What Is A Carbon Baseline?
Updated: Oct 6
Starting your carbon reporting journey can feel like a big task, particularly when you are still working out what information your business has and where to begin.
Before you can understand whether your organisation's emissions are changing over time, you need a clear starting point. This is where a carbon baseline comes in.
A carbon baseline gives your business a reference point for comparing future greenhouse gas emissions. It can help you understand where your emissions currently come from, monitor changes between reporting periods and make more informed decisions about where reductions may be possible.
If you are beginning carbon reporting for the first time, you do not necessarily need perfect information before you start. What matters is being clear about what you have measured, where estimates have been used and how the quality of your data can improve over time.
In this guide, we'll explain what a carbon baseline is, what it can include, how to choose a carbon baseline year and what happens if your business or reporting approach changes later.
What Is A Carbon Baseline?
A carbon baseline is a reference measurement of your organisation's greenhouse gas emissions over a defined reporting period, which can then be used to compare emissions over time.
For example, a business might calculate its carbon footprint for 2026 and determine that the activities included within its reporting boundary produced 500 tonnes of CO₂e. If 2026 is selected as its baseline year, future results can be compared against that starting point.
This makes your baseline different from an individual carbon footprint calculation. A carbon footprint tells you what your emissions were for a particular reporting period, while a carbon footprint baseline gives you a reference against which future results can be compared.
The GHG Protocol Corporate Standard uses the term base year for a historical reference point against which current emissions can be compared.
You can think of your carbon baseline as the starting line. Before you can understand how far your emissions have moved, you need a consistent point to compare them against.
Why Is A Carbon Baseline Important?
A carbon baseline is important because it gives your business a consistent reference point for understanding how its emissions change over time.
One carbon footprint can show you what your emissions looked like during one reporting period, but it cannot tell you whether those emissions are increasing or decreasing without something to compare them against.
Establishing baseline emissions can help your business:
Understand where significant sources of emissions are coming from
Compare greenhouse gas emissions between reporting periods
Identify areas that may deserve further investigation
Inform appropriate carbon reduction targets
Monitor whether emissions are changing over time
Build a more consistent carbon reporting process
For example, if your baseline shows that business travel, purchased goods or energy use account for a significant part of your footprint, you can investigate those areas rather than assuming where reductions should be made.
How Do Businesses Create A Carbon Baseline?
Businesses create a carbon baseline by defining what they are measuring, choosing an appropriate reporting period, collecting relevant activity data and calculating the greenhouse gas emissions associated with those activities.
The information you need will depend on your organisation and the boundary of the footprint you are calculating, but your starting data might include:
Electricity and other energy consumption
Fuel used in buildings, equipment or company vehicles
Business travel
Employee commuting
Waste
Purchased goods and services
Transport and distribution
Relevant supplier information
If you are unsure where to look for this information, you may already have more of it than you realise. Utility bills, fuel records, expense systems, travel platforms and supplier invoices can all provide useful starting points, as we explain in our guide to carbon data sources businesses may already have.
Once the relevant activity data has been collected, it can be converted into CO₂e using appropriate emission factors.
If you're creating your first carbon baseline, Scope's free Business Carbon Calculator can help you turn the activity data you already have into an initial picture of your organisation's carbon footprint.
What Should A Carbon Baseline Include?
A carbon baseline should reflect the greenhouse gas emissions included within the reporting boundary your organisation has defined, using a consistent approach that allows meaningful comparison over time.
Business greenhouse gas emissions are commonly organised into Scope 1, Scope 2 and Scope 3 emissions.
Scope 1 covers direct emissions from sources your organisation owns or controls.
Scope 2 covers emissions associated with purchased or acquired electricity, steam, heat and cooling consumed by your organisation.
Scope 3 covers other indirect emissions throughout your value chain and can include areas such as purchased goods and services, business travel, employee commuting, waste and transport.
The important point is consistency. If the activities included in your baseline are substantially different from those included in future carbon footprints, the comparison may not give you a clear picture of how emissions have actually changed.
This is why it is useful to document what your baseline includes, which methodologies have been used and where any exclusions, assumptions or estimates have been made.
What Year Should Be Your Carbon Baseline?
Your carbon baseline year should normally be a period for which you have sufficiently reliable emissions data to create a useful and consistent reference point.
There is not one universal carbon baseline year that every business needs to use. Under the GHG Protocol Corporate Standard, companies are advised to choose the earliest relevant point in time for which reliable data is available.
For example, if your business begins collecting reliable carbon data in 2026 and calculates a footprint covering that reporting period, 2026 could become your carbon baseline year.
Your reporting period might align with your organisation's existing reporting cycle, but whichever period you select, consistency is important if you want to compare your baseline emissions with future results.
Can You Create A Carbon Baseline Without Perfect Data?
