To qualify as a green bond, Apple has to pledge to use the proceeds on items such as renewable energy projects, green buildings, and resource conservation efforts. Combined with Apple’s $1.5 billion green bond issued last year, the new debt will make Apple the single largest U.S. dollar-denominated issuer in the market niche. The bond offering comes days after President Trump announced he would pull out of the Paris climate accord, a move Apple opposed.

“Leadership from the business community is essential to address the threat of climate change and protect our shared planet,” Lisa Jackson, Apple’s vice president of environment, policy, and social initiatives and the former head of the EPA, said in a statement. “We’re proud to offer investors another opportunity to join us in this important work.”

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The idea is to appeal to investors who want to help improve the environment. Globally, the green bond market should exceed $200 billion this year, more than double the $93 billion in issued in 2016, Moody’s Investors Service said in January. Some new mutual funds, like the Mirova Global Green Bond fund, are investing almost entirely in the green securities.

Apple and other major tech companies including Microsoft (MSFT) and Facebook (FB) sent a letter to the president opposing the Paris accord departure. “We believe the United States can best exercise global leadership and advance U.S. interests by remaining a full partner in this vital global effort,” the group wrote.

Apple (AAPL) says it covers the power needs of 100% of its facilities with renewable energy commitments in 24 countries including the United States and China. Overall, 96% of the electricity Apple uses worldwide is covered by renewable purchases.