Articles de revues : « Anthropogenic signal »

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Gordeev, Vasily, Sergey Malyshkov et Vitaly Polivach. « GEOPHYSICAL MONITORING OF TECHNOGENIC HAZARDS ON ANTHROPOGENIC SOILS ». Interexpo GEO-Siberia 1, n^o 2 (2019) : 65–72. http://dx.doi.org/10.33764/2618-981x-2019-1-2-65-72.

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Rock stability estimation tasks on anthropogenic soils require both preliminary survey and on-going real-time monitoring providing alerts on possible cave-in threats. Using VLF monitoring data incorporated into software-hardware geodynamical processes automated surveillance system allows to accomplish that task. Authors describe a unique method, based on Earth’s natural pulsed electro-magnetic field (ENPEMF) recording and make conclusions on the efficiency of the solutions ap-plied for hazardous geodynamic processes monitoring on anthropogenic soils. The principle of the method is to distinguish spatial variations of ENPEMF signal against diurnal oscillations and tech-nogenic signals. Correlation between relative signal intensity and stress-strained state of the rocks is experimentally demonstrated.

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Zhang, Honghai, et Thomas L. Delworth. « Detectability of Decadal Anthropogenic Hydroclimate Changes over North America ». Journal of Climate 31, n^o 7 (avril 2018) : 2579–97. http://dx.doi.org/10.1175/jcli-d-17-0366.1.

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Regional hydroclimate changes on decadal time scales contain substantial natural variability. This presents a challenge for the detection of anthropogenically forced hydroclimate changes on these spatiotemporal scales because the signal of anthropogenic changes is modest, compared to the noise of natural variability. However, previous studies have shown that this signal-to-noise ratio can be greatly improved in a large model ensemble where each member contains the same signal but different noise. Here, using multiple state-of-the-art large ensembles from two climate models, the authors quantitatively assess the detectability of anthropogenically caused decadal shifts in precipitation-minus-evaporation (PmE) mean state against natural variability, focusing on North America during 2000–50. Anthropogenic forcing is projected to cause detectable (signal larger than noise) shifts in PmE mean state relative to the 1950–99 climatology over 50%–70% of North America by 2050. The earliest detectable signals include, during November–April, a moistening over northeastern North America and a drying over southwestern North America and, during May–October, a drying over central North America. Different processes are responsible for these signals. Changes in submonthly transient eddy moisture fluxes account for the northeastern moistening and central drying, while monthly atmospheric circulation changes explain the southwestern drying. These model findings suggest that despite the dominant role of natural internal variability on decadal time scales, anthropogenic shifts in PmE mean state can be detected over most of North America before the middle of the current century.

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Svoma, Bohumil M., et Robert C. Balling. « An anthropogenic signal in Phoenix, Arizona winter precipitation ». Theoretical and Applied Climatology 98, n^o 3-4 (24 février 2009) : 315–21. http://dx.doi.org/10.1007/s00704-009-0121-1.

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Akçay, Çağlar, et Michael D. Beecher. « Multi-modal communication : song sparrows increase signal redundancy in noise ». Biology Letters 15, n^o 10 (octobre 2019) : 20190513. http://dx.doi.org/10.1098/rsbl.2019.0513.

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Although the effects of anthropogenic noise on animal communication have been studied widely, most research on the effect of noise in communication has focused on signals in a single modality. Consequently, how multi-modal communication is affected by anthropogenic noise is relatively poorly understood. Here, we ask whether song sparrows ( Melospiza melodia ) show evidence of plasticity in response to noise in two aggressive signals in acoustic and visual modalities. We test two hypotheses: (i) that song sparrows will shift signalling effort to the visual modality (the multi-modal shift hypothesis) and (ii) that they will increase redundancy of their multi-modal signalling (the back-up signal hypothesis). We presented male song sparrows with song playback and a taxidermic mount with or without a low-frequency acoustic noise from a nearby speaker. We found that males did not switch their signalling effort to visual modality (i.e. wing waves) in response to the noise. However, the correlation between warbled soft songs and wing waves increased in the noise treatment, i.e. signals became more redundant. These results suggest that when faced with anthropogenic noise, song sparrows can increase the redundancy of their multi-modal signals, which may aid in the robustness of the communication system.

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Hedegaard, G. B., J. H. Christensen et J. Brandt. « The relative importance of impacts from climate change vs. emissions change on air pollution levels in the 21st century ». Atmospheric Chemistry and Physics Discussions 12, n^o 9 (19 septembre 2012) : 24501–30. http://dx.doi.org/10.5194/acpd-12-24501-2012.

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Abstract. So far several studies have analysed the impacts of climate change on future air pollution levels. Significant changes due to impacts of climate change have been made clear. Nevertheless, these changes are not yet included in national, regional or global air pollution reduction strategies. The changes in future air pollution levels are caused by both impacts from climate change and anthropogenic emission changes and the importance of these signals needs to be quantified and compared. In this study we use the Danish Eulerian Hemispheric Model (DEHM) driven on meteorological input data from the coupled Atmosphere-Ocean General Circulation Model ECHAM5/MPI-OM and forced with the newly developed RCP4.5 emissions. The relative importance of the climate signal and the signal from changes in anthropogenic emissions on the future ozone, black carbon (BC), total particulate matter with a diameter below 2.5 μm (total PM2.5 including BC, primary organic carbon (OC), mineral dust and secondary inorganic aerosols (SIA)) and total nitrogen (including NHx + NOy) has been determined. For ozone the impacts of anthropogenic emissions dominates though a climate penalty is found in the Arctic region and the Northwestern Europe where the signal from climate change dampens the effect from the projected emission reductions of anthropogenic ozone precursors. The investigated particles are even more dominated by the impacts from emission changes. For black carbon the emission signal dominates slightly at high latitudes increasing to be up to an order of magnitude larger close to the emission sources in temperate and subtropical areas. Including all particulate matter with a diameter below 2.5 μm (total PM2.5) enhances the dominance from emissions change. In contrast, total nitrogen (NHx + NOy) in parts of the Arctic and at low latitudes is dominated by impacts of climate change.

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Lombardozzi, Danica, Gordon B. Bonan et Douglas W. Nychka. « The emerging anthropogenic signal in land–atmosphere carbon-cycle coupling ». Nature Climate Change 4, n^o 9 (27 juillet 2014) : 796–800. http://dx.doi.org/10.1038/nclimate2323.

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Francis, Clinton D., Catherine P. Ortega et Alexander Cruz. « Different behavioural responses to anthropogenic noise by two closely related passerine birds ». Biology Letters 7, n^o 6 (25 mai 2011) : 850–52. http://dx.doi.org/10.1098/rsbl.2011.0359.

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Anthropogenic noise, now common to many landscapes, can impair acoustic communication for many species, yet some birds compensate for masking by noise by altering their songs. The phylogenetic distribution of these noise-dependent signal adjustments is uncertain, and it is not known whether closely related species respond similarly to noise. Here, we investigated the influence of noise on habitat occupancy rates and vocal frequency in two congeneric vireos with similar song features. Noise exposure did not influence occupancy rates for either species, yet song features of both changed, albeit in different ways. With increases in noise levels, plumbeous vireos ( Vireo plumbeus ) sang shorter songs with higher minimum frequencies. By contrast, grey vireos ( Vireo vicinior ) sang longer songs with higher maximum frequencies. These findings support the notion that vocal plasticity may help some species occupy noisy areas, but because there were no commonalities among the signal changes exhibited by these closely related birds, it may be difficult to predict how diverse species may modify their signals in an increasingly noisy world.

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Seong, Min-Gyu, Seung-Ki Min, Yeon-Hee Kim, Xuebin Zhang et Ying Sun. « Anthropogenic Greenhouse Gas and Aerosol Contributions to Extreme Temperature Changes during 1951–2015 ». Journal of Climate 34, n^o 3 (février 2021) : 857–70. http://dx.doi.org/10.1175/jcli-d-19-1023.1.

