Perhaps surprisingly to many, 2010 marks the 25th anniversary of the discovery of the hole in the ozone layer above Antarctic.
Even more extraordinarily perhaps, in the midst of so-called ‘climate-gate’, scientists are for the first time beginning to understand how the huge gape above Antarctica might actually be shielding the frozen continent from global warming.
As the furore continues across the globe as to whether global warming does or doesn’t exist, at the base of the world, scientists are in no doubt as to what is going on.
Experts have just this month (Dec 1) published an exhaustive review of the dynamic eco-system of Antarctica – and have come to the perhaps startling conclusion that the infamous hole might actually be ‘protecting’ the unique Antarctic environment, among a raft of other key findings.
The Antarctic Climate Change and the Environment (ACCE) is a major report collating all present knowledge on the past and possible future changes in the physical environment of Antarctica and the Southern Ocean.
Preparation of the report was led by the SCAR Antarctica and the Global Climate System (AGCS) groups with input from other major external groups and experts.
Key among the findings is the extent to which the huge ozone hole – well documented since 1985 – might actually be protecting the fragile frozen environment rather than aiding its destruction.
Scientists have also discovered an array of previously unknown but linked environmental effects are at play on the planet’s coldest landmass.
Dr. Colin Summerhayes, Executive Director of the Scientific Committee on Antarctic Research (SCAR) says:
“Antarctica is an unrivalled source of information about our planet.
“This review describes what we know now and illustrates how human activity is driving rapid climate change.
“By integrating this multidisciplinary evidence into a single source, we are helping scientists and policy makers understand the distinction between environmental changes linked to the Earth’s natural cycles, and those that are human induced.
“The work is particularly important because it puts Antarctic climate change into context and reveals the impact on the rest of the planet.”
Professor John Turner of British Antarctic Survey is the lead editor of the review.
“For me the most astonishing evidence is the way that one man-made environmental impact — the ozone hole — has shielded most of Antarctica from another — global warming. Understanding the complexities surrounding these issues is a challenge for scientists — and communicating these in a meaningful way to society and to policymakers is essential.
“There is no doubt that our world is changing and human activity is accelerating global change. This review is a major step forward in making sure that the latest and best evidence is available in one place.
“It sets the scene for future Antarctic Research and provides the knowledge that we all need to help us live with environmental change.
“This review draws together important information from different scientific disciplines (such as meteorology, glaciology and biology) and many aspects of the global climate system.”
Prof Turner adds:
“The ozone hole has delayed the impact of greenhouse gas increases on the climate of the continent.
“Consequently south polar winds (the polar vortex) have intensified and affected Antarctic weather patterns, while westerly winds over the Southern Ocean that surrounds Antarctica have increased.
“The upshot is the stronger winds have effectively isolated Antarctica from the warming elsewhere on the planet.
“As a result during the past 30 years, there has been little change in surface temperature over much of the vast Antarctic continent, although West Antarctica has warmed slightly.
“An important exception is the eastern coast of the Antarctic Peninsula, which has seen rapid summer warming. This warming is caused by stronger westerly winds bringing warm, wet air into the region from the ocean.”
While the ozone hole and global warming were thought to be crucially linked in past, scientists have been puzzling for years quite how exactly this was so.
It’s generally accepted that reductions of up to 70% in the ozone layer first observed and first reported in 1985 are continuing.
The hole is in the stratosphere, which has seen ozone levels historically drop to as low as 33% of their pre-1975 values.
It occurs during the Antarctic spring, from September to early December, as strong westerly winds start to circulate around the continent and create an atmospheric container.
Within this so-called polar vortex, over 50% of the lower stratospheric ozone is destroyed annually.
Since 1981, the United Nations Environment Programme has sponsored a series of reports on scientific assessment of ozone depletion.
Prof Turner says:
““The Montreal Protocol is an international agreement that has phased out production of CFCs, Halons, and some other organic chlorides and bromides, collectively referred to as Ozone Depleting Substances (ODSs).
“Because of its success, the amounts of ODSs in the stratosphere are now starting to decrease. However, there is as yet no convincing sign of any reduction in the size or depth of the ozone hole, although the sustained increases up the 1990s have not continued.
“Great advances have been made in recent years into our understanding of Antarctic climate and environmental change. We now know that the climate system of the high southern latitudes is very complex and that there is variability on a range of time scales.
“We also know that changes in the atmospheric and oceanic circulation around Antarctica, and the volume of the ice sheets, interact and influence climate at a global scale.
“Although a great deal of data is now available with which to investigate change – both in the past and over the next century, there are still major gaps in our knowledge and many areas where we require additional instrumental data gathering and model development.
“The CFCs that are responsible for the ozone hole have a long lifetime in the atmosphere and our best estimate is that it will be 2060-2070 before stratospheric ozone concentrations above the Antarctic recover to pre-ozone hole levels.”
The Scientific Committee on Antarctic Research (SCAR) is the main body dealing with the international co-ordination of scientific research in Antarctica and the Southern Ocean.
The British Antarctic Survey (BAS), a component of the Natural Environment Research Council, delivers world-leading interdisciplinary research in the Polar Regions. Its skilled science and support staff based in Cambridge, Antarctica and the Arctic.
Key findings of the report:
· Long-term monitoring reveals that the ozone hole has delayed the impact of greenhouse gas increases on Antarctica's climate.
· The largest ocean current on Earth (the Antarctic Circumpolar Current) has warmed faster than the global ocean as a whole.
· Rapid warming has been seen along the western Antarctic Peninsula, resulting in expansion of plant, animal and microbial communities in newly available land.
· The West Antarctic Ice Sheet has significantly thinned particularly around the Amundsen Sea Embayment as a result of warmer ocean temperatures.
· Since 1980 there has been a 10% increase in Antarctic sea ice extent, particularly in the Ross Sea region, as a result of the stronger winds around the continent (due to the ozone hole).
· Ice core research shows that atmospheric concentrations of CO2 are at higher levels than experienced in the last 800,000 years and are increasing at rates unlikely to have been seen in the (geologically) recent past.
· Over this century the ozone hole is expected to heal, allowing the full effects of greenhouse gas increases to be felt across the Antarctic.
· The predicted future warming of about 3°C across the continent is not enough to melt the main ice sheet and an increase in snowfall should offset sea level rise by a few centimetres.