The meeting, also featuring current UN chief Antonio Guterres and former head Ban Ki-moon
World leaders are set to appear online on Monday at the first summit dedicated to making the planet more resilient to the effects of climate change.
Leaders including French President Emmanuel Macron, German Chancellor Angela Merkel and British Prime Minister Boris Johnson are expected to contribute by video link to the Climate Adaptation Summit, hosted by the Netherlands.
The meeting, also featuring current UN chief Antonio Guterres and former head Ban Ki-moon, will produce an "adaptation action agenda" for dealing with effects such as rising sea levels, extreme weather and crop failure.
"This year 2021, will have several milestones on where and when the world leaders and world people will really show their strong commitment. We have not done much on adaptation" so far, Ban Ki-moon told reporters last week.
Former US secretary of state and Joe Biden's newly-appointed climate envoy John Kerry will speak at the summit, as will Deputy Chinese Prime Minister Han Zheng.
Kerry has acknowledged that he will need to work to restore Washington's credibility as he seeks to build more robust global action to address the crisis.
The summit is being held almost entirely online because of the coronavirus pandemic.
Dutch Prime Minister Mark Rutte said his country, a third of which lies below sea-level, had centuries of experience in keeping out the water and hoped to teach others.
At the summit, Boris Johnson will announce the launch of an Adaptation Action Coalition, in partnership with Egypt, Bangladesh, Malawi, the Netherlands, Saint Lucia and the United Nations.
The new grouping "will work to turn international political commitments made through the United Nations Call for Action on Adaptation and Resilience into on-the-ground support for vulnerable communities," his office said in a statement.
"It is undeniable that climate change is already upon us and is already devastating lives and economies," Johnson is expected to say.
While previous summits have focused on tackling the causes of climate change, including reducing emissions, this is the first to concentrate on dealing with its effects, say organizers.
These include reducing the vulnerability of countries to rising sea levels, extreme weather and food shortages.
Plans could include shoring up sea defences but also taking advantage of opportunities including longer growing seasons for crops, and new areas for cultivating, organizers said.
Ban Ki-moon meanwhile welcomed the fact that new US President Joe Biden had decided to have the United States re-join the Paris climate agreement.