Measuring Impact:
Air Travel Carbon
Emission
Calculations
March 2024

What is the objectiveof this document?
This guide offers American Express Global Business Travel (Amex GBT)
clients an overview of the carbon emission frameworks supported byAmex GBT and CHOOOSE. The relationship between business travel
and climate change can’t be overstated. Read on to learn the industryrecognized frameworks used to calculate the carbon footprint of flights
and considerations when determining which framework to use incorporate sustainability benchmarking and reporting.

Table of contents
Introduction4Overview of supported flight emissions methodologies 6

Selecting a methodology

8Summary table: Emission calculation parameters

8Glossary and definitions

10This document is intended as a guide across those decision points.

Who is CHOOOSE?
CHOOOSE is a leader in technology-based climate action, building digital
tools so that everyone anywhere can easily integrate climate action into
everyday life and business. Through flexible integrations, customerfriendly interfaces, automated carbon measurements, and a connectedmarketplace of climate solutions, CHOOOSE delivers a complete platformthat enables its partners to build and manage high-impact climate
programs. Learn more at www.chooose.today.

2Air emission calculation frameworks for American Express Global Business Travel

Air emission calculation frameworks for American Express Global Business Travel3

Introduction
Climate change refers to long-term shifts in global temperatures and weather patterns.
In modern times, these shifts are caused by the release of greenhouse gases (GHGs)
into the atmosphere by human activity.
The effects of climate change are dramatic and farreaching. These consequences demand coordinated,urgent action from governments, businesses, andordinary people to reduce further harm.

Adverseimpacts fromhuman-causedchange will
intensify

Water scarcity and food production

Health and wellbeing

this document reflect industry-accepted standards
to estimate carbon emissions produced by aircraft,
per passenger. Air travel is the single largestemitting activity associated with business travel,
accounting for over 90% of a trip’s emissions,according to Amex GBT’s proprietary analysis using
2019 client benchmarking data.

Types of carbon emissions

Cities, settlements and infrastructure

92%Ecosystem structure, species range shifts and changes in timing

Sixth Assessment Report | Synthesis Report

Source: Intergovernmental Panel on Climate Change, Synthesis
Report Presentation, March 20, 2023.

Business travel emissions contribute to this andhave been identified in the Greenhouse Gas Protocol
as a key accounting area. Understanding the impactof travel is an important step towards reducing – andultimately eliminating – these emissions.

C02Emissions

6%

Types of carbon emissions methodologies
The GHG Protocol Scope 3.6 identifies three basic approaches to calculating GHG emissions, often referred
to as carbon emissions and normalized in reporting to CO2e (equivalents). Most calculation methods fall
into one of the categories below. The GHG Protocol recommends fuel-based methodologies are used whenpossible.

Fuel-based

Distance-based

Spend-based

Based on the amount of fuelconsumed during businesstravel and applying theappropriate emission factor
for that fuel.

Based on the distance andmode of business trips, thenapplying the appropriate
emission factor for the mode
used.

Based on the amount ofmoney spent on each modeof business travel transportand applying secondary(environmentally extended
input-output [EEIO])
emission factors.

2%
1%

The carbon calculation methodologies presented inQuality emissions data, derived
from trusted methodologies, iscrucial to taking action.

Decision tree for selecting a calculation method for emissions from business travel
Does business travel
contribute significantly toscope 3 emissions (based onscreening) or is engagementwith travel providers
otherwise relevant to thebusiness goals?

Is data available on the types
and quantities/cost of fuelsconsumed during travel?

Is data available on distancetraveled?

Use the distancebased method
Is data available on theamount of money spent on
travel providers?

Source: Greenhouse Gas Protocol, Technical Guidance for Calculating Scope 3 Emissions. Figure 6.1

4Air emission calculation frameworks for American Express Global Business Travel

Use the fuelbased method

Air emission calculation frameworks for American Express Global Business Travel

Use the spendbased method5Overview of supported flightemissions methodologies
A few methods have emerged as prominent in the travel industry to estimate perpassenger emissions. The following are supported by the CHOOOSE/Amex GBT
integration and described within this document.

Fuel-based

Distance-basedInternational Air Transport
Association (IATA) Recommended
Practice (RP) 1726:

UK Department for Business, Energy,and Industrial Strategy (BEIS):

IATA is an aviation trade association
supporting the industry with a variety of global
standards. It developed RP 1726 together withmajor airlines and aircraft manufacturers. It
is often used by airlines to quantify their own
emissions.

International Civil Aviation
Organization (ICAO):ICAO is a specialized agency of the United
Nations focused on international aviation.

The UK government’s emission factors, whichwere initially published under the Department
for Environment Food and Rural Affairs(DEFRA).

French Agence de l’Environement et dela Maitrise de l’Energie (ADEME):
The French government’s emission factors
derive from work supporting commitments
made under the Kyoto Protocol.

