Clapping From the Arena

Climate change is a serious global issue and concern that is attributed to change. A change of climate that is directly or indirectly related to human activity, that which alters the composition of the global atmosphere and which in addition to natural climate variability observed over comparable time periods. There is therefore no doubt that the earth is warming, and the climate changing. Despotism and the rule of despots as agents of democracy has created a rift in the issue of climate change on its citizenry in the southern zone of Plateau State in the area of health, water shortages, cutting meals due to the economic recession in Nigeria. Research has shown that climate change can create a conflict, and it does have a direct effect on scarce resources required to sustain life. Water is at the heart of human existence. Global warming has a major impact on global water cycle, hence on rainfall, soil moisture, rivers, and sea levels. If climate change is not tackled urgently, the calamity will be enormous.

A Framework for Methodological Options to Assess Climatic and Anthropogenic Influences on Streamflow

Climate change and human activities are having increasing impacts on the global water cycle, particularly on streamflow. Current methods for quantifying these impacts are numerous and have their merits and limitations. There is a lack of a guide to help researchers select one or more appropriate methods for attribution analysis. In this study, hydrological modeling, statistical analysis, and conceptual approaches were used jointly to develop a methodological options framework consisting of three modules, to guide researchers in selecting appropriate methods and assessing climatic and anthropogenic contributions to streamflow changes. To evaluate its effectiveness, a case study in the Upper Yangtze River Basin (UYRB) of China was conducted. The results suggest that the SWAT-based method is the best approach to quantify the influences of climate change and human activities on streamflow in the UYRB. The comprehensive assessment indicates that climate change is the dominant cause of streamflow changes in the UYRB, and the contribution of climate change, indirect human activities, and direct human activities to streamflow changes is about 7:1:2. The proposed framework is efficient and valuable in assisting researchers to find appropriate methods for attribution analysis of streamflow changes, which can help to understand the water cycle in changing environments.

Evaluation of Clumping Effects on the Estimation of Global Terrestrial Evapotranspiration

In terrestrial ecosystems, leaves are aggregated into different spatial structures and their spatial distribution is non-random. Clumping index (CI) is a key canopy structural parameter, characterizing the extent to which leaf deviates from the random distribution. To assess leaf clumping effects on global terrestrial ET, we used a global leaf area index (LAI) map and the latest version of global CI product derived from MODIS BRDF data as well as the Boreal Ecosystem Productivity Simulator (BEPS) to estimate global terrestrial ET. The results show that global terrestrial ET in 2015 was 511.9 ± 70.1 mm yr−1 for Case I, where the true LAI and CI are used. Compared to this baseline case, (1) global terrestrial ET is overestimated by 4.7% for Case II where true LAI is used ignoring clumping; (2) global terrestrial ET is underestimated by 13.0% for Case III where effective LAI is used ignoring clumping. Among all plant functional types (PFTs), evergreen needleleaf forests were most affected by foliage clumping for ET estimation in Case II, because they are most clumped with the lowest CI. Deciduous broadleaf forests are affected by leaf clumping most in Case III because they have both high LAI and low CI compared to other PFTs. The leaf clumping effects on ET estimation in both Case II and Case III is robust to the errors in major input parameters. Thus, it is necessary to consider clumping effects in the simulation of global terrestrial ET, which has considerable implications for global water cycle research.

Recharge observations indicate strengthened groundwater connection to surface fluxes

Groundwater is an invaluable global resource, but its long-term viability as a resource for consumption, agriculture, and ecosystems depends on precipitation recharging aquifers. How much precipitation recharges groundwaters varies enormously across Earth's surface, but recharge rates are uncertain because field observations are sparse and modeled global estimates remain largely unvalidated. Here we show that recharge is predictable as a simple function of climatic aridity — the ratio of long-term potential evapotranspiration to precipitation — using a global synthesis of measured recharge of 5237 sites across six continents. We use this relationship to estimate long-term recharge globally outside of permafrost regions. Our estimates double previous global estimates and are more consistent with empirical observations. These revised higher estimates of global groundwater recharge imply that much more groundwater must contribute to evapotranspiration and streamflow than previously represented in global water cycle depictions or global hydrological and Earth system models.

Imprint of the Pacific Walker Circulation in global precipitation δ18O

Characterising variability in the global water cycle is fundamental to predicting impacts of future climate change; understanding the role of the Pacific Walker circulation (PWC) in the regional expression of global water cycle changes is critical to understanding this variability. Water isotopes are ideal tracers of the role of the PWC in global water cycling, because they retain information about circulation-dependent processes including moisture source, transport, and delivery. We collated publicly-available measurements of precipitation δ18O (δ18OP), and used novel data processing techniques to synthesise long (34-year), globally-distributed composite records from temporally discontinuous δ18OP measurements. We investigated relationships between global-scale δ18OP variability and PWC strength, as well as other possible drivers of global δ18OP variability—including the El Niño Southern Oscillation (ENSO) and global mean temperature—and used isotope-enabled climate model simulations to assess potential biases arising from uneven geographical distribution of the observations or our data processing methodology. Co-variability underlying the δ18OP composites is more strongly correlated with the PWC (r = 0.74) than any other index of climate variability tested. We propose that the PWC imprint in global δ18OP arises from multiple complementary processes, including PWC-related changes in moisture source and transport length, and a PWC- or ENSO-driven ‘amount effect’ in tropical regions. The clear PWC imprint in global δ18OP implies a strong PWC influence on the regional expression of global water cycle variability on interannual to decadal timescales, and hence that uncertainty in the future state of the PWC translates to uncertainties in future changes in the global water cycle.

