Physical characteristics of frozen hydrometeors inferred with parameter estimation Atmospheric Measurement Techniques DOI 10.5194/amt-14-5369-2021 17 September 2021 Satellite observations sensitive to cloud and precipitation help improve the quality of weather forecasts. However, they are sensitive to things that models do not forecast, such as the shapes and sizes of snow and ice particles. These details can be estimated from the observations themselves and then incorporated in the satellite simulators used in weather forecasting. This approach, known as parameter estimation, will be increasingly useful to build models of poorly known physical processes. Read more
Influence of the representation of convection on the mid-Holocene West African Monsoon Climate of the Past DOI 10.5194/cp-17-1665-2021 15 September 2021 This paper investigates the impact of explicitly resolving convection on the mid-Holocene West African Monsoon rain belt by employing the ICON climate model in high resolution. While the spatial distribution and intensity of the precipitation are improved by this technique, the monsoon extents further north and the mean summer rainfall is higher in the simulation with parameterized convection. Read more
Iodide CIMS and m∕z 62: the detection of HNO3 as NO3− in the presence of PAN, peroxyacetic acid and ozone Atmospheric Measurement Techniques DOI 10.5194/amt-14-5319-2021 13 September 2021 We demonstrate in laboratory experiments that the formation of IOx anions (formed in reactions of I− with O3) or acetate anions (formed e.g. by the reaction of I− with peracetic acid) results in unexpected sensitivity of an iodide chemical ionisation mass spectrometer (I-CIMS) to HNO3 at a mass-to-charge ratio of 62. This helps explain observations of apparent high daytime levels of N2O5. Airborne measurements using I-CIMS confirm these conclusions. Read more
Recent degradation of interior Alaska permafrost mapped with ground surveys, geophysics, deep drilling, and repeat airborne lidar The Cryosphere DOI 10.5194/tc-15-3555-2021 10 September 2021 Permafrost is actively degrading across high latitudes due to climate warming. We combined thousands of end-of-summer active layer measurements, permafrost temperatures, geophysical surveys, deep borehole drilling, and repeat airborne lidar to quantify permafrost warming and thawing at sites across central Alaska. We calculate the mass of permafrost soil carbon potentially exposed to thaw over the past 7 years (0.44 Pg) is similar to the yearly carbon dioxide emissions of Australia. Read more
Spatial and temporal subsidence characteristics in Wuhan (China), during 2015–2019, inferred from Sentinel-1 synthetic aperture radar (SAR) interferometry Natural Hazards and Earth System Sciences DOI 10.5194/nhess-21-2285-2021 8 September 2021 We mapped the subsidence of Wuhan using Sentinel-1 synthetic aperture radar (SAR) images acquired during 2015–2019. Overall subsidence coincides with the distribution of engineered geological regions with soft soils, while the subsidence centers shifted with urban construction activities. Correlation between karst subsidence and concentrated rainfall was identified in Qingling–Jiangdi. Results indicate that interferometric SAR can be employed to routinely monitor and identify geohazards. Read more
Better representation of dust can improve climate models with too weak an African monsoon Atmospheric Chemistry and Physics DOI 10.5194/acp-21-11423-2021 6 September 2021 Earth system models have persistent biases that impinge on our ability to make robust future regional predictions of precipitation. For the last 15 years, there has been little improvement in these biases. This work presents an accurate representation of dust absorption based upon observed dust mineralogical composition and size distribution. The striking result is that this more accurate representation improves tropical precipitations for climate models with too weak an African monsoon. Read more
Characterization of dark current signal measurements of the ACCDs used on board the Aeolus satellite Atmospheric Measurement Techniques DOI 10.5194/amt-14-5153-2021 3 September 2021 This paper reports on dark current signal anomalies of the detectors used on board the ESA’s Earth Explorer satellite Aeolus during the first 1.5 years in orbit. After introducing sophisticated algorithms to classify dark current anomalies according to their characteristics, the impact of the different kinds of anomalies on wind measurements is discussed. In addition, mitigation approaches for the wind retrieval are presented and potential root causes are discussed. Read more
