scholarly journals The Influence of Remote Aerosol Forcing from Industrialized Economies on the Future Evolution of East and West African Rainfall

2019 ◽  
Vol 32 (23) ◽  
pp. 8335-8354 ◽  
Author(s):  
Claire Scannell ◽  
Ben B. B. Booth ◽  
Nick J. Dunstone ◽  
David P. Rowell ◽  
Dan J. Bernie ◽  
...  
Keyword(s):  
Air Quality ◽  
Climate Adaptation ◽  
Climate Projections ◽  
Rcp Scenarios ◽  
Future Evolution ◽  
African Rainfall ◽  
Aerosol Emission ◽  
Near Term ◽  
Aerosol Emissions ◽  
The Impact

Abstract Past changes in global industrial aerosol emissions have played a significant role in historical shifts in African rainfall, and yet assessment of the impact on African rainfall of near-term (10–40 yr) potential aerosol emission pathways remains largely unexplored. While existing literature links future aerosol declines to a northward shift of Sahel rainfall, existing climate projections rely on RCP scenarios that do not explore the range of air quality drivers. Here we present projections from two emission scenarios that better envelop the range of potential aerosol emissions. More aggressive emission cuts result in northward shifts of the tropical rainbands whose signal can emerge from expected internal variability on short, 10–20-yr time horizons. We also show for the first time that this northward shift also impacts East Africa, with evidence of delays to both onset and withdrawal of the short rains. However, comparisons of rainfall impacts across models suggest that only certain aspects of both the West and East African model responses may be robust, given model uncertainties. This work motivates the need for wider exploration of air quality scenarios in the climate science community to assess the robustness of these projected changes and to provide evidence to underpin climate adaptation in Africa. In particular, revised estimates of emission impacts of legislated measures every 5–10 years would have a value in providing near-term climate adaptation information for African stakeholders.

scholarly journals Quantifying the influence of short-term emission reductions on climate

2021 ◽  
Vol 7 (10) ◽  
pp. eabf7133
Author(s):  
J. C. Fyfe ◽  
V. V. Kharin ◽  
N. Swart ◽  
G. M. Flato ◽  
M. Sigmond ◽  
...  
Keyword(s):  
Regional Climate ◽  
Potential Effect ◽  
Short Term ◽  
Emission Reductions ◽  
Temperature And Precipitation ◽  
Aerosol Emission ◽  
Regional Temperature ◽  
Near Term ◽  
Aerosol Emissions ◽  
The Impact

The COVID-19 (coronavirus disease 2019) pandemic has resulted in a marked slowdown in greenhouse gas and aerosol emissions. Although the resulting emission reductions will continue to evolve, this will presumably be temporary. Here, we provide estimates of the potential effect of such short-term emission reductions on global and regional temperature and precipitation by analyzing the response of an Earth System Model to a range of idealized near-term emission pathways not considered in available model intercomparison projects. These estimates reveal the modest impact that temporary emission reductions associated with the COVID-19 pandemic will have on global and regional climate. Our simulations suggest that the impact of carbon dioxide and aerosol emission reductions is actually a temporary enhancement in warming rate. However, our results demonstrate that even large emission reductions applied for a short duration have only a small and likely undetectable impact.

The local and remote atmospheric impacts of Africa’s 21st century aerosol emission trajectory

2021 ◽  
Author(s):  
Chris Wells ◽  
Apostolos Voulgarakis
Keyword(s):  
Regional Climate ◽  
Emission Region ◽  
Anthropogenic Aerosol ◽  
Remote Locations ◽  
Aerosol Emission ◽  
Radiation Fluxes ◽  
The World ◽  
Aerosol Emissions ◽  
The Impact ◽  
Lower Biomass

