This is Planet Money from NPR.

Early last year, the CEO of Microsoft got on stage at Microsoft Headquarters.

Please welcome Satya Nadella.

He walks on and stands facing the crowd.

Behind him, there's this wall covered with these healthy looking green leaves.

Thank you so very much.

It's fantastic to be here today.

It kind of looks like a TED Talk crossed with a product announcement.

That corporations and our purpose and actions must be aligned to helping solve the world's problems, not create new ones.

And then he gets to Microsoft's new pledge to fight climate change.

Today we are making the commitment that by 2030, Microsoft will be carbon negative.

Carbon negative.

What does that even mean?

Microsoft has offices around the world that use lots of electricity.

They have fleets of cars and trucks, data centers that use diesel.

All of those things mean carbon emissions.

But somehow, the CEO of Microsoft is saying his companies going to eliminate all those carbon emissions.

Even better, reverse them.

Their plan, the answer in part, has to do with what's displayed on the screen above him.

Images of giant pristine forests.

Boris, trees. These are not just nice nature images.

Trees are going to solve some serious climate accounting problems for Microsoft.

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