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AbstractThis study conducted a detection and attribution analysis of the observed global and regional changes in extreme temperatures during 1951–2015. HadEX3 observations were compared with multimodel simulations from the Coupled Model Intercomparison Project phase 6 (CMIP6) using an optimal fingerprinting technique. Annual maximum daily maximum and minimum temperatures (TXx and TNx; warm extremes) and annual minimum daily maximum and minimum temperatures (TXn and TNn; cold extremes) over land were analyzed considering global, continental, and subcontinental scales. Response patterns (fingerprints) of extreme temperatures to anthropogenic (ANT), greenhouse gases (GHG), aerosols (AA), and natural (NAT) forcings were obtained from CMIP6 forced simulations. The internal variability ranges were estimated from preindustrial control simulations. A two-signal detection analysis where the observations are regressed onto ANT and NAT fingerprints simultaneously reveals that ANT signals are robustly detected in separation from NAT over global and all continental domains (North and South America, Europe, Asia, and Oceania) for most of the extreme indices. ANT signals are also detected over many subcontinental regions, particularly for warm extremes (more than 60% of 33 subregions). A three-signal detection analysis that considers GHG, AA, and NAT fingerprints simultaneously demonstrates that GHG signals are detected in isolation from other external forcings over global, continental, and several subcontinental domains especially for warm extremes, explaining most of the observed warming. Moreover, AA influences are detected for warm extremes over Europe and Asia, indicating significant offsetting cooling contributions. Overall, human influences are detected more frequently, compared to previous studies, particularly for cold extremes, due to the extended period and the improved spatial coverage of observations.

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Lillis, Ilse Van, et Olaf Boebel. « Marine soundscape planning : Seeking acoustic niches for anthropogenic sound ». Journal of Ecoacoustics 2, n^o 1 (29 mars 2018) : 1. http://dx.doi.org/10.22261/jea.5gsnt8.

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Both marine mammals and hydroacoustic instruments employ underwater sound to communicate, navigate or infer information about the marine environment. Concurrent timing of acoustic activities using similar frequency regimes may result in (potentially mutual) interference of acoustic signals when both sources are within audible range of the recipient. While marine mammal fitness might be negatively impacted upon, both on individual and population level, hydroacoustic studies may generate low quality data or suffer data loss as a result of bioacoustic interference. This article pursues, in analogy to landscape planning, the concept of marine soundscape planning to reconcile potentially competing uses of acoustic space by managing the anthropogenic sound sources. We here present a conceptual framework exploring the potential of soundscape planning in reducing (mutual) acoustic interference between hydroacoustic instrumentation and marine mammals. The basis of this framework is formed by the various mechanisms by which acoustic niche formation (i.e., the partitioning of the acoustic space) occurs in species-rich communities that acoustically coexist while maintaining high fidelity (hi-fi) soundscapes, i.e., by acoustically partitioning the environment on the basis of time, space, frequency and signal structure. Hydroacoustic measurements often exhibit certain flexibility in their timing, and even instrument positioning, potentially offering the opportunity to minimize the ecological imprint of their operation. This study explores how the principle of acoustic niches could contribute to reduce potential (mutual) acoustic interference based on actual acoustic data from three recording locations in polar oceans. By employing marine soundscape planning strategies, entailing shifting the timing or position of hydroacoustic experiments, or adapting signal structure or frequency, we exemplify the potential efficacy of smart planning for four different hydroacoustic instrumentation types: multibeam echosounders, air guns, RAFOS (Ranging and Fixing of Sound) and tomographic sound sources.

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Dunlop, Rebecca, Michael Noad et Dorian Houser. « Using behavioural response experiments to measure humpback whale hearing in noise ». Journal of the Acoustical Society of America 154, n^o 4_supplement (1 octobre 2023) : A46. http://dx.doi.org/10.1121/10.0022751.

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Currently, there are no direct data on mysticete hearing in noise. Available data comes from anatomical modelling, the assumption they can hear their own sounds, and studies on the effects of various sources of anthropogenic noise on their behavior. This study used a behavioral response study design to quantify humpback whale hearing in natural ocean noise. Tonal signals, ranging from 250 Hz to 16kHz, were used as the stimuli, and a change in humpback group behavior indicated the whales heard the signal. Individual whale and group behavior were quantified using a combination of land-based tracking data of groups and tag data deployed on individual whales to record fine-scale 3D movement underwater. The signal-to-noise ratio was estimated at the initial response position of the group or whale, assuming this was the level at which they first detected the tone in noise. Results confirm that humpback whales responded to signals in noise at detection levels comparable to other marine mammals and that their ability to hear signals in noise at higher frequencies is better than expected. This provides empirical data on hearing in a mysticete which can be used to better predict the acoustic impacts of anthropogenic noise on marine mammals.

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Perkins-Kirkpatrick, S. E., D. A. Stone, D. M. Mitchell, S. Rosier, A. D. King, Y. T. E. Lo, J. Pastor-Paz, D. Frame et M. Wehner. « On the attribution of the impacts of extreme weather events to anthropogenic climate change ». Environmental Research Letters 17, n^o 2 (26 janvier 2022) : 024009. http://dx.doi.org/10.1088/1748-9326/ac44c8.

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Abstract Investigations into the role of anthropogenic climate change in extreme weather events are now starting to extend into analysis of anthropogenic impacts on non-climate (e.g. socio-economic) systems. However, care needs to be taken when making this extension, because methodological choices regarding extreme weather attribution can become crucial when considering the events’ impacts. The fraction of attributable risk (FAR) method, useful in extreme weather attribution research, has a very specific interpretation concerning a class of events, and there is potential to misinterpret results from weather event analyses as being applicable to specific events and their impact outcomes. Using two case studies of meteorological extremes and their impacts, we argue that FAR is not generally appropriate when estimating the magnitude of the anthropogenic signal behind a specific impact. Attribution assessments on impacts should always be carried out in addition to assessment of the associated meteorological event, since it cannot be assumed that the anthropogenic signal behind the weather is equivalent to the signal behind the impact because of lags and nonlinearities in the processes through which the impact system reacts to weather. Whilst there are situations where employing FAR to understand the climate change signal behind a class of impacts is useful (e.g. ‘system breaking’ events), more useful results will generally be produced if attribution questions on specific impacts are reframed to focus on changes in the impact return value and magnitude across large samples of factual and counterfactual climate model and impact simulations. We advocate for constant interdisciplinary collaboration as essential for effective and robust impact attribution assessments.

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Hamlington, B. D., M. W. Strassburg, R. R. Leben, W. Han, R. S. Nerem et K.-Y. Kim. « Uncovering an anthropogenic sea-level rise signal in the Pacific Ocean ». Nature Climate Change 4, n^o 9 (20 juillet 2014) : 782–85. http://dx.doi.org/10.1038/nclimate2307.

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Plancherel, Y., K. B. Rodgers, R. M. Key, A. R. Jacobson et J. L. Sarmiento. « Role of regression model selection and station distribution on the estimation of oceanic anthropogenic carbon change by eMLR ». Biogeosciences Discussions 9, n^o 10 (19 octobre 2012) : 14589–638. http://dx.doi.org/10.5194/bgd-9-14589-2012.

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Abstract. Differencing predictions of linear regression models generated from hydrographic data collected at different times (the eMLR method) was proposed as a means of quantifying the dominant patterns of change in oceanic anthropogenic carbon in the context of sparse data sets subject to natural variability. The ability of eMLR to recover the anthropogenic carbon signal in the North Atlantic was tested using a global circulation and biogeochemistry model. Basin-scale applications of eMLR on horizontal layers can estimate the change in anthropogenic carbon inventory with an accuracy typically better than 10%. Regression model selection influences the distribution of the recovered anthropogenic carbon change signal. The systematic use of statistically optimum regression formulae does not produce the best estimates of anthropogenic carbon change if the distribution of the station locations emphasizes hydrographic features differently in time. Additional factors, such as a balanced station distribution and vertical continuity of the regression formulae should be considered to guide model selection. Accurate results are obtained when multiple formulae are used throughout the water column. Different formulae can yield results of similar quality. The fact that good results are obtained in the hydrographically complex North Atlantic suggests that eMLR can produce accurate estimates in other basins.

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Min, Seung-Ki, Xuebin Zhang, Francis Zwiers, Hideo Shiogama, Yu-Shiang Tung et Michael Wehner. « Multimodel Detection and Attribution of Extreme Temperature Changes ». Journal of Climate 26, n^o 19 (24 septembre 2013) : 7430–51. http://dx.doi.org/10.1175/jcli-d-12-00551.1.

