Substantial twentieth-century Arctic warming caused by ozone-depleting substances

2020 ◽  
Author(s):  
Lorenzo Polvani ◽  
Michael Previdi ◽  
Mark England ◽  
Gabriel Chiodo ◽  
Karen Smith
Keyword(s):  
Climate Change ◽  
Twentieth Century ◽  
Greenhouse Gases ◽  
Climate Model ◽  
Dominant Role ◽  
Montreal Protocol ◽  
The Arctic ◽  
Atmospheric Concentration ◽  
Arctic Warming ◽  
Ozone Depleting Substances

<p>The rapid warming of the Arctic, perhaps the most striking evidence of climate change, is believed to arise from increases in atmospheric concentration of greenhouse gases since the industrial revolution.  While the dominant role of carbon dioxide is undisputed, another important set of anthropogenic greenhouse gases was also being emitted over the second half of the twentieth century: ozone-depleting substances (ODS).  These compounds, in addition to causing the ozone hole over Antarctica, have long been recognized as powerful greenhouse gases.  However, their contribution to Arctic warming has not been quantified to date.  We do so here by analyzing ensembles of climate model integrations specifically designed for this purpose, spanning the period 1955-2005 when atmospheric concentrations of ODS increased rapidly.  We show that when ODS are kept fixed the forced Arctic surface warming, and the forced sea ice loss, are only half as large as when ODS are allowed to increase.  We also demonstrate that the large Arctic impact of ODS occurs primarily via direct radiative warming, not via ozone depletion.  Our findings reveal a substantial, and hitherto unrecognized, contribution of ODS to recent Arctic warming and highlight the importance of the Montreal Protocol as a major climate change mitigation treaty.</p>

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

2022 ◽  
Author(s):  
Yu-Chiao Liang ◽  
Lorenzo M. Polvani ◽  
Michael Previdi ◽  
Karen Louise Smith ◽  
Mark R. England ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Sea Ice ◽  
Climate Model ◽  
Montreal Protocol ◽  
Lapse Rate ◽  
The Arctic ◽  
Arctic Amplification ◽  
Near Surface ◽  
Arctic Warming ◽  
Ozone Depleting Substances

Abstract Arctic amplification (AA) - the greater warming of the Arctic near-surface temperature relative to its global mean value - is a prominent feature of the climate response to increasing greenhouse gases. Recent work has revealed the importance of ozone-depleting substances (ODS) in contributing to Arctic warming and sea-ice loss. Here, using ensembles of climate model integrations, we expand on that work and directly contrast Arctic warming from ODS to that from carbon dioxide (CO$_2$), over the 1955-2005 period when ODS loading peaked. We find that the Arctic warming and sea-ice loss from ODS are slightly more than half (52-59\%) those from CO$_2$. We further show that the strength of AA for ODS is 1.44 times larger than that for CO$_2$, and that this mainly stems from more positive Planck, albedo, lapse-rate, and cloud feedbacks. Our results suggest that AA would be considerably stronger than presently observed had the Montreal Protocol not been signed.

scholarly journals Improved FTIR retrieval strategy for HCFC-22 (CHClF<sub>2</sub>), comparisons with in situ and satellite datasets with the support of models, and determination of its long-term trend above Jungfraujoch

2019 ◽  
Vol 19 (19) ◽  
pp. 12309-12324 ◽  
Author(s):  
Maxime Prignon ◽  
Simon Chabrillat ◽  
Daniele Minganti ◽  
Simon O'Doherty ◽  
Christian Servais ◽  
...  
Keyword(s):  
Climate Model ◽  
Michelson Interferometer ◽  
Montreal Protocol ◽  
Swiss Alps ◽  
Retrieval Strategy ◽  
Atmospheric Concentration ◽  
New Strategy ◽  
Scientific Station ◽  
Ozone Depleting Substances

