This publication may be reproduced in whole or in part and in any form for educational or non-profit services without special permission from the copyright holder, provided acknowledgement of the source is made. UNEP would appreciate receiving a copy of any publication that uses this publication as a source.

Firn-air and ambient air measurements of CHF₃ (HFC23) from three excursions to Antarctica between 2001 and 2009 are used to construct a consistent Southern Hemisphere (SH) atmospheric history. The results show atmospheric mixing ratios of HFC-23 continuing to increase through 2008. Mean global emissions derived from this data for 2006 – 2008 are 13.5 ± 2 Gg/yr (200 ± 30 10¹² gCO₂- equivalent/yr, or MtCO2-eq./yr), 50% higher than the 8.7 ± 1 Gg/yr (130 ± 15 MtCO₂-eq./yr) derived for the 1990s. 

By comparing the ozone depletion potential–weighted anthropogenic emissions of N2O with those of other ozone-depleting substances, we show that N2O emission currently is the single most important ozone-depleting emission and is expected to remain the largest throughout the 21st century. N2O is unregulated by the Montreal Protocol. Limiting future N2O emissions would enhance the recovery of the ozone layer from its depleted state and would also reduce the anthropogenic forcing of the climate system, representing a win-win for both ozone and climate.

The 
following
 supplementary
 material
 provides
 additional
 details
 about
 our
 ozone
 depletion
potential,
 ODP, calculations,
 factors
 affecting
 the
 ODP 
of
 N₂O,
 uncertainties
 unique
 to 
the
 calculation
 of
 the
 ODP
 of
 N₂O,
 our
method
 of
 inferring 
N₂O
 emissions,
 and
 a
comparison
 of 
the
 contributions
 of
 the
 sectoral 
N₂O 
emissions
 with
 the
  emissions
 of
 methyl
 bromide.

The consumption and emissions of hydrofluorocarbons (HFCs) are projected to increase substantially in the coming decades in response to regulation of ozone depleting gases under the Montreal Protocol. The projected increases result primarily from sustained growth in demand for refrigeration, air-conditioning (AC) and insulating foam products in developing countries assuming no new regulation of HFC consumption or emissions. New HFC scenarios are presented based on current hydrochlorofluorocarbon (HCFC) consumption in leading applications, patterns of replacements of HCFCs by HFCs in developed countries, and gross domestic product (GDP) growth.

This edition comes at a time when further steps taken by the Parties to develop interlinkages with other multilateral environmental agreements are coming to fruition.

The Montreal Protocol has reduced the global consumption of chlorofluorocarbons (CFCs) by more than 95% from its peak value. CFCs are principal ozone depleting substances (ODSs). As a result, the consumption of HCFCs as substitute compounds has increased. In developing countries the increase is 20% yr-1 (in agreement with new observations).

This edition contains the full text of the Vienna Convention for the Protection of the Ozone Layer (1985) in Section 1. Section 2 updates the text of the decisions of the Conferences of the Parties by incorporating the decisions adopted at the Eighth Conference of the Parties in Doha, Qatar, in November 2008. The decisions are presented in sub-sections relating to each article of the Convention.

The Handbook is published shortly after the Protocol, along with the Vienna Convention, achieved universal participation, by 196 Parties, on 16 September 2009 – the first treaties of any kind in the history of the United Nations system to achieve that aspiration. The universal ratification of the Vienna Convention and the Montreal Protocol is the culmination of more than twenty-two years of efforts by the international community to ensure that the ozone protection treaties achieved global support and implementation.