Large contribution of organics to condensational growth and formation of cloud condensation nuclei (CCN) in the remote marine boundary layer Atmospheric Chemistry and Physics DOI 10.5194/acp-20-12515-2020 27 November 2020 Condensational growth of Aitken-mode particles is a major source of cloud condensation nuclei in the remote marine boundary layer. It has been long thought that over remote oceans, condensation growth is dominated by sulfate that derives from ocean-emitted dimethyl sulfide. In this study, we present the first long-term observational evidence that, contrary to conventional thinking, organics play an even more important role than sulfate in particle growth over remote oceans throughout the year. Read more
Beaching patterns of plastic debris along the Indian Ocean rim Ocean Science DOI 10.5194/os-16-1317-2020 26 November 2020 A large percentage of global ocean plastic enters the Indian Ocean through rivers, but the fate of these plastics is generally unknown. In this paper, we use computer simulations to show that floating plastics beach and end up on coastlines throughout the Indian Ocean. Coastlines where a lot of plastic enters the ocean are heavily affected by beaching plastic, but plastics can also beach far from the source on remote islands and countries that contribute little plastic pollution of their own. Read more
Reviews and syntheses: The mechanisms underlying carbon storage in soil Biogeosciences DOI 10.5194/bg-17-5223-2020 25 November 2020 The 4 per 1000 initiative aims to restore carbon storage in soils to both mitigate climate change and contribute to food security. The French National Institute for Agricultural Research conducted a study to determine the carbon storage potential in French soils and associated costs. This paper is a part of that study. It reviews recent advances concerning the mechanisms that controls C stabilization in soils. Synthetic figures integrating new concepts should be of pedagogical interest. Read more
Global modeling of cloud water acidity, precipitation acidity, and acidinputs to ecosystems Atmospheric Chemistry and Physics DOI 10.5194/acp-20-12223-2020 24 November 2020 Cloud water pH affects atmospheric chemistry, and acid rain damages ecosystems. We use model simulations along with observations to present a global view of cloud water and precipitation pH. Sulfuric acid, nitric acid, and ammonia control the pH in the northern midlatitudes, but carboxylic acids and dust cations are important in the tropics and subtropics. The acid inputs to many nitrogen-saturated ecosystems are high enough to cause acidification, with ammonium as the main acidifying species. Read more
The Making of the New European Wind Atlas – Part 2: Production and evaluation Geoscientific Model Development DOI 10.5194/gmd-13-5079-2020 23 November 2020 This is the second of two papers that document the creation of the New European Wind Atlas (NEWA). The paper includes a detailed description of the technical and practical aspects that went into running the mesoscale simulations and the microscale downscaling for generating the climatology. A comprehensive evaluation of each component of the NEWA model chain is presented using observations from a large set of tall masts located all over Europe. Read more
A technical description of the Balloon Lidar Experiment (BOLIDE) Atmospheric Measurement Techniques DOI 10.5194/amt-13-5681-2020 19 November 2020 The Balloon Lidar Experiment was the first lidar dedicated to measurements in the mesosphere flown on a balloon. During a 6 d flight, it made high-resolution observations of polar mesospheric clouds which form at high latitudes during summer at ~ 83 km altitude and are the highest clouds in Earth’s atmosphere. We describe the instrument and assess its performance. We could detect fainter clouds with higher resolution than what is possible with ground-based instruments. Read more
Topographic controls on divide migration, stream capture, anddiversification in riverine life Earth Surface Dynamics DOI 10.5194/esurf-8-893-2020 18 November 2020 Organisms evolve in ever-changing environments under complex process interactions. We applied a new software modelling tool to assess how changes in river course impact the evolution of riverine species. Models illustrate the climatically and tectonically forced landscape changes that can drive riverine biodiversity, especially where topographic relief is low. This research demonstrates that river course changes can contribute to the high riverine biodiversity found in real-world lowland basins. Read more
