Scope 3 emissions are, by most accounts, the hardest part of carbon accounting to get right. They cover everything that happens outside a company’s direct operations: supplier activities, purchased goods, employee commuting, product use, end-of-life disposal, and more. For most organizations, scope 3 represents the vast majority of their total carbon footprint. So when the numbers are off, the consequences for climate strategy and reporting credibility are significant. The question is: why does scope 3 data so frequently fall short of the accuracy needed to act on it?
The honest answer is that several structural problems compound each other. Supply chains are complex, standards are inconsistent, estimation methods carry built-in limitations, and data gaps are everywhere. Understanding each of these issues separately makes it much easier to see what can actually be done about them.
The data collection problem across supply chains
Collecting reliable supply chain emissions data is genuinely difficult, and it starts with a basic reality: most organizations don’t control their suppliers. A company might have thousands of tier-1 suppliers, each of whom has their own network of tier-2 and tier-3 suppliers. Requesting emissions data from all of them is a logistical challenge, and even when suppliers do respond, the quality of what they provide varies enormously.
Many suppliers, particularly smaller ones, haven’t measured their own emissions at all. Others track some categories but not others. Some provide figures based on their own internal estimates rather than measured activity data. The result is a patchwork of responses that are nearly impossible to aggregate into a coherent, comparable picture. The further down the supply chain you go, the worse the data quality tends to get, which means the emissions figures that eventually feed into scope 3 reporting often rest on a very shaky foundation.
How inconsistent standards distort scope 3 figures
Even when data is collected, a lack of consistent methodology across organizations creates serious distortions. The GHG Protocol’s Corporate Value Chain Standard is the most widely used framework for scope 3 reporting, but it allows for significant flexibility in how companies define boundaries, choose emission factors, and categorize activities. That flexibility is sometimes useful, but it also means two companies in the same industry can report scope 3 figures that are structured so differently they can’t be meaningfully compared.
Frameworks like CSRD and CDP are pushing for greater standardization in how companies disclose emissions, which is a step in the right direction. But as long as the underlying methodology varies, reported figures will continue to diverge in ways that reflect choices about measurement rather than actual differences in environmental impact. For organizations trying to benchmark themselves against peers or set science-based targets through SBTi, this inconsistency is a real obstacle.
Why estimation methods introduce systematic error
Because primary data from suppliers is so hard to obtain, most organizations rely heavily on spend-based or average-data estimation methods to fill the gaps. These approaches use financial spend data or industry-average emission factors to estimate emissions across categories where direct measurement isn’t available. They’re practical, but they introduce systematic error in ways that are worth understanding.
Spend-based methods, for example, assume that emissions scale proportionally with money spent. In reality, two suppliers charging the same price can have dramatically different carbon footprints depending on their energy sources, production processes, and locations. Average emission factors drawn from industry databases also smooth over enormous variation within sectors. A company sourcing steel from a highly efficient producer will have its emissions overestimated if it uses an average factor for the steel industry. Conversely, a company sourcing from a particularly carbon-intensive supplier will be underestimated. These errors don’t cancel out neatly, and they accumulate across dozens of spend categories.
The role of data gaps and double counting
Two problems pull in opposite directions when it comes to scope 3 accuracy: missing data and data that gets counted more than once. Both are common, and both distort the final figures in ways that are hard to detect without careful scrutiny.
Data gaps occur when certain emission categories are simply omitted, either because data isn’t available or because the reporting boundary was drawn narrowly. Companies sometimes exclude categories that are technically in scope simply because measuring them is too difficult. This leads to systematic underreporting, where the published figure looks clean but is missing significant chunks of actual impact.
Double counting works in the opposite direction. It happens when the same emission is recorded by multiple entities in a value chain. For example, a supplier’s scope 1 emissions might appear in their own report and then again as scope 3 category 1 (purchased goods and services) in a customer’s report. At the portfolio level, this can inflate aggregate figures significantly. There’s no simple fix, because eliminating double counting requires coordination across organizations that often have no direct relationship with each other.
Together, gaps and double counting mean that scope 3 figures can be simultaneously too low (due to omissions) and too high (due to duplication), sometimes within the same report. That’s a challenging combination to untangle.
How organizations can improve scope 3 data quality
Improving scope 3 accuracy is a long-term process, but there are concrete steps that move organizations in the right direction. The goal isn’t perfection immediately; it’s building progressively better data over time while being transparent about current limitations.
- Prioritize high-impact categories first. Not all scope 3 categories are equally significant. Focusing data collection efforts on the categories that represent the largest share of estimated emissions gives the biggest accuracy gains for the effort invested.
- Engage suppliers directly on emissions data. Supplier engagement programs that request actual activity data, rather than relying on spend-based proxies, produce significantly more accurate figures. This works best when it’s framed as a partnership rather than a compliance exercise.
- Move from spend-based to activity-based data where possible. Activity-based data, such as the actual quantity of goods purchased and their specific emission factors, is more accurate than spend-based approximations. It requires more effort to collect but reduces the systematic errors described earlier.
- Document methodology clearly and consistently. Transparent documentation of which categories are included, which estimation methods were used, and where primary data was obtained makes it far easier to identify errors, compare year-on-year figures, and respond to scrutiny from frameworks like CDP or CSRD.
- Work with specialists who understand the technical nuances. Scope 3 emissions reduction and carbon accounting are highly specialized areas. A scope 3 specialist or LCA expert brings a depth of knowledge that can identify errors and opportunities that generalist approaches miss.
What ties all of these steps together is a shift from treating scope 3 as a compliance checkbox to treating it as a genuine management tool. Better data quality doesn’t just improve reporting; it reveals where emissions reduction efforts will actually have an impact. That’s the point where carbon accounting starts to drive real change rather than just produce numbers for a report.
Ready to get your scope 3 data under control?
Scope 3 accuracy is one of those challenges where the right expertise makes an enormous difference. Whether you need a specialist to redesign your data collection process, work through your supplier engagement strategy, or prepare for CSRD or CDP disclosure, having someone who genuinely knows this space saves a lot of costly rework.
That’s exactly what we built Dazzle for. Our network of pre-screened sustainability experts includes specialists across scope 3 reporting, carbon accounting, and supply chain emissions, available on a project or interim basis to fit your needs. You can be working with the right person within 48 hours, without the lengthy process that comes with traditional consultancies. If you’re ready to get started, reach out to our team and we’ll match you with the right expert for your challenge.
If you’re interested in learning more, contact our team of experts today.
