Climate Penalty Research Articles

Long-Term Variability of Surface Ozone and Its Associations with NOx and Air Temperature Changes from Air Quality Monitoring at Belsk, Poland, 1995–2023

Surface ozone (O3) and nitrogen oxides (NOx = NO + NO2) measured at the rural station in Belsk (51.83° N, 20.79° E), Poland, over the period of 1995–2023, were examined for long-term variability of O3 and its relationship to changes in the air temperature and NOx. Negative and positive trends were found for the 95th and 5th percentile, respectively, in the O3 data. A weak positive correlation (statistically significant) of 0.33 was calculated between O3 and the temperature averaged from sunrise to sunset during the photoactive part of the year (April–September). Recently, O3 maxima have become less sensitive to temperature changes, reducing the incidence of photochemical smog. The ozone–climate penalty factor decreased from 4.4 µg/m3/°C in the 1995–2004 period to 3.9 µg/m3/°C in the 2015–2023 period. The relationship between Ox (O3 + NO2) and NOx concentrations averaged from sunrise to sunset determined the local and regional contribution to Ox variability. The seasonal local and regional contributions remained unchanged in the period of 1995–2023, stabilizing the average O3 level at Belsk. “NOx-limited” and “VOC-limited” photochemical regimes prevailed in the summer and autumn, respectively. For many winter and spring seasons between 1995 and 2023, the type of photochemical regime could not be accurately determined, making it difficult to build an effective O3 mitigation policy.

Climate change and winter wheat yields: the roles of freezing days and long-run adaptations

Abstract This paper employs the recently proposed climate penalty model to estimate season-specific climate change impacts on Chinese winter wheat yields and also reveals the effects of long-run adaptions by comparing the short-run and long-run estimates identified from the model. We find that Spring freezing days are critical as we estimate small yield gains when considering a reduction in the number of freezing days (induced by global warming), as opposed to large yield losses when such effects are omitted. We also find substantial influences of adaptation effects that could reverse the sign of climate change impacts.

Distinct PM2.5‐Related Near‐Term Climate Penalties Induced by Different Clean Air Measures in China

AbstractThe reductions in aerosols often exacerbate climate warming. It remains unclear how to effectively alleviate PM2.5 pollution while minimizing the penalty on climate warming. Here we identify the clean air measures in China that are associated with low aerosol climate penalty efficiency (ACPE), which is defined as aerosol radiative forcing per unit PM2.5 concentration reduction. The measures in transportation, residential combustion, and open burning sectors generally caused lower ACPE [0.07, 0.24, and 0.10 (W m−2)/(μg m−3)] than those from other sectors [0.34–0.46 (W m−2)/(μg m−3)]. This is ascribed to relatively small decreases in cloud concentration nuclei per unit PM2.5 reduction in these sectors, which is further attributed to either relatively low aerosol hygroscopicity or relatively small decrease in aerosol number. Most measures in the former three sectors have low ACPE of <0.15 [(W m−2)/(μg m−3)] and thus may be prioritized for synergistically controlling PM2.5 pollution and climate warming.

Dissecting Drivers of Ozone Pollution during the 2022 Multicity Lockdowns in China Sheds Light on Future Control Direction.

In 2022, many Chinese cities experienced lockdowns and heatwaves. We analyzed ground and satellite data using machine learning to elucidate chemical and meteorological drivers of changes in O3 pollution in 27 major Chinese cities during lockdowns. We found that there was an increase in O3 concentrations in 23 out of 27 cities compared with the corresponding period in 2021. Random forest modeling indicates that emission reductions in transportation and other sectors, as well as the changes in meteorology, increased the level of O3 in most cities. In cities with over 80% transportation reductions and temperature fluctuations within -2 to 2 °C, the increases in O3 concentrations were mainly attributable to reductions in nitrogen oxide (NOx) emissions. In cities that experienced heatwaves and droughts, increases in the O3 concentrations were primarily driven by increases in temperature and volatile organic compound (VOC) emissions, and reductions in NOx concentrations from ground transport were offset by increases in emissions from coal-fired power generation. Despite 3-99% reduction in passenger volume, most cities remained VOC-limited during lockdowns. These findings demonstrate that to alleviate urban O3 pollution, it will be necessary to further reduce industrial emissions along with transportation sources and to take into account the climate penalty and the impact of heatwaves on O3 pollution.

