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The design and implementation of targeted policies and programmes are crucial to addressing climate challenges. In this study, we sought to understand the means by and extent to which the Central American Climate-Smart Agriculture Strategy (EASAC) has contributed to addressing the specific climate challenges facing the regional agricultural sector. We applied a theory-based evaluation and contribution analysis to examine this policy and identified 252 changes at the national and regional levels that align with the EASAC theory of change (ToC). Contribution analysis revealed that none of the 23 changes we assessed could be attributed solely to the EASAC; however, it contributed directly, in combination with other actors and institutions, to 10 such changes. Our results question the efficacy of non-binding regional policies, such as the EASAC, in influencing national policy changes and highlight the dependency of climate policy implementation on international cooperation in the Central American Integration System region. Intersectoral and actor coordination, the availability of technical and research expertise, and research input appear critical to the successful implementation of regional climate policy. Key policy insights Theory-based assessments and contribution analyses are relevant and rigorous tools that can be effectively applied to climate policy. They enable a deeper understanding and more effective management of climate governance. International organizations play crucial roles in translating international agreements into policies, particularly in Central America, where public climate finance remains limited. Such organizations are responsible for developing and funding policies that align with these agreements. Many changes aligned with the EASAC ToC framework have been observed, reflecting the dynamic process of up-scaling regional climate-smart agriculture. Most changes have been focused on policy formulation and adjustment, with fewer related to establishing alliances and platforms for dialogue. The EASAC strategy of targeting non-binding regional governance to influence national governments is inherently limited and may be ineffective on its own. [ABSTRACT FROM AUTHOR]

Potential evapotranspiration (PET), as an indicator of atmospheric evaporative demand, is a critical hydrological and meteorological factor to reflect regional and global hydrological cycles and environmental change. Understanding these nuanced responses of PET to environmental changes is important for agricultural production and water demand estimation. This study rigorously evaluated fluctuations in PET using the Penman–Monteith model over a 50-year span from 1970 to 2020 in the Sichuan–Chongqing region, an area notably susceptible to climate change. The changing characteristics of PET and local meteorological factors were detected by integrating the Mann–Kendall method and Pettitt test. Furthermore, the contribution and sensitivity of key meteorological variables to the observed variation in PET were also thoroughly investigated. Breakpoint analysis revealed that abrupt changes appeared in 1996 for annual PET. The detrending method indicated that substantial decreases in net radiation and wind speed (p < 0.01) were responsible for the decrease in annual PET from 1970 to 1996. Marked increases in minimum temperature and wind speed were the driving forces behind the uptick in annual PET in 1997–2020. At seasonal scales, wind speed and net radiation predominantly influenced PET in 1970–1996 in general. However, from 1997 to 2020, the factors controlling PET fluctuations displayed considerable seasonal variation. Sensitivity analysis showed that Ws and Tmin were the second-most sensitive factors. By exploring the impacts of PET changes and shifts, attention must be paid when allocating water resources reasonably under the background of ongoing climate change and likelihood of future drought. [ABSTRACT FROM AUTHOR]

Potential evapotranspiration (PET), as an indicator of atmospheric evaporative demand, is a critical hydrological and meteorological factor to reflect regional and global hydrological cycles and environmental change. Understanding these nuanced responses of PET to environmental changes is important for agricultural production and water demand estimation. This study rigorously evaluated fluctuations in PET using the Penman–Monteith model over a 50-year span from 1970 to 2020 in the Sichuan–Chongqing region, an area notably susceptible to climate change. The changing characteristics of PET and local meteorological factors were detected by integrating the Mann–Kendall method and Pettitt test. Furthermore, the contribution and sensitivity of key meteorological variables to the observed variation in PET were also thoroughly investigated. Breakpoint analysis revealed that abrupt changes appeared in 1996 for annual PET. The detrending method indicated that substantial decreases in net radiation and wind speed (p < 0.01) were responsible for the decrease in annual PET from 1970 to 1996. Marked increases in minimum temperature and wind speed were the driving forces behind the uptick in annual PET in 1997–2020. At seasonal scales, wind speed and net radiation predominantly influenced PET in 1970–1996 in general. However, from 1997 to 2020, the factors controlling PET fluctuations displayed considerable seasonal variation. Sensitivity analysis showed that Ws and Tmin were the second-most sensitive factors. By exploring the impacts of PET changes and shifts, attention must be paid when allocating water resources reasonably under the background of ongoing climate change and likelihood of future drought.

