Moisture recycling is the atmospheric branch of the water cycle, including evaporation and precipitation. While the physical water cycle is well-understood, the social links among the recipients of precipitation back to the sources of evaporation are not. In this work, we develop a method to determine how these social connections unfold, using a mix of quantitative and qualitative methods, finding that there are distinct types of social connections with corresponding policy and management tools. Hide

Global temperature now exceeds +1.25 °C relative to 1880–1920, similar to warmth of the Eemian period. Keeping warming less than 1.5 °C or CO₂ below 350 ppm now requires extraction of CO₂ from the air. If rapid phaseout of fossil fuel emissions begins soon, most extraction can be via improved agricultural and forestry practices. In contrast, continued high emissions places a burden on young people of massive technological CO₂ extraction with large risks, high costs and uncertain feasibility. Hide

Temperature affects fire occurrence and severity. Warming will increase fire-related carbon emissions and thus atmospheric CO₂. The size of this feedback is not known. We use charcoal records to estimate pre-industrial fire emissions and a simple land–biosphere model to quantify the feedback. We infer a feedback strength of 5.6  3.2 ppm CO₂ per degree of warming and a gain of 0.09 ± 0.05 for a climate sensitivity of 2.8 K. Thus, fire feedback is a large part of the climate–carbon-cycle feedback. Hide

Around half of the carbon that humans emit into the atmosphere each year is taken up on land (by trees) and in the ocean (by absorption). We construct a simple model of carbon uptake that, unlike the complex models that are usually used, can be analysed mathematically. Our results include that changes in atmospheric carbon may affect future carbon uptake more than changes in climate. Our simple model could also study mechanisms that are currently too uncertain for complex models. Hide

Long-term variations in the Siberian river discharges of the Lena in the east and the Ob in the west were examined based on the observations, tree-ring reconstructions, and simulations with atmospheric and climate models. The discharges of the two rivers tended to be negatively correlated during the past 2 centuries. An east–west seesaw pattern of summertime large-scale atmospheric circulation frequently emerges over Siberia as an internal variability. This results in the negative correlations. Hide

This study uses a global climate model to explore the extent to which sea level rise due to thermal expansion of the ocean is reversible if the atmospheric concentration of carbon dioxide (CO₂) declines. It is found that sea level continues to rise for several decades after atmospheric CO₂ starts to decline and does not return to the pre-industrial level for over thousand years after atmospheric CO₂ is restored to the pre-industrial concentration. Hide

This paper analyses the potential role of atmospheric rivers in the explosive cyclone deepening. Using ERA-Interim reanalysis data for 1979–2011, we analyse the concurrence of atmospheric rivers and explosive cyclogenesis over the North Atlantic and North Pacific basins for the extended winter months (ONDJFM). Hide

The southern part of Pakistan (Sindh province) has been exposed to frequent and intense temperature extremes recently and is highly vulnerable to their impacts due to lack of information on recurrence of extremes. In this paper for the first time we estimated the return levels of daily maximum temperatures and daily maximum wet-bulb temperatures over the different return periods in Sindh, which would help the local administrations to prioritize the regions in terms of adaptations. Hide

Relationships between meteorological parameters between Arctic and the Baltic Sea regions were investigated using NCEP-CFSR reanalysis for 1979–2015. The Greenland and Baffin Bay regions climate have the most significant teleconnections with the Baltic Sea region temperature, specific humidity and wind speed. These relationships can be explained by the AO/NAO index variability only in winter. The results are valuable for selecting Arctic regions with the largest effect on the Baltic Sea region. Hide

Limiting global warming to 1.5 °C may require carbon removal from the atmosphere. We explore how the climate system differs when we achieve the 1.5 °C limit by rapid emissions reductions versus when we overshoot this limit, hitting 2 °C at mid-century before removing CO₂ from the atmosphere. We show that sea level, ocean acidification, regional warming, and ocean circulation are very different under the overshoot pathway at 2100, despite hitting the 1.5 °C target for surface warming. Hide

We study the impact of uncertainty on optimal greenhouse gas (GHG) emission policies for a stylized emission problem. The results suggest that uncertainties about the implementability of decisions on emission reductions (or increases) call for more precautionary policies. In contrast, uncertainties about the implications of exceeding critical cumulated emission thresholds tend to make early emission reductions less rewarding. Hide

Behaviors of terrestrial ecosystems differ in different El Niños. We analyze terrestrial carbon cycle responses to two extreme El Niños (2015/16 and 1997/98), and find large differences. We find that global land–atmosphere carbon flux anomaly was about 2 times smaller in 2015/16 than in 1997/98 event, without the obvious lagged response. Then we illustrate the climatic and biological mechanisms of the different terrestrial carbon cycle responses in 2015/16 and 1997/98 El Niños regionally. Hide