Climate change as an incentive for future human migration Earth System Dynamics DOI 10.5194/esd-11-875-2020 17 November 2020 We examine the implications of future motivation for humans to migrate by analyzing today’s relationships between climatic factors and population density, with all other factors held constant. Such analyses are unlikely to make accurate predictions but can still be useful for informing discussions about the broad range of incentives that might influence migration decisions. Areas with the highest projected population growth rates tend to be the areas most adversely affected by climate change. Read more
Resolving multiple geological events using in situ Rb–Sr geochronology:implications for metallogenesis at Tropicana, Western Australia Geochronology DOI 10.5194/gchron-2-283-2020 17 November 2020 Using a relatively new dating technique, in situ Rb–Sr geochronology, we constrain the ages of two generations of mineral assemblages from the Tropicana Zone, Western Australia. The first, dated at ca. 2535 Ma, is associated with exhumation of an Archean craton margin and gold mineralization. The second, dated at ca. 1210 Ma, has not been previously documented in the Tropicana Zone. It is probably associated with Stage II of the Albany–Fraser Orogeny and additional gold mineralization. Read more
A feasibility study to use machine learning as an inversion algorithm for aerosol profile and property retrieval from multi-axis differentialabsorption spectroscopy measurements Atmospheric Measurement Techniques DOI 10.5194/amt-13-5537-2020 12 November 2020 This paper is about a feasibility study of applying a machine learning technique to derive aerosol properties from a single MAX-DOAS sky scan, which detects sky-scattered UV–visible photons at multiple elevation angles. Evaluation of retrieved aerosol properties shows good performance of the ML algorithm, suggesting several advantages of a ML-based inversion algorithm such as fast data inversion, simple implementation and the ability to extract information not available using other algorithms. Read more
Connecting flow–topography interactions, vorticity balance, baroclinicinstability and transport in the Southern Ocean: the case of an idealizedstorm track Ocean Science DOI 10.5194/os-16-1207-2020 12 November 2020 The dynamical balance of the Antarctic Circumpolar Current and its implications on the functioning of the world ocean are not fully understood and poorly represented in global circulation models. In this study, the sensitivities of an idealized Southern Ocean (SO) storm track are explored with a set of eddy-rich numerical simulations. We show that the classical partition between barotropic and baroclinic modes is sensitive to current–topography interactions in the mesoscale range of 10–100 km. Read more
Ionic aluminium concentrations exceed thresholds for aquatic health in Nova Scotian rivers, even during conditions of high dissolved organic carbon and low flow Hydrology and Earth System Sciences DOI 10.5194/hess-24-4763-2020 10 November 2020 Wild salmon numbers in Nova Scotia, Canada, have been plummeting in recent decades. In 2014, we launched an ionic aluminium monitoring program in Nova Scotia to see if this toxic element was a threat to salmon populations. We found that all 10 monitored rivers had ionic aluminium concentrations that exceeded the threshold for aquatic health. Our results demonstrate that elevated aluminium still threatens aquatic ecosystems and that delays in recovery from acid rain remains a critical issue. Read more
Factors controlling plankton community production, export flux, and particulate matter stoichiometry in the coastal upwelling system off Peru Biogeosciences DOI 10.5194/bg-17-4831-2020 10 November 2020 The eastern boundary upwelling system off Peru is among Earth’s most productive ocean ecosystems, but the factors that control its functioning are poorly constrained. Here we used mesocosms, moored ~ 6 km offshore Peru, to investigate how processes in plankton communities drive key biogeochemical processes. We show that nutrient and light co-limitation keep productivity and export at a remarkably constant level while stoichiometry changes strongly with shifts in plankton community structure. Read more
Hydrology and water resources management in ancient India Hydrology and Earth System Sciences DOI 10.5194/hess-24-4691-2020 5 November 2020 Like in all ancient civilisations, the need to manage water propelled the growth of hydrological science in ancient India also. In this paper, we provide some fascinating glimpses into the hydrological, hydraulic, and related engineering knowledge that existed in ancient India, as discussed in contemporary literature and recent explorations and findings. Many interesting dimensions of early scientific endeavours emerge as we investigate deeper into ancient texts, including Indian mythology. Read more
