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| 2. |
- Obers, Niels A., et al.
(author)
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Quantum gravity phenomenology at the dawn of the multi-messenger era—A review
- 2022
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In: Progress in Particle and Nuclear Physics. - : Elsevier BV. - 0146-6410 .- 1873-2224. ; 125
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Research review (peer-reviewed)abstract
- The exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give us information about their sources in the universe and the properties of the intergalactic medium. Moreover, multi-messenger astronomy opens up the possibility to search for phenomenological signatures of quantum gravity. On the one hand, the most energetic events allow us to test our physical theories at energy regimes which are not directly accessible in accelerators; on the other hand, tiny effects in the propagation of very high energy particles could be amplified by cosmological distances. After decades of merely theoretical investigations, the possibility of obtaining phenomenological indications of Planck-scale effects is a revolutionary step in the quest for a quantum theory of gravity, but it requires cooperation between different communities of physicists (both theoretical and experimental). This review, prepared within the COST Action CA18108 “Quantum gravity phenomenology in the multi-messenger approach”, is aimed at promoting this cooperation by giving a state-of-the art account of the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of cosmic messengers.
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| 3. |
- Emile-Geay, J., et al.
(author)
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Data Descriptor: A global multiproxy database for temperature reconstructions of the Common Era
- 2017
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In: Scientific Data. - : Springer Science and Business Media LLC. - 2052-4463. ; 4
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Journal article (peer-reviewed)abstract
- Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850-2014. Global temperature composites show a remarkable degree of coherence between high-and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era, and is shared in the Linked Paleo Data (LiPD) format, including serializations in Matlab, R and Python. Since the pioneering work of D'Arrigo and Jacoby1-3, as well as Mann et al. 4,5, temperature reconstructions of the Common Era have become a key component of climate assessments6-9. Such reconstructions depend strongly on the composition of the underlying network of climate proxies10, and it is therefore critical for the climate community to have access to a community-vetted, quality-controlled database of temperature-sensitive records stored in a self-describing format. The Past Global Changes (PAGES) 2k consortium, a self-organized, international group of experts, recently assembled such a database, and used it to reconstruct surface temperature over continental-scale regions11 (hereafter, ` PAGES2k-2013'). This data descriptor presents version 2.0.0 of the PAGES2k proxy temperature database (Data Citation 1). It augments the PAGES2k-2013 collection of terrestrial records with marine records assembled by the Ocean2k working group at centennial12 and annual13 time scales. In addition to these previously published data compilations, this version includes substantially more records, extensive new metadata, and validation. Furthermore, the selection criteria for records included in this version are applied more uniformly and transparently across regions, resulting in a more cohesive data product. This data descriptor describes the contents of the database, the criteria for inclusion, and quantifies the relation of each record with instrumental temperature. In addition, the paleotemperature time series are summarized as composites to highlight the most salient decadal-to centennial-scale behaviour of the dataset and check mutual consistency between paleoclimate archives. We provide extensive Matlab code to probe the database-processing, filtering and aggregating it in various ways to investigate temperature variability over the Common Era. The unique approach to data stewardship and code-sharing employed here is designed to enable an unprecedented scale of investigation of the temperature history of the Common Era, by the scientific community and citizen-scientists alike.
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| 4. |
- Buntgen, U., et al.
(author)
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Tree rings reveal globally coherent signature of cosmogenic radiocarbon events in 774 and 993 CE
- 2018
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9
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Journal article (peer-reviewed)abstract
- Though tree-ring chronologies are annually resolved, their dating has never been independently validated at the global scale. Moreover, it is unknown if atmospheric radiocarbon enrichment events of cosmogenic origin leave spatiotemporally consistent fingerprints. Here we measure the 14C content in 484 individual tree rings formed in the periods 770–780 and 990–1000 CE. Distinct 14C excursions starting in the boreal summer of 774 and the boreal spring of 993 ensure the precise dating of 44 tree-ring records from five continents. We also identify a meridional decline of 11-year mean atmospheric radiocarbon concentrations across both hemispheres. Corroborated by historical eye-witness accounts of red auroras, our results suggest a global exposure to strong solar proton radiation. To improve understanding of the return frequency and intensity of past cosmic events, which is particularly important for assessing the potential threat of space weather on our society, further annually resolved 14C measurements are needed.
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| 5. |
- Sigl, M., et al.