US Environmental Protection
Agency (EPA):The US government’s emission factors.

For calendar year 2022, Amex GBT calculated
its own business travel footprint (Scope 3.6)
using UK BEIS inclusive of radiative forcing. In
the context of calculating sustainable aviationfuel (SAF), we calculate carbon emissions
on a well-to-wake full lifecycle basis (seesustainable.mit.edu/sustainablefuel/). In thecontext of influencing traveler behavior atpoint of sale, we endeavor to implement an
IATA fuel-based methodology in 2023 andbeyond.

Broadening the scope ofcalculations
UK BEIS and FR ADEME provide optional RFand WTT factors that can be included in the perpassenger carbon emission calculations. Applying
these factors will increase the emissions of a trip.

Radiative Forcing (RF)Radiative forcing is a parameter defined by theIntergovernmental Panel on Climate Change (IPCC)
that measures the influence a given climate factor
has on the amount of downward directed radiantenergy impacting Earth’s surface. Emissions froman aircraft in combination with other anthropogenic
sources modify the atmospheric composition, which
results in an increase in the global warming potential.
In simple terms, radiative forcing is associated withemissions released at higher altitudes and results ina higher global warming potential, meaning the earth
is receiving more incoming energy from sunlightthan it radiates to space. This net gain of energy willcause warming and is more impactful to climatechange effects.

Your air travel CO2 emissions may be multipliedby the RF factor to account for the higher global
warming potential from such emissions. The RF
factor is also sometimes referred to as the Radiative
Forcing Index. The exact RF impact depends on a few
factors during a flight, including altitude, weathercondition, flight path, etc.
There is not yet an industry-agreed-upon bestpractice on RF and not all methodologies provide anRF factor. If RF is used when estimating emissions,that decision should be clearly communicated.

Well to Tank (WTT)WTT estimates emissions associated with fuelproduction and distribution, excluding infrastructure
and manufacturing of equipment. It is part of themore comprehensive “well to wake” or “well to wing”(WTW) lifecycle view of emissions.

Well to Wake (WTW): Full emissions life cycle

Well to Tank (WTT):
Fuel production anddistribution

Tank to Wake (TTW):
combustion

Source: Sustainable Aviation Fuel Greenhouse Gas Emission Accounting and Insetting Guidelines,
MIT Center for Transportation and Logistics, 2021

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7

Selecting amethodology

Summary table:
Emission calculation parameters

Companies must make their own decision about
which methodology is most appropriate for their
purposes in accordance with their internal policies
and procedures and any applicable laws andregulations. Amex GBT does not recommend aparticular method over others.1 Within this context,
we suggest corporates consider how the data will beused. For example:

The following table provides a high-level overview of methodology inputs. This is a simplification of scientific and academic work and isintended to directionally inform decision-makers when considering which framework to use. The data used in calculations include factors
provided in the methodology guidance, associated reference tables, and CHOOOSE proprietary data, where needed.
Calculation
methodology

Influencing traveler choice at point of sale
Fuel burn-based methodologies such as IATAand ICAO provide higher precision than distancebased methodologies and offer travelers better
differentiation between flight operators at pointof sale.

Sustainability reporting year over year
Any calculation method can be used to benchmark
and manage a carbon footprint. However, switching
between methods will make communication andmanaging reduction targets more challenging.
Consider consistently applying your method ofchoice or rebaselining if you decide to change
methodologies.

Sustainable Aviation Fuel (SAF)

IATA RP 17261

Passenger load

Passenger vs.
cargo allocation

Fuel burnWell to Tank

Radiative
Forcing

Yes

Yes

Yes

Yes

Yes

N/A

N/A

For all routes found ina schedule database,
IATA CO2 Connect istime-based.

IATA narrow- andwide-body factors byeconomy, premium
economy, business, first

Computed using
schedule and aircraftdata

Per IATA, proportional
to passengers and their
checked baggage vs.
freight

Yes

Yes

Yes

Yes

Yes

N/A

N/A

ICAO economy andpremium factors

ICAO TSDPer ICAO, proportional
to passengers and their
checked baggage vs.
freight

ICAO fuel consumption
formula

N/A

N/A

Yes

N/A

Optional

Optional

Yes

FR ADEME

UK BEIS

Reporting requirements

US EPA8Cabin class

ICAO

Carbon accounting requires a full lifecycle analysis(i.e., well to tank + tank to wake = well to wake); both
UK BEIS and FR ADEME optionally add WTT, making
this possible.

There could be considerations related to compliancereporting by specific government organizations or
specific needs to use a specific methodology basedon current sustainability reporting program orvoluntary reporting scheme.