Micropollutant-loaded powdered activated carbon released from waste water treatment plants: a risk for sediment-dwelling organisms?

Background In order to protect aquatic environments and to reduce the presence of micropollutants in the global water cycle, wastewater treatment plants (WWTPs) often implement an additional treatment step. One of the most effective measures is the use of powdered activated carbon (PAC) as an adsorbent for micropollutants. This method provides sufficient elimination rates for several micropollutants and has been successfully employed in many WWTPs. Despite this success, there might be a drawback as the retention of the PAC in the WWTP can be challenging and losses of micropollutant-loaded PAC into the aquatic environment may occur. Upon emission, micropollutant-loaded PAC is expected to settle to the benthic zone of receiving waters, where sediment-dwelling organisms may ingest these particles. Therefore, the present study investigated possible adverse effects of micropollutant-loaded PAC from a WWTP as compared to unloaded (native) and diclofenac-loaded PAC on the sediment-dwelling annelid Lumbriculus variegatus. Results Native PAC induced the strongest effects on growth (measured as biomass) and reproduction of the annelids. The corresponding medium effective concentrations (EC50) were 1.7 g/kg and 1.8 g/kg, respectively. Diclofenac-loaded PAC showed lower effects with an EC50 of 2.5 g/kg for growth and EC50 of 3.0 g/kg for reproduction. Although tested at the same concentrations, the micropollutant-loaded PAC from the WWTP did not lead to obvious negative effects on the endpoints investigated for L.variegatus and only a slight trend of a reduced growth was detected. Conclusion We did not detect harmful effects on L. variegatus caused by the presence of MP-loaded PAC from a WWTP which gives an auspicious perspective for PAC as an advanced treatment option.

Imprint of the Pacific Walker Circulation in global precipitation δ18O

Characterising variability in the global water cycle is fundamental to predicting impacts of future climate change; understanding the role of the Pacific Walker circulation (PWC) in the regional expression of global water cycle changes is critical to understanding this variability. Water isotopes are ideal tracers of the role of the PWC in global water cycling, because they retain information about circulation-dependent processes including moisture source, transport, and delivery. We collated publicly-available measurements of precipitation δ18O (δ18OP), and used novel data processing techniques to synthesise long (34-year), globally-distributed composite records from temporally discontinuous δ18OP measurements. We investigated relationships between global-scale δ18OP variability and PWC strength, as well as other possible drivers of global δ18OP variability—including the El Niño Southern Oscillation (ENSO) and global mean temperature—and used isotope-enabled climate model simulations to assess potential biases arising from uneven geographical distribution of the observations or our data processing methodology. Co-variability underlying the δ18OP composites is more strongly correlated with the PWC (r = 0.74) than any other index of climate variability tested. We propose that the PWC imprint in global δ18OP arises from multiple complementary processes, including PWC-related changes in moisture source and transport length, and a PWC- or ENSO-driven ‘amount effect’ in tropical regions. The clear PWC imprint in global δ18OP implies a strong PWC influence on the regional expression of global water cycle variability on interannual to decadal timescales, and hence that uncertainty in the future state of the PWC translates to uncertainties in future changes in the global water cycle.

Freshwater transport from warm to cold ocean regions amplifying faster than all model estimates

Warming-induced global water cycle changes pose a significant challenge to global ecosystems and human society. The magnitude of historical water cycle change is uncertain due to a dearth of direct rainfall and evaporation observations, particularly over the ocean where 80% of global evaporation occurs. Air-sea fluxes of freshwater and river run-off imprint on ocean salinity at different temperatures, such that warmer regions tend to be saltier and cooler regions tend to be fresher. In this work, we track observed salinity trends in the warm, salty fraction of the ocean from 1970 to 2014, and infer the global poleward transport of freshwater over this period. Since 1970, 46 - 77 x10^12 m^3 of freshwater has been transported poleward from the warmest fraction of the ocean. No model in the current generation of climate models (the 6th Climate Model Intercomparison Project; CMIP6) replicates this transport, with the closest model underestimating transport by 2 - 4 times. We trace the climate model biases to a weaker than expected surface freshwater flux intensification, just 0 - 4% in CMIP6 models compared to an estimated 3 - 7.5% in observations.