A Review of Climate Change Impacts on the USA-Mexico Transboundary Santa Cruz River Basin

In this study, analysis of the long term climatology, variability and trends in the daily rainfall events of ≥5 mm [or daily rainfall (DR) events] during the southwest monsoon season (June–September) over four regions of India; south central India (SCI), north central India (NCI), northeast India (NEI) and west coast (WC) have been presented. For this purpose, a new high spatial resolution (0.25° × 0.25°) daily gridded rainfall data set covering 110 years (1901–2010) over the Indian main land has been used. The association of monsoon low pressure systems (LPSs) with the DR events of various intensities has also been examined. Major portion of the rainfall over these regions during the season was received in the form of medium rainfall (≥5–100 mm) or moderate rainfall (MR) events. The mean seasonal cycle of the daily frequency of heavy rainfall (HR) (≥100–150 mm) or HR events and very heavy rainfall (VHR) (≥150 mm) or VHR events over each of the four regions showed peak at different parts of the season. The peak in the mean daily HR and VHR events occurred during middle of July to middle of August over SCI, during late part of June to early part of July over NCI, during middle of June to early July over NEI, and during late June to middle July over WC. Significant long term trends in the frequency and intensity of the DR events were observed in all the four geographical regions. Whereas the intensity of the DR events over all the four regions showed significant positive trends during the second half and the total period, the signs and magnitude of the long term trends in the frequency of the various categories of DR events during the total period and its two halves differed from the region to the region. The trend analysis revealed increased disaster potential for instant flooding over SCI and NCI during the recent years due to significant increasing trends in the frequency (areal coverage) and intensity of the HR and VHR events during the recent half of the data period. However, there is increased disaster potential over NEI and WC due to the increasing trends in the intensity of the rainfall events. There is strong association between the LPS days and the DR events in both the spatial and temporal scales. In all the four regions, the contributions to the total MR events by the LPS days were nearly equal. On the other hand, there was relatively large regional difference in the number of combined HR and VHR events associated with LPS days particularly that associated with monsoon depression (LPS stronger than monsoon depression) days. The possible reasons for the same have also been discussed. The increasing trend in the monsoon low (low pressure) days post 1970s is the primary reason for the observed significant increasing trends in the HR and VHR events over SCI and NCI and decreasing trend in HR events over NEI during the recent half (1956–2010). This is in spite of the decreasing trend in the MD days.

The relevance of the research consists in the need for evaluating the water resources changes of the Dniester due to global warming. The mountain part of the Dniester Basin is a zone of the river's runoff formation that determines its water content. The subject of research includes a process of climate changes and their impact on the water resources of the Mountain Dniester’s catchments. The research focuses on determining the water resources changes under current and possible future climatic conditions represented by climatic scenarios.
 The research aims at evaluating the water resources changes of the mountain part of the Dniester’s catchment area at the present and in the future by the mid-21 st century (2021-2050) based on the “climate-runoff” model using meteorological observations data (up to 2018 inclusive) and scenario data (averaged data based on 14 mathematical models of the CORDEX project, RCP8.5 scenario).
 During the research the resources of humidification, heat (heat equivalent) and water content for modern (1989-2018) and scenario (RCP8.5, 2021-2050) climatic conditions based on application of the "climate-runoff" model were evaluated. The theoretical basis for estimating the natural (undisturbed by water management) annual runoff in this model is represented by the water-heat balance equation. The meteorological characteristics (average monthly air temperatures and precipitation) serve as input data. The runoff calculated using the water-heat balance equation is called a climatic runoff. One of the peculiarities of the research consists in the use of the vertical zoning law with respect to distribution of runoff and climatic factors of its formation. During the comparative analysis the dependence of annual runoff norms on height of the Mountain Dniester’s terrain specified in modern regulatory documents served as a basic dependence. Such dependence reflects an altitude-dependant distribution of runoff for the climatic conditions that preceded the significant impact of global warming on air temperature (until 1989).
 The analysis of the dependences of average long-term values of the annual runoff depending on the terrain altitude showed that the runoff changes for two studied periods (before and after 1989) are within ±12,3%. The analysis of the graphs of chronological course of annual water flow of the mountain tributaries of the Dniester made it possible to confirm the absence of statistically significant trends in their fluctuations.
 According to the RCP8.5 climate scenario over the period of 2021-2050 and following the results of calculations based on the “climate-runoff” model, the dependences of the average long-term altitude-related values of climatic factors and climatic runoff were retrieved. It was found that the effects of global warming decrease with increasing altitude. In the foothills (up to 200 m) the annual precipitation decreases (up to 11%), the maximum possible evaporation increases (up to 17%) and water resources decrease (up to 46%). Heat resources cease to increase and water resources cease to reduce at the altitudes over 800 m. The average deviation of the scenario and baseline values for precipitation over the estimated period will amount to 2.41% for precipitation, 5.79% for maximum possible evaporation and 8.87% for water resources. Thus, reduction of water resources in the mountainous part of the Dniester by the mid-21 st century will be insignificant. When evaluating the current state of water resources of the Mountain Dniester no significant changes were discovered, thereby not contradicting the other authors’ data.

