2023

1. [Dance 2023] As papers pile up, journal editors are struggling to find willing referees.
   Peer review

2. [Escribano 2023] The transition from a fossil fuel to a renewable energy regime also implies a change in the geopolitical equilibrium, with the eventual emergence of winners and losers.
   Geopolitica y cambio climático

3. [Galanaki et al. 2023] Abstract. In recent years, a considerable body of research has demonstrated the suitability of global and regional reanalysis data for human-biometeorological applications. These applications include the assessment of the outdoor thermal environment and the investigation of its relation to human health, especially in areas where the spatial coverage of surface observational networks is sparse. Here, we present the first comprehensive evaluation of the most recent pan-European regional reanalysis, namely the Copernicus European Regional Reanalysis (CERRA) dataset at 5.5 km spatial resolution, in terms of simulating the observed human bioclimate, as expressed by the modified physiologically equivalent temperature (mPET) that is computed through the RayMan Pro model, and its meteorological drivers. The validation was performed over Greece using up to 11 years of records of 2 m air temperature and relative humidity, 10 m wind speed and global solar radiation derived from 35 sites of the nationwide network of surface weather stations operated by the METEO Unit at the National Observatory of Athens. The ERA5-Land dataset at 9 km spatial resolution, which represents the current state-of-the-art reanalysis, was also compared against the same observations. Our findings show that the CERRA dataset performs significantly better compared to the ERA5-Land reanalysis with respect to the replication of the examined meteorological variables and mPET. The added value of the CERRA data is particularly evident during the warm period of the year and in regions that are characterized by complex topography and/or proximity to the coastline. Combining the CERRA dataset with population and mortality data, we further showcase its applicability for human-biometeorological and heat–health studies at a local scale, using the regional unit of Rethymno (Crete) as a pilot area for the analysis.
   Cerra evaluation over Greece

4. [García-García et al. 2023] Hot temperature extremes are changing in intensity and frequency. Quantifying these changes is key for developing adaptation strategies [1]. The conventional approach to study changes in hot extremes is based on air temperatures. However, hydrology [2] and many biogeo- chemical processes, e.g. decomposition of organic material and release of CO2 [3]- are more sensitive to soil rather than air temperature. In this study, we show that soil hot extremes are increasing faster than air hot extremes by 0.7◦C/Decade in intensity and twice as fast in frequency on average over Central Europe. Furthermore, we identify soil temperature as a factor in the soil moisture–temperature feed- back. During dry conditions, increases in net radiation yield higher soil temperature and a consequent release of sensible heat while latent heat flux is constrained by soil moisture deficits. The release of sen- sible heat from soils leads to increases in air temperature and vapour pressure deficit that may further dry out and warm up the soil. This study further highlights the contribution of soil moisture–temperature feedback to the evolution of hot extremes in a warming climate. The rapid increase in soil heat extremes shown in these results may have important implications for climate and ecological risk applications.
   Land air coupling, climate change

5. [Hopcroft et al. 2023] Abstract: The pre-industrial Holocene provides the backdrop for the emergence of civilisations and the starting point of anthropogenic climate change. Several reconstructions show an early Holocene warming that was followed by cooling for several thousand years before Industrialisation. In contrast climate simulations show warming throughout the Holocene. Whilst reconstructed trends over ocean can be reconciled with warming through either seasonality or uncertainties, a consistent explanation for cooling trends over some land areas is missing. We present a suite of transient Holocene climate model simulations with a coupled general circulation model and show that a widespread mid- to late-Holocene cooling emerges over some regions of the northern hemisphere with the inclusion of anthropogenic land-use. This is mostly because in regions of prescribed late Holocene deforestation, the simulated early to mid-Holocene is characterised by a lower albedo than the late Holocene. Whilst this cooling through time can quantitatively explain some regional aspects of the reconstructions, the model-data agreement remains imperfect, and differences between reconstructions also hinders the evaluation. Moreover, model-dependency in the response of several feedbacks, particularly sea-ice, but potentially also clouds, means that it is difficult to uniquely attribute Holocene temperature evolution to specific factors. Future work should aim to derive a consensus-signal including uncertainties from the available proxy data which could be used to fingerprint simulations covering a range of plausible feedback strengths.
   Holocene, forcings and feedbacks

