Introduction to Greenhouse Gas Emissions from Aviation

There are four main ways that aviation emissions affect climate, each of which is described in more detail:

  1. Plane landingDirect emissions of Greenhouse Gases (GHGs): notably carbon dioxide (CO2) and water vapor (H2O)
  2. Indirect impacts on GHGs: non-GHGs or weak GHGs such as nitrogen oxides (NOx) catalyze changes in concentrations of other GHGs such as ozone (O3) and methane (CH4)
  3. Emissions of aerosols: emissions of particulates that have cooling or warming effects such as sulfates and soot
  4. Formation of contrails and cirrus clouds

These emissions occur in the troposphere and lower stratosphere. The troposphere is the lowest part of Earth's atmosphere and its height extends to altitudes between 8 and 15km. The stratosphere lies between the troposphere and the mesosphere. It starts at an altitude of 8 to 15km and extends to 50 km.

Summary of Climatic Response to Aircraft Emissions:

 

CO2

NOx Ozone increase

NOx Methanedecrease

NOx Ozone decrease

Aerosols (particulates)

Contrails and Cirrus Clouds

Mean temperature response

warming

warming

cooling

cooling

warming (soot) and cooling (sulfates)

Net warming

Duration on the order of

centuries

weeks to months

decade

decade

days to weeks

contrails: hours

aviation-induced cirrus: hours - days

Spatial distribution

global

continental to global

continental to global

continental to global

soot:
local to global

sulfates: continental to global

local to continental

Scientific understanding

(Scale: good - fair - poor)

good

fair

fair

fair

fair

poor