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Abstract

Surface melting occurs across many of Antarctica’s ice shelves, mainly during the austral summer. The onset, duration, area and fate of surface melting varies spatially and temporally, and the resultant surface meltwater is stored as ponded water (lakes) or as slush (saturated firn or snow), with implications for ice-shelf hydrofracture, firn air content reduction, surface energy balance and thermal evolution. This study applies a machine-learning method to the entire Landsat 8 image catalogue to derive monthly records of slush and ponded water area across 57 ice shelves between 2013 and 2021. We find that slush and ponded water occupy roughly equal areas of Antarctica’s ice shelves in January, with inter-regional variations in partitioning. This suggests that studies that neglect slush may substantially underestimate the area of ice shelves covered by surface meltwater. Furthermore, we found that adjusting the surface albedo in a regional climate model to account for the lower albedo of surface meltwater resulted in 2.8 times greater snowmelt across five representative ice shelves. This extra melt is currently unaccounted for in regional climate models, which may lead to underestimates in projections of ice-sheet melting and ice-shelf stability.

>Understandably, material concerns dominate the policy conversation around sustainability and systemic transformation. Yet at the root level, our crises are created and perpetuated by factors in our psychology and meaning—making.

>From consumerist values to evolutionary impulses that skew our perceptions and political behaviours, these inner dynamics subtly dictate the course of our external world. It’s why Donella Meadows, the lead author of The Limits to Growth, saw this arena of “mindsets” as the “deepest leverage point for change.”

Abstract

Constraining the relationship between temperature and atmospheric concentrations of carbon dioxide (pCO2) is essential to model near-future climate. Here, we reconstruct pCO2 values over the past 15 million years (Myr), providing a series of analogues for possible near-future temperatures and pCO2, from a single continuous site (DSDP Site 467, California coast). We reconstruct pCO2 values using sterane and phytane, compounds that many phytoplankton produce and then become fossilised in sediment. From 15.0-0.3 Myr ago, our reconstructed pCO2 values steadily decline from 650 ± 150 to 280 ± 75 ppmv, mirroring global temperature decline. Using our new range of pCO2 values, we calculate average Earth system sensitivity and equilibrium climate sensitivity, resulting in 13.9 °C and 7.2 °C per doubling of pCO2, respectively. These values are significantly higher than IPCC global warming estimations, consistent or higher than some recent state-of-the-art climate models, and consistent with other proxy-based estimates.

cross-posted from: https://lemmy.world/post/16776366

> Reuters.com

cross-posted from: https://lemmy.world/post/16748184

> Axios.com

cross-posted from: https://lemmy.world/post/16748041

> "As long as humans fill the atmosphere with fossil-fuel emissions, the heat will only get worse—vulnerable people will continue to die," an author of the analysis said.

cross-posted from: https://lemmy.world/post/16705204

> As the climate crisis continues, flood victims in Brazil are building solidarity as they occupy unused buildings.

Abstract

While most studies highlight the benefits of the energy transition, it is important to recognize that this process can also yield negative consequences. In this study, we delve into this aspect of the energy transition by examining its effects on food prices and agricultural production across 32 OECD countries from 2000 to 2021. Our findings reveal that the energy transition leads to increased food prices and decreased agricultural production. Causality analysis further confirms that the energy transition is responsible for these changes. To deepen our understanding, we divided the countries into two subsamples: those in an advanced stage of the energy transition and those in a delayed stage. Our results show that the impact of the energy transition varies depending on the stage of transition. Countries further along in their energy transitions experience a greater effect. This investigation underscores a collateral effect of the energy transition, placing additional pressure on vulnerable populations. To address this social challenge, governments can implement programs and policies such as income transfers to support these groups.

Keywords: Energy Transition, Food prices, Agricultural Production, China, Commodity prices

cross-posted from: https://lemmy.world/post/16632663

> One climate scientist said a pending heatwave would "affect a bunch of highly populated areas where there hasn't been quite as many stories about extreme heat recently."

