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This paper examines efforts taking place in London, San Francisco and Stockholm to implement deep greenhouse gas emission cuts--'deep decarbonization'--through the transformation of buildings and urban energy infrastructure for increased energy efficiency and low/zero carbon energy supply. Drawing on interviews, policy document analysis, and site tours to buildings and energy infrastructure, this paper analyzes how deep decarbonization is being embedded into urban buildings, energy systems, and institutions. It argues that practitioners are finding ways to create new low/zero carbon future buildings, but are having difficulty correcting the historical development path through retrofitting. This paper examines solutions and challenges brought to light by urban decarbonization in practice targeting existing buildings from which other cities can learn. Four key lessons for low/zero carbon retrofits are highlighted: 1) shift primary targets from homeowners to owners of multiple buildings, 2) expand the suite of resources available to support zero carbon retrofits, 3) experiment and teach using public investment, and 4) institutionalize energy and carbon reporting linked to municipal department targets. Given the necessity of low-carbon, efficient, and climate-resilient building retrofits to address the climate crisis, action can be scaled up by considering buildings and energy infrastructure an infrastructure priority for public investment. Keywords: urban; cities; climate change; decarbonization Cet article examine les efforts deployes a Londres, San Francisco et Stockholm pour mettre en place une reduction profonde des emissions de gaz a effet de serre--<>--par la transformation des batiments et des infrastructures energetiques urbaines pour l'efficacite energetique et l'approvisionnement d'energie a zero ou faible intensite carbone. S'appuyant sur des entretiens, l'analyse de documents de politiques publiques et des visites de sites d'immeubles et d'infrastructures energetiques, cet article analyse comment la decarbonisation en profondeur est incorporee dans les batiments urbains, les systemes energetiques et les institutions. Il fait valoir que les praticiens trouvent des moyens de creer de nouveaux developpements a zero ou faibles emissions de carbone, mais ceux-ci ont du mal a corriger la trajectoire historique de developpement avec l'amelioration energetique. Cet article examine les solutions et les defis mis en evidence par la pratique de la decarbonisation urbaine qui cible les batiments existants, a partir desquels d'autres villes peuvent apprendre. Quatre lecons principales pour la renovation a faibles emissions ou carboneutre sont soulignees: 1) transferer les objectifs principaux des proprietaries aux proprietaries de plusieurs batiments, 2) elargir la gamme de ressources disponibles pour soutenir les ameliorations de la reduction des emissions de carbone, 3) experimenter et enseigner en utilisant les investissements publics et 4) institutionnaliser les rapports sur l'energie et le carbone lies aux objectifs des services municipaux. Compte tenu de la necessite de renover les batiments dans une optique de sobriete carbone, d'efficacite et de resilience face a la crise climatique, il est suggere d'intensifier l'action en considerant les batiments et les infrastructures energetiques comme une priorite pour les investissements publics dans les infrastructures. Mots cles: urbain; villes; changement climatique; decarbonisation, Introduction It is increasingly clear that urban climate change mitigation features diverse and multi-level action driven by actors from across government, industry and non-profit sectors. In this context, a number [...]

The current nationally determined contributions, pledged by the countries under the Paris Agreement, are far from limiting climate change to below 2 ∘C temperature increase by the end of the century. The necessary ratcheting up of climate policy is projected to come with a wide array of additional benefits, in particular a reduction of today's 4.5 million annual premature deaths due to poor air quality. This paper therefore addresses the question how climate policy and air pollution–related health impacts interplay until 2050 by developing a comprehensive global modeling framework along the cause and effect chain of air pollution–induced social costs. We find that ratcheting up climate policy to a 2 ∘ compliant pathway results in welfare benefits through reduced air pollution that are larger than mitigation costs, even with avoided climate change damages neglected. The regional analysis demonstrates that the 2 ∘C pathway is therefore, from a social cost perspective, a "no-regret option" in the global aggregate, but in particular for China and India due to high air quality benefits, and also for developed regions due to net negative mitigation costs. Energy and resource exporting regions, on the other hand, face higher mitigation cost than benefits. Our analysis further shows that the result of higher health benefits than mitigation costs is robust across various air pollution control scenarios. However, although climate mitigation results in substantial air pollution emission reductions overall, we find significant remaining emissions in the transport and industry sectors even in a 2 ∘C world. We therefore call for further research in how to optimally exploit climate policy and air pollution control, deriving climate change mitigation pathways that maximize co-benefits. [ABSTRACT FROM AUTHOR]