Impacts of future land use and land cover change on mid-21st-century surface ozone air quality: distinguishing between the biogeophysical and biogeochemical effects Atmospheric Chemistry and Physics DOI 10.5194/acp-20-11349-2020 5 November 2020 We investigate the effects of future land use and land cover change (LULCC) on surface ozone air quality worldwide and find that LULCC can significantly influence ozone in North America and Europe via modifying surface energy balance, boundary-layer meteorology, and regional circulation. The strength of such “biogeophysical effects” of LULCC is strongly dependent on forest type and generally greater than the “biogeochemical effects” via changing deposition and emission fluxes alone. Read more
Impact of horizontal resolution on global ocean–sea ice model simulationsbased on the experimental protocols of the Ocean Model IntercomparisonProject phase 2 (OMIP-2) Geoscientific Model Development DOI 10.5194/gmd-13-4595-2020 3 November 2020 This paper presents global comparisons of fundamental global climate variables from a suite of four pairs of matched low- and high-resolution ocean and sea ice simulations to assess the robustness of climate-relevant improvements in ocean simulations associated with moving from coarse (∼1°) to eddy-resolving (∼0.1°) horizontal resolutions. Despite significant improvements, greatly enhanced horizontal resolution does not deliver unambiguous bias reduction in all regions for all models. Read more
Absorption closure in highly aged biomass burning smoke Atmospheric Chemistry and Physics DOI 10.5194/acp-20-11201-2020 3 November 2020 Every year, huge plumes of smoke hundreds of miles wide travel over the south Atlantic Ocean from fires in central and southern Africa. These plumes absorb the sun’s energy and warm the climate. We used airborne optical instrumentation to determine how absorbing the smoke was as well as the relative importance of black and brown carbon. We also tested different ways of simulating these properties that could be used in a climate model. Read more
Increase in ocean acidity variability and extremes under increasing atmospheric CO2 Biogeosciences DOI 10.5194/bg-17-4633-2020 29 October 2020 Ensemble simulations of an Earth system model reveal that ocean acidity extremes have increased in the past few decades and are projected to increase further in terms of frequency, intensity, duration, and volume extent. The increase is not only caused by the long-term ocean acidification due to the uptake of anthropogenic CO 2 , but also due to changes in short-term variability. The increase in ocean acidity extremes may enhance the risk of detrimental impacts on marine organisms. Read more
Dominant process zones in a mixed fluvial–tidal delta are morphologically distinct Earth Surface Dynamics DOI 10.5194/esurf-8-809-2020 29 October 2020 We propose a machine learning approach for the classification and analysis of large delta systems. The approach uses remotely sensed data, channel network extraction, and the analysis of 10 metrics to identify clusters of islands with similar characteristics. The 12 clusters are grouped in six main classes related to morphological processes acting on the system. The approach allows us to identify spatial patterns in large river deltas to inform modeling and the collection of field observations. Read more
Timing of exotic, far-traveled boulder emplacement and paleo-outburstflooding in the central Himalayas Earth Surface Dynamics DOI 10.5194/esurf-8-769-2020 27 October 2020 Large boulders found in two Himalayan valleys show signs of long fluvial transport (>10 km). Paleo-discharges required to mobilize these boulders exceed typical monsoon discharges. Exposure dating shows that a cluster of these boulders was emplaced ca. 5 kyr ago. This period is coeval with a weakening of the Indian monsoon and glacier retreat in the area. We, therefore, suggest that glacier lake outburst floods are likely mechanisms that can explain these exceptional transport processes. Read more
An improved mechanistic model for ammonia volatilization in Earth system models: Flow of Agricultural Nitrogen version 2 (FANv2) Geoscientific Model Development DOI 10.5194/gmd-13-4459-2020 27 October 2020 Mostly emitted by the agricultural sector, ammonia has an important role in atmospheric chemistry. We developed a model to simulate how ammonia emissions respond to changes in temperature and soil moisture, and we evaluated agricultural ammonia emissions globally. The simulated emissions agree with earlier estimates over many regions, but the results highlight the variability of ammonia emissions and suggest that emissions in warm climates may be higher than previously thought. Read more
