Green infrastructure (GI) has emerged as a feasible strategy for promoting adaptive capacities of cities to climate change by alleviating urban heat island (UHI) and thus heat stress for humans. ...However, GI can also intensify the winter cold stress. To understand the extent of UHI within a city as well as the link between outdoor thermal stress both diurnally and seasonally, we carried out an empirical study in Würzburg, Germany from 2018 to 2020. At sub-urban sites, relative humidity and wind speed (WS) was considerably higher and air temperature (AT) lower compared to the inner city sites. Mean AT of inner city sites were higher by 1.3 °C during summer and 5 °C during winter compared to sub-urban sites. The magnitude followed the spatial land use patterns, in particular the amount of buildings. Consequently, out of 97 hot days (AT > 30 °C) in 3 years, 9 days above the extreme threshold of wet bulb globe temperature of 35 °C were recorded at a centre location compared to none at a sub-urban site. Extreme heat stress could be halved with 30-40% cover of greenspaces including grass lawns, green roofs, and green walls with little compromise in increasing winter cold stress.
•Human thermal comfort (PET) under different tree species have been investigated.•Eco-physiological and bio-meteorological data were measured across the city.•Tree species with higher leaf area index ...showed better below-canopy surface cooling.•Along with higher tree transpiration, they provided better PET reduction.•Cluster tree planting design provided better PET even they reduced the tree growth.
The potential of urban greenspaces in regulating temperature is widely known; however, in the heterogeneous urban landscape the process and the magnitude of human thermal comfort as well as the cumulative effects of natural and built surfaces are not yet well understood. We selected two ecologically contrasting species Tilia cordata Mill. and Robinia pseudoacacia L. planted in eight plots across five different sites in Würzburg, one of the major cities in Northern Bavaria, Germany. We monitored meteorological and edaphic variables and tree sap-flow along with the air temperature, relative humidity, within tree canopy and outside, between January 1 and December 31, 2018. Additionally, we measured surface temperature, meteorological variables below the tree canopies and outside, during the hottest summer days of 2018 (July 23 to 31). With 35% higher leaf area index, T. cordata tree canopies prevented higher incoming radiation compared to R. pseudoacacia trees. Moreover, with diffuse porous wood anatomy, T. cordata trees provided four times more transpiration compared to R. pseudoacacia, therefore, up to 2.8 °C air temperature reduction (ΔAT) within the tree canopy, and increase in absolute humidity (ΔAH) up to 2.6 g m − 3 compared to the 1.9 °C of ΔAT and 1.9 g m − 3 of ΔAH for R. pseudoacacia respectively. Thus, physiological equivalent temperature reduction was up to 4 °C under the shade of a R. pseudoacacia tree compared to 11 °C under a T. cordata tree. Finally, the research showed the importance of urban topography, such as street orientation, surrounding environment such as geometry, urban design to reduce the hindrance of wind flow and proportion of greenspaces in terms of outdoor human thermal comfort.
Air pollution is associated with morbidity and mortality worldwide. We investigated the impact of improved air quality during the economic lockdown during the SARS-Cov2 pandemic on emergency room ...(ER) admissions in Germany. Weekly aggregated clinical data from 33 hospitals were collected in 2019 and 2020. Hourly concentrations of nitrogen and sulfur dioxide (NO2, SO2), carbon and nitrogen monoxide (CO, NO), ozone (O3) and particulate matter (PM10, PM2.5) measured by ground stations and meteorological data (ERA5) were selected from a 30 km radius around the corresponding ED. Mobility was assessed using aggregated cell phone data. A linear stepwise multiple regression model was used to predict ER admissions. The average weekly emergency numbers vary from 200 to over 1600 cases (total n = 2,216,217). The mean maximum decrease in caseload was 5 standard deviations. With the enforcement of the shutdown in March, the mobility index dropped by almost 40%. Of all air pollutants, NO2 has the strongest correlation with ER visits when averaged across all departments. Using a linear stepwise multiple regression model, 63% of the variation in ER visits is explained by the mobility index, but still 6% of the variation is explained by air quality and climate change.
This study examines the relationship between variations of the Southern Annular Mode (SAM) and black carbon (BC) at 550 nm aerosol optical depth (AOD) in the Western Cape province (WC). Variations of ...the positive (negative) phase of the SAM are found to be related to regional circulation types (CTs) in southern Africa, associated with suppressed (enhanced) westerly wind over the WC through the southward (northward) migration of Southern Hemisphere mid-latitude cyclones. The CTs related to positive (negative) SAM anomalies induce stable (unstable) atmospheric conditions over the southwestern regions of the WC, especially during the austral winter and autumn seasons. Through the control of CTs, positive (negative) SAM phases tend to contribute to the build-up (dispersion and dilution) of BC in the study region because they imply dry (wet) conditions which favor the build-up (washing out) of pollutant particles in the atmosphere. Indeed, recent years with an above-average frequency of CTs related to positive (negative) SAM anomalies are associated with a high (low) BC AOD over southwesternmost Africa.
