Stronger Arctic amplification from ozone-depleting substances than from carbon dioxide

Liang, Yiqing; Polvani, Lorenzo M.; Previdi, Michael; Smith, Kay; England, Mark; Chiodo, Gabriel

doi:10.1088/1748-9326/ac4a31

Cited by 13 publications

(10 citation statements)

References 54 publications

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“…This offers important new evidence that the large Arctic impact of ODS reported in an earlier study (Polvani et al., 2020), which analyzed the same historical simulations, must be due to strong local feedbacks, notably changes in the lapse rate feedback reported in Liang et al. (2022).…”

Section: Summary and Discussionsupporting

confidence: 55%

“…Third, we have shown that the latitudinal structure of the RF caused by ODS, while broadly similar to those of other GHGs (larger at the equator than at the poles), has an even steeper latitudinal gradient than the RF of CO 2 , thus opposing Arctic Amplification even more strongly. This offers important new evidence that the large Arctic impact of ODS reported in an earlier study (Polvani et al, 2020), which analyzed the same historical simulations, must be due to strong local feedbacks, notably changes in the lapse rate feedback reported in Liang et al (2022).…”

Section: Summary and Discussionsupporting

confidence: 51%

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New Insights on the Radiative Impacts of Ozone‐Depleting Substances

Chiodo

Polvani

2022

Geophysical Research Letters

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Anthropogenic emissions of chlorofluorocarbons (CFCs) and other chlorinated species have greatly enhanced stratospheric halogen abundance over the second half of the twentieth century (World Meteorological Organization, 2018), and thereby led to substantial depletion of the ozone layer. The widespread, though indirect, climatic impacts of ODS via ozone depletion, largely linked to the the shift of the Southern Hemispheric circulation, are well documented (Polvani et al., 2011;Previdi & Polvani, 2014;Thompson & Solomon, 2002). But ODS also impact the climate system in ways that are not mediated by ozone, since they are potent well-mixed greenhouse gases (Ramanathan, 1975). Recent studies have shown that the surface warming from ODS may have played a key-role in the observed weakening trends of the Walker circulation (Polvani & Bellomo, 2019), and in the warming of the Arctic and the associated sea ice loss (Polvani et al., 2020). These studies suggest that the direct climate impacts of ODS, as greenhouse gases, may deserve closer study. In this paper, as a first step, we seek a deeper understanding of the purely radiative effects of ODS.Radiative forcing (RF) provides an important metric to evaluate and contrast the climatic impacts of different atmospheric trace gases (Ramaswamy et al., 2019). It is well established that ODS are powerful greenhouse gases (Ramanathan, 1975), with global warming potentials over a 100-year time horizon (GWP100) thousands of times larger than CO 2 (Hodnebrog, Aamaas, et al., 2020). However, the RF of ODS remains subject to some uncertainty. Detailed spectral calculations of the ODS RF using Line-by-Line (LbL) codes, routinely included in IPCC reports (e.g., Hodnebrog et al., 2013), typically employ two single (1-D) atmospheric profiles (tropical/ extratropical) as this is the best compromise between computational expediency and accuracy (errors are less than 1% compared to calculations with better spatial resolution). Moreover, ODS in these models are typically assumed to be uniformly distributed, and assumptions concerning their lifetime are made to try to capture spatial

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Section: Summary and Discussionsupporting

confidence: 55%

Section: Summary and Discussionsupporting

confidence: 51%

New Insights on the Radiative Impacts of Ozone‐Depleting Substances

Chiodo

Polvani

2022

Geophysical Research Letters

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“…Since changes in Arctic temperatures have a direct effect on sea ice loss, Polvani et al [ 59 ] concluded that ODSs contributed half of the forced Arctic sea ice loss in the latter half of the twentieth century. These results were recently confirmed [ 75 ], showing that Arctic warming and sea ice loss from ODSs are slightly more than half (52–59%) of those from CO 2 .…”