Underappreciated Emission Spikes From Power Plants During Heatwaves Observed From Space: Case Studies in India and China

AbstractThe frequency, intensity, and duration of extreme heatwaves are projected to increase in the global context of climate change. However, evidence of how anthropogenic emissions respond to heatwaves and further impact air quality remains elusive. Here, we use satellite remote sensing measurements alongside chemical transport model simulations to reveal abrupt variations in primary and secondary air pollutants introduced by extreme heatwaves. We highlight evidence from China and India, where satellite sulfur dioxide (SO2) and nitrogen dioxide (NO2) columns over thermal power plants enhance consistently responding to heatwaves. We attribute such spiked emissions to soaring electricity use and demonstrate that bottom‐up inventories underestimate the emissions from the power sector by 34.9% for the selected case. Elevated emissions facilitate fine particulate matter (PM2.5) and ozone (O3) formation over thermal power plants in an inhomogeneous manner, due to the combined effect of atmospheric oxidizing capacity, thermal decomposition of peroxyacetyl nitrate, planetary boundary layer rise, and air stagnation. Our results underscore the emerging challenge of pollution control attributable to the increasing climate penalty and the necessity of targeted control strategies and alternative energy sources during heatwaves.

Relationship between ozone and air temperature in future conditions: A case study in sichuan basin, China

The Sichuan Basin (SCB) is located in southwestern China and has a unique topography where ozone (O3) pollution is frequent during summer. Few studies have clarified the relationship between O3 and air temperature in SCB. Here, the SCB was divided into four major urban agglomerations. The weather research and forecasting model-community multiscale air quality model (WRF-CMAQ) was used to analyze the meteorology, spatial distribution characteristics of pollutants, and interactions among the urban agglomerations in the SCB. WRF-CMAQ was used to study the historical changes in the climate penalty factor (CPF) from 2015 to 2020 and the climate pathways under the SSP2-4.5 CPF in values in 2030 for the ambitious pollution NDC-goal scenario (NDC) and current-goals scenario (Current). The results show that the SCB is warmer in the summer months with prevailing northeasterly winds. Ozone accumulated in the western part of the SCB, and a high CPF of O3 concentration was most prominent in NW urban agglomeration, where the O3 concentration increased by 4.12–5.40 ppb for every 1 °C increase in air temperature. The observed CPF in the SCB in 2020 averaged 3.64 ppb/°C. The average CPF in the SCB in 2030 was 1.152 ppb/°C under the NDC scenario and 1.269 ppb/°C under the current scenario. This study is critical for understanding the relationship between O3 concentration and air temperature in China.

Connections Between Air Pollution, Climate Change, and Cardiovascular Health.

Globally, more people die from cardiovascular disease than any other cause. Climate change, through amplified environmental exposures, will promote and contribute to many noncommunicable diseases, including cardiovascular disease. Air pollution, too, is responsible for millions of deaths from cardiovascular disease each year. Although they may appear to be independent, interchangeable relationships and bidirectional cause-and-effect arrows between climate change and air pollution can eventually lead to poor cardiovascular health. In this topical review, we show that climate change and air pollution worsen each other, leading to several ecosystem-mediated effects. We highlight how increases in hot climates as a result of climate change have increased the risk of major air pollution events such as severe wildfires and dust storms. In addition, we show how altered atmospheric chemistry and changing patterns of weather conditions can promote the formation and accumulation of air pollutants: a phenomenon known as the climate penalty. We demonstrate these amplified environmental exposures and their associations to adverse cardiovascular health outcomes. The community of health professionals-and cardiologists, in particular-cannot afford to overlook the risks that climate change and air pollution bring to the public's health.

Nonlinearity of the cloud response postpones climate penalty of mitigating air pollution in polluted regions

Aerosol–cloud interactions contribute substantially to uncertainties in anthropogenic forcing, in which the sensitivity of cloud droplet number concentration (Nd) to aerosol plays a central role. Here we use satellite observations to show that the aerosol–Nd relation (in log–log space) is not linear as commonly assumed. Instead, the Nd sensitivity decreases at large aerosol concentrations due to the transition from aerosol-limited to updraft-limited regime, making the widely used linear method problematic. A sigmoidal transition is shown to adequately fit the data. When using this revised relationship, the additional warming that arises from air pollution mitigation is delayed by two to three decades in heavily polluted locations, compared to the linear relationship. This cloud-mediated climate penalty will manifest markedly starting around 2025 in China and 2050 in India after applying the strongest air quality policy, underlining the urgency of mitigating greenhouse gas emissions.