Abstract
Bioclimatic variables (BCVs) are the most widely used predictors within the field of species distribution modeling, but recent studies imply that BCVs alone are not sufficient to describe ...these limits. Unfortunately, the most popular database, WorldClim, offers only a limited selection of bioclimatological predictors; thus, other climatological datasets should be considered, and, for data consistency, the BCVs should also be derived from the respective datasets. Here, we investigate how well the BCVs are represented by different datasets for the extended Mediterranean area within the period 1970–2020, how different calculation schemes affect the representation of BCVs, and how deviations among the datasets differ regionally. We consider different calculation schemes for quarters/months, the annual mean temperature (BCV‐1), and the maximum temperature of the warmest month (BCV‐5). Additionally, we analyzed the effect of different temporal resolutions for BCV‐1 and BCV‐5. Differences resulting from different calculation schemes are presented for ERA5‐Land. Selected BCVs are analyzed to show differences between WorldClim, ERA5‐Land, E‐OBS, and CRU. Our results show that (a) differences between the two calculation schemes for BCV‐1 diminish as the temporal resolution decreases, while the differences for BCV‐5 increase; (b) with respect to the definition of the respective month/quarter, intra‐annual shifts induced by the calculation schemes can have substantially different effects on the BCVs; (c) all datasets represent the different BCVs similarly, but with partly large differences in some subregions; and (d) the largest differences occur when specific month/quarters are defined by precipitation. In summary, (a) since the definition of BCVs matches different calculation schemes, transparent communication of the BCVs calculation schemes is required; (b) the calculation, integration, or elimination of BCVs has to be examined carefully for each dataset, region, period, or species; and (c) the evaluated datasets provide, except in some areas, a consistent representation of BCVs within the extended Mediterranean region.
Plant phenology is well known to be affected by meteorology. Observed changes in the occurrence of phenological phases are commonly considered some of the most obvious effects of climate change. ...However, current climate models lack a representation of vegetation suitable for studying future changes in phenology itself. This study presents a statistical-dynamical modeling approach for Bavaria in southern Germany, using over 13,000 paired samples of phenological and meteorological data for analyses and climate change scenarios provided by a state-of-the-art regional climate model (RCM). Anomalies of several meteorological variables were used as predictors and phenological anomalies of the flowering date of the test plant
Forsythia suspensa
as predictand. Several cross-validated prediction models using various numbers and differently constructed predictors were developed, compared, and evaluated via bootstrapping. As our approach needs a small set of meteorological observations per phenological station, it allows for reliable parameter estimation and an easy transfer to other regions. The most robust and successful model comprises predictors based on mean temperature, precipitation, wind velocity, and snow depth. Its average coefficient of determination and root mean square error (RMSE) per station are 60% and ± 8.6 days, respectively. However, the prediction error strongly differs among stations. When transferred to other indicator plants, this method achieves a comparable level of predictive accuracy. Its application to two climate change scenarios reveals distinct changes for various plants and regions. The flowering date is simulated to occur between 5 and 25 days earlier at the end of the twenty-first century compared to the phenology of the reference period (1961–1990).
Human activity is supposed to affect the earth’s climate mainly via two processes: the emission of greenhouse gases and aerosols and the alteration of land cover. While the former process is well ...established in state-of-the-art climate model simulations, less attention has been paid to the latter. However, the low latitudes appear to be particularly sensitive to land use changes, especially in tropical Africa where frequent drought episodes were observed during recent decades. Here several ensembles of long-term transient climate change experiments are presented with a regional climate model to estimate the future pathway of African climate under fairly realistic forcing conditions. Therefore, the simulations are forced with increasing greenhouse gas concentrations as well as land use changes until 2050. Three different scenarios are prescribed in order to assess the range of options inferred from global political, social, and economical development. The authors find a prominent surface heating and a weakening of the hydrological cycle over most of tropical Africa, resulting in enhanced heat stress and extended dry spells. In contrast, the large-scale atmospheric circulation in upper levels is less affected, pointing to a primarily local effect of land degradation on near-surface climate. In the model study, it turns out that land use changes are primarily responsible for the simulated climate response. In general, simulated climate changes are not concealed by internal variability. Thus, the effect of land use changes has to be accounted for when developing more realistic scenarios for future African climate.
