Climate Crisis Connected To Ozone Crisis

Posted by: chaamjamal on: March 3, 2020

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RELATED POSTS ON OZONE DEPLETION: [LINK] [LINK] [LINK] [LINK]   

THIS POST IS A CRITICAL REVIEW OF THE FINDING REPORTED IN NATURE CLIMATE CHANGE THAT A THIRD OF GLOBAL WARMING AND HALF OF ARCTIC WARMING AND SEA ICE LOSS IN THE PERIOD 1955-2005 IS EXPLAINED IN TERMS OF THE HEAT TRAPPING EFFECT OF OZONE DEPLETING SUBSTANCES 

L M Polvani et al, Nat. Clim. Change, 2020, DOI: 10.1038/s41558-019-0677-4

 

 

 

PART-1: RESEARCH FINDINGS ON THE ROLE OF CFCs IN CLIMATE CHANGE

1. January 20, 2020 Ozone-depleting substances caused half of late 20th-century Arctic warming, says study by Columbia University : A new study shows that half of all Arctic warming and corresponding sea-ice loss during the late 20th century was caused by ozone-depleting substances. Here, icebergs discharged from Greenland’s Jakobshavn Glacier. A scientific paper published in 1985 was the first to report a burgeoning hole in Earth’s stratospheric ozone over Antarctica. Scientists determined the cause to be ozone-depleting substances—long-lived artificial halogen compounds. Although the ozone-destroying effects of these substances are now widely understood, there has been little research into their broader climate impacts.
2. A study published today in Nature Climate Change by researchers at Columbia University examines the greenhouse warming effects of ozone-depleting substances and finds that they caused about a third of all global warming from 1955 to 2005, and half of Arctic warming and sea ice loss during that period. They thus acted as a strong supplement to carbon dioxide, the most pervasive greenhouse gas; their effects have since started to fade, as they are no longer produced and slowly dissolve. Ozone-depleting substances, or ODS, were developed in the 1920s and ’30s and became popularly used as refrigerants, solvents and propellants. They are entirely manmade, and so did not exist in the atmosphere before this time. In the 1980s a hole in Earth’s stratospheric ozone layer, which filters much of the harmful ultraviolet radiation from the sun, was discovered over Antarctica. Scientists quickly attributed it to ODS.
3. The world sprang into action, finalizing a global agreement to phase out ODS. The Montreal Protocol, as it is called, was signed in 1987 and entered into force in 1989. Due to the swift international reaction, atmospheric concentrations of most ODS peaked in the late 20th century and have been declining since. However, for at least 50 years, the climate impacts of ODS were extensive, as the new study reveals. Scientists at Columbia’s School of Engineering and Applied Science and the Lamont-Doherty Earth Observatory used climate models to understand the effects of ODS on Arctic climate. “We showed that ODS have affected the Arctic climate in a substantial way,” said Lamont-Doherty researcher Michael Previdi. The scientists reached their conclusion using two very different climate models that are widely employed by the scientific community, both developed at the U.S. National Center for Atmospheric Research. The results highlight the importance of the Montreal Protocol, which has been signed by nearly 200 countries, say the authors. “Climate mitigation is in action as we speak because these substances are decreasing in the atmosphere, thanks to the Montreal Protocol,” said Lorenzo Polvani, lead author of the study and a professor in Columbia’s Department of Applied Physics and Applied Mathematics. “In the coming decades, they will contribute less and less to global warming. It’s a good-news story.”
4. The Montreal Protocol, an international agreement signed in 1987 to stop chlorofluorocarbons (CFCs) destroying the ozone layer, now appears to be the first international treaty to successfully slow the rate of global warming. New research published today in Environmental Research Letters has revealed that thanks to the Protocol, today’s global temperatures are considerably lower. And by mid-century the Earth will be – on average – at least 1°C cooler than it would have been without the agreement. Mitigation is even greater in regions such as the Arctic, where the avoided warming will be as much as 3°C – 4°C. “By mass CFCs are thousands of times more potent a greenhouse gas compared to CO2, so the Montreal Protocol not only saved the ozone layer but it also mitigated a substantial fraction of global warming,” said lead author of the paper Rishav Goyal. “
5. Remarkably, the Protocol has had a far greater impact on global warming than the Kyoto Agreement, which was specifically designed to reduce greenhouse gases. Action taken as part of the Kyoto Agreement will only reduce temperatures by 0.12°C by the middle of the century – compared to a full 1°C of mitigation from the Montreal Protocol.” The findings were made inadvertently when the team set out to quantify how the Montreal Protocol had affected atmospheric circulation around Antarctica. To get their results, the researchers modelled global climate under two scenarios of atmospheric chemistry – one with, and one without the Montreal Protocol being enacted. They then extended these simulations into the future using conservative estimates for unmitigated CFC emissions – set to 3% growth per annum, much less than the observed CFC growth rates at the time of establishment of the Montreal Protocol. Their results therefore likely underestimate the actual impact of the international treaty to reduce CFCs.
6. The success of the Montreal Protocol in mitigating climate change is even more striking when focusing on regional domains. For example, warming of between 0.5°C – 1°C has already been avoided over North America, Africa and Eurasia. By midcentury avoided warming in some of these areas will be 1.5°C – 2°C and over the Arctic avoided warming will be as much as 3°C – 4°C.
7. The researchers also found an amount of avoided ice melt due to the Protocol, with the extent of sea ice around the Arctic during summer around 25% greater today than it would have been without any reduction in CFC emissions. The avoided warming over Greenland also suggests that the observed accelerating ice sheet melt there and the associated sea level rise has also been reduced by the Protocol.  “Without any fanfare the Montreal Protocol has been mitigating global warming impacts for more than three decades, surpassing some treaties that were specifically aimed to ameliorate climate change impacts,” said co author Dr Martin Jucker.  Looking ahead, co-author Prof Matthew England said,
8. The success of the Montreal Protocol demonstrates superbly that international treaties to limit greenhouse gas emissions really do work; they can impact our climate in very favorable ways, and they can help us avoid dangerous levels of climate change.  “Montreal sorted out CFC’s, the next big target has to be zeroing out our emissions of carbon dioxide.”