Abstract

In palaeontological studies, groups with consistent ecological and morphological traits across a clade’s history (functional groups)1 afford different perspectives on biodiversity dynamics than do species and genera2,3, which are evolutionarily ephemeral. Here we analyse Triton, a global dataset of Cenozoic macroperforate planktonic foraminiferal occurrences4, to contextualize changes in latitudinal equitability gradients1, functional diversity, palaeolatitudinal specialization and community equitability. We identify: global morphological communities becoming less specialized preceding the richness increase after the Cretaceous–Palaeogene extinction; ecological specialization during the Early Eocene Climatic Optimum, suggesting inhibitive equatorial temperatures during the peak of the Cenozoic hothouse; increased specialization due to circulation changes across the Eocene–Oligocene transition, preceding the loss of morphological diversity; changes in morphological specialization and richness about 19 million years ago, coeval with pelagic shark extinctions5; delayed onset of changing functional group richness and specialization between hemispheres during the mid-Miocene plankton diversification. The detailed nature of the Triton dataset permits a unique spatiotemporal view of Cenozoic pelagic macroevolution, in which global biogeographic responses of functional communities and richness are decoupled during Cenozoic climate events. The global response of functional groups to similar abiotic selection pressures may depend on the background climatic state (greenhouse or icehouse) to which a group is adapted.

Abstract

Large constellations of small satellites will significantly increase the number of objects orbiting the Earth. Satellites burn up at the end of service life during reentry, generating aluminum oxides as the main byproduct. These are known catalysts for chlorine activation that depletes ozone in the stratosphere. We present the first atomic-scale molecular dynamics simulation study to resolve the oxidation process of the satellite's aluminum structure during mesospheric reentry, and investigate the ozone depletion potential from aluminum oxides. We find that the demise of a typical 250-kg satellite can generate around 30 kg of aluminum oxide nanoparticles, which may endure for decades in the atmosphere. Aluminum oxide compounds generated by the entire population of satellites reentering the atmosphere in 2022 are estimated at around 17 metric tons. Reentry scenarios involving mega-constellations point to over 360 metric tons of aluminum oxide compounds per year, which can lead to significant ozone depletion.

Abstract

Arctic amplification—the amplified surface warming in the Arctic relative to the globe—is a robust feature of climate change. However, there is a considerable spread in the reported magnitude of Arctic amplification. Whereas earlier observations and model simulations suggested that the Arctic has been warming at a rate two to three times as the globe, a recent study reports an alarming amplification factor of four since 1979. Here we reconcile this discrepancy by revealing that natural variability has substantially modulated the degree of Arctic amplification. On the basis of three observational datasets and 34 models from the Coupled Model Intercomparison Project, we show that the observed temperature evolutions are distinct from the model-simulated forced responses and that the differences are explained by modes of natural variability. Specifically, the Interdecadal Pacific Oscillation decelerated global warming after 2000, whereas an Arctic internal mode amplified Arctic warming after 2005, both contributing positively to the recent increase of Arctic amplification to fourfold. By estimating and removing the effect of natural variability on the observed temperature changes, we reveal that the externally forced Arctic amplification has consistently remained close to three throughout the historical period.

Abstract

Across the last ~50,000 years (the late Quaternary) terrestrial vertebrate faunas have experienced severe losses of large species (megafauna), with most extinctions occurring in the Late Pleistocene and Early to Middle Holocene. Debate on the causes has been ongoing for over 200 years, intensifying from the 1960s onward. Here, we outline criteria that any causal hypothesis needs to account for. Importantly, this extinction event is unique relative to other Cenozoic (the last 66 million years) extinctions in its strong size bias. For example, only 11 out of 57 species of megaherbivores (body mass ≥1,000 kg) survived to the present. In addition to mammalian megafauna, certain other groups also experienced substantial extinctions, mainly large non-mammalian vertebrates and smaller but megafauna-associated taxa. Further, extinction severity and dates varied among continents, but severely affected all biomes, from the Arctic to the tropics. We synthesise the evidence for and against climatic or modern human (Homo sapiens) causation, the only existing tenable hypotheses. Our review shows that there is little support for any major influence of climate, neither in global extinction patterns nor in fine-scale spatiotemporal and mechanistic evidence. Conversely, there is strong and increasing support for human pressures as the key driver of these extinctions, with emerging evidence for an initial onset linked to pre-sapiens hominins prior to the Late Pleistocene. Subsequently, we synthesize the evidence for ecosystem consequences of megafauna extinctions and discuss the implications for conservation and restoration. A broad range of evidence indicates that the megafauna extinctions have elicited profound changes to ecosystem structure and functioning. The late-Quaternary megafauna extinctions thereby represent an early, large-scale human-driven environmental transformation, constituting a progenitor of the Anthropocene, where humans are now a major player in planetary functioning. Finally, we conclude that megafauna restoration via trophic rewilding can be expected to have positive effects on biodiversity across varied Anthropocene settings.