The Ekman spiral for piecewise-uniform viscosity Ocean Science DOI 10.5194/os-16-1089-2020 22 October 2020 Ekman’s (1905) solution for how wind affects ocean surface currents is revisited and extended analytically for a piecewise-constant profile of vertical diffusion. This allows a comprehensive understanding of how the surface current deflection angle relative to the wind direction varies with the profile of vertical diffusion. Read more
Impact of an educational program on earthquake awareness and preparedness in Nepal Geoscience Communication DOI 10.5194/gc-3-279-2020 22 October 2020 We study the impact of an educational seismology program on earthquake awareness and preparedness in Nepal. We see that educational activities implemented in schools are effective at raising awareness levels and in improving adaptive capacities and preparedness for future earthquakes. Knowledge also reached the broader community though social learning, leading to broadscale awareness. The result observed in this study is encouraging for the continuation and expansion of the program. Read more
ISMIP6 Antarctica: a multi-model ensemble of the Antarctic ice sheet evolution over the 21st century The Cryosphere DOI 10.5194/tc-14-3033-2020 20 October 2020 The Antarctic ice sheet has been losing mass over at least the past 3 decades in response to changes in atmospheric and oceanic conditions. This study presents an ensemble of model simulations of the Antarctic evolution over the 2015–2100 period based on various ice sheet models, climate forcings and emission scenarios. Results suggest that the West Antarctic ice sheet will continue losing a large amount of ice, while the East Antarctic ice sheet could experience increased snow accumulation. Read more
A protocol for calculating basal melt rates in the ISMIP6 Antarctic ice sheet projections The Cryosphere DOI 10.5194/tc-14-3111-2020 20 October 2020 To predict the future Antarctic contribution to sea level rise, we need to use ice sheet models. The Ice Sheet Model Intercomparison Project for AR6 (ISMIP6) builds an ensemble of ice sheet projections constrained by atmosphere and ocean projections from the 6th Coupled Model Intercomparison Project (CMIP6). In this work, we present and assess a method to derive ice shelf basal melting in ISMIP6 from the CMIP6 ocean outputs, and we give examples of projected melt rates. Read more
The making of the New European Wind Atlas – Part 1: Model sensitivity Geoscientific Model Development DOI 10.5194/gmd-13-5053-2020 16 October 2020 Wind energy resource assessment routinely uses numerical weather prediction model output. We describe the evaluation procedures used for picking the suitable blend of model setup and parameterizations for simulating European wind climatology with the WRF model. We assess the simulated winds against tall mast measurements using a suite of metrics, including the Earth Mover’s Distance, which diagnoses the performance of each ensemble member using the full wind speed and direction distribution. Read more
Review article: Hilbert problems for the climate sciences in the 21st century – 20 years later Nonlinear Processes in Geophysics DOI 10.5194/npg-27-429-2020 15 October 2020 The scientific questions posed by the climate sciences are central to socioeconomic concerns today. This paper revisits several crucial questions, starting with What can we predict beyond 1 week, for how long, and by what methods?, and ending with Can we achieve enlightened climate control of our planet by the end of the century? We review the progress in dealing with the nonlinearity and stochasticity of the Earth system and emphasize major strides in coupled climate–economy modeling. Read more
The future sea-level contribution of the Greenland ice sheet: a multi-model ensemble study of ISMIP6 The Cryosphere DOI 10.5194/tc-14-3071-2020 15 October 2020 In this paper we use a large ensemble of Greenland ice sheet models forced by six different global climate models to project ice sheet changes and sea-level rise contributions over the 21st century. The results for two different greenhouse gas concentration scenarios indicate that the Greenland ice sheet will continue to lose mass until 2100, with contributions to sea-level rise of 90 ± 50 mm and 32 ± 17 mm for the high (RCP8.5) and low (RCP2.6) scenario, respectively. Read more
In situ measurements of soil and plant water isotopes: a review of approaches, practical considerations and a vision for the future Hydrology and Earth System Sciences DOI 10.5194/hess-24-4413-2020 13 October 2020 Water isotopes are a scientific tool that can be used to identify sources of water and answer questions such as From which soil depths do plants take up water?, which are highly relevant under changing climatic conditions. In the past, the measurement of water isotopes required tremendous effort. In the last decade methods have advanced and can now be applied in the field. Herein, we review the current status of direct field measurements of water isotopes and discuss future applications. Read more