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Abstract Recent studies have detected anthropogenic influences due to increases in greenhouse gases on extreme temperature changes during the latter half of the twentieth century at global and regional scales. Most of the studies, however, were based on a limited number of climate models and also separation of anthropogenic influence from natural factors due to changes in solar and volcanic activities remains challenging at regional scales. Here, the authors conduct optimal fingerprinting analyses using 12 climate models integrated under anthropogenic-only forcing or natural plus anthropogenic forcing. The authors compare observed and simulated changes in annual extreme temperature indices of coldest night and day (TNn and TXn) and warmest night and day (TNx and TXx) from 1951 to 2000. Spatial domains from global mean to continental and subcontinental regions are considered and standardization of indices is employed for better intercomparisons between regions and indices. The anthropogenic signal is detected in global and northern continental means of all four indices, albeit less robustly for TXx, which is consistent with previous findings. The detected anthropogenic signals are also found to be separable from natural forcing influence at the global scale and to a lesser extent at continental and subcontinental scales. Detection occurs more frequently in TNx and TNn than in other indices, particularly at smaller scales, supporting previous studies based on different methods. A combined detection analysis of daytime and nighttime temperature extremes suggests potential applicability to a multivariable assessment.

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Chou, Trina L., Anjali Krishna, Mark Fossesca, Avani Desai, Julia Goldberg, Sophie Jones, Morgan Stephens, Benjamin M. Basile et Megan D. Gall. « Interspecific differences in the effects of masking and distraction on anti-predator behavior in suburban anthropogenic noise ». PLOS ONE 18, n^o 8 (18 août 2023) : e0290330. http://dx.doi.org/10.1371/journal.pone.0290330.

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Predation is a common threat to animal survival. The detection of predators or anti-predator communication signals can be disrupted by anthropogenic noise; however, the mechanism by which responses are affected is unclear. Masking and distraction are the two hypotheses that have emerged as likely explanations for changes in behavior in noise. Masking occurs when the signal and noise fall within the same sensory domain; noise overlapping the energy in the signal reduces signal detection. Distraction can occur when noise in any sensory domain contributes to a greater cognitive load, thereby reducing signal detection. Here, we used a repeated measures field experiment to determine the relative contributions of masking and distraction in mediating reduced anti-predator responses in noise. We recorded the approaches and vocalizations of black-capped chickadees (Poecile atricapillus), tufted titmice (Baeolophus bicolor), and white-breasted nuthatches (Sitta carolinensis) to both visual and acoustic cues of predator presence, either with or without simultaneous exposure to anthropogenic noise. Titmice increased their calling to both visual and acoustic cues of predator presence. However, there was no significant effect of noise on the calling responses of titmice regardless of stimulus modality. Noise appeared to produce a distraction effect in chickadees; however, this effect was small, suggesting that chickadees may be relatively unaffected by low levels of anthropogenic noise in suburban environments. White-breasted nuthatch calling behavior was affected by the interaction of the modality of the predator stimulus and the noise condition. Nuthatches had a delayed response to the predator presentations, with a greater calling rate following the presentation of the acoustic stimulus in quiet compared to the presentation of the acoustic stimulus in noise. However, there was no difference in calling rate between the quiet and noise conditions for the visual stimulus. Together this suggests that even moderate levels of noise have some masking effect for white-breasted nuthatches. We suggest that the mechanisms through which noise influences anti-predator behavior may depend on the social roles, foraging ecology and auditory capabilities of each species.

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Soe, Kay Khine, Sukree Hajisamae, Penjai Sompongchaiyakul, Prawit Towatana et Siriporn Pradit. « Feeding Habits and the Occurrence of Anthropogenic Debris in the Stomach Content of Marine Fish from Pattani Bay, Gulf of Thailand ». Biology 11, n^o 2 (19 février 2022) : 331. http://dx.doi.org/10.3390/biology11020331.

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This study assessed the feeding habits and ingestion of anthropogenic debris in 34 marine fish species from the southern Gulf of Thailand. A total of 5478 fish samples of 12 families were categorised into seven groups: planktivore, Lucifer feeder, fish feeder, Acetes feeder, shrimp feeder, piscivore, and zoobenthivore fish. A total of 2477 anthropogenic debris items were extracted from 12 fish species by visual inspection. Their ingestion of anthropogenic debris was influenced by season (p < 0.0001), with the highest ingestion during the northeast monsoon season. Furthermore, planktivorous fish displayed more ingested anthropogenic debris than the other investigated species (p = 0.022). Blue-coloured anthropogenic debris was commonly detected in the stomachs of fish and significantly differed between species (p > 0.001). Water depth and season significantly influenced the availability of food types (AF) for fish (p < 0.001). These findings provide evidence of the ingestion of anthropogenic debris by fish inhabiting a natural bay and signal the future anthropogenic pollution of marine fish.

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Knutson, T. R., T. L. Delworth, K. W. Dixon, I. M. Held, J. Lu, V. Ramaswamy, M. D. Schwarzkopf, G. Stenchikov et R. J. Stouffer. « Assessment of Twentieth-Century Regional Surface Temperature Trends Using the GFDL CM2 Coupled Models ». Journal of Climate 19, n^o 9 (1 mai 2006) : 1624–51. http://dx.doi.org/10.1175/jcli3709.1.

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Abstract Historical climate simulations of the period 1861–2000 using two new Geophysical Fluid Dynamics Laboratory (GFDL) global climate models (CM2.0 and CM2.1) are compared with observed surface temperatures. All-forcing runs include the effects of changes in well-mixed greenhouse gases, ozone, sulfates, black and organic carbon, volcanic aerosols, solar flux, and land cover. Indirect effects of tropospheric aerosols on clouds and precipitation processes are not included. Ensembles of size 3 (CM2.0) and 5 (CM2.1) with all forcings are analyzed, along with smaller ensembles of natural-only and anthropogenic-only forcing, and multicentury control runs with no external forcing. Observed warming trends on the global scale and in many regions are simulated more realistically in the all-forcing and anthropogenic-only forcing runs than in experiments using natural-only forcing or no external forcing. In the all-forcing and anthropogenic-only forcing runs, the model shows some tendency for too much twentieth-century warming in lower latitudes and too little warming in higher latitudes. Differences in Arctic Oscillation behavior between models and observations contribute substantially to an underprediction of the observed warming over northern Asia. In the all-forcing and natural-only forcing runs, a temporary global cooling in the models during the 1880s not evident in the observed temperature records is volcanically forced. El Niño interactions complicate comparisons of observed and simulated temperature records for the El Chichón and Mt. Pinatubo eruptions during the early 1980s and early 1990s. The simulations support previous findings that twentieth-century global warming has resulted from a combination of natural and anthropogenic forcing, with anthropogenic forcing being the dominant cause of the pronounced late-twentieth-century warming. The regional results provide evidence for an emergent anthropogenic warming signal over many, if not most, regions of the globe. The warming signal has emerged rather monotonically in the Indian Ocean/western Pacific warm pool during the past half-century. The tropical and subtropical North Atlantic and the tropical eastern Pacific are examples of regions where the anthropogenic warming signal now appears to be emerging from a background of more substantial multidecadal variability.

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Hedegaard, G. B., J. H. Christensen et J. Brandt. « The relative importance of impacts from climate change vs. emissions change on air pollution levels in the 21st century ». Atmospheric Chemistry and Physics 13, n^o 7 (2 avril 2013) : 3569–85. http://dx.doi.org/10.5194/acp-13-3569-2013.

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Abstract. So far several studies have analysed the impacts of climate change on future air pollution levels. Significant changes due to impacts of climate change have been made clear. Nevertheless, these changes are not yet included in national, regional or global air pollution reduction strategies. The changes in future air pollution levels are caused by both impacts from climate change and anthropogenic emission changes, the importance of which needs to be quantified and compared. In this study we use the Danish Eulerian Hemispheric Model (DEHM) driven by meteorological input data from the coupled Atmosphere-Ocean General Circulation Model ECHAM5/MPI-OM and forced with the newly developed RCP4.5 emissions. The relative importance of the climate signal and the signal from changes in anthropogenic emissions on the future ozone, black carbon (BC), total particulate matter with a diameter below 2.5 μm (total PM2.5 including BC, primary organic carbon (OC), mineral dust and secondary inorganic aerosols (SIA)) and total nitrogen (including NHx + NOy) has been determined. For ozone, the impacts of anthropogenic emissions dominate, though a climate penalty is found in the Arctic region and northwestern Europe, where the signal from climate change dampens the effect from the projected emission reductions of anthropogenic ozone precursors. The investigated particles are even more dominated by the impacts from emission changes. For black carbon the emission signal dominates slightly at high latitudes, with an increase up to an order of magnitude larger, close to the emission sources in temperate and subtropical areas. Including all particulate matter with a diameter below 2.5 μm (total PM2.5) enhances the dominance from emissions change. In contrast, total nitrogen (NHx + NOy) in parts of the Arctic and at low latitudes is dominated by impacts of climate change.