Distance

ADEME based on
aircraft seat anddistance brackets

ADEME assumes eachpassenger corresponds
to 100kg of freight

Yes

Yes

BEIS distancecategories: domestic,short-haul, long-haul;(international not used)

BEIS cabin classes byaverage passenger:
economy, premium
economy, business, first
class

Yes

N/A

N/A

N/A

N/A

Optional

Optional

N/A

N/A

N/A

N/A

N/A

EPA distance categories:
short-, medium-, longhaul

Notes: N/A – Not Applicable. The methodology does not include guidance that accounts for emissions relative to the given factor. For example, N/A for Passenger
vs. Cargo Allocation means that 100% of emissions are attributed to passengers. N/A for Cabin Class means all classes are treated the same.

Global Business Consulting (GBC) at Amex GBT is an experienced team of global travel strategists delivering 360º services
and a results-oriented approach to optimize your travel program. Contact GlobalBusinessConsulting@amexgbt.com for help
creating a travel program tailored to achieve your specific sustainability goals.

Air emission calculation frameworks for American Express Global Business Travel

Air emission calculation frameworks for American Express Global Business Travel

9

Glossary and definitions
ADEME

France Environment and Energy Management Agency.

BEIS

United Kingdom Department for Business, Energy & Industrial Strategy.
UK BEIS methodology was formerly published under UK Department forEnvironment Food and Rural Affairs (DEFRA).

Carbon footprint

The total GHG emissions caused by an individual, event, etc., typically expressedas kilograms or metric tons of CO2e. Understanding the carbon footprint offlight options can help travelers make lower-impact decisions.

CO2eCarbon dioxide equivalent (CO2e) is a measure used to compare the emissionsof various GHGs (such as CO2, CH4, NO2) by converting the warming potentialof other gases to the equivalent amount of CO2. The emission results of all
methodologies are reported in this unit of measurement.

EPA

United States Environmental Protection Agency.

Fuel burn

Quantity of fuel that is burned during a flight. Aircraft that burn less fuel are less
impactful to the environment.

GHG

Greenhouse gases trap heat in the atmosphere and contribute to globalwarming. Carbon dioxide, methane, and nitrous oxide are examples of GHGs.

IATA

International Air Transport Association: an aviation trade association supporting
the industry with a variety of global standards.

ICAO

International Civil Aviation Organization: a specialized agency of the United
Nations focused on international aviation.

IPCC

Intergovernmental Panel on Climate Change: established in 1988 by the World
Meteorological Organization and the United Nations Environment Program.

Passenger loadfactor

Measures how much of an aircraft’s passenger carrying capacity is used. Planes
that are filled to capacity are more efficient per person than planes with someempty seats.

Passenger vs.
cargo allocation

Measures the percentage of flight emissions that are attributed to passengers
and their luggage vs. cargo (freight, mail). Methodologies that consider thisfactor discount the per-passenger emissions to take cargo into account.

10Air emission calculation frameworks for American Express Global Business Travel

RF

Radiative forcing is a measure of the change in energy balance as a result of achange in a forcing agent (e.g., greenhouse gases) to affect the global energybalance and contribute to climate change. When emissions are released at
higher altitudes – as they are when flying – they result in higher global warming
potential than they would at ocean level (i.e., they produce greater impact on
Earth’s surface). In the context of air travel, the carbon footprint of travel can bemultiplied by an RF factor to account for this impact.

RP 1726

RP 1726 represents IATA’s latest recommended framework for calculating CO2
emissions per passenger.

TTWTank to wake (also known as “tank to wing”) refers to emissions produced by theburning of fuel associated to an activity, such as flight.

WTT

Well to tank refers to emissions produced “upstream” of the combustion engine.
Upstream typically refers to emissions related to the production, refinement, andtransportation of fossil fuels.

WTW

Well to wake (also known as “well to wing”): Includes a more complete
consideration from the production chain, but exclusive of infrastructure andmanufacturing of equipment. WTW can be further split into two parts: well-totank (WTT)/upstream emissions and tank-to-wake (TTW)/fuel burn emissions
associated to activity.

References:
1 CO2 Connect is IATA’s proprietary climate emission solution, based on its RP1726 methodology. CO2 Connect has factors that areapplied based on flight duration rather than distance. CO2 Connect uses IATA’s proprietary fuel burn factors derived from actual
airline-reported consumption data. Learn more on IATA’s FAQ website. IATA does not provide factors for radiative forcing or well to tank;however, these may be optionally applied by the user with appropriate notation.

GBT Travel Services UK Limited (GBT UK) and its authorized sublicensees (including Ovation Travel Group and Egencia) use certain
trademarks and service marks of American Express Company or its subsidiaries (American Express) in the “American Express Global
Business Travel” and “American Express GBT Meetings & Events” brands and in connection with its business for permitted uses only undera limited license from American Express (Licensed Marks). The Licensed Marks are trademarks or service marks of, and the property of,American Express. GBT UK is a subsidiary of Global Business Travel Group, Inc. (NYSE: GBTG). American Express holds a minority interestin GBTG, which operates as a separate company from American Express. © 2023 GBT Travel Services UK Limited.

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