Storm tide amplification and habitat changes due to urbanization of a lagoonal estuary Natural Hazards and Earth System Sciences DOI 10.5194/nhess-20-2415-2020 13 October 2020 The geometry of estuaries is often altered through dredging to make room for ships and with extensive landfill over wetlands to enable development. Here, we use historical maps to help create computational models of seawater flow around and into a lagoonal bay of New York City for the 1880s and 2010s. Our results show that these past man-made changes cause higher coastal storm tides and that they result specifically from deeper depths, expanded inlet width, and landfill. Read more
A 6-year lidar survey reveals enhanced rockwall retreat and modified rockfall magnitudes/frequencies in deglaciating cirques Earth Surface Dynamics DOI 10.5194/esurf-8-753-2020 8 October 2020 Rockfall size and frequency in two deglaciating cirques in the Central Alps, Austria, is analysed based on 6-year rockwall monitoring with terrestrial lidar (2011–2017). The erosion rates derived from this dataset are very high due to a frequent occurrence of large rockfalls in freshly deglaciated areas. The results obtained are important for rockfall hazard assessments, as, in rockwalls affected by glacier retreat, historical rockfall patterns are not good predictors of future events. Read more
Current glacier recession causes significant rockfall increase: the immediate paraglacial response of deglaciating cirque walls Earth Surface Dynamics DOI 10.5194/esurf-8-729-2020 8 October 2020 Climate warming is causing significant ice surface lowering even in the uppermost parts of alpine glaciers. Using terrestrial lidar, we quantify rockfall in freshly exposed cirque walls. During 6-year monitoring (2011–2017), an extensive dataset was established and over 600 rockfall events identified. Drastically increased rockfall activity following ice retreat can clearly be observed as 60 % of the rockfall volume detached from less than 10 m above the glacier surface. Read more
A Bayesian framework for emergent constraints: case studies of climate sensitivity with PMIP Climate of the Past DOI 10.5194/cp-16-1715-2020 6 October 2020 Interest in past climates as sources of information for the climate system has grown in recent years. In particular, studies of the warm mid-Pliocene and cold Last Glacial Maximum showed relationships between the tropical surface temperature of the Earth and its sensitivity to an abrupt doubling of atmospheric CO 2 . In this study, we develop a new and promising statistical method and obtain similar results as previously observed, wherein the sensitivity does not seem to exceed extreme values. Read more
Vertical profiles of light absorption and scattering associated with black carbon particle fractions in the springtime Arctic above 79∘ N Atmospheric Chemistry and Physics DOI 10.5194/acp-20-10545-2020 6 October 2020 Black carbon is a factor in the warming of the Arctic atmosphere due to its ability to absorb light, but the uncertainty is high and few observations have been made in the high Arctic above 80° N. We combine airborne and ground-based observations in the springtime Arctic, at and above 80° N, with simulations from a global model to show that light absorption by black carbon may be much larger than modelled. However, the uncertainty remains high. Read more
Comparing secondary organic aerosol (SOA) volatility distributions derived from isothermal SOA particle evaporation data and FIGAERO–CIMS measurements Atmospheric Chemistry and Physics DOI 10.5194/acp-20-10441-2020 1 October 2020 We compared the volatility distributions of secondary organic aerosol (SOA) constituents estimated from isothermal evaporation experiments from either particle size change data, by process modelling and global optimization, or from mass spectrometer data with positive matrix factorization analysis. Our results show that, despite the two very different estimation methods, the volatility distributions are comparable if uncertainties are taken into account. Read more
Predicting the morphology of ice particles in deep convection using the super-droplet method:development and evaluation of SCALE-SDM 0.2.5-2.2.0, -2.2.1, and -2.2.2 Geoscientific Model Development DOI 10.5194/gmd-13-4107-2020 1 October 2020 Using the super-droplet method, we constructed a detailed numerical model of mixed-phase clouds based on kinetic description and subsequently demonstrated that a large-eddy simulation of a cumulonimbus which predicts ice particle morphology without assuming ice categories or mass–dimension relationships is possible. Our results strongly support the particle-based modeling methodology’s efficacy for simulating mixed-phase clouds. Read more