The important role of African emissions reductions in projected local rainfall changes

Africa is highly vulnerable to climate change but emits a small portion of global greenhouse gases. Additionally, decarbonization might lead to a ‘climate penalty’ whereby reductions in cooling aerosols offset temperature benefits from CO2 reductions for several decades. However, climate change impacts conditions other than temperatures, including precipitation. Using the NASA Goddard Institute for Space Studies climate model, we find that although African emissions cuts have weak impacts on projected African temperatures, they significantly impact rainfall. Whereas business-as-usual increasing emissions lead to substantial drying over tropical Northern Hemisphere Africa during local summer, that drying is essentially eliminated under a sustainable development pathway. The reduction in cooling aerosols is responsible for ~33–90% of the avoided drying in our model, with the remainder largely attributable to reduced absorbing aerosols. African policy choices may therefore greatly reduce regional African summer drying, giving parts of Africa substantial leverage over their own climate and air quality future.

Compound climate-pollution extremes in Santiago de Chile

Cities in the global south face dire climate impacts. It is in socioeconomically marginalized urban communities of the global south that the effects of climate change are felt most deeply. Santiago de Chile, a major mid-latitude Andean city of 7.7 million inhabitants, is already undergoing the so-called “climate penalty” as rising temperatures worsen the effects of endemic ground-level ozone pollution. As many cities in the global south, Santiago is highly segregated along socioeconomic lines, which offers an opportunity for studying the effects of concurrent heatwaves and ozone episodes on distinct zones of affluence and deprivation. Here, we combine existing datasets of social indicators and climate-sensitive health risks with weather and air quality observations to study the response to compound heat-ozone extremes of different socioeconomic strata. Attributable to spatial variations in the ground-level ozone burden (heavier for wealthy communities), we found that the mortality response to extreme heat (and the associated further ozone pollution) is stronger in affluent dwellers, regardless of comorbidities and lack of access to health care affecting disadvantaged population. These unexpected findings underline the need of a site-specific hazard assessment and a community-based risk management.

Distributional heterogeneity in climate change impacts and adaptation: Evidence from Indian agriculture

AbstractThis study estimates the distributional heterogeneity in the effects of climate change on yields of three major cereal crops: rice, maize, and wheat in India using district‐level information for the period 1966–2015. We distinguish between the effects of changes in growing season weather from those due to changes in long‐term climate trends and the heterogeneity in these effects across the distribution of crop yields by estimating naïve and climate penalty inclusive models using fixed‐effect quantile panel models. We observe an absence of adaptation against rising temperatures for rice and wheat. However, we find a statistically significant presence of adaptation for wheat and maize for changes in precipitation, though the magnitude is small. Moreover, we find that the effects are asymmetric, and are larger at the lower tail of productivity distribution and smaller at the upper tail of the distribution. A 1°C increase in temperature lowers rice and wheat productivity by 23% and 9%, respectively at the first quantile, but the damage is only 6% and 5% at the ninth quantile. Heterogeneity in impacts and adaptation estimates over the yield distribution curve and across crops suggests the importance of customizing strategies for adaptation to changing weather and climate conditions across regions, crops, and current productivity levels.

Disentangling the mechanism of temperature and water vapor modulation on ozone under a warming climate

Temperature and water vapor have been considered as important factors affecting ozone concentrations, however, their synergistic effect on ozone, as well as its response to a warming climate remains unclear. Here, numerical experiments with different combinations of climate and emissions highlighted opposite changes of annual ozone over the contiguous U.S. under scenarios with high vs. low ozone precursor emissions in the future with warming. Comparing the occurrence of heat waves on higher vs. lower ozone days, we found significant suppression of the heat wave exacerbation of ozone by anthropogenic emissions reductions. Variations of ozone with temperature (T) and water vapor (Q) over the western U.S. and southeastern U.S. in the simulations are clearly revealed through the construction of an O3-T-Q diagram. Based on the diagram, we further identified a T-dominant regime at higher temperatures where ozone increases with temperature increase, and a Q-dominant regime at lower temperatures where ozone decreases with temperature increase due to the negative effect of water vapor. With larger anthropogenic emission reductions, ozone may increase at a lower rate with temperature in the T-dominant regime, or even decrease with temperature in the Q-dominant regime. Our results show that with large emission reductions, substantial ozone pollution due to warming and increasing heat waves may be counteracted by water vapor, partly turning the ‘climate penalty’ on ozone into ‘climate benefit’. Hence controlling anthropogenic emissions may be an increasingly important strategy in a warmer and wetter climate to improve air quality and public health.