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Vázquez-Rodríguez, M., X. A. Padin, A. F. Ríos, R. G. J. Bellerby et F. F. Pérez. « An upgraded carbon-based method to estimate the anthropogenic fraction of dissolved CO<sub>2</sub> ; in the Atlantic Ocean ». Biogeosciences Discussions 6, n^o 2 (29 avril 2009) : 4527–71. http://dx.doi.org/10.5194/bgd-6-4527-2009.

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Wang, Zhuo, Yujing Jiang, Hui Wan, Jun Yan et Xuebin Zhang. « Detection and Attribution of Changes in Extreme Temperatures at Regional Scale ». Journal of Climate 30, n^o 17 (septembre 2017) : 7035–47. http://dx.doi.org/10.1175/jcli-d-15-0835.1.

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This paper improves an extreme-value-theory-based detection and attribution method and then applies it to four types of extreme temperatures, annual minimum daily minimum (TNn) and maximum (TXn) and annual maximum daily minimum (TNx) and maximum (TXx), using the HadEX2 observation and the CMIP5 multimodel simulation datasets of the period 1951–2010 at 17 subcontinent regions. The methodology is an analog of the fingerprinting method adapted to extremes using the generalized extreme value (GEV) distribution. The signals are estimated as the time-dependent location parameters of GEV distributions fitted to extremes simulated by multimodel ensembles under anthropogenic (ANT), natural (NAT), or combined anthropogenic and natural (ALL) external forcings. The observed extremes are modeled by GEV distributions whose location parameters incorporate the signals as covariates. A coordinate descent algorithm improves both computational efficiency and accuracy in comparison to the existing method, facilitating detection of multiple signals simultaneously. An overall goodness-of-fit test was performed at the regional level. The ANT signal was separated from the NAT signal in four to six regions. In these analyses, the waiting times of the 1951–55 20-yr return level in the 2006–10 climate for the temperature of the coldest night and day were found to have increased to over 20 yr; the corresponding waiting times for the warmest night and day were found to have dropped below 20 yr in a majority of the regions.

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Troïanowski, Mathieu, Camille Condette, Nathalie Mondy, Adeline Dumet et Thierry Lengagne. « Traffic noise affects colouration but not calls in the European treefrog (Hyla arborea) ». Behaviour 152, n^o 6 (2015) : 821–36. http://dx.doi.org/10.1163/1568539x-00003255.

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In terrestrial habitats, traffic noise is responsible for chronic noise exposure and impacts both signal detection and acoustic signal structure. Several species are known to adapt their call structures to cope with noise. However, compromised hearing affects more than acoustic communication, and noise should be consider as a stress factor that can also alter visual communication in the case of carotenoid-based signals. Here, we experimentally investigated the impact of traffic noise on the expression of secondary sexual signals in the European treefrog, Hyla arborea. Treefrogs use multimodal communication in the sexual selection process (mating calls and vocal sac colouration). We found that treefrogs seem unable to adjust their call structure. Nonetheless, males showed a significant decrease in colouration intensity. Our findings highlight for the first time the negative effect of traffic noise on colour signals. This suggests that anthropogenic noise could affect a wider range of species than previously thought.

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Li, Wei, Zhihong Jiang, Xuebin Zhang et Laurent Li. « On the Emergence of Anthropogenic Signal in Extreme Precipitation Change Over China ». Geophysical Research Letters 45, n^o 17 (12 septembre 2018) : 9179–85. http://dx.doi.org/10.1029/2018gl079133.

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Paull, Charles K., William Ussler, Patrick J. Mitts, David W. Caress et G. James West. « Discordant 14C-stratigraphies in upper Monterey Canyon : A signal of anthropogenic disturbance ». Marine Geology 233, n^o 1-4 (novembre 2006) : 21–36. http://dx.doi.org/10.1016/j.margeo.2006.07.008.

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Phipps, Steven J., Helen V. McGregor, Joëlle Gergis, Ailie J. E. Gallant, Raphael Neukom, Samantha Stevenson, Duncan Ackerley, Josephine R. Brown, Matt J. Fischer et Tas D. van Ommen. « Paleoclimate Data–Model Comparison and the Role of Climate Forcings over the Past 1500 Years* ». Journal of Climate 26, n^o 18 (9 septembre 2013) : 6915–36. http://dx.doi.org/10.1175/jcli-d-12-00108.1.

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Abstract The past 1500 years provide a valuable opportunity to study the response of the climate system to external forcings. However, the integration of paleoclimate proxies with climate modeling is critical to improving the understanding of climate dynamics. In this paper, a climate system model and proxy records are therefore used to study the role of natural and anthropogenic forcings in driving the global climate. The inverse and forward approaches to paleoclimate data–model comparison are applied, and sources of uncertainty are identified and discussed. In the first of two case studies, the climate model simulations are compared with multiproxy temperature reconstructions. Robust solar and volcanic signals are detected in Southern Hemisphere temperatures, with a possible volcanic signal detected in the Northern Hemisphere. The anthropogenic signal dominates during the industrial period. It is also found that seasonal and geographical biases may cause multiproxy reconstructions to overestimate the magnitude of the long-term preindustrial cooling trend. In the second case study, the model simulations are compared with a coral δ18O record from the central Pacific Ocean. It is found that greenhouse gases, solar irradiance, and volcanic eruptions all influence the mean state of the central Pacific, but there is no evidence that natural or anthropogenic forcings have any systematic impact on El Niño–Southern Oscillation. The proxy climate relationship is found to change over time, challenging the assumption of stationarity that underlies the interpretation of paleoclimate proxies. These case studies demonstrate the value of paleoclimate data–model comparison but also highlight the limitations of current techniques and demonstrate the need to develop alternative approaches.

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Moseley, Dana Lynn, Graham Earnest Derryberry, Jennifer Nicole Phillips, Julie Elizabeth Danner, Raymond Michael Danner, David Andrew Luther et Elizabeth Perrault Derryberry. « Acoustic adaptation to city noise through vocal learning by a songbird ». Proceedings of the Royal Society B : Biological Sciences 285, n^o 1888 (10 octobre 2018) : 20181356. http://dx.doi.org/10.1098/rspb.2018.1356.

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Anthropogenic noise imposes novel selection pressures, especially on species that communicate acoustically. Many animals—including insects, frogs, whales and birds—produce sounds at higher frequencies in areas with low-frequency noise pollution. Although there is support for animals changing their vocalizations in real time in response to noise (i.e. immediate flexibility), other evolutionary mechanisms for animals that learn their vocalizations remain largely unexplored. We hypothesize that cultural selection for signal structures less masked by noise is a mechanism of acoustic adaptation to anthropogenic noise. We test this hypothesis by presenting nestling white-crowned sparrows (Zonotrichia leucophyrs) with less-masked (higher-frequency) and more-masked (lower-frequency) tutor songs either during playback of anthropogenic noise (noise-tutored treatment) or at a different time from noise playback (control treatment). As predicted, we find that noise-tutored males learn less-masked songs significantly more often, whereas control males show no copying preference, providing strong experimental support for cultural selection in response to anthropogenic noise. Further, noise-tutored males reproduce songs at higher frequencies than their tutor, indicating a distinct mechanism to increase signal transmission in a noisy environment. Notably, noise-tutored males achieve lower performance songs than their tutors, suggesting potential costs in a sexual selection framework.

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Faranda, Davide, et Dimitri Defrance. « A wavelet-based approach to detect climate change on the coherent and turbulent component of the atmospheric circulation ». Earth System Dynamics 7, n^o 2 (20 juin 2016) : 517–23. http://dx.doi.org/10.5194/esd-7-517-2016.

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Abstract. The modifications of atmospheric circulation induced by anthropogenic effects are difficult to capture because wind fields feature a complex spectrum where the signal of large-scale coherent structures (planetary, baroclinic waves and other long-term oscillations) is mixed up with turbulence. Our purpose is to study the effects of climate changes on these two components separately by applying a wavelet analysis to the 700 hPa wind fields obtained in climate simulations for different forcing scenarios. We study the coherent component of the signal via a correlation analysis to detect the persistence of large-scale or long-lasting structures, whereas we use the theory of autoregressive moving-average stochastic processes to measure the spectral complexity of the turbulent component. Under strong anthropogenic forcing, we detect a significant climate change signal. The analysis suggests that coherent structures will play a dominant role in future climate, whereas turbulent spectra will approach a classical Kolmogorov behaviour.

