No. 927 - Preserve the ozone layer, protect the global climate system

No. 927 - Preserve the ozone layer, protect the global climate system



16 September 2011
Press Release Number:

For use of the information media
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New WMO Bulletin Says Antarctic Ozone Hole is currently 24 million km2

Geneva, 16 September 2011 (WMO) – This year’s International Day for the Preservation of the Ozone Layer is meant to serve as a rallying call to accelerate the phase-out of chemicals which destroy the Earth’s fragile shield and which are also powerful greenhouse gases.

“HCFC phase-out: a unique opportunity” is the theme for the celebration, marking the anniversary of the signature of an agreement known as the Montreal Protocol. This agreement has been very successful in reversing the destruction of the ozone layer, which protects us from the sun’s harmful ultraviolet rays.

Many ozone-destroying chemicals such as chlorofluorocarbons (CFCs), once present in products such as refrigerators and spray cans, have been phased out under the Montreal Protocol. However, demand for replacement substances including hydrochlorofluorcarbons (HCFCs) has increased, prompting an agreement in 2007 to accelerate the phase-out of HCFCs, which are commonly used in air conditioning.

“HCFCs are both ozone-depleting substances and powerful greenhouse gases: the most commonly used HCFC is nearly 2,000 times more potent than carbon dioxide in adding to global warming,” said U.N. Secretary-General Ban Ki-moon in a message.

“By agreeing to speed up the phase-out of HCFCs, Parties to the Montreal Protocol increased their already-substantial contributions to protecting the global climate system,” he said.

A joint assessment published last year by the World Meteorological Organization (WMO) and United Nations Environment Programme (UNEP) predicted that total emissions of HCFCs would begin to decline in the coming decade due to the measures agreed under the Montreal Protocol. In the interim, emissions continued to rise. The most abundant one, HCFC-22, increased more than 50% faster in 2007-2008 than in 2003-2004, it said.

That assessment also shed new understanding on the complex linkages between ozone and climate change.

“Changes in climate, mainly due to emissions of long-lived greenhouse gases, are expected to have an increasing influence on stratospheric ozone in the coming decades,” said WMO Secretary-General Michel Jarraud. “At the same time, the impact of the Antarctic ozone hole on the Earth’s surface climate is becoming evident, in particular on surface temperature and wind patterns,” he said.

“Human activities will continue to change the composition of the atmosphere. WMO’s Global Atmosphere Watch programme will therefore continue its crucial monitoring, research and assessment activities to provide scientific data needed to understand and ultimately predict environmental changes,” said Mr Jarraud.

“WMO’s latest Antarctic Ozone Bulletin shows that the current ozone hole is about 24 million km2 – proof that we cannot afford to be complacent.”

Antarctic Ozone Bulletin

In its Antarctic Ozone Bulletin published today (16 September), WMO reported that the ozone hole increased rapidly during the first two weeks of September from less than 10 million km2 to approximately 24 million km2. This is based on observations from the ground, from weather balloons and from satellites together with meteorological data.

This means that the 2011 ozone hole is about average in size in comparison to the ozone holes of the last decade. It is already significantly larger than in 2010, but smaller than in 2006, when there was a record large ozone hole.

The ozone hole typically reaches its maximum surface area during the second half of September and the maximum depth during the first half of October.

The Antarctic ozone hole is an annually recurring winter/spring phenomenon due to the existence of extremely low temperatures in the stratosphere and the presence of ozone-depleting substances.

Despite the success of the Montreal Protocol in cutting production and consumption of these chemicals, they have a long atmospheric lifetime and it will take several decades before their concentrations are back to pre-1980 levels. The amount of ozone depleting gases in the Antarctic stratosphere reached a maximum around year 2000 and is now decreasing at a rate of about 1% per year.

Over the past decade, global ozone and ozone in the Arctic and Antarctic regions is no longer decreasing but is not yet started to recover either. The ozone layer outside the Polar regions is projected to recover to its pre-1980 levels some time before the middle of this century. In contrast, the ozone layer over the Antarctic is expected to recover much later.

Progress in atmospheric monitoring and research has increased understanding of the dual function of ozone-depleting substances as greenhouse gases.

The 2010 WMO/UNEP joint assessment projected that the accelerated HCFC phase-out would reduce greenhouse gas emissions by about 0.5 Gigatonnes of carbon dioxide (CO2)-equivalent per year averaged over the period 2011 through 2050. In comparison, global emissions of CO2 linked to human activities were greater than 30 Gigatonnes per year in 2008.

“The level of climate benefits that can be achieved depends on what chemicals and technologies are chosen to replace HCFCs. The phase-out thus presents countries and industries with a unique opportunity to acquire cutting-edge technologies that not only eliminate ozone-depleting compounds but do so in a way that lowers energy costs and maximizes climate benefits,” said U.N. Secretary-General Ban Ki-moon.

Notes to Editors:

The International Day for the Preservation of the Ozone Layer 16 September marks the signature date, in 1987, of the Montreal Protocol on Substances that Deplete the Ozone Layer. Full details, including the UN Secretary-General’s message, are at

More information on WMO’s Global Atmosphere Watch Programme’s research on ozone, including the Antarctic Ozone Bulletin is at:

WMO will publish its annual Greenhouse Gas Bulletin in November.

World Meteorological Organization is the United Nations System’s
authoritative voice on Weather, Climate and Water

For more information, please contact the World Meteorological Organization:

Clare Nullis, Media Officer, Tel: +41 (0)22 730 8478; email:


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