<p>Aerosols are a major climate forcer, but their historical effect has the largest uncertainty of any forcing; their mechanisms and impacts are not well understood. Due to their short lifetime, aerosols have large impacts near their emission region, but they also have effects on the climate in remote locations. In recent years, studies have investigated the influences of regional aerosols on global and regional climate, and the mechanisms that lead to remote responses to their inhomogeneous forcing. Using the Shared Socioeconomic Pathway scenarios (SSPs), transient future experiments were performed in UKESM1, testing the effect of African emissions following the SSP3-RCP7.0 scenario as the rest of the world follows SSP1-RCP1.9, relative to a global SSP1-RCP1.9 control. SSP3 sees higher direct anthropogenic aerosol emissions, but lower biomass burning emissions, over Africa. Experiments were performed changing each of these sets of emissions, and both. A further set of experiments additionally accounted for changing future CO<sub>2</sub> concentrations, to investigate the impact of CO<sub>2</sub> on the responses to aerosol perturbations. Impacts on radiation fluxes, temperature, circulation and precipitation are investigated, both over the emission region (Africa), where microphysical effects dominate, and remotely, where dynamical influences become more relevant. </p>

scholarly journals The Impact of Future Emission Policies on Tropospheric Ozone using a Parameterised Approach

2018 ◽  
Author(s):  
Steven Turnock ◽  
Oliver Wild ◽  
Frank Dentener ◽  
Yanko Davila ◽  
Louisa Emmons ◽  
...  
Keyword(s):  
Air Quality ◽  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Source Attribution ◽  
The Future ◽  
Future Emission ◽  
Tropospheric O3 ◽  
Near Term ◽  
The Impact ◽  
Surface O3

Abstract. This study quantifies future changes in tropospheric ozone (O3) using a simple parameterisation of source-receptor relationships based on simulations from a range of models participating in the Task Force on Hemispheric Transport of Air Pollutants (TF-HTAP) experiments. Surface and tropospheric O3 changes are calculated globally and across 16 regions from perturbations in precursor emissions (NOx, CO, VOCs) and methane (CH4) abundance. A source attribution is provided for each source region along with an estimate of uncertainty based on the spread of the results from the models. Tests against model simulations using HadGEM2-ES confirm that the approaches used within the parameterisation are valid. The O3 response to changes in CH4 abundance is slightly larger in TF-HTAP Phase 2 than in the TF-HTAP Phase 1 assessment (2010) and provides further evidence that controlling CH4 is important for limiting future O3 concentrations. Different treatments of chemistry and meteorology in models remains one of the largest uncertainties in calculating the O3 response to perturbations in CH4 abundance and precursor emissions, particularly over the Middle East and South Asian regions. Emission changes for the future ECLIPSE scenarios and a subset of preliminary Shared Socio-economic Pathways (SSPs) indicate that surface O3 concentrations will increase by 1 to 8 ppbv in 2050 across different regions. Source attribution analysis highlights the growing importance of CH4 in the future under current legislation. A global tropospheric O3 radiative forcing of +0.07 W m−2 from 2010 to 2050 is predicted using the ECLIPSE scenarios and SSPs, based solely on changes in CH4 abundance and tropospheric O3 precursor emissions and neglecting any influence of climate change. Current legislation is shown to be inadequate in limiting the future degradation of surface ozone air quality and enhancement of near-term climate warming. More stringent future emission controls provide a large reduction in both surface O3 concentrations and O3 radiative forcing. The parameterisation provides a simple tool to highlight the different impacts and associated uncertainties of local and hemispheric emission control strategies on both surface air quality and the near-term climate forcing by tropospheric O3.

scholarly journals Future evolution of the Sahel precipitation zonal contrast in CESM1

2020 ◽  
Vol 55 (9-10) ◽  
pp. 2801-2821
Author(s):  
Paul-Arthur Monerie ◽  
Emilia Sanchez-Gomez ◽  
Marco Gaetani ◽  
Elsa Mohino ◽  
Buwen Dong
Keyword(s):  
Climate Change ◽  
Forced Response ◽  
Precipitation Change ◽  
Future Climate Change ◽  
Climate Projections ◽  
Monsoon Circulation ◽  
Future Evolution ◽  
Western Sahel ◽  
The Impact ◽  
Sahel Precipitation