Abstract. Hydrochlorofluorocarbons (HCFCs) are the first, but temporary, substitution products for the strong ozone-depleting chlorofluorocarbons (CFCs). HCFC consumption and production are currently regulated under the Montreal Protocol on Substances that Deplete the Ozone Layer and their emissions have started to stabilize or even decrease. As HCFC-22 (CHClF2) is by far the most abundant HCFC in today's atmosphere, it is crucial to continue to monitor the evolution of its atmospheric concentration. In this study, we describe an improved HCFC-22 retrieval strategy from ground-based high-resolution Fourier transform infrared (FTIR) solar spectra recorded at the high-altitude scientific station of Jungfraujoch, the Swiss Alps, 3580 m a.m.s.l. (above mean sea level). This new strategy distinguishes tropospheric and lower-stratospheric partial columns. Comparisons with independent datasets, such as the Advanced Global Atmospheric Gases Experiment (AGAGE) and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), supported by models, such as the Belgian Assimilation System for Chemical ObErvation (BASCOE) and the Whole Atmosphere Community Climate Model (WACCM), demonstrate the validity of our tropospheric and lower-stratospheric long-term time series. A trend analysis on the datasets used here, now spanning 30 years, confirms the last decade's decline in the HCFC-22 growth rate. This updated retrieval strategy can be adapted for other ozone-depleting substances (ODSs), such as CFC-12. Measuring or retrieving ODS atmospheric concentrations is essential for scrutinizing the fulfilment of the globally ratified Montreal Protocol.

scholarly journals The Key Role of Ozone-Depleting Substances in Weakening the Walker Circulation in the Second Half of the Twentieth Century

2019 ◽  
Vol 32 (5) ◽  
pp. 1411-1418 ◽  
Author(s):  
Lorenzo M. Polvani ◽  
Katinka Bellomo
Keyword(s):  
Twentieth Century ◽  
Pacific Ocean ◽  
Greenhouse Gases ◽  
Radiative Forcing ◽  
Climate Model ◽  
Walker Circulation ◽  
Surface Warming ◽  
Ozone Depleting Substances ◽  
The Antarctic ◽  
The Walker Circulation

It is widely appreciated that ozone-depleting substances (ODS), which have led to the formation of the Antarctic ozone hole, are also powerful greenhouse gases. In this study, we explore the consequence of the surface warming caused by ODS in the second half of the twentieth century over the Indo-Pacific Ocean, using the Whole Atmosphere Chemistry Climate Model (version 4). By contrasting two ensembles of chemistry–climate model integrations (with and without ODS forcing) over the period 1955–2005, we show that the additional greenhouse effect of ODS is crucial to producing a statistically significant weakening of the Walker circulation in our model over that period. When ODS concentrations are held fixed at 1955 levels, the forcing of the other well-mixed greenhouse gases alone leads to a strengthening—rather than weakening—of the Walker circulation because their warming effect is not sufficiently strong. Without increasing ODS, a surface warming delay in the eastern tropical Pacific Ocean leads to an increase in the sea surface temperature gradient between the eastern and western Pacific, with an associated strengthening of the Walker circulation. When increasing ODS are added, the considerably larger total radiative forcing produces a much faster warming in the eastern Pacific, causing the sign of the trend to reverse and the Walker circulation to weaken. Our modeling result suggests that ODS may have been key players in the observed weakening of the Walker circulation over the second half of the twentieth century.

scholarly journals Drivers of changes in stratospheric and tropospheric ozone between year 2000 and 2100

2016 ◽  
Vol 16 (5) ◽  
pp. 2727-2746 ◽  
Author(s):  
Antara Banerjee ◽  
Amanda C. Maycock ◽  
Alexander T. Archibald ◽  
N. Luke Abraham ◽  
Paul Telford ◽  
...  
Keyword(s):  
Climate Change ◽  
Greenhouse Gases ◽  
Tropospheric Ozone ◽  
Climate Forcing ◽  
Atmospheric Response ◽  
Chemical Production ◽  
The United Kingdom ◽  
Ozone Precursor ◽  
Ozone Depleting Substances ◽  
Year 2000

