COST 356
Towards the definition of a measurable environmentally sustainable transport
Final Conference
Greenhouse effect Indicators
Ménouèr Boughedaoui
University of Blida, Faculty of Engineering, Blida, Algeria
Paris, March 15, 2010
The greenhouse gas effect
1) Solar radiation
5
2
2) Reflected back to space
3) Absorbed by atmosphere
6
1
4) IR radiations emitted from
Earth
5) IR escaped
through atmosphere
4
3
6) Absorbed & re-emitted by
GHG molecules
The greenhouse gas effect
• Changes in GHGs concentrations affect
the absorption, scattering and emission of
radiation within the atmosphere and at the
Earth’s surface.
• Atmospheric concentrations of GHGs
increase when emissions are larger than
removal processes.
Cause-effect chain
Emissions
Region A
Emissions
Region B
Emissions
Region C
Emissions
Region D
Driver
Pressure
State
Concentrations
Impact in
Region A
Driver
Radiative forcing
Impact
Global average
temperature
change
Impact
Impact in
Region B
Impact in
Region C
Impact in
Region D
Impact
Greenhouse effect indicators
- Radiative Forcing: RF, RFI
- Global Warming Potential: GWP
- Global Temperature Change
Potential: GTP
- Carbon Equivalent Warming
Number: CEWN
- Impact on health
Radiative forcing definition
• Radiative forcing is a measure of the
influence a factor has in altering the
balance of incoming and outgoing energy
in the Earth-atmosphere system.
• Radiative forcing values are for changes
relative to preindustrial conditions defined
at 1750 and are expressed in watts per
square metre (W/m2)
UNFCCC need
• The approach adopted in the UNFCCC
and made operational in the Kyoto
Protocol is a multi-gas abatement strategy.
• Formulation of targets requires a metric
whereby emissions of different gases with
different atmospheric lifetimes and
different radiative properties can be
compared and weighted.
Global Warming Potential
• GWPs provide a metric for comparing the
climatic impact of different greenhouse gases.
T
 RF (t) dt
g
GWPg (T) 
0
T
 RF
CO 2
0
(t) dt
Radiative forcing
• RF which gives the change in radiative
budget of the atmopshere system
following a perturbation
• GWP compares the integration of the RF
of a pulse of emission of a GHG for
specific time horizon
CO2-equivalents
Greenhouse Gases and Global Warming
Gas
Preindustrial
Levels
Current
Levels
Increase since
1750
Global warming
potential (GWP)
(over 100 yrs)
Greenhouse
Radiative Forcing
(W/m2)
Carbon Dioxide
280 ppm
387 ppm
104 ppm
1
1.46
Methane
700 ppb
1,745 ppb
1,045 ppb
25
0.48
Nitrous oxide
270 ppb
314 ppb
44 ppb
298
0.15
CFC-12
0
533 ppt
533 ppt
>2000
0.17
Criticisms of GWPs
• The impacts of two equal GWP-weighted
emissions are equal only in terms of
integrated radiative forcing over the
chosen time horizon and not in terms of
actual temperature change along the path
or at the end of the time horizon.
• The application of integrated radiative
forcing may overestimate the effect of
short-lived species if the goal of climate
policies is to limit long-term temperature
increase.
Radiative Forcing Index
• Radiative Forcing Index (RFI) is defined as
the ratio of total radiative forcing to that
from CO2 emissions alone.
• Total radiative forcing induced by aircraft is
the sum of all forcings, including direct
changes in concentration (CO2, soot) and
indirect atmospheric responses (CH4, O3,
sulphate).
Radiative Forcing Index
• The RFI is designed to compare different
sectors with respect to their impact on
climate including their effects through nonCO2-gases.
• The RFI allows a direct comparison of
different sectors of fossil fuel use with
respect to their total radiative impacts on
the climate system (a comparison between
road transport and aviation).
Global temperature potential
T
GTP (t) 
T
TH
g
H
g
H
r
Comparison of transport modes
(Berntsen and Fuglestvedt, 2008)
Carbon Equivalent Warming Number
CEWN x 
CEWN x 
ACEWN xg
ACEWN x CO 2


t xg
0
t xCO 2
0
Ag RFt dt'
ACO 2 RFt CO 2 dt'
GTP & CEWN
• The GTP corresponds to a value after a
given period of time has elapsed
• The CEWN corresponds to an integrated
value until a given removal rate has been
reached
Greenhouse effect impact on health Indicator
GWPg  Dref
Dg 
GWPref
Dg: damage due to the unit emission of the pollutant g
(number of human life years when the health is affected)
Using the Fund model for three gases: CH4, CO2, N2O

Conclusions 1/2
• Metrics based on goals to be met
(UNFCCC & KP)
• GWP is an important tool for the
implementation of the UNFCCC and the
KP for a basket of the GHG (six gases)
• GWP is mainly from a natural science
perspective (social and economical)
• Temperature change in a cost effective
regime
Conclusions 2/2
• GWP and Dp are quite well adapted to
measure the impact of a policy action, but
only when these actions impact the
greenhouse gas emissions
• GTPp can be used for a pulse emission
change to estimate impact on temperature
for short-lived species.
• CEWN is less adapted to measure the
action of a policy.