmács, H-2657, Hungary. Email: salavec.p@met.hu Urban heat island (UHI) and climate change belong to two separate scientific fields within meteorology nowadays. Climate change, however, may affect the characteristics of UHI as well. Various atmospheric macrocirculation conditions determine the frequency of certain weather conditions at a given area, thus they influence the frequency of the occurrence of conditions advantageous for UHI development. In the present research, the time series data of conditions advantageous for UHI (advantageous meteorological conditions [AMC]) were determined in the case of Debrecen (Hungary) and similar patterns existing in the AMC time series were searched in those of North Atlantic Oscillation, East Atlantic Oscillation, East Atlantic (EA)/Western Russia (WR) Pattern and Scandinavian Oscillation indices for the period between 1961 and 2010 using Gábor–Morlet wavelet transformations. Several significantly coherent oscillations were found. The occurrence frequency of AMC can be approximated from macrocirculation conditions in these periods, according to the concept of heat island. These estimations are consistent with the calculated AMC time series. This proves that there is some relationship between macrocirculation and heat island development. Based on the results, using seasonal and climate models the changes of UHIs at seasonal and climatic scales may become predictable.

Urban heat island (UHI) and climate change belong to two separate scientific fields within meteorology nowadays. Climate change, however, may affect the characteristics of UHI as well. Various atmospheric macrocirculation conditions determine the frequency of certain weather conditions at a given area, thus they influence the frequency of the occurrence of conditions advantageous for UHI development. In the present research, the time series data of conditions advantageous for UHI (advantageous meteorological conditions [AMC]) were determined in the case of Debrecen (Hungary) and similar patterns existing in the AMC time series were searched in those of North Atlantic Oscillation, East Atlantic Oscillation, East Atlantic (EA)/Western Russia (WR) Pattern and Scandinavian Oscillation indices for the period between 1961 and 2010 using Gábor–Morlet wavelet transformations. Several significantly coherent oscillations were found. The occurrence frequency of AMC can be approximated from macrocirculation conditions in these periods, according to the concept of heat island. These estimations are consistent with the calculated AMC time series. This proves that there is some relationship between macrocirculation and heat island development. Based on the results, using seasonal and climate models the changes of UHIs at seasonal and climatic scales may become predictable.