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Lu, Chunhui, Ying Sun et Xuebin Zhang. « Anthropogenic Influence on the Diurnal Temperature Range since 1901 ». Journal of Climate 35, n^o 22 (15 novembre 2022) : 3583–98. http://dx.doi.org/10.1175/jcli-d-21-0928.1.

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Abstract The diurnal temperature range (DTR) as measured by the difference between daily maximum (Tmax) and minimum (Tmin) temperatures is of great importance to human health, ecology, and agriculture. The link of its long-term change to anthropogenic forcing is still unclear. This study shows evidence of human influence on long-term changes in DTR over the globe, five continents, and China during the past century (1901–2014). Using multiple observational datasets, we find a general decrease in the DTR over most of the global land since 1901, especially after the mid-1950s. Changes in DTR are due to different warming rates of Tmax and Tmin in response to external forcings. The climate models that participated in phase 6 of the Coupled Model Intercomparison Project Phase 6 (CMIP6) generally reproduce most of the changes in DTR, along with those in Tmax and Tmin. The models have underestimated the observed changes in DTR, however. A formal detection and attribution analysis shows that the anthropogenic forcing signal, including both greenhouse gas and aerosol emissions but dominated by the greenhouse gas emissions, is the main driver for these changes. The anthropogenic aerosol signal can be detected in Tmax and Tmin but not in DTR during the period of 1901–2014 over the globe and most continents. These indicate the observed decrease in DTR is not a simple response to anthropogenic aerosol emission. The natural signal is negligible in almost all the cases. Globally, anthropogenic influence is estimated to explain more than 90% of the observed changes in the three variables. In China, human influence is also clearly detected, although model simulated results on the regional scale have larger deviation. Significance Statement The diurnal temperature range (DTR) is of great importance in many areas. We compare multiple observational datasets with the simulations by climate models that participated in the latest phase (phase 6) of the Coupled Model Intercomparison Project (CMIP6), finding evidence of human influence on long-term changes in DTR over the past century (1901–2014) and robust evidence for the period since the early 1950s. The decrease in DTR as seen in the observational dataset is caused by different warming rates of daily maximum and daily minimum temperature in response to anthropogenic forcing, including both greenhouse gases and aerosols.

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Dayalu, Archana, J. William Munger, Steven C. Wofsy, Yuxuan Wang, Thomas Nehrkorn, Yu Zhao, Michael B. McElroy, Chris P. Nielsen et Kristina Luus. « Assessing biotic contributions to CO<sub>2</sub> ; fluxes in northern China using the Vegetation, Photosynthesis and Respiration Model (VPRM-CHINA) and observations from 2005 to 2009 ». Biogeosciences 15, n^o 21 (12 novembre 2018) : 6713–29. http://dx.doi.org/10.5194/bg-15-6713-2018.

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Abstract. Accurately quantifying the spatiotemporal distribution of the biological component of CO2 surface–atmosphere exchange is necessary to improve top-down constraints on China's anthropogenic CO2 emissions. We provide hourly fluxes of CO2 as net ecosystem exchange (NEE; µmol CO2 m−2 s−1) on a 0.25∘×0.25∘ grid by adapting the Vegetation, Photosynthesis, and Respiration Model (VPRM) to the eastern half of China for the time period from 2005 to 2009; the minimal empirical parameterization of the VPRM-CHINA makes it well suited for inverse modeling approaches. This study diverges from previous VPRM applications in that it is applied at a large scale to China's ecosystems for the first time, incorporating a novel processing framework not previously applied to existing VPRM versions. In addition, the VPRM-CHINA model prescribes methods for addressing dual-cropping regions that have two separate growing-season modes applied to the same model grid cell. We evaluate the VPRM-CHINA performance during the growing season and compare to other biospheric models. We calibrate the VPRM-CHINA with ChinaFlux and FluxNet data and scale up regionally using Weather Research and Forecasting (WRF) Model v3.6.1 meteorology and MODIS surface reflectances. When combined with an anthropogenic emissions model in a Lagrangian particle transport framework, we compare the ability of VPRM-CHINA relative to an ensemble mean of global hourly flux models (NASA CMS – Carbon Monitoring System) to reproduce observations made at a site in northern China. The measurements are heavily influenced by the northern China administrative region. Modeled hourly time series using vegetation fluxes prescribed by VPRM-CHINA exhibit low bias relative to measurements during the May–September growing season. Compared to NASA CMS subset over the study region, VPRM-CHINA agrees significantly better with measurements. NASA CMS consistently underestimates regional uptake in the growing season. We find that during the peak growing season, when the heavily cropped North China Plain significantly influences measurements, VPRM-CHINA models a CO2 uptake signal comparable in magnitude to the modeled anthropogenic signal. In addition to demonstrating efficacy as a low-bias prior for top-down CO2 inventory optimization studies using ground-based measurements, high spatiotemporal resolution models such as the VPRM are critical for interpreting retrievals from global CO2 remote-sensing platforms such as OCO-2 and OCO-3 (planned). Depending on the satellite time of day and season of crossover, efforts to interpret the relative contribution of the vegetation and anthropogenic components to the measured signal are critical in key emitting regions such as northern China – where the magnitude of the vegetation CO2 signal is shown to be equivalent to the anthropogenic signal.

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Wang, Yanjun, Mengjie Wang, Fei Teng et Yiye Ji. « Remote Sensing Monitoring and Analysis of Spatiotemporal Changes in China’s Anthropogenic Carbon Emissions Based on XCO2 Data ». Remote Sensing 15, n^o 12 (20 juin 2023) : 3207. http://dx.doi.org/10.3390/rs15123207.

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The monitoring and analysis of the spatiotemporal distribution of anthropogenic carbon emissions is an important part of realizing China’s regional “dual carbon” goals; that is, the aim is for carbon emissions to peak in 2030 an to achieve carbon neutrality by 2060, as well as achieving sustainable development of the ecological environment. The column-averaged CO2 dry air mole fraction (XCO2) of greenhouse gas remote sensing satellites has been widely used to monitor anthropogenic carbon emissions. However, selecting a reasonable background region to eliminate the influence of uncertainty factors is still an important challenge to monitor anthropogenic carbon emissions by using XCO2. Aiming at the problems of the imprecise selection of background regions, this study proposes to enhance the anthropogenic carbon emission signal in the XCO2 by using the regional comparison method based on the idea of zoning. First, this study determines the background region based on the Open-Data Inventory for Anthropogenic Carbon dioxide (ODIAC) dataset and potential temperature data. Second, the average value of the XCO2 in the background area was extracted and taken as the XCO2 background. On this basis, the XCO2 anomaly (XCO2ano) was obtained by regional comparison method. Finally, the spatiotemporal variation characteristics and trends of XCO2ano were analyzed, and the correlations between the number of residential areas and fossil fuel emissions were calculated. The results of the satellite observation data experiments over China from 2010 to 2020 show that the XCO2ano and anthropogenic carbon emissions have similar spatial distribution patterns. The XCO2ano in China changed significantly and was in a positive growth trend as a whole. The XCO2ano values have a certain positive correlation with the number of residential areas and observations of fossil fuel emissions. The purpose of this research is to enhance the anthropogenic carbon emission signals in satellite observation XCO2 data by combining ODIAC data and potential temperature data, achieve the remote sensing monitoring and analysis of spatiotemporal changes in anthropogenic carbon emissions over China, and provide technical support for the policies and paths of regional carbon emission reductions and ecological environmental protection.

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Clear, Jennifer L., Chiara Molinari et Richard H. W. Bradshaw. « Holocene fire in Fennoscandia and Denmark ». International Journal of Wildland Fire 23, n^o 6 (2014) : 781. http://dx.doi.org/10.1071/wf13188.

