Forcing Of Climate Change Research Articles

New insights into the decadal variability in glacier volume of a tropical ice cap, Antisana (0°29′ S, 78°09′ W), explained by the morpho-topographic and climatic context

Abstract. We present a comprehensive study of the evolution of the glaciers on the Antisana ice cap (tropical Andes) over the period 1956–2016. Based on geodetic observations of aerial photographs and high-resolution satellite images, we explore the effects of morpho-topographic and climate variables on glacier volumes. Contrasting behaviour was observed over the whole period, with two periods of strong mass loss, 1956–1964 (−0.72 m w.e. yr−1) and 1979–1997 (−0.82 m w.e. yr−1), and two periods with slight mass loss, 1965–1978 (0.10 m w.e. yr−1) and 1998–2016 (−0.26 m w.e. yr−1). There was a 42 % reduction in the total surface area of the ice cap. Individually, glacier responses were modulated by morpho-topographic variables (e.g. maximum and median altitude and surface area), particularly in the case of the small tongues located at low elevations (Glacier 1, 5 and 16) which have been undergoing accelerated disintegration since the 1990s and will likely disappear in the coming years. Moreover, thanks to the availability of aerial data, a surging event was detected on the Antisana Glacier 8 (G8) in the 2009–2011 period; such an event is extremely rare in this region and deserves a dedicated study. Despite the effect of the complex topography, glaciers have reacted in agreement with changes in climate forcing, with a stepwise transition towards warmer and alternating wet–dry conditions since the mid-1970s. Long-term decadal variability is consistent with the warm–cold conditions observed in the Pacific Ocean represented by the Southern Oscillation index.

Climate risk perception among women farmers in Kwara North, Nigeria

Past academic debates have identified the need to mainstream indigenous knowledge and gender perspectives in relation to climate risk analysis, perceptions of vulnerability, experiences, and coping mechanisms. The justification for this is that gender often dictates who gains and who loses in environmental disasters and because women make up almost 80% of the agricultural workforce in the tropics and are increasingly vulnerable to climate change, they have learned to adapt to climate variability and their adaptation over time has been through indigenous knowledge practices. Through questionnaires, Focus Group Discussions and observations, this study attempts to understand how women farmers perceive climate risk in rural parts of Nigeria. The women farmers’ perception of climate change was viewed from different angles, ranging from causes, weather events, rainfall to temperature. Our result indicates that the women farmers’ understanding of local forcing of climate change (i.e. local actions that contribute to climate variability) is low and it varies across the five Local Government Areas (LGAs) in the study area. Women farmers perceive climate change as a problem that could have a long-lasting effect on their livelihood systems.

Psyche within the matrix of the natural world: weaving the inner and outer

This paper explores a way of relating to self, others, and the land rooted in embodied affectivity. It explores the way in which our emotions are an inherent part of the natural world and why attention to them matters regarding the environmental crisis. Recognizing the parallel between the prevailing attitudes of Western culture towards the Earth and towards our bodies, the paper offers an alternative paradigm through a poem by a Diné woman. The poem expresses how the Diné culture honours the Earth by seeking to cultivate the beauty and wisdom intrinsic to it within the body, mind, and spirit of the individual. Interwoven in the essay are images that express the land's power and its uncanny ability to resonate with emotional states. This resonance can help us come to know and work with those states that, on the one hand, threaten to overwhelm us, while at the same time, potentially infusing us with the wisdom of their terrible and astonishing beauty. Drawing from affective neuroscience's emphasis on the primacy and embodied basis of emotion, the paper discusses how interoceptive awareness enhances emotional discernment as well as consciousness of one's way of inhabiting and responding to the Earth, including the threatening forces of climate change.