Impacts of future climate change on water resource availability of eastern Australia: A case study of the Manning River basin

Proper management of scarce water resources has in recent years become necessary to maintain sustainable societies. This article discusses the management of water resources in Botswana. It highlights the amount of water resources available, relating it to the demand, and observes that the current trend of exploiting these resources will not be sustainable in the long run unless the major strategies suggested herein are adopted. It also looks at the administration of water and water resources in Botswana, focusing on the shared water resources. Government policies and strategies towards sustainable management of scarce water resources are also discussed. The author draws particular attention to the water tariff structure, noting that the prevailing water tariff system promotes sustainable management of water resources.

Water is a very valuable resource, sustaining human life, production processes, and ecosystems; thus, particular attention should be paid to the management of water resources. China is now facing a serious water crisis, including water shortages, flooding, and water pollution, due to both natural and artificial causes. This water crisis has threatened human health and economic development. Natural water resources in China have two main characteristics. First, they are insufficient: Water availability in China is only 1780 m per capita, which is one quarter that of the global value and very close to the universally accepted figure for countries lacking water resources (≤ 1700 m per capita). Second, they are unevenly distributed: Although there are rich water resources in South China, there is a lack of water in North China. North China possesses 47% of the population and 65% of the farmland, but only 17% of China’s water resources. In addition, rainfall is unevenly distributed over the four seasons in China. Water pollution is caused by human activities. Industry, agriculture, and the activities of daily life all discharge wastewater and create water pollution. The seven major water systems in China all contain pollution to different degrees, including organic pollution, nutrient pollution, heavy metal pollution, persistent organic pollutants (POPs), and so forth. It is estimated that more than 100 million urban residents and 320 million residents in rural areas lack safe drinking water. Many accidents related to water pollution have occurred in China in recent years, seriously threatening people’s health and lives. Flooding and water-logging are sudden events. However, most of the responsibility for these issues lies with sewer systems that are not well-designed, constructed, and/or operated. For example, some cities in North China have had flood-related accidents that were mainly caused by problems with urban sewer systems. All these facts make it clear that close attention should be paid to the management of water resources in China in order to prevent the harmful effects of water crises. The targets of sustainable water resource management should include: providing sufficient water resources for economic development and the population’s daily lives; protecting a clean water environment; ensuring safe drinking water; and preventing disasters caused by flooding and water-logging. To ensure that the above targets are achieved, the sustainable management of water resources in China should be based on these strategies [1,2]: • Making water conservation the main priority, and controlling water demand; • Controlling water pollution rigorously and reducing the pollution created by sources; • Using wastewater as water, energy, and fertilizer resources; and • Preventing flooding and water-logging disasters, while using rainwater as a water resource.