Sudden events of crisis ('focusing events') trigger intense media reporting, which in turn can prompt political decision-makers to respond with an adjustment of existing policies. As such, focusing events can potentially lead to long-term policy change on a certain issue. This article explores the sudden and intense period of air pollution in Beijing in January 2013 as a focusing event. The episode, which international media referred to as 'Airpocalypse', triggered widespread discussion and policy adjustments that can be assumed to have accelerated the control of air pollution in China. The 'Airpocalypse' was not the first event of intense air pollution in Beijing, but the only one which seemingly caused lasting sociopolitical changes. The aim of this article is to explore the underlying situational factors that enabled the 'Airpocalypse' to be more relevant than other events of severe air pollution. This paper argues that a combination of historically high pollution, improved access to information, increasing government willingness to address the issue, and the ability of media to more openly discuss air pollution created a public pressure situation to which the government was prompted to respond in a stronger way than during previous events of heavy air pollution. [ABSTRACT FROM AUTHOR]

This paper studies the interplay between climate, health, and the economy in a stylized world with eleven heterogeneous regions, with special emphasis on USA, Europe, China, India, and Africa. We introduce health impacts into a simple economic integrated assessment model where both the local cooling effect of S O and the global warming effect of C O are endogenous, and investigate how these factors affect the equilibrium path. Regions do not respond in the same way to climate change. In particular, emission abatement rates and health costs depend on the economic and geographical characteristics of each region. Two policy scenarios are considered, Nash and Optimal, for which we present both global and regional results. Results for Africa and China are highlighted. [ABSTRACT FROM AUTHOR]

In 2019, South Korea's Framework Act on The Management of Disasters and Safety was revised to include respirable particulate matter as a social disaster. Urban air pollution, especially particulate matter pollution, has been a serious threat to socioeconomic development and public health. In order to address this problem, strong climate crisis response strategies and policies to improve urban air quality are necessary. Therefore, it is of great importance to assess the frequency of urban air pollution occurrence and its influencing factors. The objective of this study is to develop consistent methodologies for the construction of an index system and for assessing the influencing factors of urban particulate matter pollution based on population, social welfare, land use, environmental, transportation, and economic governance considerations. We applied the local indicators of spatial association and geographical detector methods, and 35 influencing factors were selected to assess their influence on urban air pollution occurrence in 229 cities and counties in South Korea. The results indicated the spatial pattern of the particulate matter concentration in these locations showed strong spatial correlation, and it was confirmed that there was a difference in distribution according to the season. As a result of the analysis of influencing factors, it was found that environment and land use characteristics were the main influencing factors for PM10 and PM2.5. The explanatory power between the two influencing factors of particulate matter was greater than that of a single influencing factor. In addition, most influencing factors resulted in both positive and negative effects on urban fine particulate matter pollution. The interaction relationship of all factors showed a strong action effect in the case of both PM10 and PM2.5, so it was confirmed that all influencing factors were interdependent. In particular, the findings proved that combining the two factors would have a more pronounced effect on particulate matter than when they were independent. We confirmed the significant results for the factors affecting particulate matter. This study offers suggestions on reducing urban air pollution occurrence that can be used to provide a basis and reference for the government to form policies on urban air pollution control in cities and counties. [ABSTRACT FROM AUTHOR]

