Earlier this month China and the United States jointly pledged to ratify the Paris climate change agreement, a monumental step for the world’s two largest polluting economies. Executing a dramatic reduction in greenhouse gas (GHG) emissions will require creative financing, and China is looking towards green bonds to support their commitment.

Green bonds are financial instruments that raise capital for specific projects with targeted environmental benefits. Apple made headlines in February of this year by issuing the largest green bond from a U.S. corporation. The tech giant sold $1.5 billion in green bonds earmarked for clean energy projects, green buildings, and resource conservation efforts.

Despite the large issuance from Apple, China has surpassed the United States as the largest issuer of green bonds. The country seeks to attract global investors to help finance the Chinese economy’s transition away from polluting industries and towards advanced technology and services.

China approved more than $17.4 billion of sales of green bonds so far this year — over 40% of the market — after issuing its first green bond less than two years ago. However, some of the domestic green bonds being issued do not meet international standards and require additional scrutiny by prospective investors.

For example, some of the Chinese green bonds are tagged to fund clean coal projects. While clean coal might represent environmental progress in pollution-afflicted China, internationally these bonds conflict with the majority of environmentally-friendly investment mandates, as well as the Green Bond Principles, which serve as the gold standard in green bonds.

China is currently responsible for over 20% of GHG emissions, closely trailed by the United States at just under 18%. As both countries seek financial support for their climate change commitments, investors must be wary of products that aren’t as green as they seem.