Bounding global aerosol radiative forcing of climate change

Published: March 9, 2020

<p>Aerosol radiative forcing plays an important role in the attribution of past climate changes, estimates future allowable carbon emissions, and assessment potential geoengineering solutions. Substantial progress made over 40 years observing, understanding, modelling aerosol processes helped quantify forcing, but uncertainties remain large.</p><p>In spring 2018, under auspices World Climate Research Programme's Grand Science Challenge on Clouds, Circulation Sensitivity, thirty-six experts gathered to take a fresh comprehensive look at present understanding identify prospects for some most pressing open questions. The outcome that meeting is review paper, Bellouin et al. (2019), accepted publication Reviews Geophysics. This provides new range industrial era based multiple, traceable arguable lines evidence, including approaches, theoretical considerations, observations. A substantial achievement focus evidence rather than survey results or expert judgement, make questions much more specific.</p><p>This talk will key messages arguments work show promise improving quantification forcing.</p>

Language: Английский

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Weak average liquid-cloud-water response to anthropogenic aerosols

Nature, Journal Year: 2019, Volume and Issue: 572(7767), P. 51 - 55

Published: July 31, 2019

Language: Английский

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Aerosol-cloud-climate cooling overestimated by ship-track data

Science, Journal Year: 2021, Volume and Issue: 371(6528), P. 485 - 489

Published: Jan. 28, 2021

Making tracks The magnitude of the effect anthropogenic aerosols on formation clouds is an important unknown about how humans are affecting climate. Studies stratocumulus cloud that formed by ship exhaust have been used to estimate radiative impact this process, but Glassmeier et al. now show approach overestimates cooling aerosol addition up 200%. These findings underscore need quantify responses understand climate system. Science , issue p. 485

Language: Английский

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The hemispheric contrast in cloud microphysical properties constrains aerosol forcing

Proceedings of the National Academy of Sciences, Journal Year: 2020, Volume and Issue: 117(32), P. 18998 - 19006

Published: July 27, 2020

Significance Enhancement of aerosol that can nucleate cloud droplets increases the droplet number concentration and albedo clouds. This amount sunlight reflected to space. Uncertainty in how aerosol−cloud interactions over industrial period have increased planetary by this mechanism leads significant uncertainty climate projections. Our work presents a method for observationally constraining change due anthropogenic emissions: hemispheric difference remotely sensed between pristine Southern Ocean (a preindustrial proxy) polluted Northern Hemisphere. Application constraint models reduces range estimated since industrialization suggests current underpredict era.

Language: Английский

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Opportunistic experiments to constrain aerosol effective radiative forcing

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(1), P. 641 - 674

Published: Jan. 17, 2022

Aerosol-cloud interactions (ACIs) are considered to be the most uncertain driver of present-day radiative forcing due human activities. The nonlinearity cloud-state changes aerosol perturbations make it challenging attribute causality in observed relationships forcing. Using correlations infer can when meteorological variability also drives both and cloud independently. Natural anthropogenic from well-defined sources provide "opportunistic experiments" (also known as natural experiments) investigate ACI cases where may more confidently inferred. These cover a wide range locations spatiotemporal scales, including point such volcanic eruptions or industrial sources, plumes biomass burning forest fires, tracks individual ships shipping corridors. We review different experimental conditions conduct synthesis available satellite datasets field campaigns place these opportunistic experiments on common footing, facilitating new insights clearer understanding key uncertainties Cloud albedo strongly sensitive background conditions. Strong liquid water path increases largely ruled out by averaging across experiments. Opportunistic have significantly improved process-level ACI, but remains unclear how reliably found scaled global level, thus demonstrating need for deeper investigation order improve assessments climate change.

Language: Английский

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Machine learning reveals climate forcing from aerosols is dominated by increased cloud cover

Nature Geoscience, Journal Year: 2022, Volume and Issue: 15(8), P. 609 - 614

Published: Aug. 1, 2022

Language: Английский

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Has Reducing Ship Emissions Brought Forward Global Warming?

Geophysical Research Letters, Journal Year: 2024, Volume and Issue: 51(15)

Published: Aug. 12, 2024

Abstract Ships brighten low marine clouds from emissions of sulfur and aerosols, resulting in visible “ship tracks”. In 2020, new shipping regulations mandated an ∼80% reduction the allowed fuel content. Recent observations indicate that ship tracks have decreased. Model simulations since 2020 induced a net radiative forcing +0.12 Wm −2 . Analysis recent temperature anomalies indicates Northern Hemisphere surface 2022–2023 are correlated with observed cloud is spatially simulated emission changes. Shipping changes could be accelerating global warming. To better constrain these estimates, access to position data understanding aerosol needed. Understanding risks benefits reductions difficultly robust attribution highlights large uncertainty attributing proposed deliberate climate intervention.

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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Substantial cooling effect from aerosol-induced increase in tropical marine cloud cover

Nature Geoscience, Journal Year: 2024, Volume and Issue: 17(5), P. 404 - 410

Published: April 11, 2024

Abstract With global warming currently standing at approximately +1.2 °C since pre-industrial times, climate change is a pressing issue. Marine cloud brightening one proposed method to tackle through injecting aerosols into marine clouds enhance their reflectivity and thereby planetary albedo. However, because it unclear how influence clouds, especially cover, both projections the effectiveness of remain uncertain. Here we use satellite observations volcanic eruptions in Hawaii quantify aerosol fingerprint on tropical clouds. We observe large enhancement reflected sunlight, mainly due an aerosol-induced increase cover. This observed strong negative forcing suggests that current level driven by weaker net radiative than previously thought, arising from competing effects greenhouse gases aerosols. implies greater sensitivity Earth’s therefore larger response rising gas concentrations reductions atmospheric air quality measures. our findings also indicate mitigation via plausible most effective humid stable conditions tropics where solar radiation strong.

Language: Английский

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Substantial Cloud Brightening From Shipping in Subtropical Low Clouds

AGU Advances, Journal Year: 2020, Volume and Issue: 1(1)

Published: March 1, 2020

Abstract The influence of aerosol particles on cloud reflectivity remains one the largest sources uncertainty in our understanding anthropogenic climate change. Commercial shipping constitutes a large and concentrated perturbation meteorological regime where clouds have disproportionally effect climate. Yet, to date, studies been unable detect climatologically relevant radiative effects from shipping, despite models indicating that response should produce sizable negative forcing (perturbation Earth's energy balance). We attribute significant increase enhanced droplet number concentrations within major corridor southeast Atlantic. Prevailing winds constrain emissions around corridor, which cuts through climatically important region expansive low cover. use universal kriging, classic geostatistical method, estimate what properties would absence shipping. In morning, brightening is consistent with changes microphysics alone, whereas afternoon, increases brightness microphysical are offset by decreases total amount water. calculate an effective Atlantic approximately −2 W/m 2 . Several years data required identify clear signal. Extrapolating results globally, we due aerosol‐cloud interactions −1.0 (95% confidence interval: −1.6 −0.4 ). unique setup could be ideal test for representation models.

Language: Английский

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