Astronomical calibration of a ten‐million‐year Triassic lacustrine record in the Ordos Basin, North China

AbstractThe division of geological time is of general interest as this allows a better understanding of the geological processes and Earth's evolutionary history. Astrochronology provides a way to evaluate high‐resolution timescales of Earth's climate changes. Astronomical tuning of orbitally forced stratigraphic records to construct astronomical‐calibrated timescales has led to a progressive refinement of the geological timescale over the last decades. However, the Triassic remains a relatively weak link. A large lake with an area of 370 000 square kilometres formed in the Ordos Basin in North China during the Triassic Period. It has been demonstrated that the sedimentary deposits of the seventh Oil Member (Chang 7 Member) of the Triassic Yanchang Formation in the southern Ordos Basin responded to astronomically forced climate changes. However, the constructed astronomical‐calibrated timescales failed to reach an agreement. This study presents natural gamma ray logs and geochemical climate record of Fe and Al concentrations from the southern Ordos Basin margin that are dated precisely from 239 to 229 Ma by combined U–Pb dating and astrochronology. Therefore, the Chang 7 Member was deposited during the Ladinian and Carnian (late Middle through to earliest Late Triassic), this knowledge will refine the Triassic astronomical scale. The distribution of detrital zircon dates shows that the Chang 7 Member in the southern Ordos Basin has multiple provenance characteristics. The southern Ordos Basin is far from this provenance area, which is reflected in the low sediment accumulation rate (0.5 to 2.0 cm/kyr). In contrast to the lower part of Yanchang Formation underlying the Chang 7 Member, the large tuffs and seismites from the bottom of Chang 7 Member indicate the initiation of tectonic collision between North Qinling orogenic belt and the southern margin of the Ordos Basin.

Variation and comparison of cloud cover in MODIS and four reanalysis datasets of ERA-interim, ERA5, MERRA-2 and NCEP

Cloud plays an important role in climate change and radiative forcing. Atmospheric reanalysis datasets provide an economical and efficient way to explore the worldwide cloud variation. This study compares the monthly total cloud cover (TCC) and high cloud cover (HCC) of the four commonly used atmospheric reanalysis datasets, including European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis (ERA-Interim), ECMWF's Fifth-generation Reanalysis (ERA5), Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) and National Centers for Environmental Prediction (NCEP: only TCC), with MODIS retrievals during 2001–2018. The spatial and temporal distributions of TCC for the four reanalyses are generally consistent with MODIS results, while showing better consistency over land than over ocean. The largest TCC discrepancy between MODIS and the reanalysis appears over the polar regions. Among the four reanalysis datasets, ERA5 presents the highest correlation and the smallest mean bias compared with MODIS, while NCEP shows the lowest and the largest. Although all the three reanalyses (ERA-Interim, ERA5 and MERRA-2) generally give an overestimation of HCC compared with MODIS, the ERA-Interim shows the closest to MODIS. The largest difference of HCCs between MODIS and the reanalysis is located over the Tibet Plateau. To the annual change of global means, ERA-Interim and MERRA-2 appear a significant increasing trend of TCC over both land and ocean. ERA5 and MERRA-2 show a significant decreasing trend of HCC over ocean, and MODIS gives a reduce over land. Furthermore, During the ENSO events, a positive anomaly of TCC, which is positively correlated with the ENSO intensity over the eastern equatorial Pacific, is captured by all the four reanalyses, among which ERA5 and ERA-Interim appear more distinct.

Ocean circulation and climate variability in the northern South China Sea during the Greek Minimum derived from coral Δ14C and Sr/Ca records