6. [Lin et al. 2023] Abstract. Hasselmann’s theory elucidates how short-term random noise leads to longer-term unpro- voked variations, i.e., red spectra. Here, we study ensembles of numerical model simulations of the hydrodynamics of the Bohai and Yellow Sea concerning internal variability formation. Short(/long) term variations are associated with small(/large) spatial scales, and the internal variability of long-term temporal and large-scale variations is markedly enhanced, even without external forcing on these scales, when the tides are turned off. This pattern is well explained by Hasselmann’s theory. A critical element in this theory is the concept of memory, which in our ensembles exhibits a scale dependence that aligns with the scale-dependent nature of redness. Additionally, this framework clarifies why there is a significant reduction of long-term fluctuations during winter and when tides are active: the system’s memory is notably diminished under these conditions.
   Internal variability and noise, Hasselmann SCM

7. [Rasmussen et al. 2023] A unique, high-resolution, hydroclimate reanalysis, 40-plus-year (October 1979–September 2021), 4 km (named as CONUS404), has been created using the Weather Research and Forecasting Model by dynamically downscaling of the fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis of the global climate dataset (ERA5) over the conterminous United States. The paper describes the approach for generating the dataset, provides an initial evaluation, including biases, and indicates how interested users can access the data. The motivation for creating this National Center for Atmospheric Research (NCAR)–U.S. Geological Survey (USGS) collaborative dataset is to provide research and end-user communities with a high-resolution, self-consistent, long-term, continental-scale hydroclimate dataset appropriate for forcing hydrological models and conducting hydroclimate scientific analyses over the conterminous United States. The data are archived and accessible on the USGS Black Pearl tape system and on the NCAR supercomputer Campaign storage system.
   Downscaling, convection permiting, reanalysis CONUS404

8. [Richardson et al. 2023] Abstract: This planetary boundaries framework update finds that six of the nine boundaries are transgressed, suggesting that Earth is now well outside of the safe operating space for humanity. Ocean acidification is close to being breached, while aerosol loading regionally exceeds the boundary. Stratospheric ozone levels have slightly recovered. The transgression level has increased for all boundaries earlier identified as overstepped. As primary production drives Earth system biosphere functions, human appropriation of net primary production is proposed as a control variable for functional biosphere integrity. This boundary is also transgressed. Earth system modeling of different levels of the transgression of the climate and land system change boundaries illustrates that these anthropogenic impacts on Earth system must be considered in a systemic context. Transgression of planetary boundaries by human activities have now brought humanity well beyond a “safe operating space.”
   Planetary boundaries, save operating space, precautionary principle

9. [Schicker et al. 2023] Abstract. With hydropower being the dominant source of renewable energy in Austria and recent years being disproportionally dry, alternative renewable energy sources need to be tapped to compensate the reduction of fossil fuels and account for dry conditions, this This becomes even more important given the current geo-political situation. Wind power plays an essential role in decarbonising Austria's electricity system. For local assessment of historic, recent, and future wind conditions, adequate climate data is essential. Reanalysis data, often used for such assessments, has a coarse spatial resolution and could be unable to capture local wind features, relevant for wind power modelling. Thus, raw reanalysis data need some sort of post-processing and results need to be interpreted with care.The purpose of this study is to assess the quality of three reanalysis data sets, MERRA-2, ERA5, and COSMO-REA6, for both surface level and hub height wind speed and wind power production at meteorological observation sites and wind farms in flat and mountainous terrain.
   Wind reanalyses comparison

