Guest essay by Eric Worrall
According to a new study, the Montreal protocol is protecting the ability of plants to absorb CO2, preventing an 0.8C surge in global warming.
Scientists reveal how landmark CFC ban gave planet fighting chance against global warming
18 August 2021 16:01
Without the global CFC ban we would already be facing the reality of a ‘scorched earth’, according to researchers measuring the impact of the Montreal Protocol.
Their new evidence reveals the planet’s critical ability to absorb carbon from the atmosphere could have been massively degraded sending global temperatures soaring if we still used ozone-destroying chemicals such as CFCs.
New modelling by the international team of scientists from the UK, USA and New Zealand, published today in Nature, paints a dramatic vision of a scorched planet Earth without the Montreal Protocol, what they call the “World Avoided”. This study draws a new stark link between two major environmental concerns – the hole in the ozone layer and global warming.
Their findings, outlined in the paper ‘The Montreal Protocol protects the terrestrial carbon sink’, show that banning CFCs has protected the climate in two ways – curbing their greenhouse effect and, by protecting the ozone layer, shielding plants from damaging increases in ultraviolet radiation (UV). Critically, this has protected plant’s ability to soak up and lock in carbon dioxide from the atmosphere and so prevented a further acceleration of climate change.
Overall, by the end of this century without the Montreal Protocol CFC ban:
· There would have been 580 billion tonnes less carbon stored in forests, other vegetation and soils.
· There would be an additional 165-215 parts per million of CO2 in the atmosphere, depending on the future scenario of fossil fuel emissions. Compared to today’s 420 parts per million CO2, this is an additional 40-50%.
· The huge amount of additional CO2 would have contributed to an additional 0.8°C of warming through its greenhouse effect.
The abstract of the study;
The Montreal Protocol protects the terrestrial carbon sink
The control of the production of ozone-depleting substances through the Montreal Protocol means that the stratospheric ozone layer is recovering1 and that consequent increases in harmful surface ultraviolet radiation are being avoided2,3. The Montreal Protocol has co-benefits for climate change mitigation, because ozone-depleting substances are potent greenhouse gases4,5,6,7. The avoided ultraviolet radiation and climate change also have co-benefits for plants and their capacity to store carbon through photosynthesis8, but this has not previously been investigated. Here, using a modelling framework that couples ozone depletion, climate change, damage to plants by ultraviolet radiation and the carbon cycle, we explore the benefits of avoided increases in ultraviolet radiation and changes in climate on the terrestrial biosphere and its capacity as a carbon sink. Considering a range of strengths for the effect of ultraviolet radiation on plant growth8,9,10,11,12, we estimate that there could have been 325–690 billion tonnes less carbon held in plants and soils by the end of this century (2080–2099) without the Montreal Protocol (as compared to climate projections with controls on ozone-depleting substances). This change could have resulted in an additional 115–235 parts per million of atmospheric carbon dioxide, which might have led to additional warming of global-mean surface temperature by 0.50–1.0 degrees. Our findings suggest that the Montreal Protocol may also be helping to mitigate climate change through avoided decreases in the land carbon sink.Read more: https://www.nature.com/articles/s41586-021-03737-3
Obviously there is not much wheat production in Antarctica, so the top of the page is a historic graph of Australian wheat production. I personally cannot see obvious evidence of significant UV damage to production during the period when the southern ozone hole was at its greatest extent in the 1990s.