Ocean circulation transports heat, salt and nutrients, and has profound impacts on the marine environment and climate change. However, the seasonal to centennial variations of the paleocirculation of the South China Sea (SCS) and their driving forces are still unclear due to limited records. Here we reconstructed a high-resolution Δ14C record of a coral from Sanya to investigate the seasonal variations of the SCS ocean circulation around 2300 cal yr BP during a grand solar minimum (GSM) period. The seasonal Δ14C variability shows the influence of coastal upwelling caused by the East Asian Summer Monsoon (EASM) in summer and the effect of water intrusion from the western Pacific Ocean driven by the Kuroshio Intrusion (KI) in winter. We compiled the marine radiocarbon reservoir correction (ΔR) records since 2500 cal yr BP, which indicate a gradual decrease of upwelling significantly correlated with the EASM. Comparisons with other climate records suggest that both the EASM and KI may regulate the ocean circulation variability on centennial time scales. As a good index of the sea surface temperature (SST), our Sr/Ca record and spectral analysis results show a low temperature and a low frequency of El Niño-Southern Oscillation (ENSO) events around 2300 cal yr BP. Moreover, the composite coral Sr/Ca-SST and ENSO index records since 2500 cal yr BP show relatively low SST and weak ENSO during GSMs, supporting the modulation of tropical SST and ENSO by solar activity. Our study has provided high-resolution proxy data and revealed the driving forces of ocean circulation and climate change in the SCS at multiple time scales, which should be considered in further modeling work.

Long-term trend of snow water equivalent in the Italian Alps

Snow stores a significant amount of water in mountain regions. The decrease of water storage in the snowpack can have relevant impacts on water supply for mountain and lowland areas that rely on snow melting. In this work, we modelled the Snow Water Equivalent (SWE) using daily snow depth (HS) data obtained from 19 historical HS measurement stations located in the southern European Alps (Italy). Then, we analysed the long-term (1930–2020) variability of the monthly Standardised SWE Index (SSWEI) and its links with climate change and large-scale atmospheric forcings (teleconnection indices). We found a marked variability in monthly SSWEI, with the lowermost values generally occurring in the last few decades (1991–2020), irrespective of elevation. In this recent period, highly negative values occurred at the snow season tails, mostly in spring. We found large-scale atmospheric patterns (North Atlantic Oscillation, Atlantic Multi-decadal Oscillation, and Artic Oscillation) and precipitation to be interconnected with SSWEI oscillations, although this relation changed after the 1980s, especially at low and medium elevations. This change occurred in correspondence of highly positive air temperature anomalies. In the last decades, we found increasing air temperature to be the main driver for the pronounced snow mass loss and persistent snow-drought conditions.

The effects of astronomically forced climate change on hemipelagic carbonate sedimentation in a tectonically active setting: the Albian Mioño Formation in Castro Urdiales (Cantabria, N Spain)

Our understanding of the stratigraphic expression of astronomically driven climate-change cycles in the Milankovitch frequency band has improved significantly in recent decades. However, several aspects have been little studied to date, such as the nature of the climatically regulated environmental processes that ultimately control cyclic sedimentation. Similarly, relatively little is known about the expression of Milankovitch cycles in successions accumulated in tectonically active basins. In order to fill this knowledge gap, the Albian hemipelagic deposits of the Mioño Formation exposed in Castro Urdiales (Basque-Cantabrian Basin) are studied herein. These deposits were accumulated during a rifting phase with strong tectonic activity. The sedimentological, petrographic and cyclostratigraphic analysis demonstrates that, despite the synsedimentary tectonic instabilities and some diagenetic overprinting, the hemipelagic carbonate alternation was astronomically forced 110.68–110.47 Ma. Seasonality fluctuations driven by precession cycles caused periodic (20 ky) variations in the rate of carbonate productivity (abundance of pelagic calcareous plankton and micrite exported from adjacent shallow-water areas) and/or siliceous dilution (terrestrially derived siliciclastic sediment supply and siliceous particle production by sponges). These variations resulted in the formation of marly limestone beds when annual seasonality was low (i.e., boreal summer at aphelion, winter at perihelion) and the accumulation of marlstones when seasonality increased (i.e., boreal summer at perihelion, winter at aphelion). The incidence of these processes increased and decreased in line with seasonality modulation by short-eccentricity cycles of 100 ky. In conclusion, this study shows that Milankovitch cycles can be reliably recorded in hemipelagic successions accumulated in tectonically active settings if sediment gravity flows or other disturbances do not affect autochthonous sedimentation.

