Effective radiative forcing and adjustments in CMIP6 models Atmospheric Chemistry and Physics DOI 10.5194/acp-20-9591-2020 3 September 2020 The spread in effective radiative forcing for both CO 2 and aerosols is narrower in the latest CMIP6 (Coupled Model Intercomparison Project) generation than in CMIP5. For the case of CO 2 it is likely that model radiation parameterisations have improved. Tropospheric and stratospheric radiative adjustments to the forcing behave differently for different forcing agents, and there is still significant diversity in how clouds respond to forcings, particularly for total anthropogenic forcing. Read more
Emergent constraints on transient climate response (TCR) and equilibrium climate sensitivity (ECS) from historical warming in CMIP5 and CMIP6 models Earth System Dynamics DOI 10.5194/esd-11-737-2020 3 September 2020 One of the key questions in climate science is how much more heating we will get for a given rise in carbon dioxide in the atmosphere. A new generation of models showed that this might be more than previously expected. Comparing the new models to observed temperature rise since 1970, we show that there is no need to revise the estimate upwards. Air pollution, whose effect on climate warming is poorly understood, stopped rising, allowing us to better constrain the greenhouse gas signal. Read more
Open weather and climate science in the digital era Geoscience Communication DOI 10.5194/gc-3-191-2020 1 September 2020 At the 14th IEEE International eScience Conference domain specialists and data and computer scientists discussed the road towards open weather and climate science. Open science offers manifold opportunities but goes beyond sharing code and data. Besides domain-specific technical challenges, we observed that the main challenges are non-technical and impact the system of science as a whole. Read more
A global analysis of climate-relevant aerosol properties retrieved from the network of Global AtmosphereWatch (GAW) near-surface observatories Atmospheric Measurement Techniques DOI 10.5194/amt-13-4353-2020 1 September 2020 The paper establishes the fiducial reference of the GAW aerosol network providing the fully characterized value chain to the provision of four climate-relevant aerosol properties from ground-based sites. Data from almost 90 stations worldwide are reported for a reference year, 2017, providing a unique and very robust view of the variability of these variables worldwide. Current gaps in the GAW network are analysed and requirements for the Global Climate Monitoring System are proposed. Read more
Anthropogenic climate change and glacier lake outburst flood risk: local and global drivers and responsibilities for the case of lake Palcacocha, Peru Natural Hazards and Earth System Sciences DOI 10.5194/nhess-20-2175-2020 27 August 2020 There is increasing interest and need to analyze the contribution of anthropogenic climate change to negative impacts of climate change. We study the case of glacial lake Palcacocha in Peru, which poses a significant flood risk to the city of Huaraz. We found that greenhouse gas emissions; strong urbanization processes without appropriate land use planning; and social, cultural, political, and institutional factors all contribute to the existing flood risk. Read more
The shared socio-economic pathway (SSP) greenhouse gas concentrations and their extensions to 2500 Geoscientific Model Development DOI 10.5194/gmd-13-3571-2020 27 August 2020 This study provides the future greenhouse gas (GHG) concentrations under the new set of so-called SSP scenarios (the successors of the IPCC SRES and previous representative concentration pathway (RCP) scenarios). The projected CO 2 concentrations range from 350 ppm for low-emission scenarios by 2150 to more than 2000 ppm under the high-emission scenarios. We also provide concentrations, latitudinal gradients, and seasonality for most of the other 42 considered GHGs. Read more
Rainfall intensification increases the contribution of rewetting pulses tosoil heterotrophic respiration Biogeosciences DOI 10.5194/bg-17-4007-2020 25 August 2020 Carbon dioxide is produced by soil microbes through respiration, which is particularly fast when soils are moistened by rain. Will respiration increase with future more intense rains and longer dry spells? With a mathematical model, we show that wetter conditions increase respiration. In contrast, if rainfall totals stay the same, but rain comes all at once after long dry spells, the average respiration will not change, but the contribution of the respiration bursts after rain will increase. Read more
An overview of and issues with sky radiometer technology and SKYNET Atmospheric Measurement Techniques DOI 10.5194/amt-13-4195-2020 25 August 2020 This paper overviews the progress in sky radiometer technology and the development of the network called SKYNET. It is found that the technology has produced useful on-site calibration methods, retrieval algorithms, and data analyses from sky radiometer observations of aerosol, cloud, water vapor, and ozone. The paper also discusses current issues of SKYNET to provide better information for the community. Read more
CloudRoots: integration of advanced instrumental techniques and processmodelling of sub-hourly and sub-kilometre land–atmosphere interactions Biogeosciences DOI 10.5194/bg-17-4375-2020 25 August 2020 The CloudRoots field experiment has obtained an open comprehensive observational data set that includes soil, plant, and atmospheric variables to investigate the interactions between a heterogeneous land surface and its overlying atmospheric boundary layer, including the rapid perturbations of clouds in evapotranspiration. Our findings demonstrate that in order to understand and represent diurnal variability, we need to measure and model processes from the leaf to the landscape scales. Read more
A monitoring system for spatiotemporal electrical self-potential measurements in cryospheric environments Geoscientific Instrumentation, Methods and Data Systems DOI 10.5194/gi-9-317-2020 20 August 2020 In times of global warming, permafrost is starting to degrade at alarming rates, requiring new and improved characterization approaches. We describe the design and test installation, as well as detailed data quality assessment, of a monitoring system used to capture natural electrical potentials in the subsurface. These self-potential signals are of great interest for the noninvasive investigation of water flow in the non-frozen or partially frozen subsurface. Read more