Characterizing changes in extreme ozone levels under 2050s climate conditions: An extreme-value analysis in California

Ground-level ozone has a well established climate penalty associated with changing meteorological conditions under future climate change, but most existing research focuses exclusively on ozone-temperature relationships defined at specific locations. Using an extreme-value theory approach, we model relationships between temperature, humidity, and vapor pressure deficit and maximum daily 8 h ozone concentrations (MDA8) across California using a combination of ozone station network data and Community Multiscale Air Quality Modeling System (CMAQ) model output from 2008 to 2017. We use a spatial regression with time varying bias coefficients to fuse station observations and modeled output into a spatially explicit gridded ozone dataset at 12 km resolution, then fit independent Point Process models to every grid cell to estimate 5, 20, and 50 year ozone return-levels across California. We evaluate the impact of climate change on ozone return levels and episode days under RCP4.5 conditions using an ensemble of 18 downscaled CMIP5 climate models, finding changes of -6t to 8 ppb in effective return levels and −8 to 16 episode days, Our results further strengthen the evidence for anozone climate penalty in California and show the advantages of considering multiple climate variables when modeling ground-level ozone. • Extreme ozone levels are affected by multiple meteorological variables, including temperature, relative humidity, and vapor pressure deficit. • Climate change increases extreme ozone levels across most of California. • Extreme value theory model fits are improved with meteorological covariates.

Climate benefit of a future hydrogen economy

Hydrogen is recognised as an important future energy vector for applications in many sectors. Hydrogen is an indirect climate gas which induces perturbations of methane, ozone, and stratospheric water vapour, three potent greenhouse gases. Using data from a state-of-the-art global numerical model, here we calculate the hydrogen climate metrics as a function of the considered time-horizon and derive a 100-year Global Warming Potential of 12.8 ± 5.2 and a 20-year Global Warming Potential of 40.1 ± 24.1. The considered scenarios for a future hydrogen transition show that a green hydrogen economy is beneficial in terms of mitigated carbon dioxide emissions for all policy-relevant time-horizons and leakage rates. In contrast, the carbon dioxide and methane emissions associated with blue hydrogen reduce the benefit of a hydrogen economy and lead to a climate penalty at high leakage rate or blue hydrogen share. The leakage rate and the hydrogen production pathways are key leverages to reach a clear climate benefit from a large-scale transition to a hydrogen economy.

The ozone–climate penalty over South America and Africa by 2100

Abstract. Climate change has the potential to increase surface ozone (O3) concentrations, known as the “ozone–climate penalty”, through changes to atmospheric chemistry, transport and dry deposition. In the tropics, the response of surface O3 to changing climate is relatively understudied but has important consequences for air pollution and human and ecosystem health. In this study, we evaluate the change in surface O3 due to climate change over South America and Africa using three state-of-the-art Earth system models that follow the Shared Socioeconomic Pathway 3-7.0 emission scenario from CMIP6. In order to quantify changes due to climate change alone, we evaluate the difference between simulations including climate change and simulations with a fixed present-day climate. We find that by 2100, models predict an ozone–climate penalty in areas where O3 is already predicted to be high due to the impacts of precursor emissions, namely urban and biomass burning areas, although on average, models predict a decrease in surface O3 due to climate change. We identify a small but robust positive trend in annual mean surface O3 over polluted areas. Additionally, during biomass burning seasons, seasonal mean O3 concentrations increase by 15 ppb (model range 12 to 18 ppb) in areas with substantial biomass burning such as the arc of deforestation in the Amazon. The ozone–climate penalty in polluted areas is shown to be driven by an increased rate of O3 chemical production, which is strongly influenced by NOx concentrations and is therefore specific to the emission pathway chosen. Multiple linear regression finds the change in NOx concentration to be a strong predictor of the change in O3 production, whereas increased isoprene emission rate is positively correlated with increased O3 destruction, suggesting NOx-limited conditions over the majority of tropical Africa and South America. However, models disagree on the role of climate change in remote, low-NOx regions, partly because of significant differences in NOx concentrations produced by each model. We also find that the magnitude and location of the ozone–climate penalty in the Congo Basin has greater inter-model variation than that in the Amazon, so further model development and validation are needed to constrain the response in central Africa. We conclude that if the climate were to change according to the emission scenario used here, models predict that forested areas in biomass burning locations and urban populations will be at increasing risk of high O3 exposure, irrespective of any direct impacts on O3 via the prescribed emission scenario.