A compact QCL spectrometer for mobile, high-precision methane sensing aboard drones Atmospheric Measurement Techniques DOI 10.5194/amt-13-4715-2020 29 September 2020 We describe a lightweight (2 kg) mid-IR laser spectrometer for airborne, in situ atmospheric methane (CH 4 ) measurements. The instrument, based on an open-path circular multipass cell, provides fast response (1 Hz) and sub-parts-per-billion precision. It can easily be mounted on a drone, giving access to highly resolved 4D (spatial and temporal) data. The performance was assessed during field deployments involving artificial CH 4 releases and vertical concentration gradients in the PBL. Read more
Using constructed soils for green infrastructure – challenges andlimitations SOIL DOI 10.5194/soil-6-413-2020 29 September 2020 The goal of this study was to discuss current methods to create soils adapted for various green infrastructure (GI) designs. Investigating these new soils for several design categories of GI will provide technical information for management and design agencies. Moreover, these studies can serve as pioneer experiments to prevent recurring errors and, thus, provide improved plant growth practices. Results show that these constructed soils have a high potential to provide multiple soil functions. Read more
HyLands 1.0: a hybrid landscape evolution model to simulate the impact of landslides and landslide-derived sediment on landscape evolution Geoscientific Model Development DOI 10.5194/gmd-13-3863-2020 24 September 2020 Landslides shape the Earth’s surface and are a dominant source of terrestrial sediment. Rivers, then, act as conveyor belts evacuating landslide-produced sediment. Understanding the interaction among rivers and landslides is important to predict the Earth’s surface response to past and future environmental changes and for mitigating natural hazards. We develop HyLands, a new numerical model that provides a toolbox to explore how landslides and rivers interact over several timescales. Read more
Quantifying burning efficiency in megacities using the NO2/CO ratio fromthe Tropospheric Monitoring Instrument (TROPOMI) Atmospheric Chemistry and Physics DOI 10.5194/acp-20-10295-2020 24 September 2020 Rapid urbanization has increased the consumption of fossil fuel, contributing the degradation of urban air quality. Burning efficiency is a major factor determining the impact of fuel burning on the environment. We quantify the burning efficiency of fossil fuel use over six megacities using satellite remote sensing data. City governance can use these results to understand air pollution scenarios and to formulate effective air pollution control strategies. Read more
Fire Weather Index: the skill provided by the European Centre for Medium-Range Weather Forecasts ensemble prediction system Natural Hazards and Earth System Sciences DOI 10.5194/nhess-20-2365-2020 22 September 2020 Forecasting of daily fire weather indices driven by the ECMWF ensemble prediction system is shown to have a good skill up to 10 d ahead in predicting flammable conditions in most regions of the world. The availability of these forecasts through the Copernicus Emergency Management Service can extend early warnings by up to 1–2 weeks, allowing for greater proactive coordination of resource-sharing and mobilization within and across countries. Read more
The value of remote marine aerosol measurements for constraining radiative forcing uncertainty Atmospheric Chemistry and Physics DOI 10.5194/acp-20-10063-2020 22 September 2020 The amount of energy reflected back into space because of man-made particles is highly uncertain. Processes related to naturally occurring particles cause most of the uncertainty, but these processes are poorly constrained by present-day measurements. We show that measurements over the Southern Ocean, far from pollution sources, efficiently reduce climate model uncertainties. Our results pave the way to designing experiments and measurement campaigns that reduce this uncertainty even further. Read more
Lessons from a high-CO2 world: an ocean view from ∼3 million years ago Climate of the Past DOI 10.5194/cp-16-1599-2020 17 September 2020 We examine the sea-surface temperature response to an interval of climate ~ 3.2 million years ago, when CO 2 concentrations were similar to today and the near future. Our geological data and climate models show that global mean sea-surface temperatures were 2.3 to 3.2 ºC warmer than pre-industrial climate, that the mid-latitudes and high latitudes warmed more than the tropics, and that the warming was particularly enhanced in the North Atlantic Ocean. Read more