(author)
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Timing and climate forcing of volcanic eruptions for the past 2,500 years
- 2015
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 523:7562, s. 543-549
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Journal article (peer-reviewed)abstract
- Volcanic eruptions contribute to climate variability, but quantifying these contributions has been limited by inconsistencies in the timing of atmospheric volcanic aerosol loading determined from ice cores and subsequent cooling from climate proxies such as tree rings. Here we resolve these inconsistencies and show that large eruptions in the tropics and high latitudes were primary drivers of interannual-to-decadal temperature variability in the Northern Hemisphere during the past 2,500 years. Our results are based on new records of atmospheric aerosol loading developed from high-resolution, multi-parameter measurements from an array of Greenland and Antarctic ice cores as well as distinctive age markers to constrain chronologies. Overall, cooling was proportional to the magnitude of volcanic forcing and persisted for up to ten years after some of the largest eruptive episodes. Our revised timescale more firmly implicates volcanic eruptions as catalysts in the major sixth-century pandemics, famines, and socioeconomic disruptions in Eurasia and Mesoamerica while allowing multi-millennium quantification of climate response to volcanic forcing.
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| 6. |
- Buntgen, U., et al.
(author)
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Recognising bias in Common Era temperature reconstructions
- 2022
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In: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 74
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Journal article (peer-reviewed)abstract
- A steep decline in the quality and quantity of available climate proxy records before medieval times challenges any comparison of reconstructed temperature and hydroclimate trends and extremes between the first and second half of the Common Era. Understanding of the physical causes, ecological responses and societal consequences of past climatic changes, however, demands highly-resolved, spatially-explicit, seasonally-defined and absolutely-dated archives over the entire period in question. Continuous efforts to improve existing proxy records and reconstruction methods and to develop new ones, as well as clear communication of all uncertainties (within and beyond academia) must be central tasks for the paleoclimate community.
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| 8. |
- Mekhaldi, F., et al.
(author)
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No Coincident Nitrate Enhancement Events in Polar Ice Cores Following the Largest Known Solar Storms
- 2017
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In: Journal of Geophysical Research: Atmospheres. - 2169-8996. ; 122:21, s. 11-11
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Journal article (peer-reviewed)abstract
- Knowledge on the occurrence rate of extreme solar storms is strongly limited by the relatively recent advent of satellite monitoring of the Sun. To extend our perspective of solar storms prior to the satellite era and because atmospheric ionization induced by solar energetic particles (SEPs) can lead to the production of odd nitrogen, nitrate spikes in ice cores have been tentatively used to document both the occurrence and intensity of past SEP events. However, the reliability of the use of nitrate in ice records as a proxy for SEP events is strongly debated. This is partly due to equivocal detection of nitrate spikes in single ice cores and possible alternative sources, such as biomass burning plumes. Here we present new continuous high-resolution measurements of nitrate and of the biomass burning species ammonium and black carbon, from several Antarctic and Greenland ice cores. We investigate periods covering the two largest known SEP events of 775 and 994 Common Era as well as the Carrington event and the hard SEP event of February 1956. We report no coincident nitrate spikes associated with any of these benchmark events. We also demonstrate the low reproducibility of the nitrate signal in multiple ice cores and confirm the significant relationship between biomass burning plumes and nitrate spikes in individual ice cores. In the light of these new data, there is no line of evidence that supports the hypothesis that ice cores preserve or document detectable amounts of nitrate produced by SEPs, even for the most extreme events known to date.
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| 10. |
- Barthelmi, K., et al.
(author)
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Atomistic defects as single-photon emitters in atomically thin MoS2
- 2020
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 117:7
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Journal article (peer-reviewed)abstract
- Precisely positioned and scalable single-photon emitters (SPEs) are highly desirable for applications in quantum technology. This Perspective discusses single-photon-emitting atomistic defects in monolayers of MoS2 that can be generated by focused He-ion irradiation with few nanometers positioning accuracy. We present the optical properties of the emitters and the possibilities to implement them into photonic and optoelectronic devices. We showcase the advantages of the presented emitters with respect to atomistic positioning, scalability, long (microsecond) lifetime, and a homogeneous emission energy within ensembles of the emitters. Moreover, we demonstrate that the emitters are stable in energy on a timescale exceeding several weeks and that temperature cycling narrows the ensembles' emission energy distribution.
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