Robust evidence for reversal of the trend in aerosol effective climate forcing

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(18), P. 12221 - 12239

Published: Sept. 21, 2022

Abstract. Anthropogenic aerosols exert a cooling influence that offsets part of the greenhouse gas warming. Due to their short tropospheric lifetime only several days, aerosol forcing responds quickly emissions. Here, we present and discuss evolution since 2000. There are multiple lines evidence allow us robustly conclude anthropogenic effective radiative (ERF) – both aerosol–radiation interactions (ERFari) aerosol–cloud (ERFaci) has become less negative globally, i.e. trend in changed sign from positive. Bottom-up inventories show primary precursor emissions declined most regions world; observations related burden declining trends, particular fine-mode particles make up aerosols; satellite retrievals cloud droplet numbers trends with declines consistent these sign, as do top-of-atmosphere radiation. Climate model results, including revised set is constrained by ocean heat content magnitude for positive relative year 2000 due reduced effects. This reduction leads an acceleration climate change, increase 0.1 0.3 W m−2, 12 % total 2019 compared 1750 according Intergovernmental Panel on Change (IPCC).

Language: Английский

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Physical science research needed to evaluate the viability and risks of marine cloud brightening

Science Advances, Journal Year: 2024, Volume and Issue: 10(12)

Published: March 20, 2024

Marine cloud brightening (MCB) is the deliberate injection of aerosol particles into shallow marine clouds to increase their reflection solar radiation and reduce amount energy absorbed by climate system. From physical science perspective, consensus a broad international group scientists that viability MCB will ultimately depend on whether observations models can robustly assess scale-up local-to-global in today's identify strategies ensure an equitable geographical distribution benefits risks associated with projected regional changes temperature precipitation. To address knowledge gaps required societal implications MCB, we propose substantial targeted program research-field laboratory experiments, monitoring, numerical modeling across range scales.

Language: Английский

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Hydrological Consequences of Solar Geoengineering

Annual Review of Earth and Planetary Sciences, Journal Year: 2023, Volume and Issue: 51(1), P. 447 - 470

Published: Feb. 8, 2023

As atmospheric carbon dioxide concentrations rise and climate change becomes more destructive, geoengineering has become a subject of serious consideration. By reflecting fraction incoming sunlight, solar could cool the planet quickly, but with uncertain effects on regional climatology, particularly hydrological patterns. Here, we review recent work projected hydrologic outcomes geoengineering, in context robust literature responses to change. While most approaches are expected weaken global cycle, will vary based implementation method strategy. The impacts demonstrates that its implications for human welfare depend assumptions about underlying social conditions objectives intervention as well lens through which interpreted. We conclude suggestions reduce decision-relevant uncertainties this novel field Earth science inquiry. ▪The reducing insolation among consequential (SG).▪Theoretical frameworks from broader can help explain SG's precipitation, relative humidity, other aspects hydroclimate.▪The state knowledge SG is unevenly concentrated regions.▪Projected scenario dependent difficult characterize either harmful or beneficial.

Language: Английский

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Radiative forcing from the 2020 shipping fuel regulation is large but hard to detect

Communications Earth & Environment, Journal Year: 2025, Volume and Issue: 6(1)

Published: Jan. 13, 2025

Abstract Reduction in aerosol cooling unmasks greenhouse gas warming, exacerbating the rate of future warming. The strict sulfur regulation on shipping fuel implemented 2020 (IMO2020) presents an opportunity to assess potential impacts such emission regulations and detectability deliberate perturbations for climate intervention. Here we employ machine learning capture cloud natural variability estimate a radiative forcing +0.074 ±0.005 W m −2 related IMO2020 associated with changes shortwave effect over three low-cloud regions where routes prevail. We find low this event, attributed strong albedo cover. Regionally, is higher southeastern Atlantic stratocumulus deck. These results raise concerns that reductions emissions will accelerate warming proposed as marine brightening need be substantial order overcome detectability.

Language: Английский

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Variability of Eastern North Atlantic Summertime Marine Boundary Layer Clouds and Aerosols Across Different Synoptic Regimes Identified With Multiple Conditions

Journal of Geophysical Research Atmospheres, Journal Year: 2025, Volume and Issue: 130(4)

Published: Feb. 12, 2025

Abstract This study estimates the meteorological covariations of aerosol and marine boundary layer (MBL) cloud properties in eastern North Atlantic (ENA) region, characterized by diverse synoptic conditions. Using a deep‐learning‐based clustering model with mid‐level surface daily data, we identify seven distinct regimes during summer from 2016 to 2021. Our analysis, incorporating reanalysis data satellite retrievals, shows that aerosols MBL clouds exhibit clear regime‐dependent characteristics, whereas lower tropospheric do not. discrepancy likely arises determined large‐scale conditions, which may overlook air mass histories predominantly dictate Focusing on three dominated northerly winds, analyze Atmospheric Radiation Measurement Program (ARM) ENA observations Graciosa Island Azores. In subtropical anticyclone regime, fewer cumulus more single‐layer stratocumulus light drizzle are observed, along highest droplet number concentration (Nd), condensation nuclei (CCN) levels. The post‐trough regime features broken or multi‐layer slightly higher rain rate, Nd CCN weak trough is deepest clouds, primarily strongest rate lowest Nd, levels, indicating strong wet scavenging. These findings highlight importance considering covariation driven when assessing indirect effects using observations.

