All of this has contributed to aircraft operations that today can be 70% more efficient than in the 1970s.

In 2004, ICAO adopted three major environmental goals, to:

1. limit or reduce the number of people affected by significant aircraft noise;
    
2. limit or reduce the impact of aviation emissions on local air quality; and
    
3. limit or reduce the impact of aviation greenhouse gas emissions on the global climate.

The ICAO Council also adopted six Strategic Objectives, with high priority given to environmental protection, while the new Business Plan asserts the Organization's status as the leading international organization pursuing unified and coordinated measures to reduce civil aviation's impact on the environment.

The ultimate objective of the United Nations Framework Convention on Climate Change (UNFCCC) is to achieve stabilization of greenhouses gas concentrations in atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.

The Kyoto Protocol which was adopted by the Conference of the Parties to the UNFCCC in December 1997 entered into force in 16 February 2005, calls for developed countries (Annex I parties) to pursue limitation or reduction of greenhouses gases from "aviation bunker fuels" working through ICAO (Article 2.2 of the Protocol).

The Kyoto Protocol treats international and domestic emissions from the aviation sector differently in that developed countries are called on to pursue the limitation or reduction of greenhouses gases from international aviation working through ICAO (Article 2.2 of the Protocol), while domestic aviation emissions are included in their national targets, the potential advantages of harmonizing treatments of the two categories of emissions have been noted and it has been acknowledged that some Contracting States or groups of States are already taking action to design options for reducing emissions from domestic sectors including domestic aviation emissions.

The UNFCCC's Subsidiary Body for Scientific and Technological Advice has sought the assistance of ICAO on methodological issues related to the collection and reporting of greenhouses gas emissions and ICAO provides substantial information during SBSTA 24. Reliable information is vital to the development of mitigation and prevention policies, and ICAO cooperates with various United Nations bodies and research establishments on scientific reports that shed more light on the impact of aviation on the environment.

Aviation was the first sector to request the Intergovernmental Panel on Climate Change (IPCC) to prepare a full assessment of the impact of its activities. A comprehensive assessment of aviation's impact on the atmosphere is contained in the special report on Aviation and the Global Atmosphere, which was prepared at ICAO's request by the IPCC, in collaboration with the Scientific Assessment Panel to the Montreal Protocol on Substances that Deplete the Ozone Layer and was published in 1999.

The IPCC special report recognized that the effects of some types of aircraft emissions are well understood, it revealed that the effects of others are not, and identified a number of key areas of scientific uncertainty that limit the ability to project aviation impacts on climate and ozone. Since publication of the IPCC special report, further work has been undertaken on some of these key areas of scientific uncertainty, such as the influence on contrails and aerosols on cirrus clouds and the climate impact from oxides of nitrogen and methane. Therefore, ICAO had requested that the IPCC include an update of the main findings of the special report in its Fourth Assessment Report published in 2007.

Most of the activities of the Organization are undertaken by the ICAO Council's Committee on Aviation Environmental Protection - CAEP. The seventh meeting of the CAEP was held in February 2007 and achieved good progress in the noise and emissions areas. Deliverables presented at CAEP/7 included seven new ICAO documents, proposals for amendment or update of ICAO publications, and a series of reports to be made available through the ICAO website.

The main issues considered by in CAEP/7 (pdf) were related to the studies required in response to the 35th Session of the ICAO Assembly, in particular the evaluation of the evolution of aircraft noise and emissions over the years and future trends; and items related to market-based measures to reduce emissions, such as local air quality charges and aviation emissions trading.

Much effort is being channelled to the modelling activities and in the better understanding of the interdependencies of actions to alleviate noise and emissions. All the good work in CAEP and the information accrued from the scientific advances in the understanding of aviation impacts on the environment will be brought to the attention of the next ICAO Assembly. Sound information is paramount for defining the appropriate policies for the aviation sector in this area.

The 36th Assembly in September 2007 emphasized the importance of ICAO taking a leadership role on all civil aviation matters related to the environment and we have to maintain the initiative in developing policy guidance on these matters, and not leave such initiatives to other organizations.

Although all ICAO member States agree that we need to ensure that environmental considerations are duly taken into account in ICAO's work there are different views on the urgency to address such matters and the extent to which they would be willing to take action. That is more evident in the matters related to market-based measures to reduce emissions.

ICAO held a Colloquium on Aviation Emissions in May 2007 to enhance the level of information available to States in this area and help pave the way for discussions in the 36th Session of the Assembly. ICAO issued its first Environmental Report in September 2007.

It is very important that States be engaged in the dialogue on possible future actions to address noise and emissions from aviation and that they be open to cooperation in these fields. ICAO encourages the dialogue between States and groups of States in these areas and ICAO will be ready to facilitate the wider dialogue to arrive in a consensual path forward to address the impact of aviation on the environment as the only means to achieve sustainable aviation.

ICAO activities on aviation emissions are part of the overall UN initiative of taking action on climate change.