This study provides a global analysis of the relationship between drought metrics obtained from several climatic, hydrologic and ecological variables in a climate change framework using CMIP6 model data. A comprehensive analysis of the evolution of drought severity on a global scale is carried out for the historical experiment (1850–2014) and for future simulations under a high emissions scenario (SSP5‐8.5). This study focuses on comparing trends in the magnitude and duration of drought events according to different standardized indices over the world land‐surface area. The spatial and temporal relationship between the different drought indices on a global scale was also evaluated. Overall, there is a fairly large consensus among models and drought metrics in pointing to drought increase in southern North America, Central America, the Amazon region, the Mediterranean, southern Africa and southern Australia. Our results show important spatial
differences in drought projections, which are highly dependent on the drought metric employed. While a strong relationship between climatic indices was evident, climatic and ecological drought metrics showed less dependency over both space and time. Importantly, our study demonstrates uncertainties in future projections of drought trends and their interannual variability related to the relationship among indices, stressing the importance of coherent climatic, hydrological and plant physiological patterns when analyzing CMIP6 model
simulations of droughts under a warming climate scenario., Agencia Estatal de Investigación | Ref. PCI2019‐103631, Agencia Estatal de Investigación | Ref. PID2019-108589RA-I00, Agencia Estatal de Investigación | Ref. PID2021‐122314OB‐I00, Agencia Estatal de Investigación | Ref. TED2021‐129152B‐C41, Agencia Estatal de Investigación | Ref. TED2021‐129152B‐C43, Consejo Superior de Investigaciones Científicas | Ref. LINKB20080, Agencia Estatal de Investigación | Ref. PRE2022‐101497, Xunta de Galicia | Ref. ED431C 2021/44

11 Pags.- 1 Tabl.- 4 Figs. Original content from
this work may be used
under the terms of the
Creative Commons
Attribution 4.0 licence., We present a long-term assessment of precipitation trends in Southwestern Europe (1850–2018) using data from multiple sources, including observations, gridded datasets and global climate model experiments. Contrary to previous investigations based on shorter records, we demonstrate, using new long-term, quality controlled precipitation series, the lack of statistically significant long-term decreasing trends in precipitation for the region. Rather, significant trends were mostly found for shorter periods, highlighting the prevalence of interdecadal and interannual variability at these time-scales. Global climate model outputs from three CMIP experiments are evaluated for periods concurrent with observations. Both the CMIP3 and CMIP5 ensembles show precipitation decline, with only CMIP6 showing agreement with long term trends in observations. However, for both CMIP3 and CMIP5 large interannual and internal variability among ensemble members makes it difficult to identify a trend that is statistically different from observations. Across both observations and models, our results make it difficult to associate any declining trends in precipitation in Southwestern Europe to anthropogenic forcing at this stage., This work was supported by the research projects CGL2017-82216-R, CGL2017-83866-C3-3-R and PCI2019-103631, financed by the Spanish Commission of Science and Technology and FEDER; CROSSDRO project financed by the AXIS (Assessment of Cross(X)—sectoral climate Impacts and pathways for Sustainable transformation), JPI-Climate co-funded call of the European Commission and INDECIS which is part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR) with co-funding by the European Union (Grant 690462). Dhais Peña-Angulo received a 'Juan de la Cierva' postdoctoral contract (FJCI-2017-33652 Spanish Ministry of Economy and Competitiveness, MEC). Conor Murphy was supported by the Irish Environmental Protection Agency (Grant Nos. 2019-CCRP-MS.60). Marco Turco has received funding from the Spanish Ministry of Science, Innovation and Universities through the project PREDFIRE (RTI2018-099711-J-I00), which is co-financed with the European Regional Development Fund (ERDF/FEDER)., Peer reviewed

14 Pags.- 5 Figs. Under Creative Commons License CC BY-NC-ND, The standardized precipitation evapotranspiration index (SPEI) is one of the well‐established drought metrics worldwide. It is simply computed using precipitation and atmospheric evaporative demand (AED) data. Although AED is considered a key driver of drought variability worldwide, it could have less impact on drought in specific regions and for particular times as a function of the magnitude of precipitation. Specifically, the influence of the AED might overestimate drought severity during both normal and humid periods, resulting in “false alarms” about drought impacts on physical and human environments. Here, we provided a global characterization of the sensitivity of the SPEI to changes of the AED. Results demonstrate that the contribution of AED to drought severity is largely impacted by the spatial and temporal variability of precipitation. Specifically, the impact of AED on drought severity was more pronounced during periods of low precipitation, compared to wet periods. Interestingly, drought severity in humid regions (as revealed by SPEI) also showed low sensitivity to AED under drier conditions. These results highlight the skill of SPEI in identifying the role of AED in drought evolution, especially in arid and semiarid regions whose climate is characterized typically by low precipitation. This advantage was also evident for humid environments, where SPEI did not overestimate drought severity due to the increased AED. These findings highlight the broader applicability of SPEI to accurately characterize drought severity worldwide., This work was supported by the research projects CGL2017‐82216‐R and PCI2019‐103631, financed by the Spanish Commission of Science and Technology and Fondo Europeo de Desarrollo Regional (FEDER); CROSSDRO project financed by the AXIS (Assessment of Cross(X)—sectoral climate Impacts and pathways for Sustainable transformation), JPI‐Climate cofunded call of the European Commission and INDECIS which is part of ERA4CS, an ERA‐NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), and ANR (FR) with cofunding by the European Union (Grant 690462). Dhais Peña‐Angulo received a “Juan de la Cierva” postdoctoral contract (FJCI‐2017‐33652 from Spanish Ministry of Economy and Competitiveness, MEC)., Peer reviewed

© 2021 by the authors, Flash drought is the result of strong precipitation deficits and/or anomalous increases in atmospheric evaporative demand (AED), which triggers a rapid decline in soil moisture and stresses vegetation over short periods of time. However, little is known about the role of precipitation and AED in the development of flash droughts. For this paper, we compared the standardized precipitation index (SPI) based on precipitation, the evaporative demand drought index (EDDI) based on AED, and the standardized evaporation precipitation index (SPEI) based on the differences between precipitation and AED as flash drought indicators for mainland Spain and the Balearic Islands for 1961–2018. The results show large differences in the spatial and temporal patterns of flash droughts between indices. In general, there was a high degree of consistency between the flash drought patterns identified by the SPI and SPEI, with the exception of southern Spain in the summer. The EDDI showed notable spatial and temporal differences from the SPI in winter and summer, while it exhibited great coherence with the SPEI in summer. We also examined the sensitivity of the SPEI to AED in each month of the year to explain its contribution to the possible development of flash droughts. Our findings showed that precipitation is the main driver of flash droughts in Spain, although AED can play a key role in the development of these during periods of low precipitation, especially in the driest areas and in summer., Research projects CGL2017-82216-R, PCI2019-103631, and PID2019-108589RA-I00 financed by the Spanish Commission of Science and Technology and FEDER; CROSSDRO project financed by the AXIS (Assessment of Cross(X)—sectoral climate Impacts and pathways for Sustainable transformation), JPI-Climate co-funded call of the European Commission and INDECIS which is part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR) with co-funding by the European Union (Grant 690462)., Peer reviewed

