April 01, 2020

Study: The Ozone Layer Is Repairing Itself, Affecting Wind Flows

This is a curious study.  Changes in the ozone layer may indeed be affecting wind flows but are those changes traceable to the Montreal protocol? The protocol entered into force on 1st January 1989.

The fact that the hole was at its largest extent in 2015 would indicate that the protocol had done nothing even by that stage. A quarter of a century is a long time to have an effect

I add the journal abstract to the article below.  Note that they attribute the ozone change to the year 2000.  So by even their reckoning that Montreal agreement is pretty laggard in having any effect


While most people’s focus remains directed at the coronavirus pandemic, some good news has emerged: a hole in our ozone layer is now in recovery.

The hole—located above Antarctica—is continuing to recover and bringing changes in atmospheric circulation as a result, according to New Scientist.

Many dangerous changes are being brought to a halt in the atmosphere of the Southern Hemisphere due to the ongoing recovery.

Ozone depletion began to bring air currents in the Southern Hemisphere further south in the 1980s. This caused a change in ocean currents and rainfall patterns.

Global News reported that the new changes suggest that a ban on producing ozone-depleting substances, called the 1987 Montreal Protocol, is now having a positive effect on the world.

On Wednesday, a research paper released in Science Daily showed that the ozone layer has started recovery due to changing wind patterns.

Antara Banerjee and her colleagues at the University of Colorado Boulder did the research and noted that the ozone layer in the Northern Hemisphere is on track to fully recover to its 1980s levels sometime in the 2030s.

They added that in the Southern Hemisphere should return to that state by the 2050s. The Antarctic hole is expected to take longer and is estimated to recover by the 2060s.

SOURCE 

A pause in Southern Hemisphere circulation trends due to the Montreal Protocol

Antara Banerjee et al.

Abstract

Observations show robust near-surface trends in Southern Hemisphere tropospheric circulation towards the end of the twentieth century, including a poleward shift in the mid-latitude jet1,2, a positive trend in the Southern Annular Mode1,3–6 and an expansion of the Hadley cell7,8. It has been established that these trends were driven by ozone depletion in the Antarctic stratosphere due to emissions of ozone-depleting substances9–11.

Here we show that these widely reported circulation trends paused, or slightly reversed, around the year 2000. Using a pattern-based detection and attribution analysis of atmospheric zonal wind, we show that the pause in circulation trends is forced by human activities, and has not occurred owing only to internal or natural variability of the climate system.

Furthermore, we demonstrate that stratospheric ozone recovery, resulting from the Montreal Protocol, is the key driver of the pause. Because pre-2000 circulation trends have affected precipitation, and potentially ocean circulation and salinity, we anticipate that a pause in these trends will have wider impacts on the Earth system. Signatures of the effects of the Montreal Protocol and the associated stratospheric ozone recovery might therefore manifest, or have already manifested, in other aspects of the Earth system

SOURCE 





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