The sustainable debt market is continuing its rapid expansion, with the Climate Bonds Initiative announcing that cumulative aligned issuance of green, social, sustainability, and sustainability-linked (GSS+) bonds has reached USD6.2 trillion. A total of USD555.8 billion was issued in the first half of 2025 (H1 2025), reflecting growing investor demand for climate and sustainability-linked financing.
The latest figures represent a 17% increase compared with the average semi-annual issuance since 2021 (USD474.9bn). The second quarter of 2025 alone delivered USD286.1bn, the second-highest quarterly total on record, trailing only Q1 2024’s peak of USD316.5bn.
Clodagh Muldoon, Head of Research at Climate Bonds Initiative, said: “The first half of 2025 marked a milestone, as Climate Bonds-aligned GSS+ debt volume surpassed USD6 trillion. Strong issuance from development banks, robust green bond volumes, and rising activity across sustainability and social themes set an optimistic tone for the second half of the year.”
Green bonds continued to lead market growth, accounting for 61% of issuance in H1 2025 and 67% in Q2. Quarterly green issuance hit USD193.6bn, the second-highest on record after Q1 2024 (USD207.4bn).
Sustainability-linked bonds (SLBs) also gained momentum, with H1 2025 marking their third-strongest half (USD9.7bn), underlining investor appetite for more innovative financing tools.
Development banks achieved a historic milestone in Q1 2025, surpassing USD1 trillion in cumulative aligned issuance. They now account for 45% of the sustainable debt market, joining governments, financial institutions, and corporates in the trillion-dollar issuer category. Their role in steering capital towards climate-friendly investments is expected to strengthen the net-zero transition.
While references to methane abatement in green bonds remain limited, issuances from Belgium’s Fluvius, France’s Waga Energy and US-based Kinetik Holdings signal growing momentum. The theme aligns with Climate Bonds’ “Mobilizing Sustainable Finance for Methane Abatement Programme”, backed by the Global Methane Hub, which is entering its second year with expanded reporting and events.
All figures are drawn from Climate Bonds’ Market Intelligence Methodologies, which apply stringent climate criteria to safeguard the integrity of sustainable debt data. Retrospective inclusion ensures that only verified aligned assets are counted.
The findings of the Sustainable Debt Global State of the Market H1 2025 will be further discussed at the Global Climate Bonds CONNECT conference in London on 22 October 2025.