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Natural disturbance dynamics, such as fire, have a fundamental control on forest composition and structure. Knowledge of fire history and the dominant drivers of fire are becoming increasingly important for conservation and management practice. Temporal and spatial variability in biomass burning is examined here using 170 charcoal and 15 fire scar records collated throughout Fennoscandia and Denmark. The changing fire regime is discussed in relation to local biogeographical controls, regional climatic change, anthropogenic land use and fire suppression. The region has experienced episodic variability in the dominant drivers of biomass burning throughout the Holocene, creating a frequently changing fire regime. Early Holocene biomass burning appears to be driven by fuel availability. Increased continentality during the mid-Holocene Thermal Maximum coincides with an increase in fire. The mid–late Holocene front-like spread of Picea abies (Norway spruce) and cooler, wetter climatic conditions reduce local biomass burning before the onset of intensified anthropogenic land use, and the late Holocene increase in anthropogenic activity created artificially high records of biomass burning that overshadowed the natural fire signal. An economic shift from extensive subsistence land use to agriculture and forestry as well as active fire suppression has reduced regional biomass burning. However, it is proposed that without anthropogenic fire suppression, the underlying natural fire signal would remain low because of the now widespread dominance of P. abies.

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Talento, Stefanie, et Marcelo Barreiro. « Estimation of Natural Variability and Detection of Anthropogenic Signal in Summertime Precipitation over South America ». Advances in Meteorology 2012 (2012) : 1–10. http://dx.doi.org/10.1155/2012/725343.

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We use a coupled model to estimate the natural variability of summertime rainfall over South America and to determine the time horizon when anthropogenic forcing will start having an effect on it. We use a combination of three experiments: preindustrial, 20th century, and the projected changes under A1B scenario. The first empirical orthogonal function of rainfall in December–February is used to characterize summertime variability. The model can display two different regimes of natural variability of this mode. In one regime, there is a strong coupling between the South Atlantic convergence zone (SACZ) and the Atlantic Ocean. In the other regime, the SACZ is dominated by internal atmospheric variability. The detection of the impact of anthropogenic forcing is calculated comparing the probability density functions (pdfs) of the preindustrial run with the one under the A1B scenario. We found that the detection strongly depends on the pdf used to characterize internal climate variability. If the pdf of the mode with coupling between the SACZ and the Atlantic Ocean is used, the anthropogenic influence is felt very early within the future scenario (in less than 30 years). On the contrary, with the pdf that characterizes an SACZ dominated by internal atmospheric variability, the forcing is detected only several (almost 50) years into the scenario.

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Roberts, Louise, et Aaron N. Rice. « Vibrational and acoustic communication in fishes : The overlooked overlap between the underwater vibroscape and soundscape ». Journal of the Acoustical Society of America 154, n^o 4 (1 octobre 2023) : 2708–20. http://dx.doi.org/10.1121/10.0021878.

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Substrate-borne communication via mechanical waves is widespread throughout the animal kingdom but has not been intensively studied in fishes. Families such as the salmonids and sculpins have been documented to produce vibratory signals. However, it is likely that fish taxa on or close to the substrate that produce acoustic signals will also have a vibratory component to their signal due to their proximity to substrates and energy transfer between media. Fishes present an intriguing opportunity to study vibrational communication, particularly in the context of signal production and detection, detection range, and how vibratory signals may complement or replace acoustic signals. It is highly likely that the vibrational landscape, the vibroscape, is an important component of their sensory world, which certainly includes and overlaps with the soundscape. With the wide range of anthropogenic activities modifying underwater substrates, vibrational noise presents similar risks as acoustic noise pollution for fishes that depend on vibrational communication. However, in order to understand vibrational noise, more empirical studies are required to investigate the role of vibrations in the fish environment.

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Fyke, Jeremy G., Miren Vizcaíno et William H. Lipscomb. « The pattern of anthropogenic signal emergence in Greenland Ice Sheet surface mass balance ». Geophysical Research Letters 41, n^o 16 (18 août 2014) : 6002–8. http://dx.doi.org/10.1002/2014gl060735.

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Frasier, Kaitlin E. « A machine learning pipeline for classification of cetacean echolocation clicks in large underwater acoustic datasets ». PLOS Computational Biology 17, n^o 12 (3 décembre 2021) : e1009613. http://dx.doi.org/10.1371/journal.pcbi.1009613.

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Machine learning algorithms, including recent advances in deep learning, are promising for tools for detection and classification of broadband high frequency signals in passive acoustic recordings. However, these methods are generally data-hungry and progress has been limited by challenges related to the lack of labeled datasets adequate for training and testing. Large quantities of known and as yet unidentified broadband signal types mingle in marine recordings, with variability introduced by acoustic propagation, source depths and orientations, and interacting signals. Manual classification of these datasets is unmanageable without an in-depth knowledge of the acoustic context of each recording location. A signal classification pipeline is presented which combines unsupervised and supervised learning phases with opportunities for expert oversight to label signals of interest. The method is illustrated with a case study using unsupervised clustering to identify five toothed whale echolocation click types and two anthropogenic signal categories. These categories are used to train a deep network to classify detected signals in either averaged time bins or as individual detections, in two independent datasets. Bin-level classification achieved higher overall precision (>99%) than click-level classification. However, click-level classification had the advantage of providing a label for every signal, and achieved higher overall recall, with overall precision from 92 to 94%. The results suggest that unsupervised learning is a viable solution for efficiently generating the large, representative training sets needed for applications of deep learning in passive acoustics.

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Adami, Kristian Zarb, et I. O. Farhat. « Low-frequency technology for a lunar interferometer ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 379, n^o 2188 (23 novembre 2020) : 20190575. http://dx.doi.org/10.1098/rsta.2019.0575.

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This work sketches a possible design architecture of a low-frequency radio interferometer located on the lunar surface. The design has evolved from single antenna experiments aimed at the global signal detection of the epoch of reionization (EoR) to the square kilometre array (SKA) which, when complete, will be capable of imaging the highly red-shifted H 1 -signal from the cosmic dawn through to the EoR. However, due to the opacity of the ionosphere below 10 MHz and the anthropogenic radio-frequency interference, these terrestrial facilities are incapable of detecting pre-ionization signals and the moon becomes an attractive location to build a low-frequency radio interferometer capable of detecting such cosmological signals. Even though there are enormous engineering challenges to overcome, having this scientific facility on the lunar surface also opens up several new exciting possibilities for low-frequency radio astronomy. This article is part of a discussion meeting issue ‘Astronomy from the Moon: the next decades’.

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Ekka, Shail Vijeta, Yu-Hsuan Liang, Kuo-Fang Huang et Der-Chuen Lee. « Molybdenum Isotopic Fingerprints in Taiwan Rivers : Natural versus Anthropogenic Sources ». Water 15, n^o 10 (15 mai 2023) : 1873. http://dx.doi.org/10.3390/w15101873.

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Two rivers from Taiwan with different source inputs, the Danshuei (polluted) and Liwu (non-polluted), were selected to study the behavior of molybdenum (Mo) isotopes during weathering and riverine transport. In the Danshuei River, δ98/95Mo ranges from 0.83‰ to 1.50‰ (wet season) and 0.54‰ to 1.25‰ (dry season). With a few exceptions, δ98/95Mo in the Danshuei River is lighter during the wet season, while, in contrast, heavier in the dry season. In the Liwu River, δ98/95Mo varies from 0.54‰ to 1.30‰ and gets heavier along the mainstream. Using the MixSIAR model, three Mo sources are identified in the Danshuei River: seawater intrusion, rock–water interaction, and anthropogenic inputs. Seawater intrusion can explain the heavy δ98/95Mo downstream signal during the wet season contributing 14–39% from the MixSIAR model. However, the lighter δ98/95Mo signal during the dry season is most likely due to anthropogenic inputs in the middle and lower reaches of the Danshuei River contributing 75–98%. In the Liwu River, dissolved Mo isotopes correlate with SO42−/Na and (Sr/Na) ×1000 ratio, suggesting that pyrite oxidation coupled with carbonate weathering governs the heavy δ98/95Mo signature, with sequestration of light δ98/95Mo into secondary mineral phases in bedload sediments. Furthermore, these results have important implications for riverine Mo sources to the ocean, controlled by anthropogenic activity and weathering processes.

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Knutson, Thomas R., et Jeffrey Ploshay. « Sea Level Pressure Trends : Model-Based Assessment of Detection, Attribution, and Consistency with CMIP5 Historical Simulations ». Journal of Climate 34, n^o 1 (janvier 2021) : 327–46. http://dx.doi.org/10.1175/jcli-d-19-0997.1.

