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. ESD Ideas: Global climate response scenarios for IPCC assessments">Read more