28 Pags.- 10 Figs. The definitive version is available at: https://rmets.onlinelibrary.wiley.com/journal/10970088, This study presents a climatology and trend analysis of reference crop evapotranspiration (ETo) over continental Spain and the Balearic Islands. Geographic features of the study region play a substantial role in the climatology of ETo. The highest values (in excess of 1,200 mm y−1) are found at lower elevations in the south, while the lowest values (less than 900 mm y−1) are found in the highest elevations in the north. A deep analysis reveals: (a) a low interannual variability; (b) summer accumulates more than 50% of annual values; and (c) the radiative component contribution is higher than 50%. A positive long‐term trend (1961–2014) has been detected for most of the study area, but showing contrasting situations when shorter periods (20–30 years) are analysed. A short initial period of negative trend was followed by a longer period of a positive trend. We argue that global dimming/brightening played a role in this process, as these two contrasting periods are clearly guided by the radiative component. A seasonal analysis of the trends reveals that spring and summer are the seasons showing the long‐term positive trends. Interestingly, a monthly analysis shows that spring trends are guided by March and April and summer trends are mostly guided by June, which is the month showing the highest relative changes. This could have important consequences for agriculture and natural ecosystems since this month represents the start of the summer (dry) period., This research was supported by the research projects GCL2017-82216, GCL2017-
83866-C3-3R and PCI2019-103631 financed by the Spanish Comission of Science
and Technology and FEDER; CROSSDRO project nanced by the AXIS (Assessment of Cross(X) - sectorial climate impacts and pathways for Sustainable
transformation), JPI-Climate co-funded call of the European Comission and INDECIS which is part of ERA4CS, an ERA-NET initiated by JPI Climate, and
funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO
(ES), ANR (FR) with co-funding by the European Union (Grant 690462)., Peer reviewed

19 Pags.- 15 Figs., We analyzed the impacts of drought severity on a variety of sectors in a topographically complex basin (the upper Aragón basin 2181 km2) in the Central Spanish Pyrenees. Using diverse data sources including meteorological and hydrological observations, remote sensing and tree rings, we analyze the possible hydrological implications of drought occurrence and severity on water availability in various sectors, including downstream impacts on irrigation water supply for crop production. Results suggest varying responses in forest activity, secondary growth, plant phenology, and crop yield to drought impacts. Specifically, meteorological droughts have distinct impacts downstream, mainly due to water partitioning between streamflow and irrigation channels that transport water to crop producing areas. This implies that drought severity can extend beyond the physical boundaries of the basin, with impacts on crop productivity. This complex response to drought impacts makes it difficult to develop objective basin-scale operational definitions for monitoring drought severity. Moreover, given the high spatial variability in responses to drought across sectors, it is difficult to establish reliable drought thresholds from indices that are relevant across all socio-economic sectors. The anthropogenic impacts (e.g. water regulation projects, ecosystem services, land cover and land use changes) pose further challenges to assessing the response of different systems to drought severity. This study stresses the need to consider the seasonality of drought impacts and appropriate drought time scales to adequately assess and understand their complexity., This work was supported by the research projects CGL2017-82216-R, PCI2019-103631, and PID2019-108589RA-I00 financed by the Spanish Commission of Science and Technology and FEDER; CROSSDRO project financed by the AXIS (Assessment of Cross(X) - sectoral climate Impacts and pathways for Sustainable transformation), JPI-Climate co-funded call of the European Commission and INDECIS which is part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR) with co-funding by the European Union (Grant 690462). Dhais Peña-Angulo received a “Juan de la Cierva” postdoctoral contract (FJCI-2017-33652 Spanish Ministry of Economy and Competitiveness, MEC)., Peer reviewed

8 Pags.- 3 Figs. © Te Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International
License, which permits use, sharing, adaptation, distribution and reproduction in any medium or
format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made., Climate proxy data are required for improved understanding of climate variability and change in the pre-instrumental period. We present the first international initiative to compile and share information on pro pluvia rogation ceremonies, which is a well-studied proxy of agricultural drought. Currently, the database has more than 3500 dates of celebration of rogation ceremonies, providing information for 153 locations across 11 countries spanning the period from 1333 to 1949. This product provides data for better understanding of the pre-instrumental drought variability, validating natural proxies and model simulations, and multi-proxy rainfall reconstructions, amongst other climatic exercises. The database is freely available and can be easily accessed and visualized via http://inpro.unizar.es/., This work was supported by the research projects CGL2017-82216-R, PCI2019-103631 and PID2019-
108589RA-100 financed by the Spanish Commission of Science and Technology and FEDER; CROSSDRO
project fnanced by the AXIS (Assessment of Cross (X)- sectoral climate Impacts and pathways for Sustainable
transformation), and JPI-Climate co-funded call of the European Commission and INDECIS which is part of
ERA4CS, an ERA-NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD
(DK), MINECO (ES), ANR (FR) with co-funding by the European Union (Grant 690462). Te research of Nieves
Bravo-Paredes has been supported by the predoctoral fellowship PRE2018-084897 from Agencia Estatal de
Investigación (Ministerio de Ciencia, Innovación y Universidades) of the Spanish Government. Te Portuguese
data search stems partly from the project KlimHist, fnanced by FCT (PTDC/AAC–CLI/119078/2010)., Peer reviewed

13 Pags.- 11 Figs.- 2 Tabls., The availability of water resources is a major challenge of the Mediterranean region. Intense land use transformation has impacted the headwaters of river basins that generate most of the water resources, reducing streamflow This study analyses the evolution of hydrological and climatic drought in headwater catchments of Spain and it explores the extent to which vegetation can reinforce trends in hydrological drought severity in comparison to the evolution of cFlimatic drought severity. We have used the Standardized Precipitation Evapotranspiration Index and Standardized Streamflow Index to examine hydrological and climatic drought, respectively, and examined the changes in the frequency, magnitude, and duration of climatic and hydrologic droughts over non-perturbed headwater catchments of Spain from 1961 to 2013. We quantified vegetation changes over time in the analysed catchments and we compared the changes in the climatic and hydrological droughts with changes in vegetation coverage using Pearson’s r correlations and linear regression model. The results show that the trends toward higher frequency, duration and severity of hydrological droughts are more marked than the observed trends in climatic droughts, which can be associated to the dominant increase in vegetation coverage and activity in the study domain. Finally, it is concluded that the spatial differences observed between the trends of climatic and hydrological droughts show some relationship with the patterns of forest succession observed in recent decades. Our results stress the relevance of land transformation processes on trends in water resources availability, particularly during periods of climatic droughts in which competence between vegetation water consumption and streamflow production is much more relevant., This work was supported by the research projects CGL2017-82216-R, PCI2019-103631 and PID2019-108589RA-I00, financed by the Spanish Ministry of Science and FEDER; and CROSSDRO project financed by the AXIS (Assessment of Cross(X) - sectorial climate Impacts and pathways for Sustainable transformation). Dhais Peña-Angulo received a “Juan de la Cierva” postdoctoral contract (FJCI-2017-33652 Spanish Ministry of Economy and Competitiveness, MEC)., Peer reviewed

The dynamics of blue and green water partitioning under vegetation and climate change, as well as their different interactions during wet and dry periods, are poorly understood in the literature. We analyzed the impact of vegetation changes on blue water generation in a central Spanish Pyrenees basin undergoing intense afforestation. We found that vegetation change is a key driver of large decreases in blue water availability. The effect of vegetation increase is amplified during dry years, and mainly during the dry season, with streamflow reductions of more than 50%. This pattern can be attributed primarily to increased plant water consumption. Our findings highlight the importance of vegetation changes in reinforcing the decrease in water resource availability. With aridity expected to rise in southern Europe over the next few decades, interactions between climate and land management practices appear to be amplifying future hydrological drought risk in the region., This work was supported by projects CGL2017-82216-R, PCI2019-103631, and PID2019-108589RA-I00 financed by the Spanish Commission of Science and Technology and FEDER; CROSSDRO project financed by AXIS (Assess-ment of Cross(X)-sectoral climate Impacts and pathways for Sustainable transformation), JPI-Climate co-funded call of the European Commission and INDECIS which is part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR) with co-funding by the European Union (Grant 690462). Dhais Peña-Angulo received a “Juan de la Cierva” postdoctoral contract (FJCI-2017-33652 Spanish Ministry of Economy and Competitiveness, MEC). Miquel Tomas-Burguera received a “Juan de la Cierva” postdoctoral contract (FJCI-2019-039261-I Spanish Ministry of Science and Innovation). C. Azorin-Molina and S. Grainger. acknowledge funding from the Irish Environmental Protection Agency grant 2019-CCRP-MS.60. C. Juez acknowl-edges funding from the H2020-MSCA-IF-2018 programme (Marie Sklodows-ka-Curie Actions) of the European Union under REA grant agreement, number 834329-SEDILAND.