Drought effects on leaf fall, leaf flushing and stem growth in the Amazon forest: reconciling remote sensing data and field observations Biogeosciences DOI 10.5194/bg-18-4445-2021 1 September 2021 Satellite images show that the Amazon forest has greened up during past droughts. Measurements of tree stem growth and leaf litterfall upscaled using machine-learning algorithms show that leaf flushing at the onset of a drought results in canopy rejuvenation and green-up during drought while simultaneously trees excessively shed older leaves and tree stem growth declines. Canopy green-up during drought therefore does not necessarily point to enhanced tree growth and improved forest health. Read more
Steepening of magnetosonic waves in the inner coma of comet 67P/Churyumov–Gerasimenko Annales Geophysicae DOI 10.5194/angeo-39-721-2021 30 August 2021 Plasma waves are an integral part of cometary physics, as they facilitate the transfer of energy and momentum. From intermediate to strong activity, nonlinear asymmetric plasma and magnetic field enhancements dominate the inner coma of 67P/CG. We present a statistical survey of these structures from December 2014 to June 2016, facilitated by Rosetta’s unprecedented long mission duration. Using a 1D MHD model, we show they can be described as a combination of nonlinear and dissipative effects. Read more
Controls on the rates and products of particle attrition by bed-load collisions Earth Surface Dynamics DOI 10.5194/esurf-9-755-2021 27 August 2021 The authors of this paper conducted experiments to investigate the mechanics of sediment attrition due to collisions with the channel bed during downstream transport. During this process, the grains become rounder and smaller, changing the overall distribution of sediment in the river. In this work the authors examine how material properties play a role in the breakdown of sediment due to energetic collisions and the fine particles that are produced when chipped off of larger grains. Read more
fv3gfs-wrapper: a Python wrapper of the FV3GFS atmospheric model Geoscientific Model Development DOI 10.5194/gmd-14-4401-2021 25 August 2021 FV3GFS is a weather and climate model written in Fortran. It uses Fortran so that it can run fast, but this makes it hard to add features if you do not (or even if you do) know Fortran. We have written a Python interface to FV3GFS that lets you import the Fortran model as a Python package. We show examples of how this is used to write “model” scripts, which reproduce or build on what the Fortran model can do. You could do this same wrapping for any compiled model, not just FV3GFS. Read more
Invited perspectives: The ECMWF strategy 2021–2030 challenges in the area of natural hazards Natural Hazards and Earth System Sciences DOI 10.5194/nhess-21-2163-2021 23 August 2021 The European Centre for Medium-Range Weather Forecasts mission is to deliver high-quality global medium‐range (3–15 d ahead of time) weather forecasts and monitoring of the Earth system. We have published a new strategy, and in this paper we discuss what this means for forecasting and monitoring natural hazards. Read more
Nonstationary weather and water extremes: a review of methods for their detection, attribution, and management Hydrology and Earth System Sciences DOI 10.5194/hess-25-3897-2021 20 August 2021 Weather and water extremes have devastating effects each year. One of the principal challenges for society is understanding how extremes are likely to evolve under the influence of changes in climate, land cover, and other human impacts. This paper provides a review of the methods and challenges associated with the detection, attribution, management, and projection of nonstationary weather and water extremes. Read more
Thaw-driven mass wasting couples slopes with downstream systems, and effects propagate through Arctic drainage networks The Cryosphere DOI 10.5194/tc-15-3059-2021 18 August 2021 Climate-driven landslides are transforming glacially conditioned permafrost terrain, coupling slopes with aquatic systems, and triggering a cascade of downstream effects. Nonlinear intensification of thawing slopes is primarily affecting headwater systems where slope sediment yields overwhelm stream transport capacity. The propagation of effects across watershed scales indicates that western Arctic Canada will be an interconnected hotspot of thaw-driven change through the coming millennia. Read more