Narratives of Depletion

Narratives of Depletion Chris Otter (bio) In 1849, Henry Cole rhapsodized about the avalanche of global resources to be displayed in the forthcoming 1851 Great Exhibition: With respect to raw materials, we shall most likely have, from all quarters of the globe, specimens of animal and vegetable life, as well as of minerals,—samples of what is in the earth and what is produced on the earth. In the class of animal substances, we shall probably have enormous elephants' tusks from Africa and Asia; leather from Morocco and Russia; Beaver from Baffin's Bay; the wools of Australia, of Yorkshire, and of Thibet; silk from Asia and from Europe; and furs from the Esquimaux. As the evidence of what we may expect from the suggested exposition, I may state that the Court of Directors of the East India Company intend to exhibit the best of everything that India can produce; and we shall therefore probably obtain, by this means, the best practical notion of the value of our East Indian possessions. (55) The Great Exhibition celebrated Britain's command of global materials, mineral and organic. Such unabashed cornucopianism was a leitmotif of Victorian thought, as Fredrik Jonsson has shown. In 1882, for example, Frederic Harrison argued that unprecedented material abundance had launched Britain on a spectacular trajectory of improvement: "we have hardly yet got so far as to recognise that the sudden acquisition of vast material resources is not only a great boon to humanity, but also a tremendous moral, social, and even physical and intellectual experiment" (426). This "experiment" could easily produce insouciant profligacy: "The truth is, we have coal to spare and to waste!" announced the sanitary engineer William Eassie in his 1872 Healthy Houses (181). [End Page 425] Such cornucopianism, Elizabeth Carolyn Miller argues, never went unchallenged. In Extraction Ecologies and the Literature of the Long Exhaustion (2021), she traces a more anxious, pessimistic strain of thought, which feared that the rage for extraction would lead to ruinous collapse and the exhaustion of material resources. This discourse formed what she calls "the exhaustive imaginary of the nineteenth and early twentieth centuries" (198). Moreover, she argues that these discursive frameworks recur, in multiple permutations, throughout nineteenth-and early-twentieth-century novels. This serves as a gentle critique of Amitav Ghosh, who suggests in The Great Derangement (2016) that the novelistic form has struggled to represent large-scale but slow environmental transformation, particularly climate change.1 Miller, by contrast, suggests that nineteenth-and early-twentieth-century literature routinely imagined the present and future devastation wrought by industrialization and extraction. Indeed, she notes, "There may be very few prose works published from the 1830s to the 1930s without some overt thematic interest in extraction, not to mention structuring principles rooted in extractivism" (15). Miller is surely correct: almost every resource vital to the perceived progress of Britain's industrial development generated profound fears of exhaustion. For example, rising meat consumption was routinely regarded as an index of progress, but increasing consumption of a finite resource created concerns of meat shortages generated by rising population and the failure of domestic production to keep up with demand. In 1866, Joseph Fisher published a book with the anxious title Where Shall We Get Meat?. The answer was the mass outsourcing of meat production, which merely transposed a national problem onto the entire globe. In Supplying Britain's Meat (1923), George Putnam observed that by the early twentieth century, concerns about a global meat famine were growing.2 Today, rising meat consumption, along with consumption of other resources such as wheat and guano, has become a major driving force of climate change, resource depletion, and environmental degradation.3 By using the entire planet as a resource for food, as well as many other materials (minerals, fertilizer, timber), Britain adopted what I have called the "large-planet philosophy" (Otter 5). Miller's book finds this philosophy, and its critique, to be a recurrent motif in the Victorian novel. The lust for extraction had, and has, very real consequences for our planetary present. As Miller notes, "carbon dioxide from coal burned during the Industrial Revolution still floats in our atmosphere, but it is the broader complex...