Datos geoespaciales en rejilla de SPEI., [ES] El dataset SPEICropDroughtMonitor se actualiza periódicamente, se puede consultar y descargar en el siguiente enlace:
https://global-drought-crops.csic.es/
[EN] The SPEICropDroughtMonitor dataset is updated periodically, it can be consulted and downloaded at the following link:
https://global-drought-crops.csic.es/, [EN] This dataset provides near real-time information about drought conditions in regions where corn, wheat, barley, soybeans and cotton are grown with a 0.5 degrees spatial resolution and a weekly time resolution. SPEI time-scales between 0.5 and 48 months are provided from 1979., [ES] La dataset presenta información en tiempo cuasi real de las condiciones de sequía en las regiones del mundo donde se cultiva maíz, trigo, cebada, soja y algodón a resolución temporal semanal y espacial de 0.5 grado. Se proporcionan los valores de SPEI a escalas temporales de 0.5 a 48 meses desde 1979., Ministry of Science and Technology of Spain, Grant/Award Number: PCI2019-103631., Peer reviewed

Datos geoespaciales en rejilla de SPEI., [ES] El dataset SPEISemiaridDroughtMonitor se actualiza periódicamente, se puede consultar y descargar en el siguiente enlace:
https://semiarid-drought-monitor.csic.es/
[EN] The SPEISemiaridDroughtMonitor dataset is updated periodically, it can be consulted and downloaded at the following link:
https://semiarid-drought-monitor.csic.es/, [EN] This dataset provides near real-time information about drought conditions in semi-arid regions of the world with a 0.5 degrees spatial resolution and a weekly time resolution. SPEI time-scales between 0.5 and 48 months are provided from 1979., [ES] Esta dataset presenta información en tiempo cuasi real de las condiciones de sequía en las regiones semiáridas del mundo a resolución temporal semanal y espacial de 0.5 grado. Se proporcionan los valores de SPEI a escalas temporales de 0.5 a 48 meses desde 1979., Ministry of Science and Technology of Spain, Grant/Award Number: PCI2019-103631, No

Datos geoespaciales en rejilla sobre sequía., [EN] El dataset Monitordesequíameteorológica se actualiza periódicamente, se puede consultar y descargar en el siguiente enlace:
https://monitordesequia.csic.es/monitor/
[EN] The Monitordesequíameteorológica dataset is updated periodically, it can be consulted and downloaded at the following link:
https://monitordesequia.csic.es/monitor/, [EN] This dataset offers near real-time information about drought conditions in Spain with a 1.1 km spatial resolution and a weekly time resolution. SPI and SPEI (time-scales 1, 3, 6, 9, and 12 month), drought duration and magnitude are provided from 1955 until today. The dataset is updated four times each month., [ES] Esta dataset proporciona información en tiempo cuasi real de las condiciones de sequía en España a resolución temporal semanal y espacial de 1.1 km. Proporcionan los valores de SPI y SPEI a diferentes escalas temporales (1, 3, 6, 9 y 12) así como la duración y la magnitud de las sequías desde 1961 hasta la actualidad. La dataset se actualiza cuatro veces cada mes., Spanish Ministry of Science and Technology and FEDER by the projects PCI2019-103631, AXIS (Assessment of Cross (X) - sectoral climate Impacts and pathways for Sustainable transformation), JPI Climate co-funded call of the European Commission by the project CROSSDRO, Peer reviewed

Datos geoespaciales en rejilla sobre sequía repentina., [ES] El dataset FlashDroughtMonitor se actualiza periódicamente, se puede consultar y descargar en el siguiente enlace:
https://flash-drought.csic.es/
[EN] The FlashDroughtMonitor dataset is updated periodically, it can be consulted and downloaded at the following link:
https://flash-drought.csic.es/, [EN] This dataset provides near real-time information about flash drought conditions in Spain with a 1.1 km spatial resolution and weekly frequency. Flash drought onset and spatial extend is identified based on SPEI at short time-scale (1-month)., [ES] Este dataset proporciona información en tiempo cuasi real sobre las condiciones de sequía repentina en España con una resolución espacial de 1.1 km y una frecuencia temporal semanal. El inicio y extensión espacial de la sequía repentina es identificado en base al SPEI a una escala temporal corta (1-mes)., Spanish Commission of Science and Technology and FEDER by the projects PCI2019-103631 and PID2019-108589RA-I00, Consejo Superior de Investigaciones Científicas (España) by the LINKB20080 of the program i-LINK 2021, AXIS (Assessment of Cross(X) - sectoral climate Impacts and pathways for Sustainable transformation), JPI-Climate co-funded call of the European Commission by the CROSSDRO, Peer reviewed

14 Pags.- 12 Figs. The new system and dataset are publicly available at the link https://global-drought-crops.csic.es/. © 2022 The Authors. Geoscience Data Journal published by Royal Meteorological Society and John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License., Drought monitoring systems are real-time information systems focused on drought severity data. They are useful for determining the drought onset and development and defining the spatial extent of drought at any time. Effective drought monitoring requires databases with high spatial and temporal resolution and large spatial and temporal coverage. Recent reanalysis datasets meet these requirements and offer an excellent alternative to observational data. In addition, reanalysis data allow better quantification of some variables that affect drought severity and are more seldom observed. This study presents a global drought dataset and a monitoring system based on the Standardized Precipitation Evapotranspiration Index (SPEI) and ERA5 reanalysis data. Computation of the atmospheric evaporative demand for the SPEI follows the FAO-56 Penman-Monteith equation. The system is updated weekly, providing near real-time information at a 0.5° spatial resolution and global coverage. It also contains a historical dataset with the values of the SPEI at different time scales since January 1979. The drought monitoring system includes the assessment of drought severity for dominant crop-growing areas. A comparison between SPEI computed from the ERA5 and CRU datasets shows generally good spatial and temporal agreement, albeit with some important differences originating mainly from the different spatial patterns of SPEI anomalies, as well as from employing long-term climate trends for different regions worldwide. The results show that the ERA5 dataset offers robust results and supports its use for drought monitoring. The new system and dataset are publicly available at the link https://global-drought-crops.csic.es/., This work was supported by projects PCI2019-103631 financed by the Spanish Commission of Science and Technology and FEDER and CROSSDRO project funded by AXIS (Assessment of Cross [X]- sectoral climate Impacts and pathways for Sustainable transformation), JPI- Climate co- funded call of the European Commission., Peer reviewed