This study presents the trend analysis for a specific category of variables, namely the average annual precipitation. The geospatial distribution of the obtained results in Central Serbia is visualized using Geographic Information System (GIS) numerical analysis. The primary objective of this study is to identify potential changes in the trends of average annual precipitation within the observed area. Methodologically, the MannKendall trend test, trend equation, and trend magnitude were employed for trend analysis. The data used for the analysis were sourced from the Meteorological Yearbooks of the Republic Hydrometeorological Service of Serbia, encompassing a total of 24 meteorological stations and spanning the period from 1949 to 2018. Based on the obtained results, statistically significant positive trends were observed in 17 time series, favoring the alternative hypothesis. Conversely, a decline in precipitation was noted in the remaining 7 time series. Among the time series, the largest increases in the total amount of precipitation over the past 69 years were recorded ont he area of the Dinaric Mountains. Conversely, the lowest increase in average precipitation was observed in the central part od the country.Furthermore, the time series with the greatest decrease in average annual precipitation was recorded ont he southeastern part of the country. In order to effectively address water-related challenges associated with precipitation fluctuations, it is essential to gain a comprehensive understanding of the shifting trends in precipitation over the region of Central Serbia.

<p><b>The Southern Westerly Winds (SWW) are a symmetric component of the global climate system that govern the modern climate of all Southern Hemisphere landmasses south of ~30°S. Changes in the strength and latitudinal position of the SWW influence the precipitation patterns in the southern mid-latitudes, and have been postulated as fundamental drivers of ocean-atmospheric CO2 exchange since the Last Glacial Maximum (LGM: ~34.0-18.0 ka). Despite their role in modern and past climatic dynamics, the evolution of the SWW at locations within their zone of influence is still uncertain; this is largely because of the paucity of paleoclimate records with well constrained chronology, adequate sampling resolution and an appropriate depositional setting. Resolving these issues will help understand the behaviour of the SWW in the past at different spatial (regional and hemisphere) and temporal (centennial to multi-millennial) scales. Here I present new paleoclimate data based on the examination of detailed chronologies of fossil pollen, charcoal and chironomids preserved in lake sediments from western Patagonia: Lago Emerenciana (43°S) and Lago Pintito (52°S) and New Zealand’s southwestern South Island: Lake Von (45°S). These data, spanning a broad range of the SWW zone of influence, provide insights into the role of shifting SWW in environmental and climate dynamics of the middle latitudes of the Southern Hemisphere spanning the last ~24,000 years.</b></p> <p>In the first study site, I performed detailed fossil pollen and charcoal analyses from sediment cores collected from Lago Emerenciana, a relatively small closed-basin lake located in northwestern Patagonian (43°S), to examine past vegetation, fire regime and climate change during the last ~24,000 years. I detect very low temperature and increased precipitation between ~24.0 and ~17.0 ka, followed by a warming trend and reduced precipitation between ~17.0 and ~14.3 ka. A cold reversal and increased precipitation regime occurred between ~14.3 and ~12.4 ka, followed by a return to warming and a slight decline in precipitation between ~12.4 and ~11.0 ka. I identify warmer