Abstract The main focus of this study is the zonal contrast of the Sahel precipitation shown in the CMIP5 climate projections: precipitation decreases over the western Sahel (i.e., Senegal and western Mali) and increases over the central Sahel (i.e., eastern Mali, Burkina Faso and Niger). This zonal contrast in future precipitation change is a robust model response to climate change but suffers from a lack of an explanation. To this aim, we study the impact of current and future climate change on Sahel precipitation by using the Large Ensemble of the Community Earth System Model version 1 (CESM1). In CESM1, global warming leads to a strengthening of the zonal contrast, as shown by the difference between the 2060–2099 period (under a high emission scenario) and the 1960–1999 period (under the historical forcing). The zonal contrast is associated with dynamic shifts in the atmospheric circulation. We show that, in absence of a forced response, that is, when only accounting for internal climate variability, the zonal contrast is associated with the Pacific and the tropical Atlantic oceans variability. However, future patterns in sea surface temperature (SST) anomalies are not necessary to explaining the projected strengthening of the zonal contrast. The mechanisms underlying the simulated changes are elucidated by analysing a set of CMIP5 idealised simulations. We show the increase in precipitation over the central Sahel to be mostly associated with the surface warming over northern Africa, which favour the displacement of the monsoon cell northwards. Over the western Sahel, the decrease in Sahel precipitation is associated with a southward shift of the monsoon circulation, and is mostly due to the warming of the SST. These two mechanisms allow explaining the zonal contrast in precipitation change.

scholarly journals Climate and air quality impacts due to mitigation of non-methane near-term climate forcers

2020 ◽  
Vol 20 (16) ◽  
pp. 9641-9663 ◽  
Author(s):  
Robert J. Allen ◽  
Steven Turnock ◽  
Pierre Nabat ◽  
David Neubauer ◽  
Ulrike Lohmann ◽  
...  
Keyword(s):  
Climate Change ◽  
Air Quality ◽  
Carbon Dioxide Emissions ◽  
The Arctic ◽  
Climate Mitigation ◽  
Model Simulations ◽  
Surface Warming ◽  
North Asia ◽  
Near Term ◽  
The Impact

Abstract. It is important to understand how future environmental policies will impact both climate change and air pollution. Although targeting near-term climate forcers (NTCFs), defined here as aerosols, tropospheric ozone, and precursor gases, should improve air quality, NTCF reductions will also impact climate. Prior assessments of the impact of NTCF mitigation on air quality and climate have been limited. This is related to the idealized nature of some prior studies, simplified treatment of aerosols and chemically reactive gases, as well as a lack of a sufficiently large number of models to quantify model diversity and robust responses. Here, we quantify the 2015–2055 climate and air quality effects of non-methane NTCFs using nine state-of-the-art chemistry–climate model simulations conducted for the Aerosol and Chemistry Model Intercomparison Project (AerChemMIP). Simulations are driven by two future scenarios featuring similar increases in greenhouse gases (GHGs) but with “weak” (SSP3-7.0) versus “strong” (SSP3-7.0-lowNTCF) levels of air quality control measures. As SSP3-7.0 lacks climate policy and has the highest levels of NTCFs, our results (e.g., surface warming) represent an upper bound. Unsurprisingly, we find significant improvements in air quality under NTCF mitigation (strong versus weak air quality controls). Surface fine particulate matter (PM2.5) and ozone (O3) decrease by -2.2±0.32 µg m−3 and -4.6±0.88 ppb, respectively (changes quoted here are for the entire 2015–2055 time period; uncertainty represents the 95 % confidence interval), over global land surfaces, with larger reductions in some regions including south and southeast Asia. Non-methane NTCF mitigation, however, leads to additional climate change due to the removal of aerosol which causes a net warming effect, including global mean surface temperature and precipitation increases of 0.25±0.12 K and 0.03±0.012 mm d−1, respectively. Similarly, increases in extreme weather indices, including the hottest and wettest days, also occur. Regionally, the largest warming and wetting occurs over Asia, including central and north Asia (0.66±0.20 K and 0.03±0.02 mm d−1), south Asia (0.47±0.16 K and 0.17±0.09 mm d−1), and east Asia (0.46±0.20 K and 0.15±0.06 mm d−1). Relatively large warming and wetting of the Arctic also occur at 0.59±0.36 K and 0.04±0.02 mm d−1, respectively. Similar surface warming occurs in model simulations with aerosol-only mitigation, implying weak cooling due to ozone reductions. Our findings suggest that future policies that aggressively target non-methane NTCF reductions will improve air quality but will lead to additional surface warming, particularly in Asia and the Arctic. Policies that address other NTCFs including methane, as well as carbon dioxide emissions, must also be adopted to meet climate mitigation goals.