The Vapor Pressure Deficit (VPD) is one of the most relevant surface meteorological variables; with important implications in ecology, hydrology, and atmosphere. By understanding the processes involved in the variability and trend of the VPD, it is possible to assess the possible impacts and implications related to both physical and human environments, like plant function, water use efficiency, net ecosystem production, atmospheric CO2 growth rate, etc. This study analysed recent temporal variability and trends in VPD in Spain between 1980 and 2020 using a recently developed high-quality dataset. Also, the connection between VPD and soil moisture and other key climate variables (e.g. air temperature, precipitation, and relative humidity) was assessed on different time scales varying from weekly to annual. The objective was to determine if changes in land-atmosphere feedbacks connected with soil moisture and evapotranspiration anomalies have been relevant to assess the interannual variability and trends in VPD. Results demonstrate that VPD exhibited a clear seasonality and dominant positive trends on both the seasonal (mainly spring and summer) and annual scales. Rather, trends were statistically non-significant (p > 0.05) during winter and autumn. Spatially, VPD positive trends were more pronounced in southern and eastern of Spain. Also, results suggest that recent trends of VPD shows low contribution of variables that drive land-atmosphere feedbacks (e.g. evapotranspiration, and soil moisture) in comparison to the role of global warming processes. Notably, the variability of VPD seems to be less coupled with soil moisture variability during summertime, while it is better interrelated during winter, indicating that VPD variability would be mostly related to climate variability mechanisms that control temperature and relative humidity than to land-atmosohere feedbacks. Overall, our findings highlight the importance of assessing driving forces and physical mechanisms that control VPD variability using high-quality climate datasets, especially, in semiarid and sub-humid regions of the world., This work was supported by projects PCI2019-103631, and PID2019-108589RA-I00 financed by the Spanish Commission of Science and Technology and FEDER; LINKB20080 of the programme i-LINK 2021 of CSIC, CROSSDRO financed by AXIS (Assessment of Cross(X) - sectoral climate Impacts and pathways for Sustainable transformation), JPI-Climate co-funded call of the European Commission and CSIC Interdisciplinary Thematic Platform (PTI) clima y servicios climáticos (PTI-CSC).

[EN] This paper analyzes the influence of the interannual variability of climatic drought on ecological and hydrological droughts for a basin in the central Spanish Pyrenees using variables derived from observations and hydro-ecological simulation in order to determine the possible connection between meteorological, ecological and hydrological drought considering a cascading approach and encompassing different variables that give insights into water availability in the basin (e.g., soil moisture, streamflow, reservoir storages and releases). Using different climatic, ecological and hydrological standardized drought indices, we show the greater role of meteorological droughts in hydrological systems than in ecological systems, and the small influence of vegetation activity and growth in explaining the interannual variability of water resources in the basin. By contrast,hydrological droughts are strongly affected by precipitation variability with relationships characterized by seasonal differences and the role of different time-scales in the standardized drought metrics., [ES] Este trabajo analiza la influencia de la variabilidad de la sequía meteorológica sobre las sequías ecológica e hidrológica en una cuenca del Pirineo central español. Para ello se utilizan variables derivadas de observaciones y simulación hidroecológica con la finalidad de determinar la posible conexión entre la sequía meteorológica, ecológica e hidrológica considerando un enfoque en cascada, de tal manera que abarca diferentes variables que aportan información sobre la disponibilidad de agua en la cuenca (p. ej., la humedad del suelo, el caudal, la reserva embalsada y las descargas de agua fuera del sistema). Utilizando diferentes índices de sequía estandarizados, tanto meteorológicos, ecológicos e hidrológicos, se ha comprobado la mayor importancia de las sequías meteorológicas en los sistemas hidrológicos que en los sistemas ecológicos, y la poca influencia de la actividad y el crecimiento de la vegetación en la explicación de la variabilidad interanual de los recursos hídricos en la cuenca. Por el contrario, las sequías hidrológicas se ven fuertemente afectadas por la variabilidad de las precipitaciones, pero con importantes diferencias estacionales y escalas de tiempo a la hora de medir las sequías., This work was supported by the research projects PCI2019-103631, PID2019-108589RA-I00, TED2021-129152B-C41, financed by the Spanish Ministry of Science and FEDER, 2857/2022 financed by the Spanish organism of National Parks, MEHYDRO (LINKB20080) financed by the iLINK 2021 programme financed by CSIC, and the CROSSDRO project financed by the AXIS (Assessment of Cross(X)- sectorial climate impacts and pathways for Sustainable transformation), the JPI-Climate co-funded call of the European Commission., Peer reviewed

This study analyzes the long-term observed changes of mean (Tmean), maximum (Tmax) and minimum (Tmin) air temperatures, relative humidity (RH) and vapour pressure deficit (VPD) at different elevation ranges across Bolivia from 1950 to 2019. The linear trends in air temperature series present a significant increase, with no substantial seasonal or spatial differences. On an annual basis, RH exhibited a non-significant decrease (−0.08% decade−1), while VPD showed a significant increase (0.01 hPa decade−1) (p < 0.05). Although prior research has suggested that highland elevations experience faster warming than the global average, we have not identified a distinct correlation between elevation gradients and differential warming rates in Bolivia. Future research could investigate elevation-dependent climate trends by examining seasonal and monthly patterns of climatic variables in relation to topographical gradients in various highland regions., This work was supported by the research projects PCI2019-103631, PID2019-108589RA-I00, TED2021-129152B-C41, financed by the Spanish Ministry of Science and FEDER, 2857/2022 financed by the Spanish organism of National Parks, MEHYDRO (LINKB20080) financed by the i-LINK 2021 Program financed by CSIC, the CROSSDRO project financed by the AXIS (Assessment of Cross(X)-sectorial climate impacts and pathways for Sustainable transformation), the JPI-Climate co-funded call of the European Commission and the LINCGLOBAL-CSIC project (INCGLO0023, RED-CLIMA). This research has also been conducted in the framework of the CSIC Interdisciplinary Thematic Platform (PTI) Clima (PTI+CLIMA). Fernández-Duque, B would like to acknowledge the FJC2021-047322-I contract funded by MCIN/AEI/10.13039/501100011033 and the European Union ‘Next Generation EU’/‘PRTR’ Program., Peer reviewed

© 2023 American Meteorological Society. This published article is licensed under the terms of the default AMS reuse license. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses)., In 1639, the German naturalist Georg Marcgraf established the first astronomical observatory in the Americas, located in Recife (Brazil). There, he made the first daily systematic meteorological observations of wind direction, precipitation, fog, and thunder and lightning from 1640 to 1642. We outline the circumstances that led to this observatory being established and analyze the observations. The range of values obtained from all the variables recorded by Marcgraf corresponds well with Recife’s current climate. However, wetter-than-normal conditions were recorded during 1640, while anomalous concentrations of foggy days occurred from May to December 1641. We hypothesize that these anomalous record foggy days could be associated with the highly explosive eruptions of the Komagatake and Parker volcanoes, both in 1640., This work was supported by projects PID2019-108589RA-I00 and PCI2019-103631 that were financed by the Spanish Commission of Science and Technology and FEDER; CROSSDRO project financed by AXIS [Assessment of Cross(X)—Sectoral Climate Impacts and Pathways for Sustainable Transformation], JPI-Climate co-funded call of the European Commission., Peer reviewed