Surface Ozone‐Temperature Relationship: The Meridional Gradient Ratio Approximation

AbstractThe daily variation of ground‐level ozone (O3), a harmful pollutant, is positively correlated with air temperature (T) in many midlatitude land regions in the summer. The observed temporal regression slope between O3 and T (dO3/dT) is referred to as the “ozone‐climate change penalty” and has been proposed as a way to predict the impact of future climate warming on O3 from observations. Here, we use two chemical transport models to show that the spatial variation of dO3/dT is primarily determined by simultaneous meridional advection of O3 and T. Furthermore, the sign and magnitude of dO3/dT can be approximated by their climatological meridional gradient ratio (O3 gradient divided by T gradient). Consideration of expected changes in the meridional gradients of T and O3 due to climate change indicates that dO3/dT will likely change. Caution is needed when using the observed climate penalty to predict O3 changes.

Investigation of the Community Multiscale air quality (CMAQ) model representation of the Climate Penalty Factor (CPF)

Elevated levels of tropospheric ozone (O3) caused by anthropogenic emissions of NOx and VOCs have a negative impact on human health, crops, and ecosystems. Even if precursor emissions are reduced compared to current levels, predicted higher temperatures due to increased greenhouse gas emissions could impede resulting air quality benefits. The Climate Penalty Factor (CPF) has been devised to quantify the adverse impact of increasing temperatures on surface O3. We compute the CPF from surface observations at CASTNET (mostly rural) and AQS (mostly urban) sites and compare these values to CMAQ output for the contiguous U.S. and seven sub-regions for the O3 season (May 1 through September 30) for each year from 2002 through 2012. Here we show that CMAQ can in general reproduce with reasonable accuracy the CPF for the CONUS. In predominantly rural regions (CASTNET) observed CPFs are 1.94 ppb/°C while simulated CPFs are 2.11 ppb/°C. Observed CPFs are 2.00 ppb/°C in predominantly urban regions (AQS), lower than simulated CPFs of 2.39 ppb/°C. CMAQ reproduces CPFs at rural sites reasonably well but tends to somewhat overestimate CPFs at urban sites. Upon examination of each region, the CMAQ simulation for the Southeast shows a substantial overestimate (43%) of CPF for urban (AQS) sites. Conversely, the CMAQ simulations for the Northeast show a slight underestimate (8%) of the CPF at rural (CASTNET) sites. Both results for CPF (overestimated for urban sites and either underestimated or close to observed for rural sites) could be related to the tendency of CMAQ with CB05-TUCL (an excessively long lifetime of alkyl nitrates with respect to photolysis) to overestimate NOx or keep it too close to the urban source locations. Our analysis suggests that CMAQ may attribute a somewhat greater fraction of O3 production to an increase in temperature than observed. Finally, there is a ∼2% per year decrease in CPF throughout the CONUS during the 11-year period in both measurements and the CMAQ simulations, suggesting that reductions in NOx emissions can mitigate the impact of climate change on surface ozone.

Reducing future air-pollution-related premature mortality over Europe by mitigating emissions from the energy sector: assessing an 80 % renewable energies scenario