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AbstractObserved sea level pressure (SLP) trends for 1901–10, 1951–10, and 1981–2010 are assessed using two observed data sources (HadSLP2_lowvar and 20CRv3) compared to a CMIP5 multimodel ensemble. The CMIP5 simulations include runs with (i) no external forcing (Control runs), (ii) natural external forcing only (Natural-Forcing), or (iii) natural plus anthropogenic forcings combined (All-Forcings). We assess whether the CMIP5 All-Forcing ensemble is consistent with observations and whether there is model-based evidence for detectable anthropogenic influence for the observed SLP trends. For the 1901–2010 and 1951–2010 trends, a robustly detectable anthropogenic signal in both observational data products is a zonal band of SLP increase extending over much of the Southern Hemisphere extratropics (30°–50°S). In contrast, the HadSLP2_lowvar and 20CRv3 observed data products disagree on the sign of the century-scale trends in SLP over much of the low-latitude region 25°N–25°S. These differences will limit confident detection/attribution/consistency conclusions for lower-latitude regions, at least until the observational data product discrepancies are better reconciled. The Northern Hemisphere extratropics remains a difficult region for identifying any detectable anthropogenic influence for annual- or seasonal-mean SLP trends. Overall, our results highlight the difficulty in detecting and attributing anthropogenic signals in SLP for relatively short time scales. The observed 1981–2010 regional trends typically have a different pattern and magnitude from the simulated externally forced trends. Consequently, our results suggest that internal variability is likely the dominant driver of most observed 1981–2010 regional trend features, including the pronounced increase in SLP over the central and eastern equatorial Pacific.

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Verbitsky, Mikhail Y., Michael E. Mann, Byron A. Steinman et Dmitry M. Volobuev. « Detecting causality signal in instrumental measurements and climate model simulations : global warming case study ». Geoscientific Model Development 12, n^o 9 (17 septembre 2019) : 4053–60. http://dx.doi.org/10.5194/gmd-12-4053-2019.

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Abstract. Detecting the direction and strength of the causality signal in observed time series is becoming a popular tool for exploration of distributed systems such as Earth's climate system. Here, we suggest that in addition to reproducing observed time series of climate variables within required accuracy a model should also exhibit the causality relationship between variables found in nature. Specifically, we propose a novel framework for a comprehensive analysis of climate model responses to external natural and anthropogenic forcing based on the method of conditional dispersion. As an illustration, we assess the causal relationship between anthropogenic forcing (i.e., atmospheric carbon dioxide concentration) and surface temperature anomalies. We demonstrate a strong directional causality between global temperatures and carbon dioxide concentrations (meaning that carbon dioxide affects temperature more than temperature affects carbon dioxide) in both the observations and in (Coupled Model Intercomparison Project phase 5; CMIP5) climate model simulated temperatures.

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Dong, Siyan, Ying Sun et Chao Li. « Detection of Human Influence on Precipitation Extremes in Asia ». Journal of Climate 33, n^o 12 (15 juin 2020) : 5293–304. http://dx.doi.org/10.1175/jcli-d-19-0371.1.

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AbstractThis paper examines the possible influence of external forcings on observed changes in precipitation extremes in the mid-to-high latitudes of Asia during 1958–2012 and attempts to identify particular extreme precipitation indices on which there are better chances to detect the influence of external forcings. We compare a recently compiled dataset of observed extreme indices with those from phase 5 of the Coupled Model Intercomparison Project (CMIP5) simulations using an optimal fingerprinting method. We consider six indices that characterize different aspects of extreme precipitation, including annual maximum amount of precipitation falling in 1 day (Rx1day) or 5 days (Rx5day), the total amount of precipitation from the top 5% or top 1% daily amount on wet days, and the fraction of the annual total precipitation from these events. For single-signal analysis, the fingerprints of external forcings including anthropogenic agents are robustly detected in most studied extreme indices over all Asia and for midlatitude Asia but not for high-latitude Asia. For two-signal analysis, anthropogenic influence is detectable in these indices over Asia at 5% or slightly less than 5% significance level, whereas natural influence is not detectable. In high-latitude Asia, anthropogenic influence is detected only in a fractional index, representing a stark contrast to the midlatitude and full Asia results. We find relatively smaller internal variability and thus higher signal-to-noise ratio in the fractional indices when compared with the other ones. Our results point to the need for studying precipitation extreme indices that are less affected by internal variability while still representing the relevant nature of precipitation extremes to improve the possibility of detecting a forced signal if one is present in the data.

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Lu, Chunhui, Fraser C. Lott, Ying Sun, Peter A. Stott et Nikolaos Christidis. « Detectable Anthropogenic Influence on Changes in Summer Precipitation in China ». Journal of Climate 33, n^o 13 (1 juillet 2020) : 5357–69. http://dx.doi.org/10.1175/jcli-d-19-0285.1.

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AbstractIn China, summer precipitation contributes a major part of the total precipitation amount in a year and has major impacts on society and human life. Whether any changes in summer precipitation are affected by external forcing on the climate system is an important issue. In this study, an optimal fingerprinting method was used to compare the observed changes of total, heavy, moderate, and light precipitation in summer derived from newly homogenized observation data with the simulations from multiple climate models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5). The results demonstrate that the anthropogenic forcing signal can be detected and separated from the natural forcing signal in the observed increase of seasonal accumulated precipitation amount for heavy precipitation in summer in China and eastern China (EC). The simulated changes in heavy precipitation are generally consistent with observed change in China but are underestimated in EC. When the changes in precipitation of different intensities are considered simultaneously, the human influence on simultaneous changes in moderate and light precipitation can be detected in China and EC in summer. Changes attributable to anthropogenic forcing explain most of the observed regional changes for all categories of summer precipitation, and natural forcing contributes little. In the future, with increasing anthropogenic influence, the attribution-constrained projection suggests that heavy precipitation in summer will increase more than that from the model raw outputs. Society may therefore face a higher risk of heavy precipitation in the future.

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Koblitz, Jens C. « Arrayvolution : using microphone arrays to study bats in the field ». Canadian Journal of Zoology 96, n^o 9 (septembre 2018) : 933–38. http://dx.doi.org/10.1139/cjz-2017-0187.

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Some parameters of echolocation signals can be studied using a single receiver. However, studying parameters such as source level, echolocation beam shape, and direction of signal emission require the use of multireceiver arrays. Acoustic localization allows for determination of the position of bats at the time of signal emission. When multiple animals are present, calls can be assigned to individuals based on their location. This combination makes large multireceiver arrays a powerful tool in bioacoustics research. Here, an overview of different array configurations used to record bats in the field is presented. In some studies, the absolute position of bats and not only relative to the array is crucial. Combining acoustic localizations from a source with geo-referenced receivers allows for determining geo-referenced movements of bats. Current applications of arrays aim to improve acoustic monitoring of bats and study anthropogenic impact.

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Hochet, Antoine, Guillaume Dodet, Fabrice Ardhuin, Mark Hemer et Ian Young. « Sea State Decadal Variability in the North Atlantic : A Review ». Climate 9, n^o 12 (1 décembre 2021) : 173. http://dx.doi.org/10.3390/cli9120173.

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Long-term changes of wind-generated ocean waves have important consequences for marine engineering, coastal management, ship routing, and marine spatial planning. It is well-known that the multi-annual variability of wave parameters in the North Atlantic is tightly linked to natural fluctuations of the atmospheric circulation, such as the North Atlantic Oscillation. However, anthropogenic climate change is also expected to influence sea states over the long-term through the modification of atmospheric and ocean circulation and melting of sea ice. Due to the relatively short duration of historical sea state observations and the significant multi-decadal variability in the sea state signal, disentangling the anthropogenic signal from the natural variability is a challenging task. In this article, the literature on inter-annual to multi-decadal variability of sea states in the North Atlantic is reviewed using data from both observations and model reanalysis.

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Matveenko, E. A., et D. V. Chebrov. « ANOMALOUS REDUCTION IN THE LEVEL OF SEISMIC NOISE IN PETROPAVLOVSK-KAMCHATSKY IN APRIL 2020 ». Bulletin of Kamchatka Regional Association «Educational-Scientific Center». Earth Sciences, n^o 3(59) (2023) : 42–52. http://dx.doi.org/10.31431/1816-5524-2023-3-59-42-52.