Appendix A. Supplementary data: Supplementary Figures S1-S23 and Table S1., The Vapor Pressure Deficit (VPD) is one of the most relevant surface meteorological variables; with important implications in ecology, hydrology, and atmosphere. By understanding the processes involved in the variability and trend of the VPD, it is possible to assess the possible impacts and implications related to both physical and human environments, like plant function, water use efficiency, net ecosystem production, atmospheric CO2 growth rate, etc. This study analysed recent temporal variability and trends in VPD in Spain between 1980 and 2020 using a recently developed high-quality dataset. Also, the connection between VPD and soil moisture and other key climate variables (e.g. air temperature, precipitation, and relative humidity) was assessed on different time scales varying from weekly to annual. The objective was to determine if changes in land-atmosphere feedbacks connected with soil moisture and evapotranspiration anomalies have been relevant to assess the interannual variability and trends in VPD. Results demonstrate that VPD exhibited a clear seasonality and dominant positive trends on both the seasonal (mainly spring and summer) and annual scales. Rather, trends were statistically non-significant (p > 0.05) during winter and autumn. Spatially, VPD positive trends were more pronounced in southern and eastern of Spain. Also, results suggest that recent trends of VPD shows low contribution of variables that drive land-atmosphere feedbacks (e.g. evapotranspiration, and soil moisture) in comparison to the role of global warming processes. Notably, the variability of VPD seems to be less coupled with soil moisture variability during summertime, while it is better interrelated during winter, indicating that VPD variability would be mostly related to climate variability mechanisms that control temperature and relative humidity than to land-atmosohere feedbacks. Overall, our findings highlight the importance of assessing driving forces and physical mechanisms that control VPD variability using high-quality climate datasets, especially, in semiarid and sub-humid regions of the world., This work was supported by projects PCI2019-103631, and PID2019-108589RA-I00 financed by the Spanish Commission of Science and Technology and FEDER; LINKB20080 of the programme i-LINK 2021 of CSIC, CROSSDRO financed by AXIS (Assessment of Cross(X) - sectoral climate Impacts and pathways for Sustainable transformation), JPI-Climate co-funded call of the European Commission and CSIC Interdisciplinary Thematic Platform (PTI) clima y servicios climáticos (PTI-CSC)., Peer reviewed

© 2021 The Authors. International Journal of Climatology published by John Wiley & Sons Ltd on behalf of Royal Meteorological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited., The Evaporative Demand Drought Index (EDDI), based on atmospheric evaporative demand, was proposed by Hobbins et al. (2016) to analyse and monitor drought. The EDDI uses a nonparametric approach in which empirically derived probabilities are converted to standardized values. This study evaluates the suitability of eight probability distributions to compute the EDDI at 1-, 3- and 12-month time scales, in order to provide more robust calculations. The results showed that the Log-logistic distribution is the best option for generating standardized values over very different climate conditions. Likewise, we contrasted this new parametric methodology to compute EDDI with the original nonparametric formulation. Our findings demonstrate the advantages of adopting a robust parametric approach based on the Log-logistic distribution for drought analysis, as opposed to the original nonparametric approach. The method proposed in this study enables effective implementation of EDDI in the characterization and monitoring of droughts., This work was supported by the research projects CGL2017-82216-R, PCI2019-103631 and PID2019-108589RA-I00 financed by the Spanish Commission of Science and Technology and FEDER; CROSSDRO project financed by the AXIS (Assessment of Cross(X)—sectoral climate Impacts and pathways for Sustainable transformation), JPI-Climate co-funded call of the European Commission and INDECIS which is part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR) with co-funding by the European Union (grant 690462). The first author is the beneficiary of the predoctoral fellowship ‘Subvenciones destinadas a la contratación de personal investigador predoctoral en formación (2017)’ awarded by the Gobierno de Aragón (Government of Aragón, Spain)., Peer reviewed

© 2022. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited., This study presents a new data set of gauged streamflow (N = 3,224) for Europe spanning the period 1962–2017. The Monthly Streamflow of Europe Dataset (MSED) is freely available at http://msed.csic.es/. Based on this data set, changes in the characteristics of hydrological drought (i.e., frequency, duration, and severity) were assessed for different regions of Europe. Due to the density of the database, it is possible to delimit spatial patterns in hydrological droughts trend with the greatest detail available to date. Results reveal bidirectional changes in monthly streamflow, with negative changes predominating over central and southern Europe, while positive trends dominate over northern Europe. Temporally, two dominant patterns were noted. The first pattern corresponds to a consistent downward trend in all months, evident for southern Europe. A second pattern was noted over central and northern Europe and western France, with a predominant negative trend during warm months and a positive trend in cold months. For hydrological drought events, results suggest a positive trend toward more frequent and severe droughts in southern and central Europe and conversely a negative trend over northern Europe. This study emphasizes that hydrological droughts show complex spatial patterns across Europe over the past six decades, implying that hydrological drought behavior in Europe has a regional character. Accordingly it is challenging to adopt “efficient” strategies and policies to monitor and mitigate drought impacts at the continental level., This work was supported by the research projects CGL2017-82216-R and CGL2017-83866-C3-1-R and PCI2019-103631, financed by the Spanish Commission of Science and Technology and FEDER; CROSSDRO project financed by the AXIS (Assessment of Cross(X)—Sectorial climate Impacts and pathways for Sustainable transformation), JPI-Climate co-funded call of the European Commission and INDECIS which is part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR) with co-funding by the European Union (Grant 690462)., Peer reviewed

© 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)., As CO2 concentration in the atmosphere rises, there is a need for improved physical understanding of its impact on global plant transpiration. This knowledge gap poses a major hurdle in robustly projecting changes in the global hydrologic cycle. For this reason, here we review the different processes by which atmospheric CO2 concentration affects plant transpiration, the several uncertainties related to the complex physiological and radiative processes involved, and the knowledge gaps which need to be filled in order to improve predictions of plant transpiration. Although there is a high degree of certainty that rising CO2 will impact plant transpiration, the exact nature of this impact remains unclear due to complex interactions between CO2 and climate, and key aspects of plant morphology and physiology. The interplay between these factors has substantial consequences not only for future climate and global vegetation, but also for water availability needed for sustaining the productivity of terrestrial ecosystems. Future changes in global plant transpiration in response to enhanced CO2 are expected to be driven by water availability, atmospheric evaporative demand, plant physiological processes, emergent plant disturbances related to increasing temperatures, and the modification of plant physiology and coverage. Considering the universal sensitivity of natural and agricultural systems to terrestrial water availability we argue that reliable future projections of transpiration is an issue of the highest priority, which can only be achieved by integrating monitoring and modeling efforts to improve the representation of CO2 effects on plant transpiration in the next generation of earth system models., This work was supported by the research projects CGL2017-82216-R, PCI2019-103631 and PID2019-108589RA-I00, financed by the Spanish Ministry of Science and FEDER; CROSSDRO project financed by the AXIS (Assessment of Cross(X) - sectorial climate Impacts and pathways for Sustainable transformation), JPI-Climate co-funded call of the European Commission; NGM and LRL were supported by the Department of Energy’s Next Generation Ecosystem Experiment-Tropics. DGM acknowledges support from the European Research Council (ERC) under grant agreement no. 715254 (DRY–2–DRY). AK acknowledges support from the European Union Horizon 2020 program, project no. 869550 (DOWN2EARTH)., Peer reviewed

