With a single Instagram post, Jeff Bezos pledged to become one of the most generous philanthropists in history. His gains this year have already covered the cost.

The Amazon.com Inc. founder announced on Monday that he’s created the Bezos Earth Fund to help counter the effects of climate change. The commitment is one of the largest on record after Warren Buffett’s US$36 billion pledge to the Bill & Melinda Gates Foundation in 2006 and Helen Walton’s US$16 billion bequest to the Walton Family Foundation in 2007, according to data compiled by the Chronicle of Philanthropy.

It’s a good time for Bezos to make the donation. He’s already added US$15.6 billion to his fortune -- or about US$325 million a day -- in the first seven weeks of 2020. Even if the full value of the gift were to be immediately subtracted from his wealth, Bezos would still be the richest person on the planet with a US$120.5 billion fortune, just ahead of Gates, according to the Bloomberg Billionaires Index.

Buffett and Gates also have seen their fortunes hit new heights even as their philanthropy grows. That reflects gains in the stock market, but also the difficulty of giving away such massive sums and making sure it’s put to work efficiently. The post by Bezos didn’t specify a time frame for his donation.

Bezos, 56, has stepped up his philanthropy after years of relative restraint. Unlike many of his wealthy peers -- including his ex-wife MacKenzie Bezos -- he hasn’t signed the Giving Pledge, established by Buffett and the Gates, in which billionaires agree to donate the majority of their fortunes to charity.

Bezos previously took to Twitter in 2017 to ask how he could best use his wealth to help people “right now.” That set off a frenzy of responses -- the tweet has more than 46,000 comments -- from every corner of the world. A year later he committed US$2 billion to projects working to alleviate homelessness and improve education.

Monday’s social media announcement, which has attracted about 300,000 likes, is another sign of the increasingly public posture Bezos is adopting. He’s upped the pace of his Amazon sales in recent months, bought a storied Los Angeles mansion, reportedly set records in the art market and increasingly frequents the red carpet with girlfriend Lauren Sanchez.

Bezos will have to ramp up his giving before he can match the Bill & Melinda Gates Foundation, the world’s largest private foundation. It had an endowment of US$47 billion at the end of 2018, largely thanks to donations by Buffett and the Gates family.