 

 

PART-2 CRITICAL COMMENTARY

1. AGW climate change is a theory about the role of the Industrial Revolution in bringing about the end of the Little Ice Age and and the initiation of the current warming period by way of the combustion of fossil fuels such that the current warming trend is explained in terms of the the fossil fuel emissions of the industrial economy with the reference temperature and atmospheric CO2 concentration described as “pre-industrial”. The “pre-industrial” reference point is currently marked by James Hansen and by NASA as 1950 wherein we find the AGW described as “It started in 1950 because from then the relationship between CO2 and temperature we see in the climate models closely matches the observational data”. The claimed role for CFCs in the period 1955-2005 is inconsistent with the findings by NASA and by James Hansen.
2. The claim that the the faster warming of the Arctic because of the GHG effect of ozone depleting substances is causing faster sea ice melt is inconsistent with the finding reported in a related post that the data do not support a causal relationship between AGW warming and year to year changes in Arctic sea ice [LINK] .
3. Stratospheric ozone also causes warming such that ozone losses caused by ozone depleting substances would have a cooling effect on the Earth’s surface ([LINK] ). Therefore, the warming effect of ozone depleting substances should be computed net of the ozone depletion cooling they cause.
4. Also the choice of the study period as 1955-2005 is curious. Of course 1971 falls somewhere in the middle here and that is when Lovelock found CFCs in the atmosphere and also 1989 is in there somewhere and that is when the Montreal Protocol went into effect and so perhaps by 2005, the CFCs were gone and we returned to the old fossil fuel theory. Yet, the essential nature of CFCs noted by Lovelock and also by Rowland Molina is that it is inert and that it can hang around in the atmosphere for 150 years. This property of CFCs makes it difficult to understand why the CFC warming effect ended in 2005. Of course, in 1989 we stopped making them but their gradual decline given their their inert property would take much longer.
5. Yet another aspect of the ozone to climate connection with the success of anti CFC activism perhaps serving as an encouraging note for continued anti fossil fuel activism, is that empirical evidence of anthropogenic ozone depletion was presented in only one study that being Farman etal 1985 using data only from the South Pole and over a very short interval of time. The ozone depletion noted in that study is not found in long term trends of latitudinally weighted global mean total column ozone as shown in a related post  [LINK] .
6. A key aspect of these findings is the strong support it provides for the Montreal Protocol as an effective international agreement that not only ended the ozone depletion crisis but also moderated climate change by reducing the contribution of ozone depleting substances. This glorious assessment of the Montreal Protocol is stated as “The success of the Montreal Protocol demonstrates superbly that international treaties to limit greenhouse gas emissions really do work; they can impact our climate in very favorable ways, and they can help us avoid dangerous levels of climate change“.  
7. The insertion of this otherwise irrelevant statement into an investigation of warming anomalies in the period 1955-2005 may be the key to understanding this particular line of research and its odd findings. On the eve of COP26, and in the heels of 25 COP failures, climate activists may be giving up hope of the UN’s COP effort and its ability to put together a binding and effective international agreement for an overhaul of the world’s energy infrastructure away from fossil fuels. It is also noted that the study was based entirely on climate models.
8. In that context, the finding of the research on the role of CFCs in global warming that leads to the conclusion of a glorious UN success of the Montreal Protocol in putting together a binding and effective international agreement that saved the ozone and even cooled the planet, is best understood as the needed encouragement and positive outlook for the upcoming COP26.