© 2024 The Authors. Earth's Future published by Wiley Periodicals LLC on behalf of American Geophysical Union. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited., This study provides a global analysis of the relationship between drought metrics obtained from several climatic, hydrologic and ecological variables in a climate change framework using CMIP6 model data. A comprehensive analysis of the evolution of drought severity on a global scale is carried out for the historical experiment (1850–2014) and for future simulations under a high emissions scenario (SSP5-8.5). This study focuses on comparing trends in the magnitude and duration of drought events according to different standardized indices over the world land-surface area. The spatial and temporal relationship between the different drought indices on a global scale was also evaluated. Overall, there is a fairly large consensus among models and drought metrics in pointing to drought increase in southern North America, Central America, the Amazon region, the Mediterranean, southern Africa and southern Australia. Our results show important spatial differences in drought projections, which are highly dependent on the drought metric employed. While a strong relationship between climatic indices was evident, climatic and ecological drought metrics showed less dependency over both space and time. Importantly, our study demonstrates uncertainties in future projections of drought trends and their interannual variability related to the relationship among indices, stressing the importance of coherent climatic, hydrological and plant physiological patterns when analyzing CMIP6 model simulations of droughts under a warming climate scenario., This work was supported by projects PCI2019-103631, PID2019-108589RA-I00, PID2021-122314OB-I00, SPIP2022-02857, TED2021-129152B-C41 and TED2021-129152B-C43, financed by the Ministerio de Ciencia, Innovación y Universidades, Spain (MCIN/10.13039/501100011033) and “ERDF A way of making Europe”; LINKB20080 of the programme i-LINK 2021 of CSIC and CROSSDRO financed by AXIS (Assessment of Cross(X) - sectoral climate Impacts and pathways for Sustainable transformation), JPI-Climate co-funded call of the European Commission. This study was also supported by the “Unidad Asociada CSIC–Universidade de Vigo: Grupo de Física de la Atmósfera y del Océano.” The work of Luis Gimeno-Sotelo was financially supported by CSIC Programa JAE and a “Ministerio de Ciencia, Innovación y Universidades” PhD grant (reference: PRE2022-101497). The EPhysLab group was also funded by Xunta de Galicia and ERDF, under project ED431C 2021/44 “Programa de Consolidación e Estructuración de Unidades de Investigación Competitivas.”, Peer reviewed

10 pages, 3 figures, 6 tables, Drought is a complex natural hazard increasing in frequency, duration, and severity worldwide. Although droughts cause both market and non-market impacts, the latter suffers from a dearth of economic studies quantifying their magnitude. In this paper, we investigated how droughts affect selected ecosystem services expected to result in welfare losses in Spain. This study is aimed at quantifying and simulating societal losses given the expected potential increase in drought severity in the coming decades. We estimated a Discrete Choice Latent Class Model by which we distinguished three broad classes of individuals. The common behavior across all classes is that people consistently choose to avoid the negative effects of droughts. However, there are substantial differences among the three classes; while class 1 chooses options regardless of cost, even when selecting the most expensive ones, the other two classes account for the size of the payment. Moreover, health and water use restrictions have been decisive factors in individuals' choices. We have also observed that the perception of climate change is related to individual decisions. We quantified the enormous damage drought causes to societal well-being. Policymakers should take this information into account when addressing the increasing likelihood of extreme weather events, This work was supported by projects PCI2019-103631 financed by the Spanish Ministry of Science and Technology and FEDER and CROSSDRO project funded by AXIS (Assessment of Cross (X) - sectoral climate Impacts and pathways for Sustainable transformation), JPIClimate co-funded call of the European Commission, Peer reviewed

We present a long-term assessment of precipitation trends in Southwestern Europe (1850-2018) using data from multiple sources, including observations, gridded datasets and global climate model experiments. Contrary to previous investigations based on shorter records, we demonstrate, using new long-term, quality controlled precipitation series, the lack of statistically significant long-term decreasing trends in precipitation for the region. Rather, significant trends were mostly found for shorter periods, highlighting the prevalence of interdecadal and interannual variability at these time-scales. Global climate model outputs from three CMIP experiments are evaluated for periods concurrent with observations. Both the CMIP3 and CMIP5 ensembles show precipitation decline, with only CMIP6 showing agreement with long term trends in observations. However, for both CMIP3 and CMIP5 large interannual and internal variability among ensemble members makes it difficult to identify a trend that is statistically different from observations. Across both observations and models, our results make it difficult to associate any declining trends in precipitation in Southwestern Europe to anthropogenic forcing at this stage.

Flash drought is the result of strong precipitation deficits and/or anomalous increases in atmospheric evaporative demand (AED), which triggers a rapid decline in soil moisture and stresses vegetation over short periods of time. However, little is known about the role of precipitation and AED in the development of flash droughts. For this paper, we compared the standardized precipitation index (SPI) based on precipitation, the evaporative demand drought index (EDDI) based on AED, and the standardized evaporation precipitation index (SPEI) based on the differences between precipitation and AED as flash drought indicators for mainland Spain and the Balearic Islands for 1961–2018. The results show large differences in the spatial and temporal patterns of flash droughts between indices. In general, there was a high degree of consistency between the flash drought patterns identified by the SPI and SPEI, with the exception of southern Spain in the summer. The EDDI showed notable spatial and temporal differences from the SPI in winter and summer, while it exhibited great coherence with the SPEI in summer. We also examined the sensitivity of the SPEI to AED in each month of the year to explain its contribution to the possible development of flash droughts. Our findings showed that precipitation is the main driver of flash droughts in Spain, although AED can play a key role in the development of these during periods of low precipitation, especially in the driest areas and in summer.

A fundamental key to understanding climate change and its implications is the availability of databases with wide spatial coverage, over a long period of time, with constant updates and high spatial resolution. This study describes a newly gridded data set and its map viewer “European Climatology and Trend Atlas of Climate Indices” (ECTACI), which contains four statistical parameters (climatology, coefficient of variation, slope, and significant trend) from 125 standard climate indices for the whole Europe at 0.25° grid intervals from 1979 to 2017 at various temporal scales (monthly, seasonal, and annual). In addition, this study shows, for the first time, the general trends of a wide variety of updated standard climate indices at seasonal and annual scales for the whole of Europe, which could be a useful tool for climate analysis and its impact on different sectors and socioeconomic activities. The data set and ECTACI map viewer are available for free (http://ECTACI.csic.es/).

The standardized precipitation evapotranspiration index (SPEI) is one of the well-established drought metrics worldwide. It is simply computed using precipitation and atmospheric evaporative demand (AED) data. Although AED is considered a key driver of drought variability worldwide, it could have less impact on drought in specific regions and for particular times as a function of the magnitude of precipitation. Specifically, the influence of the AED might overestimate drought severity during both normal and humid periods, resulting in “false alarms” about drought impacts on physical and human environments. Here, we provided a global characterization of the sensitivity of the SPEI to changes of the AED. Results demonstrate that the contribution of AED to drought severity is largely impacted by the spatial and temporal variability of precipitation. Specifically, the impact of AED on drought severity was more pronounced during periods of low precipitation, compared to wet periods. Interestingly, drought severity in humid regions (as revealed by SPEI) also showed low sensitivity to AED under drier conditions. These results highlight the skill of SPEI in identifying the role of AED in drought evolution, especially in arid and semiarid regions whose climate is characterized typically by low precipitation. This advantage was also evident for humid environments, where SPEI did not overestimate drought severity due to the increased AED. These findings highlight the broader applicability of SPEI to accurately characterize drought severity worldwide.