Additional carbon inputs to reach a 4 per 1000 objective in Europe: feasibility and projected impacts of climate change based on Century simulations of long-term arable experiments Biogeosciences DOI 10.5194/bg-18-3981-2021 16 August 2021 Increasing soil organic carbon (SOC) stocks is beneficial for climate change mitigation and food security. One way to enhance SOC stocks is to increase carbon input to the soil. We estimate the amount of carbon input required to reach a 4 % annual increase in SOC stocks in 14 long-term agricultural experiments around Europe. We found that annual carbon input should increase by 43 % under current temperature conditions, by 54 % for a 1 °C warming scenario and by 120 % for a 5 °C warming scenario. Read more
Tropical deoxygenation sites revisited to investigate oxygen and nutrient trends Ocean Science DOI 10.5194/os-17-833-2021 13 August 2021 Six tropical areas in the Pacific, Atlantic and Indian oceans were investigated for trends for the years since 1950 for temperature, salinity, oxygen and nutrients at 50 to 300 m and 300 to 700 m depth. Generally, temperature increases, oxygen decreases and nutrients often increase. Overlain variability on the trends seem to be related to climate modes. Different trends indicate that oxygen and nutrient trends cannot by completely explained by local warming. Read more
Disparities in particulate matter (PM10) origins and oxidative potential at a city scale (Grenoble, France) – Part 2. Atmospheric Chemistry and Physics DOI 10.5194/acp-21-9719-2021 11 August 2021 With an enhanced source apportionment obtained in a companion paper, this paper acquires more understanding of the spatiotemporal associations of the sources of PM to oxidative potential (OP), an emerging health-based metric. Multilayer perceptron neural network analysis was used to apportion OP from PM sources. Results showed that such a methodology is as robust as the linear classical inversion and permits an improvement in the OP prediction when local features or non-linear effects occur. Read more
Continental-scale controls on soil organic carbon across sub-Saharan Africa SOIL DOI 10.5194/soil-7-305-2021 9 August 2021 We investigated various soil and climate properties that influence soil organic carbon (SOC) concentrations in sub-Saharan Africa. Our findings indicate that climate and geochemistry are equally important for explaining SOC variations. The key SOC-controlling factors are broadly similar to those for temperate regions, despite differences in soil development history between the two regions. Read more
Investigations on the anthropogenic reversal of the natural ozone gradient between northern and southern midlatitudes Atmospheric Chemistry and Physics DOI 10.5194/acp-21-9669-2021 6 August 2021 The few ozone measurements made before the 1980s indicate that industrial development increased ozone concentrations by a factor of ~ 2 at northern midlatitudes, which are now larger than at southern midlatitudes. This difference was much smaller, and likely reversed, in the pre-industrial atmosphere. Earth system models find similar increases, but not higher pre-industrial ozone in the south. This disagreement may indicate that modeled natural ozone sources and/or deposition loss are inadequate. Read more
Evaluation of ocean dimethylsulfide concentration and emission in CMIP6 models Biogeosciences DOI 10.5194/bg-18-3823-2021 4 August 2021 In this study we analyse surface ocean dimethylsulfide (DMS) concentration and flux to the atmosphere from four CMIP6 Earth system models over the historical and ssp585 simulations. Our analysis of contemporary (1980–2009) climatologies shows that models better reproduce observations in mid to high latitudes. The models disagree on the sign of the trend of the global DMS flux from 1980 onwards. The models agree on a positive trend of DMS over polar latitudes following sea-ice retreat dynamics. Read more
Committed and projected future changes in global peatlands – continued transient model simulations since the Last Glacial Maximum Biogeosciences DOI 10.5194/bg-18-3657-2021 2 August 2021 We present long-term projections of global peatland area and carbon with a continuous transient history since the Last Glacial Maximum. Our novel results show that large parts of today’s northern peatlands are at risk from past and future climate change, with larger emissions clearly connected to larger risks. The study includes comparisons between different emission and land-use scenarios, driver attribution through factorial simulations, and assessments of uncertainty from climate forcing. Read more
Rarefied particle motions on hillslopes – Part 1: Theory Earth Surface Dynamics DOI 10.5194/esurf-9-539-2021 30 July 2021 Sediment particles skitter down steep hillslopes on Earth and Mars. Particles gain speed in going downhill but are slowed down and sometimes stop due to collisions with the rough surface. The likelihood of stopping depends on the energetics of speeding up (heating) versus slowing down (cooling). Statistical physics predicts that particle travel distances are described by a generalized Pareto distribution whose form varies with the Kirkby number – the ratio of heating to cooling. Read more