A semi-empirical potential energy surface and line list for H216O extending into the near-ultraviolet Atmospheric Chemistry and Physics DOI 10.5194/acp-20-10015-2020 17 September 2020 Water vapour has a complex spectrum and absorbs from the microwave to the near-UV where it dissociates. There is limited knowledge of the absorption features in the near-UV, and there is a large disagreement for the available models and experiments. We created a new ab initio model that is in good agreement with observation at 363 nm. At lower wavelengths, our calculations suggest that the latest experiments overestimate absorption. This has implications for trace gas retrievals in the near-UV. Read more
Revisiting global satellite observations of stratospheric cirrus clouds Atmospheric Chemistry and Physics DOI 10.5194/acp-20-9939-2020 15 September 2020 Cirrus clouds appearing in the upper troposphere and lower stratosphere have important impacts on the radiation budget and climate change. We revisited global stratospheric cirrus clouds with CALIPSO and for the first time with MIPAS satellite observations. Stratospheric cirrus clouds related to deep convection are frequently detected in the tropics. At middle latitudes, MIPAS detects more than twice as many stratospheric cirrus clouds due to higher detection sensitivity. Read more
Groundwater storage dynamics in the world’s large aquifer systems fromGRACE: uncertainty and role of extreme precipitation Earth System Dynamics DOI 10.5194/esd-11-755-2020 15 September 2020 Recent assessments of the sustainability of global groundwater resources using the Gravity Recovery and Climate Experiment (GRACE) satellites assume that the underlying trends are linear. Here, we assess recent changes in groundwater storage (ΔGWS) in the world’s large aquifer systems using an ensemble of GRACE datasets and show that trends are mostly non-linear. Non-linearity in ΔGWS derives, in part, from the episodic nature of groundwater replenishment associated with extreme precipitation. Read more
Inconsistencies between chemistry–climate models and observed lower stratospheric ozone trends since 1998 Atmospheric Chemistry and Physics DOI 10.5194/acp-20-9737-2020 10 September 2020 Recent lower stratospheric ozone decreases remain unexplained. We show that chemistry–climate models are not generally able to reproduce mid-latitude ozone and water vapour changes. Our analysis of observations provides evidence that climate change may be responsible for the ozone trends. While model projections suggest that extratropical ozone should recover by 2100, our study raises questions about their efficacy in simulating lower stratospheric changes in this region. Read more
Climatic information archived in ice cores: impact of intermittency and diffusion on the recorded isotopic signal in Antarctica Climate of the Past DOI 10.5194/cp-16-1581-2020 10 September 2020 The isotopic composition in ice cores from Antarctica is usually interpreted as a temperature proxy. Using a forward model, we show how different the signal in ice cores and the actual climatic signal are. Precipitation intermittency and diffusion do indeed affect the archived signal, leading to the reshuffling of the signal which limits the ability to reconstruct high-resolution climatic variations with ice cores. Read more
Bipolar volcanic synchronization of abrupt climate change in Greenland and Antarctic ice cores during the last glacial period Climate of the Past DOI 10.5194/cp-16-1565-2020 8 September 2020 We identify signatures of large bipolar volcanic eruptions in Greenland and Antarctic ice cores during the last glacial period, which allows for a precise temporal alignment of the ice cores. Thereby the exact timing of unexplained, abrupt climatic changes occurring during the last glacial period can be determined in a global context. The study thus provides a step towards a full understanding of elements of the climate system that may also play an important role in the future. Read more
ESD Ideas: Global climate response scenarios for IPCC assessments Earth System Dynamics DOI 10.5194/esd-11-751-2020 8 September 2020 Policy making on climate change routinely employs socioeconomic scenarios to sample the uncertainty in future forcing of the climate system, but the Intergovernmental Panel on Climate Change has not employed similar discrete scenarios to sample the uncertainty in the global climate response. Here, we argue that to enable risk assessments and development of robust policies this gap should be addressed, and we propose a simple methodology. Read more