Robust evidence for reversal of the trend in aerosol effective climate forcing

Abstract. Anthropogenic aerosols exert a cooling influence that offsets part of the greenhouse gas warming. Due to their short tropospheric lifetime of only several days, the aerosol forcing responds quickly to emissions. Here, we present and discuss the evolution of the aerosol forcing since 2000. There are multiple lines of evidence that allow us to robustly conclude that the anthropogenic aerosol effective radiative forcing (ERF) – both aerosol–radiation interactions (ERFari) and aerosol–cloud interactions (ERFaci) – has become less negative globally, i.e. the trend in aerosol effective radiative forcing changed sign from negative to positive. Bottom-up inventories show that anthropogenic primary aerosol and aerosol precursor emissions declined in most regions of the world; observations related to aerosol burden show declining trends, in particular of the fine-mode particles that make up most of the anthropogenic aerosols; satellite retrievals of cloud droplet numbers show trends in regions with aerosol declines that are consistent with these in sign, as do observations of top-of-atmosphere radiation. Climate model results, including a revised set that is constrained by observations of the ocean heat content evolution show a consistent sign and magnitude for a positive forcing relative to the year 2000 due to reduced aerosol effects. This reduction leads to an acceleration of the forcing of climate change, i.e. an increase in forcing by 0.1 to 0.3 W m−2, up to 12 % of the total climate forcing in 2019 compared to 1750 according to the Intergovernmental Panel on Climate Change (IPCC).

Systematic Climate Model Biases in the Large‐Scale Patterns of Recent Sea‐Surface Temperature and Sea‐Level Pressure Change

AbstractObserved surface temperature trends over recent decades are characterized by (a) intensified warming in the Indo‐Pacific Warm Pool and slight cooling in the eastern equatorial Pacific, consistent with Walker circulation strengthening, and (b) Southern Ocean cooling. In contrast, state‐of‐the‐art coupled climate models generally project enhanced warming in the eastern equatorial Pacific, Walker circulation weakening, and Southern Ocean warming. Here we investigate the ability of 16 climate model large ensembles to reproduce observed sea‐surface temperature and sea‐level pressure trends over 1979–2020 through a combination of externally forced climate change and internal variability. We find large‐scale differences between observed and modeled trends that are very unlikely (<5% probability) to occur due to internal variability as represented in models. Disparate trends in the ratio of Indo‐Pacific Warm Pool to tropical‐mean warming, which shows little multi‐decadal variability in models, hint that model biases in the response to historical forcing constitute part of the discrepancy.

Effects of Land Use and Land Cover Change on Temperature in Summer over the Yellow River Basin, China

As the main driving force of global climate change, land use and land cover change (LUCC) can affect the surface energy balance and the interaction between the surface and atmosphere. This effect will cause further surface temperature changes. The Yellow River Basin is an important ecological security barrier in China. Therefore, exploring the impact of its LUCC on temperature changes can provide certain help for future land-use planning in the Yellow River Basin. Here, we conducted two numerical simulation experiments (Case2015 and Case1995) by using the weather research and forecasting (WRF) model to quantify the effect of LUCC in the Yellow River Basin on the summer 2 m air temperature (T2 m). The results showed that LUCC led to an overall warming trend in T2 m in the Yellow River Basin. Urban expansion caused T2 m to rise by approximately 0.3 °C to 0.6 °C. A warming effect was also identified in the areas where farmland and bare areas were converted to grassland, with T2 m increasing by around 0.4 °C.

Climate change and Arenicola marina: Heat waves and the southern limit of an ecosystem engineer

