'Proud to be back' in climate fight: John Kerry

World leaders are holding a high-level and largely virtual summit on climate change -- with a return appearance by the United States.

The event, called the Climate Adaptation Summit, comes only days since President Biden's order last week to rejoin the Paris climate agreement.

John Kerry, the former secretary of state and presidential candidate, is Biden's new climate change envoy:

"President Biden knows that we have to mobilize in unprecedented ways to meet a challenge that is fast accelerating. And he knows we have limited time to get it under control (...) So we're proud to be back. We come back, I want you to know, with humility for the absence of the last four years, and we'll do everything in our power to make up for it."

The summit is being hosted by the Netherlands and is focused on finding practical solutions and ways to deal with the changes to our planet that are already happening.

The other attending leaders have largely welcomed the U.S.'s return to the table.

Meanwhile, on the same day that the summit opened, a study has found that the Earth's ice sheets, such as icebergs and glaciers, are melting even faster now than in the 1990s.

It was conducted by researchers from the UK, including England's University of Leeds.

President Biden is expected to roll out new measures on climate and the environment this week.