temperatures and a major decline in precipitation at the beginning of the Holocene between ~11.0 and ~9.0 ka, conditions that persisted until ~6.2 ka. Centennial to millennial precipitation variability occurred during the last ~6200 years. </p> <p>In the second study site, I developed high resolution fossil pollen and charcoal records, along with an exploratory chironomid record from sediment cores obtained from Lake Von, a small closed-basin lake located in the southwestern sector of the South Island of New Zealand (45°S), to examine vegetation, fire and climate trends spanning the last ~18,000 years. I observe a trend toward warming and relatively dry conditions between ~18.0 and ~14.8 ka with relatively wet conditions between ~18.0 and ~16.7 ka, increased precipitation between ~16.7 and ~14.8 ka, and cooling conditions and enhanced precipitation between ~14.8 and ~12.8 ka, followed by a marked drop in precipitation between ~12.6 and ~11.2 ka. I detect warmer and diminished precipitation between ~10.8 and ~7.2 ka, followed by lower temperature and enhanced precipitation between ~7.2 and ~3.7 ka. The mid-late Holocene is also characterised by alternating dry and wet oscillations of millennial- and centennial-scale phases with low precipitation between ~6.0 and ~5.2, ~4.4 and ~4.1, ~3.7 and ~2.9, and ~1.9 and ~0.56 ka, and increased precipitation in the intervening intervals. In the third study site, I produced high resolution fossil pollen and charcoal records from sediment cores I collected from Lago Pintito, a small and shallow closed-basin lake located in southwestern Patagonia (52°S). This record allows the detection of past vegetation, fire and hydroclimatic shifts at millennial and centennial scales over the last ~17,000 years. From these data, I identify cold and dry conditions between ~17.0 and ~16.4 ka, increased precipitation between ~16.4 and ~14.2 ka and ~12.5 and ~11.4 ka, and intense precipitation but lower in magnitude than the neighbouring intervals between ~14.2 and~12.5 ka. I detect a major decline in precipitation at the beginning of the Holocene between ~11.4 and ~6.8 ka, followed by centennial-scale changes in precipitation until the present. </p> <p>The comparison between precipitation variability reconstructed from the records from western Patagonia (Lago Emerenciana and Lago Pintito) and New Zealand’s southwestern South Island (Lake Von) allows the inference of SWW changes at a hemispheric scale during and since the LGM, based on the premise that there is a strong and positive correlation between zonal wind speeds and local precipitation in these regions. The results of this thesis suggest: i) strong SWW influence at 43°S between ~24.0 and ~17.5 ka, ii) a southward shift of the SWW between ~17.5 and ~16.5 ka and reduced SWW influence north of 52°S, iii) strengthening and/or a northward shift of the SWW between ~16.5 and ~ 14.5 ka, with strong SWW influence between 52°S and 43°S, iv) a northward shift of the SWW between ~14.5 and ~12.6 ka which resulted in stronger SWW influence between 43°S and 46° S and weaker SWW influence at 52°S, v) a southward shift of the SWW between ~12.6 and ~11.2 ka leading to weaker SWW influence between 43°S and 46°S and stronger SWW influence at 52°S, vi) a generalized multi-millennial decline in the strength of the SWW between ~11.2 and ~7.2 ka, and vii) high variability in the SWW in Western Patagonian and New Zealand’s southwestern South Island during the last ~7200 years. Based on these findings, I postulate that hemisphere-wide changes in the position and/or strength of the SWW have modulated the atmospheric CO2 concentration through wind-driven upwelling of CO2-rich deep waters in the high southern latitudes during and since the LGM.</p>