Plant growth and crop harvest are impacted by both climate change and air pollution. However, their relative importance in crop yields remains elusive, especially in heavily polluted regions. Here we develop crop yield prediction models, based on a large volume of historical crop data, as well as climate and pollution records in China since 1980. A long‐term surface ozone concentration data set is developed from a machine‐learning model and various observations. An assessment of four climate and pollution factors reveals the critical role of particulate and ozone pollution in regulating interannual variations of crop yields in China. During 2010–2018, we find that the particulate pollution mitigation outweighs the negative impacts of concurrent climate change, resulting in 0.5%–1.9% net yield increases nationwide, despite of the ozone increases in the North China Plain. Looking to the future, the impacts of climate change, particularly from surface temperature increase, will dominate over pollution factors and profoundly reduce future maize and rice yields by 0.6 to 2.8% 10 yr−1 by 2050. Our findings call for attention on the threat to future global food security from the absence of pollution mitigation and the persistence of global warming. Plain Language Summary: We capitalize on 39‐year historical records of crop yields, climate variables, and pollution data to develop a robust crop yield prediction model. Utilizing this model, we show a critical role of particulate pollution in determining annual crop yields. Moreover, our analyses reveal that the recent abatement of anthropogenic emission in China results in a net crop gain, which masks the crop loss due to the increased temperature and precipitation. In the next 30 years, temperature dominant climate effects will emerge to steer the future trend of crop yields. The present study demonstrates the co‐benefit of the recent air pollution control policy from agriculture and food perspectives. However, this benefit will eventually be diminished after the air pollution becomes alleviated in the full scale, while persisting or even exacerbated global warming will pose larger threat on the future food security. Key Points: Robust crop yield prediction models are developed to assess climate change and air pollution impacts on agricultureDuring 2010–2018, the particulate pollution mitigation outweighs the negative impacts of concurrent climate change in ChinaExacerbated global warming will lead to crop yield reduction in spite of pollution alleviation in the future scenarios [ABSTRACT FROM AUTHOR]

The most important reason for the rapid increase of global warming and the occurrence of related climate changes is the contamination caused by greenhouse gases released into the air. Whereas air pollution affects human health significantly, it also threatens the lives of plants and animals. As it is known, the majority of the human population contemporarily lives in cities. In these circumstances, air pollution occurring in cities is of great importance. When the sources of air pollution occurring in cities are examined, it is seen that the pollution caused by emissions originating from vehicles and industry is the leading cause among these reasons. Exhaust gas emission values originating from ships occupy an important place in the emission amounts emitted by vehicles. Considering both emissions from ships and operational reasons, it is understood that air pollution can occur at levels that will seriously affect human health at port areas. Keeping these facts in mind, Trabzon port, which is considered to be a major threat to human life due to released exhaust gases because of being in the city center and one of the biggest ports in the region, was chosen in this study. Emissions originating from ship movements and operations at this port were measured, mapped and the flow trends of these emissions were determined by the AERMOD model and the effect on the environment was investigated. Within the scope of the study, the exhaust emission measurements of the ships and the vehicles serving for operational purposes were performed all the year round. Afterwards, the annual distribution of gases was determined by modeling the measured emissions with the AERMOD model program. As a result of the analyses, it was found out that a large part of the exhaust emissions occurring at the port area originated from the ships and the amount of CO2 gas emission constituted approximately 97% of the total exhaust gas emission. Also, it was determined that the exhaust gas emitted to the widest area was NOx and the gases emitted to the environment were spread over an area of approximately 40 km2 around the port area. [ABSTRACT FROM AUTHOR]

On-road freight is a significant source of air pollutant and greenhouse gas emissions. The resulting economic damages can cross borders through processes of atmospheric fate and transport, regardless of whether that freight serves local or regional demand. Understanding patterns of freight demand and atmospheric processes can thus inform inter-jurisdictional efforts to mitigate multipollutant damages. We quantify how different freight trips across 49 census divisions in the Province of Ontario, Canada create an economic burden on downwind US receptors. We apply an integrated modeling approach combining a travel demand model, a mobile emissions simulator, and marginal damages from emissions. Economic damages include the increased risk of premature death from PM2.5 related to primary PM2.5 (represented by damages from inert primary PM2.5), NOX, SO2, and NH3, and the global effects of climate change from greenhouse gases (CO2, CH4, N2O). Over 90% of the $1.4 billion (2010USD) in transboundary air pollutant damages at US receptors result from regional freight demand across Ontario in 2012. A single major freight corridor, the ON-401 expressway, contributes more than half of all damages. Most of these damages impact the states situated to the south and east of the province. Mean estimates of annual damages range from millions to tens of millions (2010USD) across major eastern metropolitan areas including New York, Boston, Philadelphia, and D.C. Most of these damages result from NOX, which constitutes 95% of inorganic PM2.5-related pollutant emissions by mass. Thus, targeting NOx from freight movements along the ON-401 expressway could avoid millions to tens of millions of damages annually in eastern US cities. These results indicate that local green freight policies may be unable to address the environmental burden at cross-border receptors. Cooperation is needed among local, provincial, and federal governments to encourage policies targeting the most harmful emissions along routes servicing regional freight demands. Implications: On-road freight movement in Ontario can yield billions of dollars in annual economic damages to US residents through its effects on air pollution and climate change. We use an integrated modeling approach combining an on-road freight travel demand, mobile emissions, and marginal damages of emissions to quantify and study these economic damages. Regional freight contributes approximately 90% of damages, with one major freight corridor, the ON-401 expressway, contributing 59%. Most damages derive from emissions of NOx and amount to millions to tens of millions of dollars in annual damages across major Eastern US cities. Thus, targeting NOx from freight movements along the ON-401 expressway could avoid millions of damages annually in eastern US cities. [ABSTRACT FROM AUTHOR]