10. [Schug et al. 2023] Climate change is an indisputable threat to human health, especially for societies already confronted with rising social inequality, political and economic uncertainty, and a cascade of concurrent environmental challenges. Archaeological data about past climate and environment provide an important source of evidence about the potential challenges humans face and the long-term outcomes of alternative short-term adaptive strategies. Evidence from well-dated archaeological human skeletons and mummified remains speaks directly to patterns of human health over time through changing circumstances. Here, we describe variation in human epidemiological patterns in the context of past rapid climate change (RCC) events and other periods of past environmental change. Case studies confirm that human communities responded to environmental changes in diverse ways depending on historical, sociocultural, and biological contingencies. Certain factors, such as social inequality and disproportionate access to resources in large, complex societies may influence the probability of major sociopolitical disruptions and reorganizations—commonly known as “collapse.” This survey of Holocene human–environmental relations demonstrates how flexibility, variation, and maintenance of Indigenous knowledge can be mitigating factors in the face of environmental challenges. Although contemporary climate change is more rapid and of greater magnitude than the RCC events and other environmental changes we discuss here, these lessons from the past provide clarity about potential priorities for equitable, sustainable development and the constraints of modernity we must address
    Climate adaptation, vulnerability, health, holocene

11. [von Storch 2023] Abstract. Forages,the topic of climate –in the sense of “usualweather” –has in the western tradition attracted attention as a possible explanatory factor for differences in societies and in human behavior. Climate, and its purported impact on society, is an integrated element in western thinking and perception. In this essay, the history of ideas about the climatic impact on humans and society and the emergence of the ideology of climatic determinism are sketched from the viewpoint of a natural scientist. This ideology favored the perception of westerners being superior to the people in the rest of the world, giving legitimacy to colonialism. In modern times, when natural sciences instituted self-critical processes (repeatability, falsification) and norms (such as the Mertonian norms named CUDOS), the traditional host for climate issues, namely, geography, lost its grip, and physics took over. This “scientification” of climate science led to a more systematic, critical and rigorous approach of building and testing hypotheses and concepts. This gain in methodical rigor, however, went along with the loss of understanding that climate is hardly a key explanatory factor for societal differences and developments. Consequently, large segments of the field tacitly and unknowingly began reviving the abandoned concept of climatic determinism. Climate science finds itself in a “post-normal” condition, which leads to a frequent dominance of political utility over methodical rigor.
    Climate change science, postnormal

12. [Torres-Vázquez et al. 2023] Abstract. Drought remains a costly natural disaster, with strong socio-economic and environmental impacts. Skilful seasonal drought forecasts can help to make early decisions. Here we assess the quality of a prototype seasonal forecasting system for a Mediterranean region (peninsular Spain + Balearic Islands) to predict meteorological drought as measured by the standardised precipitation index (SPI). We first show that there is a high agreement between the official data provided by the Spanish Meteorological Agency and the state-of-the art ERA5 rean- alysis, building confidence in using these datasets. Thus, since the ERA5 data are provided in near-real time as it is updated on a monthly basis, it can be used to monitor drought evolution. Then, we demonstrate that it is possible to obtain skilful and reliable seasonal drought predictions several months in advance by applying an ensemble-based streamflow prediction system (ESP, an ensemble based on the rearrangement of historical data) using ERA5 data as initial conditions. The results indicate that a statistical persistence-based model could lead to an actionable seasonal drought forecasting skill thus providing the basis for a cheap and fast prototype for drought early warning.
    Initialization, drought simulations

13. [Yao et al. 2023] Abstract. There is a general agreement that Northern Hemisphere temperatures have cooled over the past two millennia, culminating in the Little Ice Age. However, this understanding partly relies on the compilation of existing proxy records, the majority of which carry a warm season bias such that there is an underrepresentation of cold-season temperatures. Here we report a unique cold-season temperature record based on the alkenone paleothermometer from the northeastern Tibetan Plateau that spans the last two millennia. In contrast to the regional- and hemisphere-scale summer cooling, our reconstruction shows a long-term warming through the Medieval Climate Anomaly into Little Ice Age. We attribute these opposing temperature trends to combined effects of seasonally divergent insolation and North Atlantic subpolar gyre circulation. Our study indicates that the cold season during the Little Ice Age was not the coldest period of the last two millennia at least on the northeastern Tibetan Plateau.
    Internal variability and noise, Hasselmann SCM