scholarly journals Effects of anthropogenic aerosol and greenhouse gas emissions on Northern Hemisphere monsoon precipitation: mechanisms and uncertainty

2022 ◽  
pp. 1-66
Keyword(s):  
Greenhouse Gas ◽  
Atmospheric Circulation ◽  
Northern Hemisphere ◽  
Ghg Emissions ◽  
Monsoon Precipitation ◽  
Anthropogenic Aerosol ◽  
Global Monsoon ◽  
Moisture Advection ◽  
Large Ensembles ◽  
Precipitation Trends

Abstract Northern Hemisphere Land monsoon precipitation (NHLM) exhibits multidecadal variability, decreasing over the second half of the 20st century and increasing after the 1980s. We use a novel combination of CMIP6 simulations and several large ensembles to assess the relative roles of drivers of monsoon precipitation trends, analyzing the effects of anthropogenic aerosol (AA), greenhouse gas (GHG) emissions and natural forcing. We decomposed summer global monsoon precipitation anomalies into dynamic and thermodynamic terms to assess the drivers of precipitation trends. We show that the drying trends are likely to be mainly due to increased AA emissions, which cause shifts of the atmospheric circulation and a decrease in moisture advection. Increases in GHG emissions cause monsoon precipitation to increase due to strengthened moisture advection. The uncertainty in summer monsoon precipitation trends is explored using three initial condition large ensembles. AA emissions have strong controls on monsoon precipitation trends, exceeding the effects of internal climate variability. However, uncertainties in the effects of external forcings on monsoon precipitation are high for specific periods and monsoon domains, and due to differences in how models simulate shifts in atmospheric circulation. The effect of AA emissions is uncertain over the northern African monsoon domain, due to differences among climate models in simulating the effects of AA emissions on net shortwave radiation over the North Atlantic Ocean.

The Global Monsoon Variability Simulated by CMIP3 Coupled Climate Models*

2008 ◽  
Vol 21 (20) ◽  
pp. 5271-5294 ◽  
Author(s):  
Hyung-Jin Kim ◽  
Bin Wang ◽  
Qinghua Ding
Keyword(s):  
Twentieth Century ◽  
Northern Hemisphere ◽  
Climate Models ◽  
Global Ocean ◽  
Windward Side ◽  
Monsoon Precipitation ◽  
Monsoon Climate ◽  
Global Monsoon ◽  
Monsoon Index ◽  
Volcanic Aerosols

Abstract The global monsoon climate variability during the second half of the twentieth century simulated by 21 coupled global climate models (CGCMs) that participated in the World Climate Research Programme’s Coupled Model Intercomparison Project phase 3 (CMIP3) is evaluated. Emphasis was placed on climatology, multidecadal trend, and the response of the global monsoon precipitation to volcanic aerosols. The impact of the atmospheric model’s horizontal resolution on the group ensemble mean (GEM; obtained from the three resolution groups) simulations of global monsoon climate is also examined. The CMIP3 CGCMs’ multimodel ensemble simulates a reasonably realistic climatology of the global monsoon precipitation and circulation. The GEMs are also able to capture the gross features of the global monsoon precipitation and westerly domains. However, the spreading among the rainfall GEMs is large, particularly at the windward side of narrow mountains (e.g., the western coast of India, the Philippines, Mexico, and the steep slope of the Tibetan Plateau). Main common biases in modeling rainfall climatology include a northeastward shift of the intertropical convergence zone (ITCZ) in the tropical North Pacific and a southward migration of the North Atlantic ITCZ during boreal winter. The trend in the Northern Hemisphere land monsoon index (NHMI) detected in the CMIP3 models is generally consistent with the observations, albeit with much weaker magnitude. The significant decreasing NHMI trend during 1951–85 and 1951–99 occurs mainly in the models with volcanic aerosols (VOL models). This volcanic signal is detectable by comparison of the forced and free runs. It is estimated that from about one-quarter to one-third of the drying trend in the Northern Hemisphere land monsoon precipitation over the latter half of the twentieth century was likely due to the effects of the external volcanic forcings. On the other hand, the significant increasing trend in the global ocean monsoon index (GOMI) during 1980–99 appears chiefly in those models that are free of volcanic aerosols (No-VOL models). The exclusion of the volcanic aerosols is significant in simulating the positive GOMI trend against the internal variability of each model. These results suggest the climatic importance of the volcanic forcings in the global monsoon precipitation variability.

