Counting the cost of adaptation

Two countries can report very different adaptation budgets while doing much the same thing. The divergence is usually an accounting artefact, not a difference in ambition.

Where the numbers part ways

• Tagging. Some systems label a road that happens to be flood-resistant as adaptation; others record only the marginal cost of the resistance.
• Boundaries. Maintenance may sit inside the adaptation line in one budget and outside it in another.
• Timing. Multi-year commitments are booked up front in some accounts and spread in others.

Reconciling the figures

In our comparative study we re-state each budget to a common boundary — marginal cost, consistent tagging, and annualised commitments — before any country is compared to another. The re-stated figures are often less striking than the headline ones, and considerably more useful.

We publish both the raw and the re-stated series. A reader who disagrees with our boundary can rebuild the comparison on their own terms; that is the point of showing the working.