<p><b>The Southern Westerly Winds (SWW) are a symmetric component of the global climate system that govern the modern climate of all Southern Hemisphere landmasses south of ~30°S. Changes in the strength and latitudinal position of the SWW influence the precipitation patterns in the southern mid-latitudes, and have been postulated as fundamental drivers of ocean-atmospheric CO2 exchange since the Last Glacial Maximum (LGM: ~34.0-18.0 ka). Despite their role in modern and past climatic dynamics, the evolution of the SWW at locations within their zone of influence is still uncertain; this is largely because of the paucity of paleoclimate records with well constrained chronology, adequate sampling resolution and an appropriate depositional setting. Resolving these issues will help understand the behaviour of the SWW in the past at different spatial (regional and hemisphere) and temporal (centennial to multi-millennial) scales. Here I present new paleoclimate data based on the examination of detailed chronologies of fossil pollen, charcoal and chironomids preserved in lake sediments from western Patagonia: Lago Emerenciana (43°S) and Lago Pintito (52°S) and New Zealand’s southwestern South Island: Lake Von (45°S). These data, spanning a broad range of the SWW zone of influence, provide insights into the role of shifting SWW in environmental and climate dynamics of the middle latitudes of the Southern Hemisphere spanning the last ~24,000 years.</b></p> <p>In the first study site, I performed detailed fossil pollen and charcoal analyses from sediment cores collected from Lago Emerenciana, a relatively small closed-basin lake located in northwestern Patagonian (43°S), to examine past vegetation, fire regime and climate change during the last ~24,000 years. I detect very low temperature and increased precipitation between ~24.0 and ~17.0 ka, followed by a warming trend and reduced precipitation between ~17.0 and ~14.3 ka. A cold reversal and increased precipitation regime occurred between ~14.3 and ~12.4 ka, followed by a return to warming and a slight decline in precipitation between ~12.4 and ~11.0 ka. I identify warmer temperatures and a major decline in precipitation at the beginning of the Holocene between ~11.0 and ~9.0 ka, conditions that persisted until ~6.2 ka. Centennial to millennial precipitation variability occurred during the last ~6200 years. </p> <p>In the second study site, I developed high resolution fossil pollen and charcoal records, along with an exploratory chironomid record from sediment cores obtained from Lake Von, a small closed-basin lake located in the southwestern sector of the South Island of New Zealand (45°S), to examine vegetation, fire and climate trends spanning the last ~18,000 years. I observe a trend toward warming and relatively dry conditions between ~18.0 and ~14.8 ka with relatively wet conditions between ~18.0 and ~16.7 ka, increased precipitation between ~16.7 and ~14.8 ka, and cooling conditions and enhanced precipitation between ~14.8 and ~12.8 ka, followed by a marked drop in precipitation between ~12.6 and ~11.2 ka. I detect warmer and diminished precipitation between ~10.8 and ~7.2 ka, followed by lower temperature and enhanced precipitation between ~7.2 and ~3.7 ka. The mid-late Holocene is also characterised by alternating dry and wet oscillations of millennial- and centennial-scale phases with low precipitation between ~6.0 and ~5.2, ~4.4 and ~4.1, ~3.7 and ~2.9, and ~1.9 and ~0.56 ka, and increased precipitation in the intervening intervals. In the third study site, I produced high resolution fossil pollen and charcoal records from sediment cores I collected from Lago Pintito, a small and shallow closed-basin lake located in southwestern Patagonia (52°S). This record allows the detection of past vegetation, fire and hydroclimatic shifts at millennial and centennial scales over the last ~17,000 years. From these data, I identify cold and dry conditions between ~17.0 and ~16.4 ka, increased precipitation between ~16.4 and ~14.2 ka and ~12.5 and ~11.4 ka, and intense precipitation but lower in magnitude than the neighbouring intervals between ~14.2 and~12.5 ka. I detect a major decline in precipitation at the beginning of the Holocene between ~11.4 and ~6.8 ka, followed by centennial-scale changes in precipitation until the present. </p> <p>The comparison between precipitation variability reconstructed from the records from western Patagonia (Lago Emerenciana and Lago Pintito) and New Zealand’s southwestern South Island (Lake Von) allows the inference of SWW changes at a hemispheric scale during and since the LGM, based on the premise that there is a strong and positive correlation between zonal wind speeds and local precipitation in these regions. The results of this thesis suggest: i) strong SWW influence at 43°S between ~24.0 and ~17.5 ka, ii) a southward shift of the SWW between ~17.5 and ~16.5 ka and reduced SWW influence north of 52°S, iii) strengthening and/or a northward shift of the SWW between ~16.5 and ~ 14.5 ka, with strong SWW influence between 52°S and 43°S, iv) a northward shift of the SWW between ~14.5 and ~12.6 ka which resulted in stronger SWW influence between 43°S and 46° S and weaker SWW influence at 52°S, v) a southward shift of the SWW between ~12.6 and ~11.2 ka leading to weaker SWW influence between 43°S and 46°S and stronger SWW influence at 52°S, vi) a generalized multi-millennial decline in the strength of the SWW between ~11.2 and ~7.2 ka, and vii) high variability in the SWW in Western Patagonian and New Zealand’s southwestern South Island during the last ~7200 years. Based on these findings, I postulate that hemisphere-wide changes in the position and/or strength of the SWW have modulated the atmospheric CO2 concentration through wind-driven upwelling of CO2-rich deep waters in the high southern latitudes during and since the LGM.</p>