You can begin building a carbon baseline when some information is incomplete, provided estimates and assumptions are clearly identified and the limitations of the data are understood.
This matters because businesses beginning carbon reporting often discover that some information is easier to access than others, particularly when they start looking beyond energy and fuel towards Scope 3 emissions.
Rather than treating imperfect data as a reason not to begin, you can identify what information is available, document where estimates or proxies have been used and decide which gaps should be improved in future reporting periods.
Our guide to estimating carbon emissions explains where estimates can provide a useful starting point and why they should not be presented as exact measurements.
As your reporting develops, you may be able to replace estimates with actual activity data, collect better information from suppliers or begin measuring emission sources that were previously unavailable.
This means your first carbon footprint does not need to represent the final quality of your carbon data. What matters is knowing where the limitations are and having a process for improving your carbon data over time.
Can You Change Your Carbon Baseline?
A carbon baseline should provide a consistent reference point, but significant changes to your organisation, reporting boundary, calculation methodology or underlying data can sometimes mean that baseline emissions need to be recalculated.
The GHG Protocol requires base-year recalculation in certain circumstances so that businesses can continue making meaningful like-for-like comparisons.
For example, significant changes could include:
A merger, acquisition or divestment that changes the organisation's reporting boundary
Significant changes to calculation methodologies
Major improvements in data accuracy
The discovery of significant errors
Significant changes to the activities included within a Scope 3 inventory
This does not mean changing your baseline simply because emissions have gone up or because a different year would make progress look better.
The purpose of recalculation is to maintain comparability. Businesses following the GHG Protocol should establish a base-year recalculation policy and apply it consistently. You can read the GHG Protocol's guidance on base-year adjustments for more detail.
How Does A Carbon Baseline Help With Emission Reductions?
A carbon baseline can support emissions reduction by showing where your organisation started and giving you a consistent reference against which future greenhouse gas emissions can be compared.
Understand where your biggest emissions come from
Breaking down your baseline can help you identify significant emission sources and decide which areas deserve closer attention.
Understand whether emissions are changing
Regular carbon reporting allows you to compare future results with your baseline and see whether total emissions, or emissions from particular activities, are increasing or decreasing.
Investigate what caused the change
A reduction in emissions does not automatically tell you why it happened. Changes in business activity, data quality, organisational structure or calculation methodology can all affect reported results.
Looking at the information behind your footprint helps you understand whether changes are associated with deliberate reduction measures or other factors.
Make more informed decisions
Once you have a clearer picture of your emissions, you can use that information to investigate realistic reduction opportunities and monitor what happens over subsequent reporting periods.
A carbon baseline does not reduce emissions by itself, but it gives you a much stronger starting point for understanding where action may be appropriate.
Carbon Baseline FAQs
Is a carbon baseline the same as a carbon footprint?
A carbon baseline and a carbon footprint are closely related, but they are not exactly the same. A carbon footprint measures greenhouse gas emissions for a defined period and boundary, while a carbon baseline is the reference footprint or base-year emissions used to compare results over time.
What are baseline emissions?
Baseline emissions are the greenhouse gas emissions associated with the period selected as your reference point for future comparison. They provide the starting figure against which subsequent reporting periods can be assessed.
Do small businesses need a carbon baseline?
A carbon baseline can be useful for a small business that wants to understand and track how its greenhouse gas emissions change over time, although whether one is formally required will depend on the reporting requirements or commitments that apply to the organisation.
Even where formal carbon reporting is not required, establishing a baseline can provide a more structured way to understand your footprint and monitor future changes.
How often should a carbon baseline be updated?
A fixed carbon baseline is generally retained so that emissions can be compared consistently over time, rather than being replaced every year.
However, significant changes to an organisation, its inventory boundary, methodologies or data can trigger the need for recalculation under frameworks such as the GHG Protocol.
Can a carbon baseline include Scope 1, 2 and 3 emissions?
Yes, a carbon baseline can cover Scope 1, Scope 2 and relevant Scope 3 emissions where these are included within the organisation's greenhouse gas inventory.
The important consideration is being clear about the reporting boundary and applying it consistently so that future comparisons remain meaningful.
Start Your Carbon Reporting Journey With Scope
Creating a carbon baseline gives your organisation a reference point for understanding how its greenhouse gas emissions change over time.
You may not have every piece of information available when you first start. By documenting the data you have, being clear about estimates and assumptions and improving the quality of your information over time, you can build a stronger picture of your organisation's emissions.
As the amount of information grows, carbon tracking software can help businesses bring emissions data together and monitor changes between reporting periods without relying on disconnected spreadsheets.
Scope Carbon Tracking Solutions helps businesses collect, manage and understand their emissions data, making it easier to maintain a clearer picture of their carbon footprint as reporting develops.
Ready to establish your first carbon baseline? Use Scope's free Business Carbon Calculator to start building a picture of your organisation's emissions using the data you already have.
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