scholarly journals Black carbon and dust alter the response of mountain snow cover under climate change

2021 ◽  
Author(s):  
Marion REVEILLET ◽  
Marie Dumont ◽  
Simon Gascoin ◽  
Matthieu Lafaysse ◽  
Pierre Nabat ◽  
...  
Keyword(s):  
Snow Cover ◽  
Black Carbon ◽  
Regional Scale ◽  
Climate Projections ◽  
Economic Implications ◽  
Future Evolution ◽  
Social Ecological Systems ◽  
Long Term Impact ◽  
Surface Mineral ◽  
The Impact

Abstract By darkening the snow surface, mineral dust and black carbon (BC) deposition enhances snowmelt and triggers numerous feedbacks. Assessments of their long-term impact at the regional scale are still largely missing despite the environmental and socio-economic implications of snow cover changes. Here we show, using numerical simulations, that dust and BC deposition has advanced snowmelt by 17 days on average in the French Alps and the Pyrenees over the 1979–2018 period, with major implications for water availability. We demonstrate that the decrease in BC deposition since the 1980s moderates the impact of current warming on snow cover decline. Hence, accounting for changes in light-absorbing particles deposition is required to improve the accuracy of snow cover reanalyses and climate projections, that are crucial for better understanding the past and future evolution of mountain social-ecological systems.

Global temperature response to regional and sectoral air pollutant and greenhouse gas emissions under the Shared Socioeconomic Pathways

2020 ◽  
Author(s):  
Marianne T. Lund ◽  
Borgar Aamaas ◽  
Camilla W. Stjern ◽  
Zbigniew Klimont ◽  
Terje K. Berntsen ◽  
...  
Keyword(s):  
Sustainable Development ◽  
Air Quality ◽  
Air Pollutant ◽  
Global Temperature ◽  
Strong Increase ◽  
Detailed Knowledge ◽  
Data Set ◽  
Trade Offs ◽  
Near Term ◽  
The Impact

<p>Achieving the ambition of the Paris Agreement and meeting the Sustainable Development Goals require both near-zero levels of long-lived greenhouse gases and deep cuts in emissions of so-called short-lived climate forcers (SLCFs), including methane and black carbon. Here we present a comprehensive dataset of contributions to future global temperature change from emissions of CO<sub>2</sub> and individual SLCFs from 7 economic sectors and 13 source regions, both as they are today and as they are projected to change under the Shared Socioeconomic Pathways (SSPs). Such detailed knowledge about the mix of emissions from individual sources and benefits and trade-offs of reductions is essential for designing efficient mitigation strategies at the national and international levels, as well as for informing policy processes on how to best address linkages between climate, sustainable development and air quality.</p><p>Our results demonstrate that the mitigation potential inherent in the present SLCF emissions is highly inhomogeneous across region and sector, and that co-emissions of all species – including CO<sub>2</sub> – should be considered in any targeted climate policy. We also reinforce the importance of reducing methane emissions, from agriculture, waste management and energy production, for reducing warming in the near-term. In contrast, in many regions, reducing industry emissions brings air quality benefits but may cause a net additional near-term warming. The spatiotemporal heterogeneity is expected to continue under the SSPs. Most scenarios project a particularly strong increase in aerosol and other SLCF emissions in South Asia and Africa South of the Sahara, suggesting that technology development and air pollution legislation in these regions is a key step in the transition to a low emission future. Moreover, both rapidly increasing and decreasing emissions of SLCFs will play an important role in shaping the regional climate and air quality.</p><p>By using an analytical climate model, we build a methodological framework that can be used to estimate the impact of any emission scenarios. Our data set hence provide a toolkit for further studies of implications of mitigation pathways and policy responses, and support assessments of environmental impacts.</p>

Volcanic Aerosol Impacts on Hawai‘i Island Rainfall

2021 ◽  
Author(s):  
Tianqi Zuo ◽  
Alison D. Nugent ◽  
Gregory Thompson
Keyword(s):  
Air Quality ◽  
Cloud Droplet ◽  
Kilauea Volcano ◽  
Number Concentration ◽  
Volcanic Aerosol ◽  
Aerosol Emission ◽  
Kīlauea Volcano ◽  
Cloud Water Content ◽  
Volcanic Aerosols ◽  
The Impact