Changes in the frequency and magnitude of extreme weather events represent one of the key indicators of climate change and variability. These events can have an important impact on mortality rates, especially in the ageing population. This study assessed the spatial and seasonal distributions of mortality rates in mainland Spain and their association with climatic conditions over the period 1979–2016. The analysis was done on a seasonal and annual basis using 79 climatic indices and regional natural deaths data. Results indicate large spatial variability of natural deaths, which is mostly related to how the share of the elderly in the population varied across the studied regions. Spatially, both the highest mortality rates and the largest percentage of elders were found in the northwest areas of the study domain, where an extreme climate prevails, with very cold winters and hot summers. A strong seasonality effect was observed, winter shows more than 10% of natural deaths compared to the rest of the seasons. Also, results suggest a strong relation between climatic indices and natural deaths, albeit with a high spatial and seasonal variability. Climatic indices and natural deaths show a stronger correlation in winter and summer than in spring and autumn. © 2021 The Authors

Climate proxy data are required for improved understanding of climate variability and change in the pre-instrumental period. We present the first international initiative to compile and share information on pro pluvia rogation ceremonies, which is a well-studied proxy of agricultural drought. Currently, the database has more than 3500 dates of celebration of rogation ceremonies, providing information for 153 locations across 11 countries spanning the period from 1333 to 1949. This product provides data for better understanding of the pre-instrumental drought variability, validating natural proxies and model simulations, and multi-proxy rainfall reconstructions, amongst other climatic exercises. The database is freely available and can be easily accessed and visualized via http://inpro.unizar.es/.

This study presents a new data set of gauged streamflow (N = 3, 224) for Europe spanning the period 1962-2017. The Monthly Streamflow of Europe Dataset (MSED) is freely available at . Based on this data set, changes in the characteristics of hydrological drought (i.e., frequency, duration, and severity) were assessed for different regions of Europe. Due to the density of the database, it is possible to delimit spatial patterns in hydrological droughts trend with the greatest detail available to date. Results reveal bidirectional changes in monthly streamflow, with negative changes predominating over central and southern Europe, while positive trends dominate over northern Europe. Temporally, two dominant patterns were noted. The first pattern corresponds to a consistent downward trend in all months, evident for southern Europe. A second pattern was noted over central and northern Europe and western France, with a predominant negative trend during warm months and a positive trend in cold months. For hydrological drought events, results suggest a positive trend toward more frequent and severe droughts in southern and central Europe and conversely a negative trend over northern Europe. This study emphasizes that hydrological droughts show complex spatial patterns across Europe over the past six decades, implying that hydrological drought behavior in Europe has a regional character. Accordingly it is challenging to adopt "efficient" strategies and policies to monitor and mitigate drought impacts at the continental level.

Flash droughts are characterized by rapid development and intensification, generating a new risk for drought impacts on natural and socio-economic systems. In the current climate change scenario, the meteorological drivers involved in triggering flash droughts are uncertain. We analyzed the role of meteorological drivers underlying the development of flash droughts in Spain over the last six decades, evidencing that the effect of atmospheric evaporative demand (AED) on flash drought is mainly restricted to water-limited regions and the warm season. However, the contribution of the AED has increased notably in recent years and particularly in summer (~3.5% per decade), thus becoming a decisive driver in explaining the occurrence of the latest flash droughts in some regions of Spain. Our findings have strong implications for proper understanding of the recent spatiotemporal behavior of flash droughts in Spain and illustrate how this type of event can be related to global warming processes.

As CO2 concentration in the atmosphere rises, there is a need for improved physical understanding of its impact on global plant transpiration. This knowledge gap poses a major hurdle in robustly projecting changes in the global hydrologic cycle. For this reason, here we review the different processes by which atmospheric CO2 concentration affects plant transpiration, the several uncertainties related to the complex physiological and radiative processes involved, and the knowledge gaps which need to be filled in order to improve predictions of plant transpiration. Although there is a high degree of certainty that rising CO2 will impact plant transpiration, the exact nature of this impact remains unclear due to complex interactions between CO2 and climate, and key aspects of plant morphology and physiology. The interplay between these factors has substantial consequences not only for future climate and global vegetation, but also for water availability needed for sustaining the productivity of terrestrial ecosystems. Future changes in global plant transpiration in response to enhanced CO2 are expected to be driven by water availability, atmospheric evaporative demand, plant physiological processes, emergent plant disturbances related to increasing temperatures, and the modification of plant physiology and coverage. Considering the universal sensitivity of natural and agricultural systems to terrestrial water availability we argue that reliable future projections of transpiration is an issue of the highest priority, which can only be achieved by integrating monitoring and modeling efforts to improve the representation of CO2 effects on plant transpiration in the next generation of earth system models. © 2022 The Authors

This study provides a long-term (1891–2014) global assessment of precipitation trends using data from two station-based gridded datasets and climate model outputs evolved through the fifth and sixth phases of the Coupled Model Intercomparison Project (CMIP5 and CMIP6, respectively). Our analysis employs a variety of modeling groups that incorporate low- and high-top level members, with the aim of assessing the possible effects of including a well-resolved stratosphere on the model’s ability to reproduce long-term observed annual precipitation trends. Results demonstrate that only a few regions show statistically significant differences in precipitation trends between observations and models. Nevertheless, this pattern is mostly caused by the strong interannual variability of precipitation in most of the world regions. Thus, statistically significant model-observation differences on trends (1891–2014) are found at the zonal mean scale. The different model groups clearly fail to reproduce the spatial patterns of annual precipitation trends and the regions where stronger increases or decreases are recorded. This study also stresses that there are no significant differences between low- and high-top models in capturing observed precipitation trends, indicating that having a well-resolved stratosphere has a low impact on the accuracy of precipitation projections.

The Evaporative Demand Drought Index (EDDI), based on atmospheric evaporative demand, was proposed by Hobbins et al. (2016) to analyse and monitor drought. The EDDI uses a nonparametric approach in which empirically derived probabilities are converted to standardized values. This study evaluates the suitability of eight probability distributions to compute the EDDI at 1-, 3- and 12-month time scales, in order to provide more robust calculations. The results showed that the Log-logistic distribution is the best option for generating standardized values over very different climate conditions. Likewise, we contrasted this new parametric methodology to compute EDDI with the original nonparametric formulation. Our findings demonstrate the advantages of adopting a robust parametric approach based on the Log-logistic distribution for drought analysis, as opposed to the original nonparametric approach. The method proposed in this study enables effective implementation of EDDI in the characterization and monitoring of droughts. © 2021 The Authors. International Journal of Climatology published by John Wiley & Sons Ltd on behalf of Royal Meteorological Society.

Drought is one of the most difficult natural hazards to quantify and is divided into categories (meteorological, agricultural, ecological and hydrological), which makes assessing recent changes and future scenarios extremely difficult. This opinion piece includes a review of the recent scientific literature on the topic and analyses trends in meteorological droughts by using long-term precipitation records and different drought metrics to evaluate the role of global warming processes in trends of agricultural, hydrological and ecological drought severity over the last four decades, during which a sharp increase in atmospheric evaporative demand (AED) has been recorded. Meteorological droughts do not show any substantial changes at the global scale in at least the last 120 years, but an increase in the severity of agricultural and ecological droughts seems to emerge as a consequence of the increase in the severity of AED. Lastly, this study evaluates drought projections from earth system models and focuses on the most important aspects that need to be considered when evaluating drought processes in a changing climate, such as the use of different metrics and the uncertainty of modelling approaches.
This article is part of the Royal Society Science+ meeting issue ‘Drought risk in the Anthropocene’.