scholarly journals Transient Climate Impacts for Scenarios of Aerosol Emissions from Asia: A Story of Coal versus Gas

2016 ◽  
Vol 29 (8) ◽  
pp. 2849-2867 ◽  
Author(s):  
Benjamin S. Grandey ◽  
Haiwen Cheng ◽  
Chien Wang
Keyword(s):  
Northern Hemisphere ◽  
Summer Monsoon ◽  
Initial Conditions ◽  
Asian Summer Monsoon ◽  
Climate Impacts ◽  
West African ◽  
Monsoon Precipitation ◽  
South Asian Summer Monsoon ◽  
Anthropogenic Aerosol ◽  
Aerosol Emissions

Abstract Fuel usage is an important driver of anthropogenic aerosol emissions. In Asia, it is possible that aerosol emissions may increase if business continues as usual, with economic growth driving an increase in coal burning. But it is also possible that emissions may decrease rapidly as a result of the widespread adoption of cleaner technologies or a shift toward noncoal fuels, such as natural gas. In this study, the transient climate impacts of two aerosol emissions scenarios are investigated: a representative concentration pathway 4.5 (RCP4.5) control, which projects a decrease in anthropogenic aerosol emissions, and a scenario with enhanced anthropogenic aerosol emissions from Asia. A coupled atmosphere–ocean configuration of the Community Earth System Model (CESM), including the Community Atmosphere Model, version 5 (CAM5), is used. Three sets of initial conditions are used to produce a three-member ensemble for each scenario. Enhanced Asian aerosol emissions are found to exert a large cooling effect across the Northern Hemisphere, partially offsetting greenhouse gas–induced warming. Aerosol-induced suppression of the East Asian and South Asian summer monsoon precipitation occurs. The enhanced Asian aerosol emissions also remotely impact precipitation in other parts of the world. Over Australia, austral summer monsoon precipitation is enhanced, an effect associated with a southward shift of the intertropical convergence zone, driven by the aerosol-induced cooling of the Northern Hemisphere. Over the Sahel, West African monsoon precipitation is suppressed, likely via a weakening of the West African westerly jet. These results indicate that fuel usage in Asia, through the consequent aerosol emissions and associated radiative effects, might significantly influence future climate both locally and globally.

scholarly journals Global Monsoon Precipitation: Trends, Leading Modes, and Associated Drought and Heat Wave in the Northern Hemisphere

2018 ◽  
Vol 31 (17) ◽  
pp. 6947-6966 ◽  
Author(s):  
Kaiqiang Deng ◽  
Song Yang ◽  
Mingfang Ting ◽  
Yaheng Tan ◽  
Shan He
Keyword(s):  
Northern Hemisphere ◽  
El Niño ◽  
El Nino ◽  
Boreal Summer ◽  
Soil Conditions ◽  
Monsoon Precipitation ◽  
Central Pacific ◽  
Global Monsoon ◽  
Cp El Niño ◽  
Ep El Niño