Elevation plays a crucial role in modulating the spatiotemporal distributions of climatic variables in mountainous regions, which affects water and energy balances, among which reference evapotranspiration (ET0) is a key hydrological indicator. However, the response of ET0 to climate change with elevation continues to be poorly understood, especially in the Tibetan Plateau (TP) which has elevation variations of more than 4,000 m. The spatiotemporal variations of ET0 with elevation were investigated using long‐term (1960–2017) meteorological observations from 82 stations on the TP. The results suggest that the average annual ET0 showed an insignificant increasing trend. A significant negative correlation between ET0 and elevation was found (p <.01). The positive trends of ET0 decreased with elevation, whereas the negative trends of ET0 increased significantly with elevation (p <.05). The magnitude of trends of ET0 becomes smaller at higher‐elevation stations. Sensitivity analysis indicated that ET0 was most sensitive to shortwave radiation (Rs). Moreover, the sensitivities of temperature (T) and wind speed (U) significantly decreased with elevation, whereas those of Rs and vapour pressure deficit (VPD) increased slightly with elevation. The contribution and path analyse indicated that increasing VPD was the dominant contributor to the increase in ET0. The effect of elevation on ET0 variation mainly depended on the tradeoff between the contributions of U and VPD. U was the largest contributing factor for the change in ET0 below 2,500 m, whereas VPD was the primary contributor to the increase in ET0 above 2,500 m. This study provides insights into the response of ET0 to climate change with elevation on the TP, which is of great significance to hydrometeorological processes in high‐altitude regions. [ABSTRACT FROM AUTHOR]

Study region: The Tibetan Plateau Study focus: Evapotranspiration (ET) plays a critical role in the water balance, energy budget, and carbon cycle. However, the variations, trends, and controls of ET on the Tibetan Plateau (TP) are poorly understood because of uncertainties in ET estimates and sparse observations. In this study, the variations in ET and its components and their drivers and controls in the TP were analyzed at seasonal and annual scales during 1982–2015. New hydrological insights for the region: Spatially, the multiyear mean annual ET decreased from the southeastern to northwestern TP. Canopy transpiration (Ec) was the main component of ET (52.7%), followed by soil evaporation (Es) (34.4%) and interception (Ei) (10.7%). Regionally, the averaged ET and its components increased significantly at the seasonal and annual scales. Spatially, the controlling factor for ET changed from water to energy as the climatic zones transferred from aridity to humidity. The annual ET was controlled by soil moisture (SM) in arid and semi-arid zones, whereas Ta was the dominant factor in the other regions. The increased annual Es and Ei were primarily caused by SM, while the annual Ec was determined by Ta. In addition, NDVI played a certain role in regulating the annual Ec and Ei variations. This study improves our understanding of hydrological processes and water resource management under global climate change.

The aerosol at the previous time (initial aerosol) and climate conditions control the next step annual variation of global air pollution through the complex aerosol-climate interaction. However, the individual influences remain unclear, leaving a great gap for understanding the mechanism of air pollution evolution and supporting the environment management. We estimate the annual variation using statistical methods and satellite observations at global scale from 2001 to 2016 Results show that significant variation of annual aerosol occurs over 13.6% of land areas, in which a perturbation of aerosol may cause 0.58 ± 0.45 times change in the next phase. Initial aerosol and climate influences contribute 48.4–51.6% of the total variation, respectively. Specifically, the influences of precipitation, air temperature and surface temperature represent 0.1, 18.3 and 33.2% of the total variation. Physically, the observed variation is strongly correlated with fine mode aerosols, radiative scattering and warm/hot summers in temperate and cold zones. The environmental management therefore should implement cause-oriented strategies for emission control or climatic adaption.

The present study is an attempt toward the quantification of the impact of climate and land-use change on the hydrological prospect of the Kangshabati river basin of West Bengal. The study also simulates runoff characteristics as a response to hypothetical climatic scenarios. The scope of the study involves, first, to quantify the relative contribution of climate change and land-use change to runoff response and second, to simulate runoff characteristics as a response to hypothetical climatic scenarios. Using a combination of the SWAT model, SWAT Cup, Sequential Mann Kendall Trend Tests, surface and total runoff were generated for 1982–2017, and the mutation point was identified. The results indicate that post-2010, climate change has an overwhelming impact on runoff with its contribution being as high as 99% in the case of total runoff and 89% for surface runoff. And this finding is cemented by dynamic contribution analysis which indicates over-arching climatic impact for every decade, with a sudden increase post-2010. Change in temperature and rainfall has an expected impact on runoff, with a rise in rainfall and decrease in temperature resulting in the higher runoff than the normal, except beyond 2 °C, post which there is a sudden increase in surface runoff response, even in scenarios where there is a decrease in rainfall. While surface runoff rises 2% for every 1% increase in precipitation and decreases by 1.7% for every 1% decrease, the corresponding change for total runoff is 1.4%. The novelty of the work lies in its capacity to provide a rapid framework to the immediate stakeholders in understanding runoff response to different change-based scenario independently and in combination. [ABSTRACT FROM AUTHOR]