Abstract. A stratosphere-resolving configuration of the Met Office's Unified Model (UM) with the United Kingdom Chemistry and Aerosols (UKCA) scheme is used to investigate the atmospheric response to changes in (a) greenhouse gases and climate, (b) ozone-depleting substances (ODSs) and (c) non-methane ozone precursor emissions. A suite of time-slice experiments show the separate, as well as pairwise, impacts of these perturbations between the years 2000 and 2100. Sensitivity to uncertainties in future greenhouse gases and aerosols is explored through the use of the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios. The results highlight an important role for the stratosphere in determining the annual mean tropospheric ozone response, primarily through stratosphere–troposphere exchange (STE) of ozone. Under both climate change and reductions in ODSs, increases in STE offset decreases in net chemical production and act to increase the tropospheric ozone burden. This opposes the effects of projected decreases in ozone precursors through measures to improve air quality, which act to reduce the ozone burden. The global tropospheric lifetime of ozone (τO3) does not change significantly under climate change at RCP4.5, but it decreases at RCP8.5. This opposes the increases in τO3 simulated under reductions in ODSs and ozone precursor emissions. The additivity of the changes in ozone is examined by comparing the sum of the responses in the single-forcing experiments to those from equivalent combined-forcing experiments. Whilst the ozone responses to most forcing combinations are found to be approximately additive, non-additive changes are found in both the stratosphere and troposphere when a large climate forcing (RCP8.5) is combined with the effects of ODSs.

scholarly journals Addendum: Substantial twentieth-century Arctic warming caused by ozone-depleting substances

2020 ◽  
Vol 10 (2) ◽  
pp. 167-167
Author(s):  
L. M. Polvani ◽  
M. Previdi ◽  
M. R. England ◽  
G. Chiodo ◽  
K. L. Smith
Keyword(s):  
Twentieth Century ◽  
Arctic Warming ◽  
Ozone Depleting Substances

scholarly journals Multimodel Multisignal Climate Change Detection at Regional Scale

2006 ◽  
Vol 19 (17) ◽  
pp. 4294-4307 ◽  
Author(s):  
Xuebin Zhang ◽  
Francis W. Zwiers ◽  
P. A. Stott
Keyword(s):  
Climate Change ◽  
Twentieth Century ◽  
Greenhouse Gases ◽  
Regional Scale ◽  
Internal Variability ◽  
Anthropogenic Forcing ◽  
Internal Climate Variability ◽  
Aerosol Forcing ◽  
Spatial Domains ◽  
Northern Hemispheric

Abstract Using an optimal detection technique and climate change simulations produced with two versions of two GCMs, we have assessed the causes of twentieth-century temperature changes from global to regional scales. Our analysis is conducted in nine spatial domains: 1) the globe; 2) the Northern Hemisphere; four large regions in the Northern Hemispheric midlatitudes covering 30°–70°N including 3) Eurasia, 4) North America, 5) Northern Hemispheric land only, 6) the entire 30°–70°N belt; and three smaller regions over 7) southern Canada, 8) southern Europe, and 9) China. We find that the effect of anthropogenic forcing on climate is clearly detectable at global through regional scales. The effect of combined greenhouse gases and sulfate aerosol forcing is detectable in all nine domains in annual and seasonal mean temperatures observed during the second half of the twentieth century. The effect of greenhouse gases can also be separated from that of sulfate aerosols over this period at continental and regional scales. Uncertainty in these results is larger in the smaller spatial domains. Detection is improved when an ensemble of models is used to estimate the response to anthropogenic forcing and the underlying internal variability of the climate system. Our detection results hold after removal of North Atlantic Oscillation (NAO)-related variability in temperature observations—variability that may or may not be associated with anthropogenic forcing. They also continue to hold when our estimates of natural internal climate variability are doubled.