The past decades have seen rapid advancements in space-based monitoring of essential water cycle variables, providing products related to precipitation, evapotranspiration, and soil moisture, often at tens of kilometer scales. Whilst these data effectively characterize water cycle variability at regional to global scales, they are less suitable for sustainable management of local water resources, which needs detailed information to represent the spatial heterogeneity of soil and vegetation. The following questions are critical to effectively exploit information from remotely sensed and in situ Earth observations (EOs): How to downscale the global water cycle products to the local scale using multiple sources and scales of EO data? How to explore and apply the downscaled information at the management level for a better understanding of soil-water-vegetation-energy processes? How can such fine-scale information be used to improve the management of soil and water resources? An integrative information flow (i.e., iAqueduct theoretical framework) is developed to close the gaps between satellite water cycle products and local information necessary for sustainable management of water resources. The integrated iAqueduct framework aims to address the abovementioned scientific questions by combining medium-resolution (10 m–1 km) Copernicus satellite data with high-resolution (cm) unmanned aerial system (UAS) data, in situ observations, analytical- and physical-based models, as well as big-data analytics with machine learning algorithms. This paper provides a general overview of the iAqueduct theoretical framework and introduces some preliminary results.

Untangling the dynamics of heavy rainfall events (HRE) in the Northeast monsoon season and exploring its connection to the Indian Ocean warming and the Madden Julian Oscillation

Drought: a global environmental concern

This study investigates the quantitative remote sensing assessment of climate change on water resources and explores integrated approaches for fostering climate resilience and sustainable land management in its degraded ecosystems. Using remote sensing data from 2003 to 2023, the study identifies the water bodies, moisture level, and land surface temperature in the Punjab province of Pakistan. The research leverages multi‐temporal remote sensing data using Landsat satellite imagery to analyze hydrological shifts using the Normalized Difference Water Index (NDWI), Normalized Difference Moisture Index (NDMI), Land Surface Temperature (LST), and precipitation across eight agroclimatic zones of the province. The NDWI analysis reveals a persistent decline in water availability, with the value dropping from 0.8380 to 0.4429, while LST surged from 31.62°C to 50.04°C, exacerbating thermal stress. The 7.4% decline in precipitation signifies escalating water scarcity and directly contributes to ecosystem degradation and heightened vulnerability to climate change, reinforcing the complex feedback loop between climate change and land degradation. The study provides essential empirical evidence quantifying the rapid escalation of hydro‐thermal stress in the province and underscores the urgent need for integrated water and land resources management, sustainable urban planning, and region‐specific climate adaptation strategies to address escalating hydroclimatic risks and combat land degradation.