Global monsoon precipitation (GMP) brings the majority of water for the local agriculture and ecosystem. The Northern Hemisphere (NH) GMP shows an upward trend over the past decades, while the trend in the Southern Hemisphere (SH) GMP is weak and insignificant. The first three singular value decomposition modes between NH GMP and global SST during boreal summer reflect, in order, the Atlantic multidecadal oscillation (AMO), eastern Pacific (EP) El Niño, and central Pacific (CP) El Niño, when the AMO dominates the NH climate and contributes to the increased trend. However, the first three modes between SH GMP and global SST during boreal winter are revealed as EP El Niño, the AMO, and CP El Niño, when the EP El Niño becomes the most significant driver of the SH GMP, and the AMO-induced rainfall anomalies may cancel out each other within the SH global monsoon domain and thus result in a weak trend. The intensification of NH GMP is proposed to favor the occurrences of droughts and heat waves (HWs) in the midlatitudes through a monsoon–desert-like mechanism. That is, the diabatic heating associated with the monsoonal rainfall may drive large-scale circulation anomalies and trigger intensified subsidence in remote regions. The anomalous descending motions over the midlatitudes are usually accompanied by clear skies, which result in less precipitation and more downward solar radiation, and thus drier and hotter soil conditions that favor the occurrences of droughts and HWs. In comparison, the SH GMP may exert much smaller impacts on the NH extremes in spring and summer, probably because the winter signals associated with SH GMP cannot sufficiently persist into the following seasons.

Contribution of anthropogenic aerosols to changes in the Northern Hemisphere storm tracks during the 20th and 21st centuries

2021 ◽  
Author(s):  
Kerry Black ◽  
Ioana Colfescu ◽  
Massimo Bollasina
Keyword(s):  
Atmospheric Circulation ◽  
Northern Hemisphere ◽  
Large Scale ◽  
Storm Track ◽  
Storm Tracks ◽  
Historical Period ◽  
Climate Projections ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol

<p>Midlatitude storm tracks are a key component of the global atmospheric circulation. Extratropical cyclones associated with and evolving along the storm tracks dominate the day‐to‐day weather variability in the mid-latitudes, and changes in storm track activity or location strongly impact regional climate variations. Baroclinic waves that form the storm tracks are also responsible for transporting much of the heat, moisture, and momentum poleward in the midlatitudes. Therefore, investigating how storm tracks may respond to future changes in anthropogenic forcing is of significant interest. Yet, while most of the studies have focused on the role of increased greenhouse gases and the associated response at the end of the 21<sup>st</sup> century, the role of anthropogenic aerosols has been comparatively less studied. Furthermore, identifying robust changes in the atmospheric circulation is challenging and a major source of uncertainty in climate projections given the variety of responses in different models. This study aims to address these two aspects, benefitting from the use of large ensembles of single forcing experiments for the historical period and the future under RCP8.5, which allow to better identify the contribution of internal variability and its interplay with external forcing. We will discuss changes of the northern hemisphere storm tracks over both the Atlantic and Pacific regions, disentangle the contribution of anthropogenic aerosol changes, and build a physical link with large-scale circulation and surface climate over the two-basins.</p>

scholarly journals Fisheries: A Missing Link in Greenhouse Gas Emission Policies in South Korea

2021 ◽  
Vol 13 (11) ◽  
pp. 5858
Author(s):  
Kyumin Kim ◽  
Do-Hoon Kim ◽  
Yeonghye Kim
Keyword(s):  
Greenhouse Gas ◽  
Greenhouse Gas Emission ◽  
Ghg Emissions ◽  
Bioeconomic Model ◽  
Negative Externalities ◽  
Fishing Vessel ◽  
Gas Emission ◽  
Fishing Vessels ◽  
The Government ◽  
Different Levels

Recent studies demonstrate that fisheries are massive contributors to global greenhouse gas (GHG) emissions. The average Korean fishing vessel is old, fuel-inefficient, and creates a large volume of emissions. Yet, there is little research on how to address the GHG emissions in Korean fisheries. This study estimated the change in GHG emissions and emission costs at different levels of fishing operations using a steady-state bioeconomic model based on the case of the Anchovy Tow Net Fishery (ATNF) and the Large Purse Seine Fishery (LPSF). We conclude that reducing the fishing efforts of the ATNF and LPSF by 37% and 8% respectively would not only eliminate negative externalities on the anchovy and mackerel stock respectively, but also mitigate emissions and emission costs in the fishing industry. To limit emissions, we propose that the Korean government reduce fishing efforts through a vessel-buyback program and set an annual catch limit. Alternatively, the government should provide loans for modernizing old fishing vessels or a subsidy for installing emission abatement equipment to reduce the excessive emissions from Korean fisheries.

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