SoilGrids 2.0: producing soil information for the globe with quantified spatial uncertainty SOIL DOI 10.5194/soil-7-217-2021 28 July 2021 This paper focuses on the production of global maps of soil properties with quantified spatial uncertainty, as implemented in the SoilGrids version 2.0 product using DSM practices and adapting them for global digital soil mapping with legacy data. The quantitative evaluation showed metrics in line with previous studies. The qualitative evaluation showed that coarse-scale patterns are well reproduced. The spatial uncertainty at global scale highlighted the need for more soil observations. Read more
Mapping the aerodynamic roughness of the Greenland Ice Sheet surface using ICESat-2: evaluation over the K-transect The Cryosphere DOI 10.5194/tc-15-2601-2021 26 July 2021 We developed a method to estimate the aerodynamic properties of the Greenland Ice Sheet surface using either UAV or ICESat-2 elevation data. We show that this new method is able to reproduce the important spatiotemporal variability in surface aerodynamic roughness, measured by the field observations. The new maps of surface roughness can be used in atmospheric models to improve simulations of surface turbulent heat fluxes and therefore surface energy and mass balance over rough ice worldwide. Read more
A discontinuous Galerkin finite-element model for fast channelized lava flows v1.0 Geoscientific Model Development DOI 10.5194/gmd-14-3553-2021 23 July 2021 Lava flows present a natural hazard to communities around volcanoes and are usually slow-moving (< 1-5 cm/s). Lava flows during the 2018 eruption of Kilauea volcano, Hawai’i, however, reached speeds as high as 11 m/s. To investigate these dynamics we develop a new lava flow computer model that incorporates a nonlinear expression for the fluid viscosity. Model results indicate that the lava flows at Site 8 of the eruption displayed shear thickening behavior due to the flow’s high bubble content. Read more
Fracking bad language – hydraulic fracturing and earthquake risks Geoscience Communication DOI 10.5194/gc-4-303-2021 21 July 2021 The potential for hydraulic fracturing (fracking) to induce seismicity is a topic of widespread interest. We find that terms used to describe induced seismicity are poorly defined and ambiguous and do not translate into everyday language. Such bad language has led to challenges in understanding, perceiving, and communicating risks around seismicity and fracking. Our findings and recommendations are relevant to other geoenergy topics that are potentially associated with induced seismicity. Read more
Microbial and geo-archaeological records reveal the growth rate, origin and composition of desert rock surface communities Biogeosciences DOI 10.5194/bg-18-3331-2021 19 July 2021 Biological rock crusts (BRCs) are common microbial-based assemblages covering rocks in drylands. BRCs play a crucial role in arid environments because of the limited activity of plants and soil. Nevertheless, BRC development rates have never been dated. Here we integrated archaeological, microbiological and geological methods to provide a first estimation of the growth rate of BRCs under natural conditions. This can serve as an affordable dating tool in archaeological sites in arid regions. Read more
Faster decline and higher variability in the sea ice thickness of the marginal Arctic seas when accounting for dynamic snow cover The Cryosphere DOI 10.5194/tc-15-2429-2021 16 July 2021 We re-estimate pan-Arctic sea ice thickness (SIT) values by combining data from the Envisat and CryoSat-2 missions with data from a new, reanalysis-driven snow model. Because a decreasing amount of ice is being hidden below the waterline by the weight of overlying snow, we argue that SIT may be declining faster than previously calculated in some regions. Because the snow product varies from year to year, our new SIT calculations also display much more year-to-year variability. Read more
Oxygen isotope exchange between water and carbon dioxide in soils is controlled by pH, nitrate and microbial biomass through links to carbonic anhydrase activity SOIL DOI 10.5194/soil-7-145-2021 14 July 2021 Understanding how the rate of oxygen isotope exchange between water and CO2 varies in soils is key for using the oxygen isotope composition of atmospheric CO2 as a tracer of biosphere CO2 fluxes at large scales. Across 44 diverse soils the rate of this exchange responded to pH, nitrate and microbial biomass, which are hypothesised to alter activity of the enzyme carbonic anhydrase in soils. Using these three soil traits, it is now possible to predict how this isotopic exchange varies spatially. Read more
