Carbon offsets are issued by certified projects that either reduce emissions (renewable energy, efficient cookstoves), avoid them (preventing deforestation) or remove existing CO₂ (afforestation, direct air capture).
Quality varies wildly. Reputable standards include Gold Standard, Verified Carbon Standard (VCS / Verra), Climate Action Reserve and American Carbon Registry. Avoidance credits are systematically over-credited; removal credits are scarcer but more credible. Use the SBTi mitigation hierarchy: reduce first, offset residuals only.