In asking how ecosystems will change with the forces of climate change, one approach is to identify the biotic forcing functions and focus on the ecologically dominant species, because as those species are affected, results will cascade through the system altering components such as biological diversity. Given the status of A. marina as an important ecosystem driver, it is of interest to ask how increasing temperatures will impact its distribution. The literature strongly suggests that the period during which it is most susceptible is late summer when the metabolic load of gametes is maximal and sediment temperatures at burrow depth during low tide are likely to exceed 25 °C. We used the probability of occurrence of fatal heat waves that penetrate to animal burrow depth as a primary factor in our modeling of past, present and future climates and the distribution of A. marina. Modeled sediment temperatures were validated against in situ temperature logger data and then used to develop the relationship between August SST and the occurrence of fatal heat waves to enable use of SST data directly. Modeled thermal gradients corresponded well to high resolution remotely sensed temperatures along the French and Iberian coasts and to distribution shifts in A. marina, known both from the literature and field surveys done by the authors in 2005–2014. Model hindcasts suggest that published occurrences of A. marina within the Mediterranean after 1860 except within the Gulf of Lions are unlikely. Given the known sensitivity of A. marina to anaerobiosis during heat waves, particularly when ripe, the forecasts based on CMIP6 25 km scale ocean models all predict the complete disappearance of A. marina from the Mediterranean and restriction to the upwelling zone on the western margin of Iberia and to the Atlantic coast of Europe north of 45°N with the suggestion of more limited populations in the English Channel and perhaps into the Wadden Sea. These biogeographic shifts will likely cause fundamental changes in ecosystem function along the coasts of Iberia, France, UK, and perhaps into Belgium and the Netherlands.

Everyday Life in extremis

Everyday Life <i>in extremis</i>

Astronomical climate changes trigger Late Devonian bio- and environmental events in South China

One of the five great mass extinctions of the Phanerozoic is the Frasnian–Famennian (F F) mass extinction, for which the causes have not yet been identified. In this study, cyclostratigraphic analysis of two F F transition sections was carried out in South China: the Yangdi section, a marine slope facies, and the Lali section, a marine basin facies. Paleoclimate proxy data collected at high resolution along these sections include magnetic susceptibility and X-ray fluorescence geochemistry (Ca and Fe concentrations). Time series analysis and modeling of the proxy data reveal that frequencies comparable to those of the Earth's long and short orbital eccentricity, obliquity, and precession index characterize the two successions. Metronomic 405-kyr long orbital eccentricity cycles identified along the two sections were used to construct a floating astronomical time scale across the F F transition, revealing that 1000 kyr separates the Lower and Upper Kellwasser horizons (LKH and UKH), and ~1600 kyr separates the maximum values of the LKH and UKH δ 13 C excursions. The estimated duration of the UKH is 150 kyr, during which the first, second, and third extinctions of the F F biotic crisis lasted 120 kyr, 20 kyr, and 10 kyr, respectively. Sedimentary noise models of the magnetic susceptibility and Ca concentration time series indicate that changes in sedimentary noise correspond to sea level variations. Modeling suggests that the long orbital eccentricity cycles controlled sea surface temperatures, and that third-order eustatic changes were forced by the combined orbital eccentricity and obliquity variations. Finally, we propose an “astronomical climate change” model as a defining mechanism of the F F biotic crisis. • Milankovitch cycles were recognized from the Upper Devonian Yangdi and Lali sections. • Two FATSs (~4.2 and 4.8 myr) were constructed across the F F transition. • Timing and pacing of the F F mass extinction were determined based on the FATS. • Astronomical forced sea level and climate changes were detected in F F transition. • Astronomical forcing of climate triggers the F F mass extinction.

Linear and Non-Linear Vegetation Trend Analysis throughout Iran Using Two Decades of MODIS NDVI Imagery