Borneo is the third largest island in the world and famous for its majestic rainforests (Figure 1a). Southeast Asian tropical forests have the highest relative deforestation rate in the world (Canadell et al., 2007). More than 80% of the total land area of Borneo was covered with pristine forest in the 1950s; however, the high deforestation rate (1.7% year−1), which is almost double that of the already intense deforestation rate of the whole Southeast Asian region, has resulted in the current estimation of forest cover being ~50% (Langner et al., 2007) (Figure 1b). Since 1965, production of tropical hardwood timber in Borneo sharply increased and reached a plateau and maximum in the early 1980s (Brookfield and Byron, 1990). Although the recent and rapid decline in timber production has been evident throughout Borneo owing to over-logging, over the past decades, more timber was exported from Borneo than from tropical Africa and Latin America combined (Curran et al., 2004). The land cover area categorized as ‘degraded forest and regrowth’, ‘cultivation forest mosaic’ and ‘dry/wet bare soil; grasslands; agriculture’ reached up to 33 million ha, ~45% of the total area of Borneo (Langner et al., 2007). Tropical forests are a major source of global hydrologic fluxes, and thus, this forest cover change has potential to significantly alter the global and regional climate and hydrologic cycling (Nobre et al., 1991; Kanae et al., 2001; Avissar and Werth, 2005). Because tropical rainforests exist where ecosystem water resources are greatest, the hydrologic changes could significantly alter ecological patterns and processes (Malhi et al., 2009; Phillips et al., 2009; Kumagai and Porporato, 2012), in turn affecting feedback to the atmosphere (Meir et al., 2006; Bonan, 2008). It is a matter of course that the drastic deforestation and forest degradation in Borneo should be anticipated to impact the regional hydro-climate; in fact, the long-term daily grid precipitation datasets (APHRODITE's Water Resources, available via http://www.chikyu.ac.jp/precip/, Yatagai et al., 2012) over Borneo showed a significant decline in precipitation over the period 1951–2007 (Figure 1c). An abrupt decline in precipitation in the late 1980s can be seen (Figure 1c), which was consistent with a time when deforestation, i.e. logging for timber production, might have become intensive (Brookfield and Byron, 1990; Curran et al., 2004). Furthermore, it should be noted that such a decreasing trend in precipitation might cause frequent extreme droughts and subsequent fires, resulting in more severe deforestation and forest degradation (van Nieuwstadt and Sheil, 2005; Wooster et al., 2012). A spatial distribution of atmospheric moisture convergence averaged over 1998–2010 in the eastern Pacific Ocean (built using a reanalyzed and gridded four-dimensional meteorology dataset, Japanese 25-year ReAnalysis and the Japan Meteorological Agency Climate Data Assimilation System available via http://jra.kishou.go.jp/JRA-25/index_en.html) suggests less moisture convergence and divergence over Borneo compared with other regions (Figure 2a). On the other hand, the Tropical Rainfall Measuring Mission satellite measurements from 1998 to 2010 (NASA Goddard Earth Sciences Data and Information Services Center, available via http://disc.sci.gsfc.nasa.gov/about-us) showed a larger amount of precipitation above islands of the maritime continent in the western Pacific Ocean compared with sea areas, suggesting a notably large amount of precipitation over Borneo (Figure 2b). In short, although little atmospheric moisture horizontally moves into and out of the atmospheric space over Borneo, this area has plenty of precipitation (Figure 2c). Therefore, a question arises: where does water for precipitation come from? According to the atmospheric water budget equation, assuming that the time change of local available precipitable water content is negligible (Oki et al., 1995), annual evapotranspiration over Borneo was roughly estimated to be ~7 mm day−1 and balanced with the annual precipitation, implying that most of the precipitation was recycled from terrestrial evapotranspiration over Borneo (Figure 2c). However, this evapotranspiration value surpassed the upper limit of the potential evaporation when taking into consideration basic meteorological variables in this region (Kumagai et al., 2005). The computation of the budget equation using the combination of the reanalysis and the satellite measurement data, which are different in their derivations, might cause such a discrepancy. Nevertheless, in light of comparisons with the other areas, it is certain that there are large amounts of precipitation in, and little moisture advection into or out of, the Bornean region (Figure 2a, b). Also, a yearly eddy covariance observation conducted at a Bornean tropical rainforest site indicated the high rate of pristine rainforest evapotranspiration, which can be approximated using the same mechanism as the evaporation from an extensive water surface, to be ~4 mm day−1 as an annual mean (Kumagai et al., 2005). Thus, we concluded that there is a higher ratio of recycling from terrestrial evapotranspiration into the precipitation over Borneo (Figure 2c) and that deforestation and forest degradation could alter this eco-hydro-climatological cycling. Therefore, it is plausible that the deforestation and forest degradation has led to a long-term decline in precipitation in Borneo (Figure 1c). In addition, it was pointed out that a slowdown of the Walker circulation over the last 60 years suppressed moisture convergence over the maritime continent including Borneo, resulting in the historical decline in land precipitation (Tokinaga et al., 2012). We argue that deforestation and forest degradation can be still a major factor inducing the decline in precipitation because such a weakening of moisture convergence would promote recycling of the terrestrial evapotranspiration into the precipitation. Certainly, fire is the major driver for the deforestation and forest degradation in Borneo (Langner et al., 2007), and evapotranspiration from lands where fires occur decreases appreciably. The land cover of deforested areas does not always end up as bare land; they are usually converted to other vegetation types like oil palm plantations (Carlson et al., 2012) (Figure 1b). This suggests that the land cover change and deforestation does not necessarily decrease land evapotranspiration. Thus, a reliable assessment of the deforestation-induced impacts on the regional hydro-climate firstly requires new data on characteristics of energy and mass exchange between the atmosphere and the land surfaces resulting from the land conversion. For example, the flux data on oil palm plantations, a major resultant land cover (Carlson et al., 2012), are seriously lacking for describing changes in the land surface process. Numerical experiments with cloud resolving models (e.g. The Weather Research & Forecasting Model available at http://www.wrf-model.org/index.php) using the land surface-atmosphere exchange data as well as satellite monitoring of land cover classification can help elaborate the reduction in precipitation from the deforestation and forest degradation over Borneo. This work is supported by a Grant-in-Aid for Scientific Research (#25281005) and the granted project ‘Program for risk information on climate change’ from the Ministry of Education, Science and Culture, Japan. The authors would like to thank Tomoko Tanaka for drawing.

