The GHG Protocol's three-scope framework was designed in 2001 and it's still the foundation of corporate carbon accounting. Most business leaders have heard the terms. Fewer can explain what each scope actually covers, why the boundaries were drawn where they were, or what the practical data challenges look like for each one.
This is the guide that fills that gap — without the jargon.
Scope 1: what you directly control
Scope 1 covers emissions from sources owned or controlled by your organization. If your company burns fuel, it's Scope 1. If you operate manufacturing processes that release greenhouse gases, it's Scope 1. If your fleet runs on diesel, Scope 1.
The categories are: stationary combustion (boilers, furnaces, generators), mobile combustion (company-owned vehicles), process emissions (chemical reactions in industrial processes), and fugitive emissions (refrigerant leaks, gas pipeline losses).
Data for Scope 1 is usually the most accessible. Fuel purchase records, utility invoices, fleet management systems — these exist inside the organization. The challenge is completeness: making sure you've identified every source, including the ones that aren't obvious. A small backup generator running twice a year still needs to be counted.
Scope 2: purchased energy
Scope 2 covers emissions from generating the electricity, heat, steam, or cooling that you buy and consume. You're not burning fuel directly, but somewhere upstream, a power plant is doing it on your behalf.
There are two accounting methods. Location-based uses average grid emission factors for your country or region. Market-based uses the specific emissions associated with the electricity you've contracted — relevant if you've signed a green power purchase agreement or bought renewable energy certificates.
Both numbers are required under GHG Protocol's Scope 2 Guidance, which creates some confusion. The market-based figure is what shows up in most sustainability targets because it reflects procurement decisions. The location-based figure is what matters for physical infrastructure planning.
Scope 2 data is relatively clean to collect — electricity invoices, utility bills — but multinational companies operating in 20+ countries need emission factors for each grid. These factors change annually and vary significantly between countries.
Scope 3: the rest of the picture
Scope 3 is everything else — emissions that occur as a consequence of your activities but from sources not owned or controlled by you. The GHG Protocol breaks it into 15 categories, split between upstream (activities that happen before your product reaches you) and downstream (what happens after it leaves).
Upstream examples: purchased goods and services, capital goods, fuel and energy activities not in Scope 1/2, transportation and distribution from suppliers, waste generated in operations, business travel, employee commuting, upstream leased assets.
Downstream examples: transportation and distribution to customers, processing of sold products, use of sold products, end-of-life treatment, downstream leased assets, franchises, investments.
For most companies, Scope 3 is 70-90% of total emissions. It's also the hardest to measure. Supplier data is often unavailable or unreliable. Product use-phase emissions require assumptions about customer behavior. Investment portfolios require financed emissions calculations that most finance teams have never done.
The standard approach is to start with spend-based estimation — using the financial value of purchases multiplied by industry-average emission factors — and progressively replace estimates with primary data for the highest-impact categories.
Boundaries and organizational structure
Before you calculate anything, you need to decide your organizational boundary. Two approaches: equity share (report emissions in proportion to your ownership stake) and operational control (report 100% of emissions from operations you control). Most companies choose operational control because it aligns with management accountability. Choose one approach and stick with it across reporting years.
Subsidiaries, joint ventures, and outsourced operations all create boundary questions. If you outsource your logistics, do you report the emissions? Under operational control, no — your 3PL reports them in their Scope 1. But they show up in your Scope 3 Category 4 (upstream transportation). The accounting framework ensures everything gets counted somewhere.
What business leaders actually need to do
Start with Scope 1 and 2. These are the ones you have the most control over and the most accessible data for. Get a defensible methodology in place, document your calculation approach, and establish a baseline year.
Then tackle the material Scope 3 categories. You don't need all 15 on day one. Focus on categories where your exposure is highest — for a manufacturer, that's likely purchased goods and services and use of sold products. For a financial institution, it's financed emissions (Category 15).
Set targets. Science-based targets require Scope 3 coverage above certain thresholds, so your ambition level will determine how deep you need to go. But even without formal SBTs, having a documented Scope 3 approach puts you ahead of most of your competitors and makes your next CSRD disclosure considerably less stressful.