The Food and Agriculture Organizations' (FAO) Penman–Monteith reference evapotranspiration (ET0) is a crucial index in the research of water and energy balance. Temporal and spatial variations in ET0 from 1981–2017 were investigated in the Hengduan Mountains, China. The results showed a change point around the year 2000 in ET0 series. ET0 decreased and increased significantly by +3.200 mm/year (p < 0.01) from 1981–2000 and by +4.109 mm/year (p < 0.01) from 2001–2017, respectively. The contribution analysis shows that the positive significant contribution of air temperature (TA) was offset by negative effects of decreases in downward shortwave radiation (Rs) and wind speed (WS) and an increase in actual vapour pressure (ea), causing the decrease in ET0 from 1981 to 2000. WS was the largest contributing factor for the decrease in ET0 from 1981 to 2000 during spring, winter and annually, while Rs and ea were the largest negative contributors in summer and autumn, respectively. An increase in TA was responsible for the increase in ET0 in all seasons except winter and the annual scale in 2001–2017. The sensitivity analysis shows that ET0 was most sensitive to TA, and WS was the least sensitive variable. The trends of ET0 increased with elevation; we denote this as the elevation‐dependence of ET0 changes. The elevation‐dependence was also noted for the trends of WS and ea, with higher elevations showing larger changes in WS and lower changes in ea. Besides, the sensitivities of TA, Rs and ea decreased with elevation, while that of WS increased slightly with elevation. A comprehensive investigation into the trends of climatic drivers and their sensitivities revealed complex trends of the contributions of climatic variables on ET0 with elevation, with no uniform trend existed in seasons. The results will contribute to our understanding of the response of ET0 to climate change in a mountainous area, and provide a guideline for the water resources management under climate change. [ABSTRACT FROM AUTHOR]

Studying the spatiotemporal variation of precipitation in China under the background of climate change and its impact on surface dry-wet conditions is of great significance in revealing the dynamic responses and changes of land surface systems to climate change and disaster prevention and mitigation. Based on measured meteorological data from 1961 to 2010, the spatiotemporal variations of precipitation and surface dry-wet conditions were analyzed. Furthermore, sensitivity and contribution analysis were used to quantify the impact of precipitation on dry-wet conditions. Results showed that the annual precipitation in national scale showed a slight increasing trend over the past 50 years, but the variations of annual precipitation in different temperature zones were significant, the Qinghai-Tibet Plateau (Plateau sub-cold zone and Plateau temperate zone), the northwestern (the west of both Medium temperate zone and Warm temperate zone) and southern regions of China (Subtropical zone and Tropical zone) showed an increasing trend, while the northeastern (Cold temperate zone and the east of Medium temperate zone) and northern regions of China (middle and east of Medium temperate zone and east of Warm temperate zone) showed a decreasing trend. In terms of dry-wet conditions, it varied greatly in different regions, the northern and northeastern regions of China got dried while the Qinghai-Tibet Plateau, the northwestern and the southern regions got wet. The dry-wet conditions were sensitive to the change of precipitation (mean annual sensitivity coefficient: - 1.13). The dry-wet index was negatively correlated with precipitation. In the inland arid regions, precipitation contributed more to the change of dry and wet conditions than that in humid regions, and some of the regions exceeded 60%. [ABSTRACT FROM AUTHOR]

• A crop VWC contribution analysis framework is presented. • The crop VWC variation is separated into changes induced by climate change and human activities. • The contribution analysis framework combined VWC calculation with the hydrological sensitivity method. • Validation with a case study in an agricultural district in northern China. • Human activities were the dominant factors that contributed to the decrease of VWC of crops. The virtual water content (VWC), which quantified the water consumption per unit of a food product, serves as a critical variable to the virtual water study. Because of the climate-dependent nature of VWC and its vulnerability to human influence, we still have little knowledge to interpret VWC variation regarding the contribution of climate change and human activities. This study aims to address this gap by proposing a VWC contribution analysis framework. In this framework, we applied the hydrological sensitivity method to a newly developed crop VWC calculation formula. We firstly separated the study period into baseline and change periods to calculate the change of VWC over time (ΔVWC). Based on the VWC calculation formula, the partial derivatives of VWC to precipitation (P) and potential evapotranspiration (PET) are mathematically derived. These partial derivatives were served as the sensitivity coefficients in the hydrological sensitivity method. We used them to differentiate and quantify the impact of climate change and human activities on ΔVWC and finally calculate its corresponding relative contribution. We demonstrate this framework in Shijiazhuang Plain, an agricultural district in northern China where the VWC of major crops has decreased in recent decades. We found that the relative contribution of human activities to the changes of VWC was greater than 97%, versus less than 3% for climate change. This finding suggests that human activities play a dominant and essential role in shaping the evolution of VWC as the region's water scarcity increases. [ABSTRACT FROM AUTHOR]