AbstractIn recent decades, a significant rainfall decline over the Island of Hawai‘i has been noted, with many hypothesizing that the drying is associated with the volcanic aerosols emitted from the Kīlauea Volcano. While it is clear that volcanic emissions can create hazardous air quality for Hawaiian communities, the impacts on rainfall are less clear. Here we investigate the impact of volcanic aerosol emissions on Hawai‘i Island rainfall. Based on observed daily rainfall and SO2 emissions, it is found that days with high SO2 emissions have on average 8 mm day−1 less rainfall downstream of the Kīlauea Volcano. Sensitivity studies with varying volcanic aerosol emission sources from the Kīlauea vent locations have also been conducted by the Weather Research and Forecasting (WRF) Model in order to examine the detailed physical processes. Consistent with SO2 air quality observations, it is found that the diurnal change in aerosol number concentration is strongly dependent on the diurnal variation of local circulations. The added aerosols are lofted into the orographic convection where they modify the microphysical properties of the warm clouds by increasing the cloud droplet number concentration, decreasing the cloud droplet size, increasing cloud water content and enhancing cloud evaporation. The volcanic aerosols also delay precipitation production and modify the spatial distribution of rainfall on the downstream mountainside. The modification of precipitation on an island has far reaching consequences. For this reason, we work to quantify the sensitivity of the orographic precipitation to volcanic aerosols and move beyond hypothesized relationships towork toward understanding the underlying problem.

scholarly journals Using statistical models to explore ensemble uncertainty in climate impact studies: the example of air pollution in Europe

2016 ◽  
Vol 16 (4) ◽  
pp. 2559-2574 ◽  
Author(s):  
Vincent E. P. Lemaire ◽  
Augustin Colette ◽  
Laurent Menut
Keyword(s):  
Climate Change ◽  
Air Pollution ◽  
Air Quality ◽  
Statistical Model ◽  
Eastern Europe ◽  
Statistical Models ◽  
Regional Climate ◽  
Northern Italy ◽  
Climate Projections ◽  
The Impact

Abstract. Because of its sensitivity to unfavorable weather patterns, air pollution is sensitive to climate change so that, in the future, a climate penalty could jeopardize the expected efficiency of air pollution mitigation measures. A common method to assess the impact of climate on air quality consists in implementing chemistry-transport models forced by climate projections. However, the computing cost of such methods requires optimizing ensemble exploration techniques. By using a training data set from a deterministic projection of climate and air quality over Europe, we identified the main meteorological drivers of air quality for eight regions in Europe and developed statistical models that could be used to predict air pollutant concentrations. The evolution of the key climate variables driving either particulate or gaseous pollution allows selecting the members of the EuroCordex ensemble of regional climate projections that should be used in priority for future air quality projections (CanESM2/RCA4; CNRM-CM5-LR/RCA4 and CSIRO-Mk3-6-0/RCA4 and MPI-ESM-LR/CCLM following the EuroCordex terminology). After having tested the validity of the statistical model in predictive mode, we can provide ranges of uncertainty attributed to the spread of the regional climate projection ensemble by the end of the century (2071–2100) for the RCP8.5. In the three regions where the statistical model of the impact of climate change on PM2.5 offers satisfactory performances, we find a climate benefit (a decrease of PM2.5 concentrations under future climate) of −1.08 (±0.21), −1.03 (±0.32), −0.83 (±0.14) µg m−3, for respectively Eastern Europe, Mid-Europe and Northern Italy. In the British-Irish Isles, Scandinavia, France, the Iberian Peninsula and the Mediterranean, the statistical model is not considered skillful enough to draw any conclusion for PM2.5. In Eastern Europe, France, the Iberian Peninsula, Mid-Europe and Northern Italy, the statistical model of the impact of climate change on ozone was considered satisfactory and it confirms the climate penalty bearing upon ozone of 10.51 (±3.06), 11.70 (±3.63), 11.53 (±1.55), 9.86 (±4.41), 4.82 (±1.79) µg m−3, respectively. In the British-Irish Isles, Scandinavia and the Mediterranean, the skill of the statistical model was not considered robust enough to draw any conclusion for ozone pollution.

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