Interactions between deforestation, landscape rejuvenation, and shallow landslides in the North Tanganyika–Kivu rift region, Africa Earth Surface Dynamics DOI 10.5194/esurf-9-445-2021 12 July 2021 We investigated how shallow landslide occurrence is impacted by deforestation and rifting in the North Tanganyika–Kivu rift region (Africa). We developed a new approach to calculate landslide erosion rates based on an inventory compiled in biased © Google Earth imagery. We find that deforestation increases landslide erosion by a factor of 2–8 and for a period of roughly 15 years. However, the exact impact of deforestation depends on the geomorphic context of the landscape (rejuvenated/relict). Read more
FaIRv2.0.0: a generalized impulse response model for climate uncertainty and future scenario exploration Geoscientific Model Development DOI 10.5194/gmd-14-3007-2021 9 July 2021 This paper presents an update of the FaIR simple climate model, which can estimate the impact of anthropogenic greenhouse gas and aerosol emissions on the global climate. This update aims to significantly increase the structural simplicity of the model, making it more understandable and transparent. This simplicity allows it to be implemented in a wide range of environments, including Excel. We suggest that it could be used widely in academia, corporate research, and education. Read more
VAHCOLI, a new concept for lidars: technical setup, science applications, and first measurements Atmospheric Measurement Techniques DOI 10.5194/amt-14-3815-2021 7 July 2021 We present a new concept for a cluster of lidars that allows us to measure time-resolved profiles of temperatures, winds, and aerosols in the entire middle atmosphere for the first time, also covering regional horizontal scales (“four-dimensional coverage”). Measurements are performed during day and night. The essential component is a newly developed laser with unprecedented performance. We present the first measurements. New observational capabilities in atmospheric physics are established. Read more
Comment on “Exceptionally high heat flux needed to sustain the Northeast Greenland Ice Stream” by Smith-Johnsen et al. (2020) The Cryosphere DOI 10.5194/tc-15-2251-2021 5 July 2021 The modelling of Smith-Johnson et al. (The Cryosphere, 14, 841–854, 2020) suggests that a very large heat flux of more than 10 times the usual geothermal heat flux is required to have initiated or to control the huge Northeast Greenland Ice Stream. Our comparison with known hotspots, such as Iceland and Yellowstone, shows that such an exceptional heat flux would be unique in the world and is incompatible with known geological processes that can raise the heat flux. Read more
Deoxygenation dynamics on the western Nile deep-sea fan during sapropel S1 from seasonal to millennial timescales Climate of the Past DOI 10.5194/cp-17-1025-2021 2 July 2021 The Mediterranean Sea turned repeatedly into an oxygen-deprived basin during the geological past, as evidenced by distinct sediment layers called sapropels. We use here records of the last sapropel S1 retrieved in front of the Nile River to explore the relationships between riverine input and seawater oxygenation. We decipher the seasonal cycle of fluvial input and seawater chemistry as well as the decisive influence of primary productivity on deoxygenation at millennial timescales. Read more
Invited perspectives: Landslide populations – can they be predicted? Natural Hazards and Earth System Sciences DOI 10.5194/nhess-21-1467-2021 1 July 2021 This is a perspective based on personal experience on whether a large number of landslides caused by a single trigger (e.g. an earthquake, an intense rainfall, a rapid snowmelt event) or by multiple triggers in a period can be predicted, in space and time, considering the consequences of slope failures. Read more
Smoke-charged vortices in the stratosphere generated by wildfires and their behaviour in both hemispheres: comparing Australia 2020 to Canada 2017 Atmospheric Chemistry and Physics DOI 10.5194/acp-21-7113-2021 30 June 2021 Following the 2020 Australian fires, it was recently discovered that stratospheric wildfire smoke plumes self-organize as anticyclonic vortices that persist for months and rise by 10 km due to the radiative heating from the absorbing smoke. In this study, we show that smoke-charged vortices previously occurred in the aftermath of the 2017 Canadian fires. We use meteorological analysis to characterize this new object in geophysical fluid dynamics, which likely impacts radiation and climate. Read more
