Jeff Bezos is throwing his weight — and wealth — behind the fight against climate change months after Amazon employees publicly pressured him and the company to do more to address the issue. The Amazon (AMZN) CEO on Monday announced a new fund to back scientists, activists and organizations working to mitigate the impact of climate change. Bezos will commit $10 billion "to start," he said in an Instagram post. The initiative, called the Bezos Earth Fund, will begin giving out grants this summer. The $10 billion commitment constitutes less than 8% of the world's richest man's estimated $130 billion net worth. Even so, it is one of the biggest charitable pledges ever, according to a ranking by the Chronicle of Philanthropy, behind a $36 billion commitment by billionaire Warren Buffett in 2006 and an estimated $16.4 billion pledge by Helen Walton, the late wife of Walmart (WMT) founder Sam Walton, in 2007.

"Climate change is the biggest threat to our planet," Bezos said in the post. "I want to work alongside others both to amplify known ways and to explore new ways of fighting the devastating impact of climate change." Bezos has been under pressure from his employees to do more to protect the environment. Thousands of Amazon employees signed a letter last May asking how the company planned to respond to climate change, and many of them staged a walkout in September calling on it to do more. A day before the walkout, Amazon announced a pledge to go carbon neutral by 2040, ten years before the deadline set out by the Paris climate agreement. The company also said it will deploy 100,000 electric delivery vans by 2024. "It's going to take collective action from big companies, small companies, nation states, global organizations, and individuals," Bezos said. Amazon Employees for Climate Justice, the group that staged last year's walkout, responded to Bezos' latest pledge by saying more needs to be done to address underlying causes like fossil fuel consumption.

"We applaud Jeff Bezos' philanthropy, but one hand cannot give what the other is taking away," the group said in a statement Monday, calling on Amazon to stop working with oil and gas companies or funding think tanks that deny climate change. "Will Jeff Bezos show us true leadership or will he continue to be complicit in the acceleration of the climate crisis, while supposedly trying to help?" it added.