Federal Aviation Administration

Aviation’s contribution to climate change

The direct impact of aviation on climate via the emission of green house gases is small relative to other anthropogenic sources. However, the potential impact of aviation on climate is unique because aviation associated sources occur at high altitude where other anthropogenic sources are absent.  But, there are large uncertainties in relating aviation emissions to changes in radiative forcing or surface temperature that must be addressed to inform appropriate action.  These uncertainties include the influence of contrails and particles on cirrus clouds, the role of oxides of nitrogen (NOx) in changing ozone and methane concentrations, and the atmospheric processing of water near the tropopause.  Also, the consequences associated with using radiative forcing versus surface temperature as a basis for measuring impact may introduce further complexities that will need to be addressed by the scientific community at-large. 

The Federal Aviation Administration (FAA) through the Partnership for Air Transportation Noise and Emissions Reduction (PARTNER) Center of Excellence and in collaboration with the National Aeronautics and Space Administration (NASA) is pursuing research to reduce uncertainties regarding the contribution of aviation to climate change to levels that enable appropriate action.  Uncertainties are particularly high concerning the contribution of aircraft-induced contrails.  PARTNER is pursuing research to evaluate the extent to which emissions from different aircraft/engines, and ambient relative humidity and temperature have a lasting impact on contrail properties, and if these dependencies are large enough to warrant improvements in existing models. The research will allow a better scientific understanding of the uncertainty associated with the use of these models to assess the impacts of contrails.

This research project could influence aircraft operational procedures and aircraft/engine technology development that could exceed the $500 million per year threshold definition for highly influential scientific disseminations.  The findings could also be controversial.  A work product on contrails should be available to initiate the peer review process in FY 2009.   The overall effort to reduce uncertainty in aviation’s contribution to climate change is a long-term effort, however, and other work products focusing on other emissions might be peer-reviewed in the future.

Highly influential scientific information

Influential scientific information

The Peer Review Plan is still being developed.  The preliminary plan includes the following elements:

(1) The peer review would occur in the second half of Fiscal Year 2009.

(2) This review would most likely be conducted by individual letters.  The PARTNER Center of Excellence, which operates independently of the FAA, will be charged with facilitating the peer review.

(3) The details of the plans for public comments are being refined.  There will be opportunities for public comment on the work product through symposia and public meetings. 

(4) All public comments will be made available to the peer reviewers

(5) We expect to have more than 10 Peer Reviewers.

(6) The peer reviewers should have expertise including, but not limited to, atmospheric chemistry, contrail dynamics and modeling of contrail scale processes, climate change, aircraft/ engine design, aircraft emissions, air traffic management, and aircraft operations.

(7) The plan for selecting the peer reviewers is still under development.  Reviewers will be designated by an outside organization (most likely PARTNER in collaboration with its Advisory Board).

(8) The plan to nominate peer reviewers is still being developed. Scientific and professional societies and the public could be asked to nominate peer reviewers.

Dr. Lourdes Maurice

E-mail:

Lourdes.Maurice@faa.gov

Phone:

(202) 493-4293