Revisiting the global hydrological cycle: is it intensifying? Hydrology and Earth System Sciences DOI 10.5194/hess-24-3899-2020 20 August 2020 We overview and retrieve a great amount of global hydroclimatic data sets. We improve the quantification of the global hydrological cycle, its variability and its uncertainties through the surge of newly available data sets. We test (but do not confirm) established climatological hypotheses, according to which the hydrological cycle should be intensifying due to global warming. We outline a stochastic view of hydroclimate, which provides a reliable means of dealing with its variability. Read more
Molecular understanding of new-particle formation from α-pinene between-50 and +25 ∘C Atmospheric Chemistry and Physics DOI 10.5194/acp-20-9183-2020 18 August 2020 Highly oxygenated organic compounds (HOMs) have been identified as key vapors involved in atmospheric new-particle formation (NPF). The molecular distribution, HOM yield, and NPF from α-pinene oxidation experiments were measured at the CLOUD chamber over a wide tropospheric-temperature range. This study shows on a molecular scale that despite the sharp reduction in HOM yield at lower temperatures, the reduced volatility counteracts this effect and leads to an overall increase in the NPF rate. Read more
Relating climate sensitivity indices to projection uncertainty Earth System Dynamics DOI 10.5194/esd-11-721-2020 18 August 2020 Here, we assess the degree to which the idealized responses to transient forcing increase and step change forcing increase relate to warming under future scenarios. We find a possible explanation for the poor performance of transient metrics (relative to equilibrium response) as a metric of high-emission future warming in terms of their sensitivity to non-equilibrated initial conditions, and propose alternative metrics which better describe warming under high mitigation scenarios. Read more
Incremental improvements of 2030 targets insufficient to achieve the Paris Agreement goals Earth System Dynamics DOI 10.5194/esd-11-697-2020 13 August 2020 Current global mitigation ambition in the National Determined Contributions (NDCs) up to 2030 is insufficient to achieve the 1.5 °C long-term temperature limit. As governments are preparing new and updated NDCs for 2020, we address the question of what level of collective ambition is pivotal regarding the Paris Agreement goals. We provide estimates for global mean temperature increase by 2100 for different incremental NDC update scenarios and illustrate climate impacts under those scenarios. Read more
Remote sensing of methane leakage from natural gas and petroleum systems revisited Atmospheric Chemistry and Physics DOI 10.5194/acp-20-9169-2020 13 August 2020 The switch from the use of coal to natural gas or oil for energy generation potentially reduces the impact on global warming due to lower CO 2 emissions with the same energy content. However, this climate benefit is offset by fugitive methane emissions during the production and distribution process. We quantify emission and leakage rates relative to production for several large production regions based on satellite observations to evaluate the climate footprint of the gas and oil industry. Read more
Survival of the Qaidam mega-lake system under mid-Pliocene climates and itsrestoration under future climates Hydrology and Earth System Sciences DOI 10.5194/hess-24-3835-2020 11 August 2020 During the Pliocene, the Qaidam Basin on the Tibetan Plateau contained a mega-lake system. During the Pleistocene, it disappeared almost completely. Today, hyperarid climates prevail in the low-altitude parts of the basin. This study reveals that today’s mean water balance of the Qaidam Basin is nearly zero and is positive during warmer, less dry years. The results explain how the mega-lake system could survive for a long time in the past and could eventually be restored in the future. Read more
The recent state and variability of the carbonate system of the CanadianArctic Archipelago and adjacent basins in the context of ocean acidification Biogeosciences DOI 10.5194/bg-17-3923-2020 11 August 2020 Ocean acidification is the process by which the oceans are changing due to carbon dioxide emissions from human activities. Studying this process in the Arctic Ocean is essential as this ocean and its ecosystems are more vulnerable to the effects of acidification. Water chemistry measurements made in recent years show that waters in and around the Canadian Arctic Archipelago are considerably affected by this process and show dynamic conditions that might have an impact on local marine organisms. Read more
Impact of environmental changes and land management practices on wheatproduction in India Earth System Dynamics DOI 10.5194/esd-11-641-2020 6 August 2020 Spring wheat, a staple for millions of people in India and the world, is vulnerable to changing environmental and management factors. Using a new spring wheat model, we find that over the 1980–2016 period elevated CO 2 levels, irrigation, and nitrogen fertilizers led to an increase of 30 %, 12 %, and 15 % in countrywide production, respectively. In contrast, rising temperatures have reduced production by 18 %. These effects vary across the country, thereby affecting production at regional scales. Read more
Multidecadal trend analysis of in situ aerosol radiative properties around the world Atmospheric Chemistry and Physics DOI 10.5194/acp-20-8867-2020 6 August 2020 Long-term trends of aerosol radiative properties (52 stations) prove that aerosol load has significantly decreased over the last 20 years. Scattering trends are negative in Europe (EU) and North America (NA), not ss in Asia, and show a mix of positive and negative trends at polar stations. Absorption has mainly negative trends. The single scattering albedo has positive trends in Asia and eastern EU and negative in western EU and NA, leading to a global positive median trend of 0.02 % per year. Read more
Reviewing global estimates of surface reactive nitrogen concentration anddeposition using satellite retrievals Atmospheric Chemistry and Physics DOI 10.5194/acp-20-8641-2020 4 August 2020 Excessive atmospheric reactive nitrogen (N r ) deposition can cause a series of negative effects. Thus, it is necessary to accurately estimate N r deposition to evaluate its impact on the ecosystems and environment. Scientists attempted to estimate surface N r concentration and deposition using satellite retrievals. We give a thorough review of recent advances in estimating surface N r concentration and deposition using satellite retrievals of NO 2 and NH 3 and summarize the existing challenges. Read more