The Sudbury region of northeastern Ontario, Canada, provides one of the world's best examples of the resilience of aquatic ecosystems after reductions in atmospheric contaminant deposition. Thousands of lakes around the Sudbury metal smelters were badly damaged by acid deposition. Lakes closest to the smelters were also contaminated by metal particulates. However, large reductions in atmospheric S[O.sub.2] and metal emissions starting in the early 1970s have led to widespread chemical improvements in these lakes, and recovery has been observed for various aquatic biota. Studies of Sudbury-area lakes are advancing our understanding of chemical and biological lake recovery; however, recovery is a complicated process and much remains to be learned. Biological recovery has often been slow to follow chemical recovery, and it has become apparent that the recovery of lakes from acidification is closely linked to interactions with other large-scale environmental stressors like climate change and Ca declines. Thus, in our multiple-stressor world, recovery may not bring individual lakes back to their exact former state. However, with time, substantial natural biological recovery toward typical lake communities can be reasonably expected for most but not necessarily all biota. For organisms with limited dispersal ability, particularly fish, human assistance may be necessary to re-establish typical communities. In lakes where food webs have been severely altered, re-establishment of typical diverse fish communities may in fact be an important element aiding the recovery of other important components of aquatic ecosystems including zooplankton and benthic macroinvertebrates. In the lakes closest to the smelters, where historically watersheds as well as lakes were severely damaged, the recovery of aquatic systems will be closely linked to ongoing terrestrial recovery and rehabilitation, particularly through the benefits of increased inputs of terrestrially derived organic matter. The dramatic lake recovery observed in the Sudbury area points to a brighter future for these lakes. However, continued monitoring will be needed to determine future changes and help guide the management and protection of Sudbury-area lakes in this multiple-stressor age. Key words: acidification, lakes, biota, recovery, Sudbury. La region de Sudbury au nord-est de l'Ontario, Canada, fournit un des meilleurs exemples au monde de la resistance des ecosystemes aquatiques a la suite de reductions de depot de contaminants atmospheriques. Des milliers de lacs autour des fonderies de Sudbury ont ete serieusement endommages par le depot d'acides. Les lacs les plus proches des fonderies ont aussi ete contamines par des matieres particulaires metalliques. Cependant, les grandes reductions des emissions de S[O.sub.2] et metalliques atmospheriques ayant commence au debut des annees 1970 ont donne lieu a d'importantes ameliorations chimiques dans ces lacs et la recuperation a ete observee au niveau de divers biotes aquatiques. Les etudes au sujet des lacs de la region de Sudbury font progresser notre comprehension de la recuperation chimique et biologique des lacs; cependant, la recuperation est un processus complexe et il nous reste beaucoup a apprendre. La recuperation biologique a souvent tarde a suivre la recuperation chimique et il est devenu apparent que la recuperation des lacs a la suite des effets d'acidification soit etroitement liee aux interactions avec d'autres facteurs agressifs agissant agrande echelle comme le changement climatique et les baisses de Ca. Ainsi, en ce monde de facteurs agressifs multiples, la recuperation ne peut pas retablir exactement les lacs individuellement a leur ancien etat. Cependant, avec le temps, on peut raisonnablement s'attendre a une importante recuperation biologique naturelle retablissant les communautes de lac typiques pour la plupart, mais pas necessairement tout le biote. Pour les organismes avec un pouvoir de dispersion limite, particulierement les poissons, l'intervention humaine peut etre necessaire afin de retablir les communautes typiques. Dans les lacs ou les reseaux alimentaires ont ete severement changes, le retablissement de communautes typiques composees de differents poissons peut en fait etre un element important aidant a la recuperation d'autres composants importants d'ecosystemes aquatiques y compris le zooplancton et les macroinvertebres benthiques. Dans les lacs plus pres des fonderies, ou historiquement les lignes de partage des eaux aussi bien que les lacs ont ete severement endommagees, la recuperation des systemes aquatiques sera etroitement liee au retablissement et a la remise en etat terrestre en cours, particulierement par les avantages des apports accrus de matiere organique issue de la terre. La dramatique recuperation des lacs observee dans la region de Sudbury presage un avenir plus brillant pour ces lacs. Cependant, la surveillance continue sera necessaire afin de determiner les changements futurs et pour aider a guider la gestion de la protection de lacs de la region de Sudbury en cette ere de facteurs agressifs multiples. [Traduit par la Redaction] Mots-cles: acidification, lacs, biote, recuperation, Sudbury., Introduction The mining and smelting of metals in the Sudbury, Ontario, Canada, area began in the late 1800s (Winterhalder 1995a), and over time the Sudbury smelters became one of the [...]