Using observations and model simulations from the 5th and 6th phases of the Coupled Model Intercomparison Project (CMIP5 and CMIP6, respectively), this study evaluated changes in monthly, seasonal, and annual precipitation over Bolivia from 1950 to 2019. Results demonstrate that observed precipitation is characterized by strong interannual and decadal variability. However, long-term precipitation trends were not identified on the annual scale. Similarly, changes in seasonal precipitation were almost nonsignificant (p > .05) for the study period. Spatially, albeit with its complex orography, no substantial regional variations in observed precipitation trends can be identified across Bolivia. In contrast, long-term precipitation trends, based on CMIP5 and CMIP6 models, suggest a dominance of negative trends, mainly during austral winter (JJA) (−10%) and spring (SON) (−15%). These negative trends were more pronounced in the lowlands of Bolivia (−20%). Overall, these contradictory results highlight the need for validating precipitation trend outputs from model simulations, especially in areas of complex topography like Bolivia.

The Vapor Pressure Deficit (VPD) is one of the most relevant surface meteorological variables; with important implications in ecology, hydrology, and atmosphere. By understanding the processes involved in the variability and trend of the VPD, it is possible to assess the possible impacts and implications related to both physical and human environments, like plant function, water use efficiency, net ecosystem production, atmospheric CO2 growth rate, etc. This study analysed recent temporal variability and trends in VPD in Spain between 1980 and 2020 using a recently developed high-quality dataset. Also, the connection between VPD and soil moisture and other key climate variables (e.g. air temperature, precipitation, and relative humidity) was assessed on different time scales varying from weekly to annual. The objective was to determine if changes in land-atmosphere feedbacks connected with soil moisture and evapotranspiration anomalies have been relevant to assess the interannual variability and trends in VPD. Results demonstrate that VPD exhibited a clear seasonality and dominant positive trends on both the seasonal (mainly spring and summer) and annual scales. Rather, trends were statistically non-significant (p > 0.05) during winter and autumn. Spatially, VPD positive trends were more pronounced in southern and eastern of Spain. Also, results suggest that recent trends of VPD shows low contribution of variables that drive land-atmosphere feedbacks (e.g. evapotranspiration, and soil moisture) in comparison to the role of global warming processes. Notably, the variability of VPD seems to be less coupled with soil moisture variability during summertime, while it is better interrelated during winter, indicating that VPD variability would be mostly related to climate variability mechanisms that control temperature and relative humidity than to land-atmosohere feedbacks. Overall, our findings highlight the importance of assessing driving forces and physical mechanisms that control VPD variability using high-quality climate datasets, especially, in semiarid and sub-humid regions of the world.

Flash droughts are characterized by rapid development and intensification, which makes early warning and monitoring difficult. Flash drought monitor (FDM) is a near-real time monitoring system for Spain (https://flash-drought.csic.es) based on the Standardized Precipitation Evapotranspiration Index (SPEI). Flash drought identification was based on rapid and anomalous declines in SPEI at a short time scale (1-month). Thus, FDM enables operational tracking of flash drought conditions in Spain at high spatial resolution (1.1 × 1.1 km) and high temporal frequency (weekly). Likewise, to put flash drought monitoring into a temporal context, the FDM also provides weekly flash drought conditions recorded in Spain from 1961 to the present. The FDM is a useful tool for preparedness and mitigation of flash droughts in Spain. Furthermore, the data provided by the FDM could be useful to develop future studies in relation to the flash drought in Spain.

This paper analyzes the influence of the interannual variability of climatic drought on ecological and hydrological droughts for a basin in the central Spanish Pyrenees using variables derived from observations and hydro-ecological simulation in order to determine the possible connection between meteorological, ecological and hydrological drought considering a cascading approach and encompassing different variables that give insights into water availability in the basin (e.g., soil moisture, streamflow, reservoir storages and releases). Using different climatic, ecological and hydrological standardized drought indices, we show the greater role of meteorological droughts in hydrological systems than in ecological systems, and the small influence of vegetation activity and growth in explaining the interannual variability of water resources in the basin. By contrast,hydrological droughts are strongly affected by precipitation variability with relationships characterized by seasonal differences and the role of different time-scales in the standardized drought metrics.

In 1639, the German naturalist Georg Marcgraf established the first astronomical observatory in the Americas, located in Recife (Brazil). There, he made the first daily systematic meteorological observations of wind direction, precipitation, fog, and thunder and lightning from 1640 to 1642. We outline the circumstances that led to this observatory being established and analyze the observations. The range of values obtained from all the variables recorded by Marcgraf corresponds well with Recife’s current climate. However, wetter-than-normal conditions were recorded during 1640, while anomalous concentrations of foggy days occurred from May to December 1641. We hypothesize that these anomalous record foggy days could be associated with the highly explosive eruptions of the Komagatake and Parker volcanoes, both in 1640.

This study analyzes the long‐term observed changes of mean (Tmean), maximum (Tmax) and minimum (Tmin) air temperatures, relative humidity (RH) and vapour pressure deficit (VPD) at different elevation ranges across Bolivia from 1950 to 2019. The linear trends in air temperature series present a significant increase, with no substantial seasonal or spatial differences. On an annual basis, RH exhibited a non‐significant decrease (−0.08% decade−1), while VPD showed a significant increase (0.01 hPa decade−1) (p &lt; 0.05). Although prior research has suggested that highland elevations experience faster warming than the global average, we have not identified a distinct correlation between elevation gradients and differential warming rates in Bolivia. Future research could investigate elevation‐dependent climate trends by examining seasonal and monthly patterns of climatic variables in relation to topographical gradients in various highland regions.

This study provides a global analysis of the relationship between drought metrics obtained from several climatic, hydrologic and ecological variables in a climate change framework using CMIP6 model data. A comprehensive analysis of the evolution of drought severity on a global scale is carried out for the historical experiment (1850–2014) and for future simulations under a high emissions scenario (SSP5‐8.5). This study focuses on comparing trends in the magnitude and duration of drought events according to different standardized indices over the world land‐surface area. The spatial and temporal relationship between the different drought indices on a global scale was also evaluated. Overall, there is a fairly large consensus among models and drought metrics in pointing to drought increase in southern North America, Central America, the Amazon region, the Mediterranean, southern Africa and southern Australia. Our results show important spatial differences in drought projections, which are highly dependent on the drought metric employed. While a strong relationship between climatic indices was evident, climatic and ecological drought metrics showed less dependency over both space and time. Importantly, our study demonstrates uncertainties in future projections of drought trends and their interannual variability related to the relationship among indices, stressing the importance of coherent climatic, hydrological and plant physiological patterns when analyzing CMIP6 model simulations of droughts under a warming climate scenario.

Drought is a complex natural hazard increasing in frequency, duration, and severity worldwide. Although droughts cause both market and non-market impacts, the latter suffers from a dearth of economic studies quantifying their magnitude. In this paper, we investigated how droughts affect selected ecosystem services expected to result in welfare losses in Spain. This study is aimed at quantifying and simulating societal losses given the expected potential increase in drought severity in the coming decades. We estimated a Discrete Choice Latent Class Model by which we distinguished three broad classes of individuals. The common behavior across all classes is that people consistently choose to avoid the negative effects of droughts. However, there are substantial differences among the three classes; while class 1 chooses options regardless of cost, even when selecting the most expensive ones, the other two classes account for the size of the payment. Moreover, health and water use restrictions have been decisive factors in individuals' choices. We have also observed that the perception of climate change is related to individual decisions. We quantified the enormous damage drought causes to societal well-being. Policymakers should take this information into account when addressing the increasing likelihood of extreme weather events.