Vegetation is the main component of the terrestrial Earth, and it plays an imperative role in carbon cycle regulation and surface water/energy exchange/balance. The coupled effects of climate change and anthropogenic forcing have undoubtfully impacted the vegetation cover in linear/non-linear manners. Considering the essential benefits of vegetation to the environment, it is vital to investigate the vegetation dynamics through spatially and temporally consistent workflows. In this regard, remote sensing, especially Normalized Difference Vegetation Index (NDVI), has offered a reliable data source for vegetation monitoring and trend analysis. In this paper, two decades (2000 to 2020) of Moderate Resolution Imaging Spectroradiometer (MODIS) NDVI datasets (MOD13Q1) were used for vegetation trend analysis throughout Iran. First, the per-pixel annual NDVI dataset was prepared using the Google Earth Engine (GEE) by averaging all available NDVI values within the growing season and was then fed into the PolyTrend algorithm for linear/non-linear trend identification. In total, nearly 14 million pixels (44% of Iran) were subjected to trend analysis, and the results indicated a higher rate of greening than browning across the country. Regarding the trend types, linear was the dominant trend type with 14%, followed by concealed (11%), cubic (8%), and quadratic (2%), while 9% of the vegetation area remained stable (no trend). Both positive and negative directions were observed in all trend types, with the slope magnitudes ranging between −0.048 and 0.047 (NDVI units) per year. Later, precipitation and land cover datasets were employed to further investigate the vegetation dynamics. The correlation coefficient between precipitation and vegetation (NDVI) was 0.54 based on all corresponding observations (n = 1785). The comparison between vegetation and precipitation trends revealed matched trend directions in 60% of cases, suggesting the potential impact of precipitation dynamics on vegetation covers. Further incorporation of land cover data showed that grassland areas experienced significant dynamics with the highest proportion compared to other vegetation land cover types. Moreover, forest and cropland had the highest positive and negative trend direction proportions. Finally, independent (from trend analysis) sources were used to examine the vegetation dynamics (greening/browning) from other perspectives, confirming Iran’s greening process and agreeing with the trend analysis results. It is believed that the results could support achieving Sustainable Development Goals (SDGs) by serving as an initial stage study for establishing conservation and restoration practices.

Intercomparison of Aerosol Types Reported as Part of Aerosol Product Retrieval over Diverse Geographic Regions

This study examines uncertainties in the retrieval of the Aerosol Optical Depth (AOD) for different aerosol types, which are obtained from different satellite-borne aerosol retrieval products over North Africa, California, Germany, and India and Pakistan in the years 2007–2019. In particular, we compared the aerosol types reported as part of the AOD retrieval from MODIS/MAIAC and CALIOP, with the latter reporting richer aerosol types than the former, and from the Ozone Monitoring Instrument (OMI) and MODIS Deep Blue (DB), which retrieve aerosol products at a lower spatial resolution than MODIS/MAIAC. Whereas MODIS and OMI provide aerosol products nearly every day over of the study areas, CALIOP has only a limited surface footprint, which limits using its data products together with aerosol products from other platforms for, e.g., estimation of surface particulate matter (PM) concentrations. In general, CALIOP and MAIAC AOD showed good agreement with the AERONET AOD (r: 0.708, 0.883; RMSE: 0.317, 0.123, respectively), but both CALIOP and MAIAC AOD retrievals were overestimated (36–57%) with respect to the AERONET AOD. The aerosol type reported by CALIOP (an active sensor) and by MODIS/MAIAC (a passive sensor) were examined against aerosol types derived from a combination of satellite data products retrieved by MODIS/DB (Angstrom Exponent, AE) and OMI (Aerosols Index, AI, the aerosol absorption at the UV band). Together, the OMI-DB (AI-AE) classification, which has wide spatiotemporal cover, unlike aerosol types reported by CALIOP or derived from AERONET measurements, was examined as auxiliary data for a better interpretation of the MAIAC aerosol type classification. Our results suggest that the systematic differences we found between CALIOP and MODIS/MAIAC AOD were closely related to the reported aerosol types. Hence, accounting for the aerosol type may be useful when predicting surface PM and may allow for the improved quantification of the broader environmental impacts of aerosols, including on air pollution and haze, visibility, climate change and radiative forcing, and human health.

An Efficient Modeling Approach for Probabilistic Assessments of Present-Day and Future Fluvial Flooding