First assessment of the earth heat inventory within CMIP5 historical simulations Earth System Dynamics DOI 10.5194/esd-12-581-2021 29 June 2021 The current radiative imbalance at the top of the atmosphere is increasing the heat stored in the oceans, atmosphere, continental subsurface and cryosphere, with consequences for societies and ecosystems (e.g. sea level rise). We performed the first assessment of the ability of global climate models to represent such heat storage in the climate subsystems. Models are able to reproduce the observed atmosphere heat content, with biases in the simulation of heat content in the rest of components. Read more
Captive Aerosol Growth and Evolution (CAGE) chamber system to investigate particle growth due to secondary aerosol formation Atmospheric Measurement Techniques DOI 10.5194/amt-14-3351-2021 28 June 2021 The newly developed portable 1 m3 CAGE chamber systems were characterized using data acquired during a 2-month field study in 2016 in a forested area north of Houston, TX, USA. Concentrations of several oxidant and organic compounds measured in the chamber were found to closely agree with those calculated with a zero-dimensional model. By tracking the modes of injected monodisperse particles, a pattern change was observed for hourly averaged growth rates between late summer and early fall. Read more
Assimilation of DAWN Doppler wind lidar data during the 2017 Convective Processes Experiment (CPEX): impact on precipitation and flow structure Atmospheric Measurement Techniques DOI 10.5194/amt-14-3333-2021 25 June 2021 The assimilation of airborne-based three-dimensional winds into a mesoscale weather forecast model resulted in better agreement with airborne radar-derived precipitation 3-D structure at later model time steps. More importantly, there was also a discernible impact on the resultant wind and moisture structure, in accord with independent analysis of the wind structure and external satellite observations. Read more
Glacier detachments and rock-ice avalanches in the Petra Pervogo range, Tajikistan (1973–2019) Natural Hazards and Earth System Sciences DOI 10.5194/nhess-21-1409-2021 24 June 2021 A cluster of 13 large mass flow events including five detachments of entire valley glaciers was observed in the Petra Pervogo range, Tajikistan, in 1973–2019. The local clustering provides additional understanding of the influence of temperature, seismic activity, and geology. Most events occurred in summer of years with mean annual air temperatures higher than the past 46-year trend. The glaciers rest on weak bedrock and are rather short, making them sensitive to friction loss due to meltwater. Read more
Regional variation in the effectiveness of methane-based and land-based climate mitigation options Earth System Dynamics DOI 10.5194/esd-12-513-2021 23 June 2021 We model greenhouse gas emission scenarios consistent with limiting global warming to either 1.5 or 2 °C above pre-industrial levels. We quantify the effectiveness of methane emission control and land-based mitigation options regionally. Our results highlight the importance of reducing methane emissions for realistic emission pathways that meet the global warming targets. For land-based mitigation, growing bioenergy crops on existing agricultural land is preferable to replacing forests. Read more
Atmospheric extremes caused high oceanward sea surface slope triggering the biggest calving event in more than 50 years at the Amery Ice Shelf The Cryosphere DOI 10.5194/tc-15-2147-2021 22 June 2021 The unexpected September 2019 calving event from the Amery Ice Shelf, the largest since 1963 and which occurred almost a decade earlier than expected, was triggered by atmospheric extremes. Explosive twin polar cyclones provided a deterministic role in this event by creating oceanward sea surface slope triggering the calving. The observed record-anomalous atmospheric conditions were promoted by blocking ridges and Antarctic-wide anomalous poleward transport of heat and moisture. Read more
Heterogeneous interactions between SO2 and organic peroxides in submicron aerosol Atmospheric Chemistry and Physics DOI 10.5194/acp-21-6647-2021 21 June 2021 Discrepancies between atmospheric modeling and field observations, especially in highly polluted cities, have highlighted the lack of understanding of sulfate formation mechanisms and kinetics. Here, we directly quantify the reactive uptake coefficient of SO2 onto organic peroxides and study the important governing factors. The SO2 uptake rate was observed to depend on RH, peroxide amount and reactivity, pH, and ionic strength, which provides a framework to better predict sulfate formation. Read more