Sustainable management of water resources is one of the greatest challenges facing society in the 21st century. In terms of adequate drinking water supply, ever-increasing population, accompanied by urbanization, has affected one third of the world population. Both Australia and China have identified water resources issues as a priority research area and both countries have been conducting significant R&D activities. They have supported extensive national collaborative efforts to enable the future deployment of large scale water resources management systems. The sharing of data resources, and the experience of managing water resources among practitioners will be invaluable in a collaborative effort to solve the problem of sustainable water resources. A workshop on whole-of-water cycle approach to sustainable management of water resources took place on the Gold Coast, Australia, 4-5 July 2005. The main outcomes of the workshop included the willingness to collaborate among the participants in sharing of data sets and work together towards providing policy advice for sustainable water resources in both countries. It was suggested that a three-stage approach be adopted to study various possibilities of sustainable water resources. The aim of this three-stage approach is to provide analysis and development of management policies for sustainable management of water resources in both countries.

Abstract. The enhanced warming trend and precipitation decline in the Mediterranean region make it a climate change hotspot. We compare projections of multiple Coupled Model Intercomparison Project Phase 5 (CMIP5) and Phase 6 (CMIP6) historical and future scenario simulations to quantify the impacts of the already changing climate in the region. In particular, we investigate changes in temperature and precipitation during the 21st century following scenarios RCP2.6, RCP4.5 and RCP8.5 for CMIP5 and SSP1-2.6, SSP2-4.5 and SSP5-8.5 from CMIP6, as well as for the HighResMIP high-resolution experiments. A model weighting scheme is applied to obtain constrained estimates of projected changes, which accounts for historical model performance and inter-independence in the multi-model ensembles, using an observational ensemble as reference. Results indicate a robust and significant warming over the Mediterranean region during the 21st century over all seasons, ensembles and experiments. The temperature changes vary between CMIPs, CMIP6 being the ensemble that projects a stronger warming. The Mediterranean amplified warming with respect to the global mean is mainly found during summer. The projected Mediterranean warming during the summer season can span from 1.83 to 8.49 ∘C in CMIP6 and 1.22 to 6.63 ∘C in CMIP5 considering three different scenarios and the 50 % of inter-model spread by the end of the century. Contrarily to temperature projections, precipitation changes show greater uncertainties and spatial heterogeneity. However, a robust and significant precipitation decline is projected over large parts of the region during summer by the end of the century and for the high emission scenario (−49 % to −16 % in CMIP6 and −47 % to −22 % in CMIP5). While there is less disagreement in projected precipitation than in temperature between CMIP5 and CMIP6, the latter shows larger precipitation declines in some regions. Results obtained from the model weighting scheme indicate larger warming trends in CMIP5 and a weaker warming trend in CMIP6, thereby reducing the difference between the multi-model ensemble means from 1.32 ∘C before weighting to 0.68 ∘C after weighting.