In California's Central Valley, tule fog frequency increased 85% from 1930 to 1970, then declined 76% in the last 36 winters. Throughout these changes, fog frequency exhibited a consistent north‐south trend, with maxima in southern latitudes. We analyzed seven decades of meteorological data and five decades of air pollution data to determine the most likely drivers changing fog, including temperature, dew point depression, precipitation, wind speed, and NOx (oxides of nitrogen) concentration. Climate variables, most critically dew point depression, strongly influence the short‐term (annual) variability in fog frequency; however, the frequency of optimal conditions for fog formation show no observable trend from 1980 to 2016. NOx concentration, which has a decreasing north‐south concentration gradient, declined continuously over this period, consistent with the long‐term temporal and spatial trends in fog. As development in the Central Valley increased direct particle and other pollutant emissions from 1930 to 1970, fog frequency increased. Following the Clean Air Act, particle emissions quickly declined, and NOx emissions declined steadily, reducing the cloud condensation nuclei (CCN) available for fog formation. As a precursor of ammonium nitrate aerosols, which are efficient CCN, we used NOx measurements and emission trends as a proxy for the CCN trend. We conclude that while the short‐term fog variability is dominantly driven by climate fluctuations, the longer‐term temporal and spatial changes in fog have been driven by changes in air pollution. For conditions close to the dew point, a decrease in fog of 5 days/year per 10 parts per billion NOx decrease occurred across the Central Valley. Plain Language Summary: California's Central Valley is known for dense wintertime ground fog, called tule fog, which dramatically reduces visibility, causing weather‐related accidents, while also helping provide the "winter chill" required to improve productivity of fruit and nut trees. Fog frequency changed dramatically over the past century, increasing 85% from 1930 to 1970 then decreasing by ~75% since 1980. We found that climate variables, most importantly dew point depression (a measure of how low the temperature must drop for water droplets to form) is the main controller of short‐term (year‐to‐year) changes in fog frequency. However, changing air pollution is the main driver of the long‐term trends in fog frequency because it provides water‐attracting particles on which fog droplets form. Air pollution increased in the Central Valley of California prior to 1970 due to development with lack of emissions regulation, then decreased since 1980 due to effective air pollution control, matching the observed long‐term trend in fog frequency. Key Points: Central Valley fog frequency increased 85% from 1930 to 1970, then declined 76% in the last 36 winters, with large short‐term variabilityShort‐term fog variability is dominantly driven by climate fluctuationsLong‐term temporal and spatial trends in fog are dominantly driven by changes in air pollution [ABSTRACT FROM AUTHOR]