Atmospheric impacts of short-lived chlorinated species over the recent past: a chemistry-climate perspective

2021 ◽  
Author(s):  
Ewa Bednarz ◽  
Ryan Hossaini ◽  
Luke Abraham ◽  
Peter Braesicke ◽  
Martyn Chipperfield
Keyword(s):  
Atmospheric Chemistry ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Lower Boundary ◽  
Montreal Protocol ◽  
Recent Past ◽  
Substantial Impact ◽  
Ozone Depleting Substances ◽  
The Impact

&lt;p&gt;The emissions of most long-lived halogenated ozone-depleting substances (ODSs) are now decreasing, owing to controls on their production introduced by Montreal Protocol and its amendments. However, short-lived halogenated compounds can also have substantial impact on atmospheric chemistry, including stratospheric ozone, particularly if emitted near climatological uplift regions. It has recently become evident that emissions of some chlorinated very short-lived species (VSLSs), such as chloroform (CHCl&lt;sub&gt;3&lt;/sub&gt;) and dichloromethane (CH&lt;sub&gt;2&lt;/sub&gt;Cl&lt;sub&gt;2&lt;/sub&gt;), could be larger than previously believed and increasing, particularly in Asia. While these may exert a significant influence on atmospheric chemistry and climate, their impacts remain poorly characterised.&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;We address this issue using the UM-UKCA chemistry-climate model (CCM). While not only the first, to our knowledge, model study addressing this problem using a CCM, it is also the first such study employing a whole atmosphere model, thereby simulating the tropospheric Cl-VSLSs emissions and the resulting stratospheric impacts in a fully consistent manner. We use a newly developed Double-Extended Stratospheric-Tropospheric (DEST) chemistry scheme, which includes emissions of all major chlorinated and brominated VSLSs alongside an extended treatment of long-lived ODSs.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;We examine the impacts of rising Cl-VSLSs emissions on atmospheric chlorine tracers and ozone, including their long-term trends. We pay particular attention to the role of &amp;#8216;nudging&amp;#8217;, as opposed to the free-running model set up, for the simulated Cl-VSLSs impacts, thereby demostrating the role of atmospheric dynamics in modulating the atmospheric responses to Cl-VSLSs. In addition, we employ novel estimates of Cl-VSLS emissions over the recent past and compare the results with the simulations that prescribe Cl-VSLSs using simple lower boundary conditions. This allows us to demonstrate the impact such choice has on the dominant location and seasonality of the Cl-VSLSs transport into the stratosphere.&lt;/p&gt;

Substantial twentieth-century Arctic warming caused by ozone-depleting substances

2020 ◽  
Vol 10 (2) ◽  
pp. 130-133 ◽  
Author(s):  
L. M. Polvani ◽  
M. Previdi ◽  
M. R. England ◽  
G. Chiodo ◽  
K. L. Smith
Keyword(s):  
Twentieth Century ◽  
Arctic Warming ◽  
Ozone Depleting Substances

THE SCIENCE UNDERLYING THE ISSUE OF CLIMATE CHANGE AND PROSPECTS FOR ADAPTATION

2001 ◽  
Vol 41 (1) ◽  
pp. 689
Author(s):  
C.D. Mitchell ◽  
G.I. Pearman
Keyword(s):  
Climate Change ◽  
Risk Management ◽  
Greenhouse Gas ◽  
Climate Model ◽  
Global Climate ◽  
Regional Climate ◽  
Initial Response ◽  
Lower Atmosphere ◽  
Future Climate Change ◽  
Atmospheric Concentration