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Estimation of the influence of anthropogenic factors on the seismic signal is an important problem in ensuring the quality of seismological data and, accordingly, the quality of scientific research. Due to the unprecedented situation associated with the introduction of measures to prevent the spread of COVID-19, non-working days were established in Russia from April 4 to April 30, 2020. It became possible to assess the impact of a notable decrease in anthropogenic activity on the seismic signal (noise) recorded by seismic instruments in the territory of the largest city of the Kamchatka, Petropavlovsk-Kamchatsky. We study seismic noise by standard technique, based on the analysis of the probability density function of the noise power spectral density obtained from the data of the digital archive of the noise spectra of seismic stations. A decrease in the seismic noise power level below the minimum values of the same periods of previous years was registered at stations installed in schools, residential buildings (boarding schools) or near public and office buildings. The minimal anthropogenic influence stations were selected. The obtained data can be used for determination the features of the work of both stations and individual channels, taking into account their direction and position, relative to the objects of human activity.

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Zhong, Shuping, Jun Ying et Matthew Collins. « Sources of Uncertainty in the Time of Emergence of Tropical Pacific Climate Change Signal : Role of Internal Variability ». Journal of Climate 36, n^o 8 (15 avril 2023) : 2535–49. http://dx.doi.org/10.1175/jcli-d-22-0554.1.

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Abstract Determining the time of emergence of anthropogenic climate change signals from natural variability, for both the tropical Pacific mean state and El Niño–Southern Oscillation (ENSO), are critical for early climate warning and adaptation planning. However, there remains considerable uncertainty in estimating those times of emergence in state-of-the-art climate models. In this study, the role of internal variability in the uncertainty of the times of emergence of tropical Pacific annual-mean sea surface temperature (SST) and rainfall, and ENSO-related SST and rainfall are investigated by using three large ensembles of model simulations under the historical and RCP8.5 emission scenarios, as well as the multimodel ensemble from phase 6 of the Coupled Model Intercomparison Project under the historical and SSP5–8.5 emission scenarios. Specific attention is paid to the eastern equatorial Pacific. It is found that internal variability contributes to less than half of the total uncertainty in both the times of emergence of annual-mean SST and rainfall in all the three large ensembles, with more contribution to the latter than to the former. Hence, model differences dominate. Conversely, internal variability contributes to a major part of the total uncertainty in the times of emergence of ENSO-related SST and rainfall in one large ensemble that has sufficient members to show emergent signals. These results imply that we could have a relatively high confidence in claiming that anthropogenic climate change has impacted the annual-mean state, if an emergent annual-mean signal is observed in the real world. However, in claiming changes in ENSO variability, the signal is easily obscured by internal variability.

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Husby, Magne, et Tore Slagsvold. « The number of syllables per phrase in Great Tit (Parus major) song decreases in strong anthropogenic noise and at northern latitudes ». Ornis Norvegica 46 (27 octobre 2023) : 28–42. http://dx.doi.org/10.15845/on.v46.3854.

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Cover photo: Great Tit male. Photo: Alf Tore Mjøs. Birds may sing to defend a territory and to attract a mate. However, despite many studies clear conclusions remain on how ecological conditions affect the song, such as physical obstacles that may reduce the sound transmission, and anthropogenic noise that may mask the signal. The social environment of the local populations may also be important, such as breeding density and sex ratio, influencing the number of competing males with which to song match, and the distances to the neighbouring males and to prospecting females. During 2016-19, we counted the number of syllables (notes) per phrase of singing male Great Tits Parus major by visiting seven countries in Europe and one in North Africa. A total of 946 songs were observed by visiting 554 territories. We also recorded study year, anthropogenic noise, calendar date, time of day, type of habitat and vegetation density, latitude, longitude and altitude. The most important explanatory variables were anthropogenic noise and the latitude of the focal site; the number of syllables per phrase decreasing both with increasing anthropogenic noise and with the latitude. The latter result was also supported when analysing sonograms of the species found on the Internet (Xeno-canto), namely fewer syllables per phrase in Norway than in Spain and Portugal. We suggest that repetition of a short phrase is fast interpreted by conspecifics in noisy environments, and that such signals are more readily detected by conspecifics over a wider area where the density of the tits is low.

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Alberti, Marina, Cristian Correa, John M. Marzluff, Andrew P. Hendry, Eric P. Palkovacs, Kiyoko M. Gotanda, Victoria M. Hunt, Travis M. Apgar et Yuyu Zhou. « Global urban signatures of phenotypic change in animal and plant populations ». Proceedings of the National Academy of Sciences 114, n^o 34 (3 janvier 2017) : 8951–56. http://dx.doi.org/10.1073/pnas.1606034114.

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Humans challenge the phenotypic, genetic, and cultural makeup of species by affecting the fitness landscapes on which they evolve. Recent studies show that cities might play a major role in contemporary evolution by accelerating phenotypic changes in wildlife, including animals, plants, fungi, and other organisms. Many studies of ecoevolutionary change have focused on anthropogenic drivers, but none of these studies has specifically examined the role that urbanization plays in ecoevolution or explicitly examined its mechanisms. This paper presents evidence on the mechanisms linking urban development patterns to rapid evolutionary changes for species that play important functional roles in communities and ecosystems. Through a metaanalysis of experimental and observational studies reporting more than 1,600 phenotypic changes in species across multiple regions, we ask whether we can discriminate an urban signature of phenotypic change beyond the established natural baselines and other anthropogenic signals. We then assess the relative impact of five types of urban disturbances including habitat modifications, biotic interactions, habitat heterogeneity, novel disturbances, and social interactions. Our study shows a clear urban signal; rates of phenotypic change are greater in urbanizing systems compared with natural and nonurban anthropogenic systems. By explicitly linking urban development to traits that affect ecosystem function, we can map potential ecoevolutionary implications of emerging patterns of urban agglomerations and uncover insights for maintaining key ecosystem functions upon which the sustainability of human well-being depends.

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Barnett, Tim P., Gabriele C. Hegerl, Ben Santer et Karl Taylor. « The Potential Effect of GCM Uncertainties and Internal Atmospheric Variability on Anthropogenic Signal Detection ». Journal of Climate 11, n^o 4 (avril 1998) : 659–75. http://dx.doi.org/10.1175/1520-0442(1998)011<0659:tpeogu>2.0.co;2.

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Legates, David R., et Robert E. Davis. « The continuing search for an anthropogenic climate change signal : Limitations of correlation-based approaches ». Geophysical Research Letters 24, n^o 18 (15 septembre 1997) : 2319–22. http://dx.doi.org/10.1029/97gl02207.

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Stambaugh, Michael C., Joseph M. Marschall, Erin R. Abadir, Benjamin C. Jones, Patrick H. Brose, Daniel C. Dey et Richard P. Guyette. « Wave of fire : an anthropogenic signal in historical fire regimes across central Pennsylvania, USA ». Ecosphere 9, n^o 5 (mai 2018) : e02222. http://dx.doi.org/10.1002/ecs2.2222.

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Hoerling, Martin, James Hurrell, Arun Kumar, Laurent Terray, Jon Eischeid, Philip Pegion, Tao Zhang, Xiaowei Quan et TaiYi Xu. « On North American Decadal Climate for 2011–20 ». Journal of Climate 24, n^o 16 (15 août 2011) : 4519–28. http://dx.doi.org/10.1175/2011jcli4137.1.

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Abstract The predictability of North American climate is diagnosed by taking into account both forced climate change and natural decadal-scale climate variability over the next decade. In particular, the “signal” in North American surface air temperature and precipitation over 2011–20 associated with the expected change in boundary conditions related to future anthropogenic greenhouse gas (GHG) forcing, as well as the “noise” around that signal due to internally generated ocean–atmosphere variability, is estimated. The structural uncertainty in the estimate of decadal predictability is diagnosed by examining the sensitivity to plausible scenarios for the GHG-induced change in boundary forcing, the model dependency of the forced signals, and the dependency on methods for estimating internal decadal noise. The signal-to-noise analysis by the authors is thus different from other published decadal prediction studies, in that this study does not follow a trajectory from a particular initial state but rather considers the statistics of internal variability in comparison with the GHG signal. The 2011–20 decadal signal is characterized by surface warming over the entire North American continent, precipitation decreases over the contiguous United States, and precipitation increases over Canada relative to 1971–2000 climatological conditions. The signs of these forced responses are robust across different sea surface temperature (SST) scenarios and the different models employed, though the amplitude of the response differs. The North American decadal noise is considerably smaller than the signal associated with boundary forcing, implying a potential for high forecast skill for 2011–20 North American climate even for prediction methods that do not attempt to initialize climate models. However, the results do suggest that initialized decadal predictions, which seek to forecast externally forced signals and also constrain the internal variability, could potentially improve upon uninitialized methods in regions where the external signal is small relative to internal variability.

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