Language: Английский

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Effective radiative forcing of anthropogenic aerosols in E3SM version 1: historical changes, causality, decomposition, and parameterization sensitivities

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(13), P. 9129 - 9160

Published: July 14, 2022

Abstract. The effective radiative forcing of anthropogenic aerosols (ERFaer) is an important measure the aerosol effects simulated by a global climate model. Here we analyze ERFaer E3SM version 1 (E3SMv1) atmospheric model using both century-long free-running atmosphere–land simulations and short nudged simulations. We relate to characteristics composition optical properties, evaluate relationships between key cloud properties. In terms historical changes from year 1870 2014, our results show that mean burden depth increase during simulation period as expected, but regional averages large differences in temporal evolution. largest are found emission-induced evolution sulfate aerosol: strong decreasing trend seen Northern Hemisphere high-latitude region after around 1970, while continued tropics. properties (relative pre-industrial present-day conditions) also evident diverging linear exhibited for 1870–1969. addition relationships, reduced sensitivity droplet number other perturbations when perturbation large. Consequently, annual magnitude does not 1970. E3SMv1 relatively compared recently published multi-model estimates; primary reason indirect effect (i.e., through aerosol–cloud interactions). Compared models, features relative radius response perturbations. Large liquid depth, which determined water path. Aerosol-induced ice have correlation, affects formation homogeneous nucleation cirrus clouds (that causes on longwave ERFaer). As suggested previous study, appears be one reasons why cannot reproduce observed temperature second half 20th century. Sensitivity performed understand parameterization and/or parameter impact ERFaer. estimates shortwave components sensitive processes. When processes modified, top-of-model largely offset each other, so net negligible. This suggests that, reduce ERFaer, it would more or mixed-phase clouds.

Language: Английский

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The Role of Mesoscale Cloud Morphology in the Shortwave Cloud Feedback

Geophysical Research Letters, Journal Year: 2023, Volume and Issue: 50(2)

Published: Jan. 18, 2023

Abstract A supervised neural network algorithm is used to categorize near‐global satellite retrievals into three mesoscale cellular convective (MCC) cloud morphology patterns. At constant amount, patterns differ in brightness associated with the amount of optically thin features. Environmentally driven transitions from closed MCC other patterns, typically accompanied by more features, are as a framework quantify contribution optical depth component shortwave feedback. marine heat wave an out‐of‐sample test occurrence predictions. Morphology shifts between 65°S and 65°N under projected environmental changes (i.e., abrupt quadrupling CO 2 ) assuming cover contributes 0.04 0.07 W m −2 K −1 (aggregate 0.06) global mean

Language: Английский

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Distinct regional meteorological influences on low-cloud albedo susceptibility over global marine stratocumulus regions

Atmospheric chemistry and physics, Journal Year: 2023, Volume and Issue: 23(2), P. 1073 - 1090

Published: Jan. 20, 2023

Abstract. Marine stratocumuli cool the Earth effectively due to their high reflectance of incoming solar radiation and persistent occurrence. The susceptibility cloud albedo droplet number concentration perturbations depends strongly on large-scale meteorological conditions. Studies focused dependence adjustments often overlook covariability among factors geographical temporal variability. We use 8 years satellite observations sorted by day location show global distribution marine low-cloud susceptibility. find an overall brightening potential for most warm clouds, which is more pronounced over subtropical coastal regions. A weak darkening in annual mean evident remote SE Pacific Atlantic. that fields from ERA5 reanalysis data, including lower-tropospheric stability, free-tropospheric relative humidity, sea surface temperature, boundary layer depth, have distinct covariabilities each eastern ocean basins where prevail. This leads a markedly different cycle basin. Moreover, we basin-specific regional relationships between key susceptibilities are absent analysis. Our results stress importance considering distinctiveness when scaling up local-to-global response aerosol perturbations.

Language: Английский

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Microphysical, macrophysical, and radiative responses of subtropical marine clouds to aerosol injections

Atmospheric chemistry and physics, Journal Year: 2023, Volume and Issue: 23(2), P. 1345 - 1368

Published: Jan. 25, 2023

Abstract. Ship tracks in subtropical marine low clouds are simulated and investigated using large-eddy simulations. Five variants of a shallow stratocumulus-topped boundary layer (MBL) chosen to span range background aerosol concentrations variations free-tropospheric moisture. Idealized time-invariant meteorological forcings approximately steady-state constitute the conditions. We investigate processes controlling cloud microphysical, macrophysical, radiative responses injections. For analysis, we use novel methods decompose liquid water path (LWP) adjustment into changes boundary-layer properties effect (CRE) contributions from macro- microphysics. The key results that (a) cloud-top entrainment rate increases all cases, with stronger for thicker than thinner clouds; (b) drying warming induced by increased is offset differing degrees corresponding surface fluxes, precipitation, radiation; (c) MBL turbulence responds caused perturbation, this significantly affects macrophysics; (d) across 2 d simulation, were brightened cases. In pristine MBL, significant drizzle suppression injections not only greater retention but also intensification, leading increase amount. case, Twomey brightening strongly augmented an thickness cover. addition, reduction loss through coalescence scavenging more offsets dilution. This interplay precludes estimation lifetime perturbation. combined microphysics lead 10–100 times effective these cases relative those non-precipitating moderate polluted MBLs, enhancement makes drier, warmer, stratified, decrease thickness. LWP response greatest fraction moderately moist free troposphere. finding differs previous studies found larger drier troposphere, it initially clouds, so offsetting effects weaker. injected MBLs estimated be 2–3 d, which much longer estimates typical ship track lifetimes satellite images.

Language: Английский

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Diminished efficacy of regional marine cloud brightening in a warmer world

Nature Climate Change, Journal Year: 2024, Volume and Issue: 14(8), P. 808 - 814

Published: June 21, 2024

Language: Английский

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