Section: Benefits Of the Montreal Protocolsupporting

confidence: 65%

Stratospheric ozone, UV radiation, and climate interactions

Bernhard

Bais

Aucamp³

et al. 2023

Photochem Photobiol Sci

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This assessment provides a comprehensive update of the effects of changes in stratospheric ozone and other factors (aerosols, surface reflectivity, solar activity, and climate) on the intensity of ultraviolet (UV) radiation at the Earth’s surface. The assessment is performed in the context of the Montreal Protocol on Substances that Deplete the Ozone Layer and its Amendments and Adjustments. Changes in UV radiation at low- and mid-latitudes (0–60°) during the last 25 years have generally been small (e.g., typically less than 4% per decade, increasing at some sites and decreasing at others) and were mostly driven by changes in cloud cover and atmospheric aerosol content, caused partly by climate change and partly by measures to control tropospheric pollution. Without the Montreal Protocol, erythemal (sunburning) UV irradiance at northern and southern latitudes of less than 50° would have increased by 10–20% between 1996 and 2020. For southern latitudes exceeding 50°, the UV Index (UVI) would have surged by between 25% (year-round at the southern tip of South America) and more than 100% (South Pole in spring). Variability of erythemal irradiance in Antarctica was very large during the last four years. In spring 2019, erythemal UV radiation was at the minimum of the historical (1991–2018) range at the South Pole, while near record-high values were observed in spring 2020, which were up to 80% above the historical mean. In the Arctic, some of the highest erythemal irradiances on record were measured in March and April 2020. For example in March 2020, the monthly average UVI over a site in the Canadian Arctic was up to 70% higher than the historical (2005–2019) average, often exceeding this mean by three standard deviations. Under the presumption that all countries will adhere to the Montreal Protocol in the future and that atmospheric aerosol concentrations remain constant, erythemal irradiance at mid-latitudes (30–60°) is projected to decrease between 2015 and 2090 by 2–5% in the north and by 4–6% in the south due to recovering ozone. Changes projected for the tropics are ≤ 3%. However, in industrial regions that are currently affected by air pollution, UV radiation will increase as measures to reduce air pollutants will gradually restore UV radiation intensities to those of a cleaner atmosphere. Since most substances controlled by the Montreal Protocol are also greenhouse gases, the phase-out of these substances may have avoided warming by 0.5–1.0 °C over mid-latitude regions of the continents, and by more than 1.0 °C in the Arctic; however, the uncertainty of these calculations is large. We also assess the effects of changes in stratospheric ozone on climate, focusing on the poleward shift of climate zones, and discuss the role of the small Antarctic ozone hole in 2019 on the devastating “Black Summer” fires in Australia. Additional topics include the assessment of advances in measuring and modeling of UV radiation; methods for determining personal UV exposure; the effect of solar radiation management (stratospheric aerosol injections) on UV radiation relevant for plants; and possible revisions to the vitamin D action spectrum, which describes the wavelength dependence of the synthesis of previtamin D3 in human skin upon exposure to UV radiation. Graphical abstract

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“…Note that the ERF of ODSs opposes Arctic amplification even more than the ERF of CO 2 , making their large contribution to Arctic climate change even more unexpected. This may be due to stronger local feedbacks as suggested by Liang et al (2022).…”

Section: Discussionmentioning

confidence: 92%

Large Contribution of Ozone‐Depleting Substances to Global and Arctic Warming in the Late 20th Century

Sigmond

Polvani

Fyfe

et al. 2023

Geophysical Research Letters

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While previous studies have suggested a substantial role of ozone‐depleting substances (ODSs) in historical climate change, their relative contribution to historical anthropogenic warming has not been quantified before. Analyzing all‐but‐one‐forcing, 20‐member ensembles of historical simulations with a state‐of‐the‐art Earth System Model, we find that over the 1955–2005 period ODSs are responsible for 30% of global warming, 37% of Arctic warming, and 33% of summertime Arctic sea ice loss. Effective Radiative Forcing (ERF) calculations reveal that the global warming response to ODSs per unit of ERF is about 20% larger than for CO2, which may be due to stronger feedbacks and the difference in temporal evolution with ODSs having leveled off and CO2 still increasing in 2005. While the response to both peaks in the Arctic, the ODS ERF opposes Arctic amplification more than the CO2 ERF. Our findings highlight the importance of the Montreal Protocol for mitigating future climate change.

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Stronger Arctic amplification from ozone-depleting substances than from carbon dioxide

Cited by 13 publications

References 54 publications

New Insights on the Radiative Impacts of Ozone‐Depleting Substances

New Insights on the Radiative Impacts of Ozone‐Depleting Substances

Stratospheric ozone, UV radiation, and climate interactions

Large Contribution of Ozone‐Depleting Substances to Global and Arctic Warming in the Late 20th Century

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