The prospect of global-scale changes in climate resulting from changes in atmospheric greenhouse gas concentrations has produced a complex set of public and private- sector responses. This paper reviews several elements of this issue that are likely to be most important to industry.Scientific research continues to provide evidence to suggest that global climate will change significantly over the coming decades due to increases in the atmospheric concentration of greenhouse gases. Nonetheless, there exists a debate over the difference between observations of temperature retrieved from satellite and temperature measurements taken from the surface. Recent research undertaken to inform the debate is discussed, with the conclusion that there are real differences in trend between the surface and the lower atmosphere that can be explained in physical terms. Attention is turning to developing an understanding as to why climate model results show apparently consistent trends between the surface and the lower atmosphere, in contrast to these observations.While such uncertainties in the underlying science have been used to question whether action on the greenhouse issues is necessary, the initial response, as evidenced by international negotiations, has been to start mitigating greenhouse gas emissions. Adaptation to future climate change has received less attention than mitigation. A number of reasons for this are discussed, including the fact that regional scenarios of climate change are uncertain.The principles of risk management may be one way to manage the uncertainties associated with projections of regional climate change. Although the application of risk management to the potential impacts of climate change requires further investigation, elements of such a framework are identified, and include:Identifying the critical climate-related thresholds that are important to industry and its operations (for example, a 1-in-100 year return tropical cyclone).Using this understanding to analyse, and where possible quantify, industry’s pre-existing or baseline adaptive state through the use of sensitivity surfaces and quantified thresholds (for example, were facilities designed for a 1-in-100 event or a 1-in-500 year event?)Establishing probabilistic statements or scenarios of climate that are relevant to industry practice (for example, risk of a storm surge may be more important to operations than elevated wind strength; if so, what is the probability that an event will exceed the design threshold during the lifetime of the facility?).Bringing information on existing adaptive mechanisms together with climate scenarios to produce a quantitative risk assessment.Deciding on risk treatment (additional adaptive measures).

Climate Change Scenarios and African Climate Change

2018 ◽  
Author(s):  
Kerry H. Cook
Keyword(s):  
Climate Change ◽  
Greenhouse Gases ◽  
Greenhouse Gas ◽  
Climate Model ◽  
Congo Basin ◽  
Climate Change Scenarios ◽  
Precipitation Regimes ◽  
Intense Storm ◽  
Short Rains ◽  
Projected Changes

Accurate projections of climate change under increasing atmospheric greenhouse gas levels are needed to evaluate the environmental cost of anthropogenic emissions, and to guide mitigation efforts. These projections are nowhere more important than Africa, with its high dependence on rain-fed agriculture and, in many regions, limited resources for adaptation. Climate models provide our best method for climate prediction but there are uncertainties in projections, especially on regional space scale. In Africa, limitations of observational networks add to this uncertainty since a crucial step in improving model projections is comparisons with observations. Exceeding uncertainties associated with climate model simulation are uncertainties due to projections of future emissions of CO2 and other greenhouse gases. Humanity’s choices in emissions pathways will have profound effects on climate, especially after the mid-century.The African Sahel is a transition zone characterized by strong meridional precipitation and temperature gradients. Over West Africa, the Sahel marks the northernmost extent of the West African monsoon system. The region’s climate is known to be sensitive to sea surface temperatures, both regional and global, as well as to land surface conditions. Increasing atmospheric greenhouse gases are already causing amplified warming over the Sahara Desert and, consequently, increased rainfall in parts of the Sahel. Climate model projections indicate that much of this increased rainfall will be delivered in the form of more intense storm systems.The complicated and highly regional precipitation regimes of East Africa present a challenge for climate modeling. Within roughly 5º of latitude of the equator, rainfall is delivered in two seasons—the long rains in the spring, and the short rains in the fall. Regional climate model projections suggest that the long rains will weaken under greenhouse gas forcing, and the short rains season will extend farther into the winter months. Observations indicate that the long rains are already weakening.Changes in seasonal rainfall over parts of subtropical southern Africa are observed, with repercussions and challenges for agriculture and water availability. Some elements of these observed changes are captured in model simulations of greenhouse gas-induced climate change, especially an early demise of the rainy season. The projected changes are quite regional, however, and more high-resolution study is needed. In addition, there has been very limited study of climate change in the Congo Basin and across northern Africa. Continued efforts to understand and predict climate using higher-resolution simulation must be sustained to better understand observed and projected changes in the physical processes that support African precipitation systems as well as the teleconnections that communicate remote forcings into the continent.

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