On the phenomenon of the blue sun Climate of the Past DOI 10.5194/cp-17-969-2021 18 June 2021 This study investigates the physical processes leading to the rare phenomenon of the sun appearing blue or green. The phenomenon is caused by anomalous scattering by, e.g., volcanic or forest fire aerosols. Unlike most other studies, our study includes a full treatment of the effect of Rayleigh scattering on the colour of the sun. We investigate different factors and revisit a historic example, i.e. the Canadian forest fires in 1950, that led to blue sun events in different European countries. Read more
Effects of Earth system feedbacks on the potential mitigation of large-scale tropical forest restoration Biogeosciences DOI 10.5194/bg-18-2627-2021 17 June 2021 Estimates of large-scale tree planting and forest restoration as a carbon sequestration tool typically miss a crucial aspect: the Earth system response to the increased land carbon sink from new vegetation. We assess the impact of tropical forest restoration using an Earth system model under a scenario that limits warming to 2 °C. Almost two-thirds of the carbon impact of forest restoration is offset by negative carbon cycle feedbacks, suggesting a more modest benefit than in previous studies. Read more
Revision of the World Meteorological Organization Global Atmosphere Watch (WMO/GAW) CO2 calibration scale Atmospheric Measurement Techniques DOI 10.5194/amt-14-3015-2021 16 June 2021 We have recently revised the carbon dioxide calibration scale used by numerous laboratories that measure atmospheric CO2. The revision follows from an improved understanding of the manometric method used to determine the absolute amount of CO2 in an atmospheric air sample. The new scale is 0.18 μmol mol−1 (ppm) greater than the previous scale at 400 ppm CO2. While this difference is small in relative terms (0.045 %), it is significant in terms of atmospheric monitoring. Read more
Observing the timescales of aerosol–cloud interactions in snapshot satellite images Atmospheric Chemistry and Physics DOI 10.5194/acp-21-6093-2021 15 June 2021 Cloud responses to aerosol are time-sensitive, but this development is rarely observed. This study uses isolated aerosol perturbations from ships to measure this development and shows that macrophysical (width, cloud fraction, detectability) and microphysical (droplet number) properties of ship tracks vary strongly with time since emission, background cloud and meteorological state. This temporal development should be considered when constraining aerosol–cloud interactions with observations. Read more
On the attribution of industrial-era glacier mass loss to anthropogenic climate change The Cryosphere DOI 10.5194/tc-15-1889-2021 14 June 2021 The worldwide retreat of mountain glaciers and consequent loss of ice mass is one of the most obvious signs of a changing climate and has significant implications for the hydrology and natural hazards in mountain landscapes. Consistent with our understanding of the human role in temperature change, we demonstrate that the central estimate of the size of the human-caused mass loss is essentially 100 % of the observed loss. This assessment resolves some important inconsistencies in the literature. Read more
Development of smart boulders to monitor mass movements via the Internet of Things: a pilot study in Nepal Earth Surface Dynamics DOI 10.5194/esurf-9-295-2021 11 June 2021 We use long-range smart sensors connected to a network based on the Internet of Things to explore the possibility of detecting hazardous boulder movements in real time. Prior to the 2019 monsoon season we inserted the devices in 23 boulders spread over debris flow channels and a landslide in northeastern Nepal. The data obtained in this pilot study show the potential of this technology to be used in remote hazard-prone areas in future early warning systems. Read more
Robust increase of Indian monsoon rainfall and its variability under future warming in CMIP6 models Earth System Dynamics DOI 10.5194/esd-12-367-2021 10 June 2021 All state-of-the-art global climate models that contributed to the latest Coupled Model Intercomparison Project (CMIP6) show a robust increase in Indian summer monsoon rainfall that is even stronger than in the previous intercomparison (CMIP5). Furthermore, they show an increase in the year-to-year variability of this seasonal rainfall that crucially influences the livelihood of more than 1 billion people in India. Read more