We present the results of a set of climate simulations designed to simulate futures in which the Earth's temperature is stabilized at the levels referred to in the 2015 Paris Agreement. We consider the necessary future emissions reductions and the aspects of extreme weather which differ significantly between the 2 and 1.5 °C climate in the simulations. Hide

Recent UNFCCC climate meetings have placed much emphasis on constraining global warming to remain below 2 °C. The 2015 Paris meeting went further and gave an aspiration to fulfil a 1.5 °C threshold. We provide a flexible set of algebraic global temperature profiles that stabilise to either target. This will potentially allow the climate research community to estimate local climatic implications for these temperature profiles, along with emissions trajectories to fulfil them. Hide

In lowland Bolivia, satellite images show rivers collapsing and the replacement of forest with savannah. This was first described in 1996 as the result of logjams (river dams created by fallen trees). I have investigated how the logjams form and affect the forest through remote sensing and fieldwork. Logjams occur nearly every year and propagate upriver until the river changes course. This region offers a unique opportunity to study how frequent forest die-off events affect biodiversity. Hide

Monsoon systems have undergone abrupt changes in past climates, and theoretical considerations show that threshold behavior can follow from the internal dynamics of monsoons. So far, however, the possibility of abrupt changes has not been explored for modern monsoon systems. We analyze state-of-the-art climate model simulations and show that some models project abrupt changes in Sahel rainfall in response to a dynamic shift in the West African monsoon under 21st century climate change. Hide

The article analysed the problems of aeolian relief changes. The changes are determined by climate, neo-tectonics, and human impact. The most important climate factors are wind speed and wind direction. Strong permanent winds induced fast sand drying and activated deflation processes, which were further accelerated by a constant stream of visitors to the dunes. The neo-tectonic movements formed micro-terraces on the eastern dune slope, which changes on wet sand pressure. Hide

A key question in climate science is how the global mean surface temperature responds to changes in greenhouse gases. This dependency is quantified by the climate sensitivity, which is determined by the complex feedbacks in the climate system. In this study observations of past climate change are used to estimate this sensitivity. Our estimate is consistent with values for the equilibrium climate sensitivity estimated by complex climate models but sensitive to the use of uncertain input data. Hide

Cultural processes are underrepresented in Earth system models, although they decisively shape humanity’s planetary imprint. We set forth ideas on how Earth system analysis can be enriched by formalising aspects of religion (understood broadly as a collective belief in things held sacred). We sketch possible modelling avenues (extensions of existing Earth system models and new co-evolutionary models) and suggest research primers to explicate and quantify mental aspects of the Anthropocene. Hide

Using climate simulations, we investigate the role of water recycling in shaping the climate of low-obliquity Earth-like terra-planets. By such a mechanism feeding water back from the extra-tropics to the tropics, the planet can assume two drastically different climate states differing by more than 35 K in global temperature. We describe the bifurcation between the two states occurring upon changes in surface albedo and argue that the bistability hints at a wider habitable zone for such planets. Hide

It has been shown that regional temperature and precipitation changes in future climate change scenarios often scale quasi-linearly with global mean temperature change (∆GMT). We show that an important consequence of these physical climate changes, namely changes in agricultural crop yields, can also be described in terms of ∆GMT to a large extent. This makes it possible to efficiently estimate future crop yield changes for different climate change scenarios without need for complex models. Hide

Artificial ocean alkalinization (AOA) is capable of reducing atmospheric carbon dioxide concentrations and surface warming while also addressing ocean acidification. We simulate the Earth system response to a fixed addition of AOA under low and high emissions. We explore the regional and global response to AOA. A key finding is that AOA is much more effective at reducing warming and ocean acidification under low emissions, despite lower carbon uptake. Hide

This study is the first risk-based assessment of changes in global drought at 1.5 and 2 °C warmer worlds using CMIP5 models. By keeping the warming at 1.5 °C above the preindustrial levels instead of 2 °C, the risks of drought and the affected total, urban and rural populations would decrease at global and regional scales. While challenging for both East Africa and South Asia, the benefits of limiting warming to below 1.5 °C in terms of global drought risk and impact reduction are significant. Hide

Assessing projected hydroclimatological changes is crucial, but associated with large uncertainties. We statistically assess here the response of precipitation and water availability to global temperature change, enabling us to estimate the significance of drying/wetting tendencies under anthropogenic climate change. We further show that opting for a 1.5 K warming target just slightly influences the mean response but could substantially reduce the risk of experiencing extreme changes. Hide

This paper presents a new equation for the dispersion of salinity in alluvial estuaries based on the maximum power concept. The new equation is physically based and replaces previous empirical equations. It is very useful for application in practice because in contrast to previous methods it no longer requires a calibration parameter, turning the method into a predictive method. The paper presents successful applications in more than 23 estuaries in different parts of the world. Hide

The United Nations Framework Convention on Climate Change invited the scientific community to explore the impacts of a world in which anthropogenic global warming is stabilized at only 1.5 °C above preindustrial average temperatures. We present a projection of future tropical cyclone statistics for both 1.5 and 2.0 °C stabilized warming scenarios using a high-resolution global climate model. We find more frequent and intense tropical cyclones, but a reduction in weaker storms. Hide