Risk-informed flood risk management requires a comprehensive and quantitative risk assessment, which often demands multiple (thousands of) river and flood model simulations. Performing such a large number of model simulations is a challenge, especially for large, complex river systems (e.g., Mekong) due to the associated computational and resource demands. This article presents an efficient probabilistic modeling approach that combines a simplified 1D hydrodynamic model for the entire Mekong Delta with a detailed 1D/2D coupled model and demonstrates its application at Can Tho city in the Mekong Delta. Probabilistic flood-hazard maps, ranging from 0.5 to 100 year return period events, are obtained for the urban center of Can Tho city under different future scenarios taking into account the impact of climate change forcing (river flow, sea-level rise, storm surge) and land subsidence. Results obtained under present conditions show that more than 12% of the study area is inundated by the present-day 100 year return period of water level. Future projections show that, if the present rate of land subsidence continues, by 2050 (under both RCP 4.5 and RCP 8.5 climate scenarios), the 0.5 and 100 year return period flood extents will increase by around 15- and 8-fold, respectively, relative to the present-day flood extent. However, without land subsidence, the projected increases in the 0.5 and 100 year return period flood extents by 2050 (under RCP 4.5 and RCP 8.5) are limited to between a doubling to tripling of the present-day flood extent. Therefore, adaptation measures that can reduce the rate of land subsidence (e.g., limiting groundwater extraction), would substantially mitigate future flood hazards in the study area. A combination of restricted groundwater extraction and the construction of a new and more efficient urban drainage network would facilitate even further reductions in the flood hazard. The projected 15-fold increase in flood extent projected by 2050 for the twice per year (0.5 year return period) flood event implies that the “do nothing” management approach is not a feasible option for Can Tho.

Rescue and homogenization of 140 years of glacier mass balance data in Switzerland

Abstract. Glacier monitoring in Switzerland has resulted in some of the longest and most complete data series globally. Mass balance observations at individual locations, starting in the 19th century, are the backbone of the monitoring as they represent the raw and original glaciological data demonstrating the response of snow accumulation and snow/ice melt to changes in climate forcing. So far, however, the variety of sources of historic measurements has not been systematically processed and documented. Here, we present a new complete and extensive point glacier mass balance dataset for the Swiss Alps that provides attributes for data quality and corresponding uncertainties. Original sources were digitized or re-assessed to validate or to correct existing entries and to identify metadata. The sources of data are highly diverse and stem from almost 140 years of records, originating from handwritten field notes, unpublished project documents, various digital sources, published reports, and meta-knowledge of the observers. The project resulted in data series with metadata for 63 individual Swiss glaciers, including more than 60 000 point observations of mass balance. Data were systematically analysed and homogenized, e.g. by supplementing partly missing information based on correlations inferred from direct measurements. A system to estimate uncertainty in all individual observations was developed indicating that annual point balance is measured with a typical error of 0.07 m water equivalent (w.e.), while the average error in winter snow measurements is 0.20 m w.e. Our dataset permits further investigating the climate change impacts on Swiss glaciers. Results show an absence of long-term trends in snow accumulation over glaciers while melt rates have substantially increased over the last 3 decades. The complete dataset is available at DOI https://doi.org/10.18750/massbalance.point.2021.r2021 (GLAMOS, 2021).

Detection of Forced Change Within Combined Climate Fields Using Explainable Neural Networks

AbstractAssessing forced climate change requires the extraction of the forced signal from the background of climate noise. Traditionally, tools for extracting forced climate change signals have focused on one atmospheric variable at a time, however, using multiple variables can reduce noise and allow for easier detection of the forced response. Following previous work, we train artificial neural networks to predict the year of single‐ and multi‐variable maps from forced climate model simulations. To perform this task, the neural networks learn patterns that allow them to discriminate between maps from different years—that is, the neural networks learn the patterns of the forced signal amidst the shroud of internal variability and climate model disagreement. When presented with combined input fields (multiple seasons, variables, or both), the neural networks are able to detect the signal of forced change earlier than when given single fields alone by utilizing complex, nonlinear relationships between multiple variables and seasons. We use layer‐wise relevance propagation, a neural network explainability tool, to identify the multivariate patterns learned by the neural networks that serve as reliable indicators of the forced response. These “indicator patterns” vary in time and between climate models, providing a template for investigating inter‐model differences in the time evolution of the forced response. This work demonstrates how neural networks and their explainability tools can be harnessed to identify patterns of the forced signal within combined fields.