Abstract. Overall, European air quality has worsened in recent decades as a consequence of increased anthropogenic emissions, in particular from the power generation sector. The evidence of the effects of atmospheric pollution (and particularly fine particulate matter, PM2.5) on human health is now unquestionable; it is mainly associated with cardiovascular and respiratory diseases, along with morbidity and even mortality. These effects may even strengthen in the future as a consequence of climate penalties and future changes in the projected population. For all these reasons, the main objective of this contribution is the estimation of the annual excess premature deaths (PD) associated with PM2.5 in the present (1991–2010) and future (2031–2050) European population using non-linear exposure–response functions. The endpoints included are lung cancer (LC), chronic obstructive pulmonary disease (COPD), low respiratory infections (LRI), ischaemic heart disease (IHD), cerebrovascular disease (CEV) and other non-communicable diseases (other NCD). PM2.5 concentrations come from coupled chemistry–climate regional simulations under present and future (RCP8.5) scenarios. The cases assessed include the estimation of the present incidence of PD (PRE-P2010), the quantification of the role of a changing climate in PD (FUT-P2010) and the importance of changes in the population projected for the year 2050 in the incidence of excess PD (FUT-P2050). Two additional cases (REN80-P2010 and REN80-P2050) evaluate the impact on premature mortality rates of a mitigation scenario in which 80 % of European energy production comes from renewable sources. The results indicate that PM2.5 accounts for nearly 895 000 (95 % confidence interval (95 % CI) 725 000–1 056 000) annual excess PD over Europe, with IHD being the largest contributor to premature mortality associated with fine particles in both present and future scenarios. The case that isolates the effects of a climate penalty (FUT-P2010) estimates a variation of +0.2 % in mortality rates over the whole domain. However, under this scenario, the incidence of PD over central Europe will benefit from a decrease in PM2.5 (−2.2 PD/100 000 inhabitants), while in eastern (+1.3 PD/100 000 inhabitants) and western (+0.4 PD/100 000 inhabitants) Europe, PD will increase due to increased PM2.5 levels. The changes in the projected population (FUT-P2050) will lead to a large increase in annual excess PD (1 540 000, 95 % CI 1 247 000–1 818 000; +71.96 % with respect to PRE-P2010 and +71.67 % with respect to FUT-P2010) due to the ageing of the European population. Last, the mitigation scenario (REN80-P2050) demonstrates that the effects of a mitigation policy of increasing the ratio of renewable sources in the energy mix could lead to a decrease of over 60 000 (95 % CI 48 500–70 900) annual PD for the year 2050 (a decrease of −4 % in comparison with the no-mitigation scenario FUT-P2050). In spite of the uncertainties inherent in future estimations, this contribution reveals the need of governments and public entities to take action and choose air pollution mitigation policies.

Societal shifts due to COVID-19 reveal large-scale complexities and feedbacks between atmospheric chemistry and climate change.

The COVID-19 global pandemic and associated government lockdowns dramatically altered human activity, providing a window into how changes in individual behavior, enacted en masse, impact atmospheric composition. The resulting reductions in anthropogenic activity represent an unprecedented event that yields a glimpse into a future where emissions to the atmosphere are reduced. Furthermore, the abrupt reduction in emissions during the lockdown periods led to clearly observable changes in atmospheric composition, which provide direct insight into feedbacks between the Earth system and human activity. While air pollutants and greenhouse gases share many common anthropogenic sources, there is a sharp difference in the response of their atmospheric concentrations to COVID-19 emissions changes, due in large part to their different lifetimes. Here, we discuss several key takeaways from modeling and observational studies. First, despite dramatic declines in mobility and associated vehicular emissions, the atmospheric growth rates of greenhouse gases were not slowed, in part due to decreased ocean uptake of CO2 and a likely increase in CH4 lifetime from reduced NO x emissions. Second, the response of O3 to decreased NO x emissions showed significant spatial and temporal variability, due to differing chemical regimes around the world. Finally, the overall response of atmospheric composition to emissions changes is heavily modulated by factors including carbon-cycle feedbacks to CH4 and CO2, background pollutant levels, the timing and location of emissions changes, and climate feedbacks on air quality, such as wildfires and the ozone climate penalty.

Effects of air pollution on dementia over Europe for present and future climate change scenarios

The scientific literature is scarce when referring to the influence of atmospheric pollutants on neurodegenerative diseases for present and future climate change scenarios. In this sense, this contribution evaluates the incidence of dementia (Alzheimer's disease, AD, and dementia from unspecified cause, DU) occurring in Europe associated with the exposure to air pollution (essentially NO2 and PM2.5) for the present climatic period (1991–2010) and for a future climate change scenario (RCP8.5, 2031–2050). The GEMM methodology has been applied to air pollution simulations using the chemistry/climate regional model WRF-Chem. Present population data were obtained from NASA's Center for Socioeconomic Data and Applications (SEDAC); while future population projections for the year 2050 were derived from the United Nations (UN) Department of Economic and Social Affairs-Population Dynamics. Overall, the estimated incidence rate (cases per year) of AD and DU associated with exposure to air pollution over Europe is 498,000 [95% confidence interval (95% CI) 348,600–647,400] and 314,000 (95% CI 257,500-401,900), respectively. An important increase in the future incidence rate is projected (around 72% for both types of dementia) when considering the effect of climate change together with the foreseen changes in the future population, because of the expected aging of European population. The climate penalty (impacts of future climate change alone on air quality) has a limited effect on the total changes of dementia (approx. 0.5%), because the large increase in the incidence rate over southern Europe is offset by its decrease over more northern countries, favored by an improvement of air pollution caused by the projected enhancement of rainfall.