We present here a newly implemented water vapor tracer tool into the WRF meteorological model (WRF-WVT). A detailed validation shows high accuracy, with an error of much less than 1 % in moisture traceability. As an example application, we show that for the 2014 Great Lake-effect snowstorm, above 30 % of precipitation in the regions immediately downwind originated from lake evaporation, with contributions exceeding 50 % in the areas with highest snowfall accumulations. Hide

We present an analysis of three crops in West Africa and their response to short-term climate change in a world where temperatures are 1.5 °C above the preindustrial levels. We show that the number of crop failures for all crops is due to increase in the future climate. We further show the difference in yield change across several West African countries and show that the yields are not expected to increase fast enough to prevent food shortages. Hide

Ensuring sustainable food and water security is an urgent and complex challenge. As the world becomes increasingly globalised and interdependent, food and water management policies may have unintended consequences across regions, sectors and scales. Current decision-making tools do not capture these complexities and thus miss important dynamics. We present a modelling framework to capture regional and sectoral interdependence and cross-scale feedbacks within the global food system. Hide

This paper analyzes the origin of the moisture in two extremely important atmospheric river (and extreme precipitation) events. The distribution of the moisture with regard to the low-level jet is analyzed as well, and the classic association of the atmospheric river to the former is discussed. Hide

Local mean sea level often varies strongly from year to year (on the order of a few decimeters). This is mainly due to interannual variability in wind climate and atmospheric pressure. In this paper, regional differences in the sensitivity of mean sea level to atmospheric forcing are studied in an inter-tidal basin. Correcting for the atmospheric effects removes most of the interannual variability in mean sea level. Hide

The UN sustainable development goals for eradicating hunger are at high risk for failure in the Sahel. We show that the demand for food and feed biomass will begin to outstrip its supply in the 2040s if current trends continue. Though supply continues to increase it is outpaced by a greater increase in demand due to a combination of population growth and a shift to diets rich in animal proteins. This underscores the importance of policy interventions that would act to mitigate such developments. Hide

Nitrogen input in natural ecosystems usually has a positive effect on plant growth. However, too much N causes N leaching, which contributes to water pollution. Using a global model we estimated that N leaching from natural lands has increased by 73 % during the 20th century, mainly due to rising N deposition from the atmosphere caused by emissions from fossil fuels and agriculture. Climate change and increasing CO₂ concentration had positive and negative effects (respectively) on N leaching. Hide

Floods are the main natural disaster in Brazil, causing substantial economic damage and loss of life. Here we seek to better understand the flood-generating mechanisms in the flood-prone Paraná River basin, including large-scale patterns of the ocean and atmospheric circulation. This study provides new insights for understanding causes of floods in the region and around the world and is a step forward to improve flood risk management, statistical assessments, and short-term flood forecasts. Hide

We statistically analysed the mechanisms of the variability in decadal sea-level trends for the whole Baltic Sea basin over the last century. We used two different sea-level data sets and several climatic data sets. The results of this study showed that precipitation has a lagged effect on decadal sea-level trend variations from which the signature of atmospheric effect is removed. This detected underlying factor is not connected to oceanic forcing driven from the North Atlantic region. Hide

The snow cover fractions (SCFs) from the CESM 1.5°C and 2°C projects and CMIP5 are assessed. The spatiotemporal variations in the above products are grossly consistent with observations. The SFC change in RCP2.6 is comparable to that in 1.5°C, but lower than that in 2°C. The contribution of surface temperature change to SCF differs by season. The model physical parameterization plays a predominant role in snow simulations triggered by climate internal variability. Hide

The paper investigates variability in the gravity wave drag in the stratosphere in connection with climate phenomena like the El Niño–Southern Oscillation. This link represents a possible mechanism of tropospheric influence on the higher atmospheric layers, a mechanism of utmost importance that has not been studied in detail yet. The results illustrate that there are indeed significant changes in the gravity wave drag distribution and strength depending on the phase of the studied oscillations. Hide

Focusing on the usage of integrated models and in situ Earth observatory networks, three challenges are identified to advance understanding of ESD, in particular to strengthen links between biotic and abiotic, and above- and below-ground processes. We propose developing a model platform for interdisciplinary usage, to formalize current network infrastructure based on complementarities and operational synergies, and to extend the reanalysis concept to the ecosystem and critical zone. Hide

Computer simulations show that during an ice age a strong atmospheric CO₂ increase would have resulted in stronger carbon uptake of the continents than today. Causes are the larger potential of glacial vegetation to increase its photosynthetic efficiency under increasing CO₂ and the smaller amount of carbon in extratropical soils during an ice age that can be released under greenhouse warming. Hence, for different climates the Earth system is differently sensitive to carbon cycle perturbations. Hide