President Clinton’s annual summit of world leaders and celebrities opened yesterday with the former president sharing the stage with the rock star Bono and dignitaries including Vice President Gore, who warned that humanity is struggling in the fight against climate change.

Mr. Gore pointed to a number of natural disasters, from storms in Haiti to hurricanes on the Gulf Coast to fires in California, as evidence.

“Since we met here last year, the world has lost ground to the climate crisis,” Mr. Gore said at the opening session of the Clinton Global Initiative. “This is a rout. We are losing badly.”

“This is the result of a dysfunctional, insane global system pattern that we have to change,” he said.

The Clinton Global Initiative, now in its fourth year, draws world leaders, celebrities, activists, and scholars for three days of discussions about pressing global issues such as climate change and poverty. It coincides with the General Assembly meeting taking place on the other side of town at the United Nations.

Mr. Gore was joined at the opening plenary session by Mr. Clinton, Queen Rania of Jordan, President Ellen Johnson-Sirleaf of Liberia, Bono, and E. Neville Isdell, chairman of the board of directors for Coca-Cola.

That put Mr. Clinton and his former vice president together on the same stage, eight years after they left the White House and just weeks before another election. They avoided politics and exchanged pleasantries as Mr. Gore thanked Mr. Clinton for his efforts with the summit.