Urban populations are significantly affected by air pollution, which poses a major threat to public health. However, standardized and public mobility data, essential for an exposure assessment, are ...frequently unavailable. Earth observation-derived and model datasets can support large-scale health studies, especially in remote areas with limited data availability. This study investigates the use of a globally derivable variable from remote sensing data to estimate the static versus dynamic population exposure difference. A health risk assessment using a higher and a lower resolution air pollution data was performed. This was achieved by examining air pollution concentrations in two European regions, Lombardy, in Italy, and Germany, incorporating commuting datasets. Accordingly, a retrospective long-term exposure assessment to particulate matter less than 2.5 microns (PM 2.5 ), nitrogen dioxide (NO 2 ), and ozone (O 3 ) was performed from 2013 to 2022. The study evaluates the difference between the resident and the dynamic population exposed to concentrations exceeding the new limits set by the World Health Organization (WHO). The relation between pollutant concentration and the Fraction of Settlement Area (FSA), a proxy of urbanization levels, derived from the global World Settlement Footprint dataset was explored. Two pollution datasets were used: with European, and global coverage. The analysis decouples daytime and nighttime hours. For each region and pollutant specific FSA thresholds were identified, that maximize the population exposure gap. Our findings highlight the impact of air pollution on population health, revealing widespread exposure exceeding WHO limits, particularly for PM 2.5 , and emphasizing the importance of considering diurnal exposure variations in health risk assessments.
Megacities exert substantial demands on the world's energy resources, thereby producing large shares of atmospheric emissions and air pollution. Despite several studies on nitrogen dioxide (NO 2 ) ...changes in megacities, a systematic analysis in relation to settlement growth is still pending. This study examines the trends of tropospheric NO 2 pollution in 38 megacities regarding settlement growth by analyzing Earth Observation data. Multiannual records of tropospheric NO 2 from Global Ozone Monitoring Experiment (GOME), Scanning Imaging Absorption Spectrometer for Atmospheric Chartography, GOME-2A, and GOME-2B are evaluated regarding the World Settlement Footprint evolution from 1996 to 2015. Compared to previous studies, this work strictly uses remote sensing data and the spatial concept of functional urban areas. Therefore, uncertainties due to inconsistent spatial references, incomparable administrative units, as well as heterogeneously reported local data are widely excluded to enable an appropriate comparison of megacities across the globe. On average, we observe an increase in tropospheric NO 2 burden of 5.06 ± 0.83%/year and a relative settlement growth of 2.87%/year for the time period considered. We find a wide range of trends: relative NO 2 pollution ranges from an increase of 44.0 ± 5.9%/year to a decrease of −3.2 ± 0.2%/year, settlement growth rates vary from 0.3%/year to 9.5%/year. Despite this variety, the results exhibit a pronounced relation to the income group following the world's economies classification of the World Bank. Complemented by a cluster analysis and ranking of the megacities, the study provides indicators to develop a better understanding of the drivers and impacts of urbanization and air pollution.
The safety band of Antarctica, consisting of floating
glacier tongues and ice shelves, buttresses ice discharge of the Antarctic
Ice Sheet. Recent disintegration events of ice shelves along with ...glacier
retreat indicate a weakening of this important safety band. Predicting
calving front retreat is a real challenge due to complex ice dynamics in a
data-scarce environment that are unique for each ice shelf and glacier. We
explore the extent to which easy-to-access remote sensing and modeling data can
help to define environmental conditions leading to calving front retreat.
For the first time, we present a circum-Antarctic record of glacier and ice
shelf front change over the last two decades in combination with
environmental variables such as air temperature, sea ice days, snowmelt, sea
surface temperature, and wind direction. We find that the Antarctic Ice Sheet
area decreased by −29 618 ± 1193 km2 in extent between 1997–2008
and gained an area of 7108 ± 1029 km2 between 2009 and 2018.
Retreat concentrated along the Antarctic Peninsula and West Antarctica
including the biggest ice shelves (Ross and Ronne). In several cases,
glacier and ice shelf retreat occurred in conjunction with one or several
changes in environmental variables. Decreasing sea ice days, intense
snowmelt, weakening easterlies, and relative changes in sea surface
temperature were identified as enabling factors for retreat. In contrast,
relative increases in mean air temperature did not correlate with calving
front retreat. For future studies a more appropriate measure for atmospheric
forcing should be considered, including above-zero-degree days and
temperature extreme events. To better understand drivers of glacier and ice
shelf retreat, it is critical to analyze the magnitude of basal melt through
the intrusion of warm Circumpolar Deep Water that is driven by strengthening
westerlies and to further assess surface hydrology processes such as
meltwater ponding, runoff, and lake drainage.
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