OSLO, Norway — About 42 million people were forced to flee their homes because of natural disasters around the world in 2010, more than double the number during 2009, experts said Monday.

The Internal Displacement Monitoring Centre stated in a report that the increase from 17 million displaced people in 2009 was mainly due to the impact of “mega-disasters” such as the massive floods in China and Pakistan and the earthquakes in Chile and Haiti.

More than 90 percent of the disaster displacements were caused by weather-related hazards such as floods and storms that were probably affected by global warming, according to a report, but it couldn’t say to what extent.

Elisabeth Rasmusson, the secretary general of the Norwegian Refugee Council, said the intensity and frequency of extreme weather events is increasing.

“This trend is only set to continue,” Rasmusson said. “With all probability, the number of those affected and displaced will rise as human-induced climate change comes into full force.”

The monitoring center and refugee council presented the report at an international conference about climate change and displacement in Oslo.

The number of people displaced last year — about 42 million — is roughly the size of Argentina’s entire population, and the onslaught of natural disasters so far this year also has been grim.

The March 11 earthquake and tsunami in Japan left more than 10,000 people dead, some 17,500 missing and about a half-million homeless.

In the United States, tornadoes have wreaked havoc from Alabama to Massachusetts, while floods have inundated states from Montana to Louisiana. In the southwest Missouri city of Joplin, the U.S.’s deadliest tornado in six decades killed at least 141 people and destroyed more than 8,000 homes in a city of about 50,000 people.

Speaking at the Oslo conference, U.N. High Commissioner for Refugees Antonio Guterres called the issue of climate-related displacement “the defining challenge of our times” and criticized the international community for lacking the political will to reduce to pace of climate change.

“There is increasing evidence to suggest that natural disasters are growing in frequency and intensity and that this is linked to the longer-term process of climate change,” Guterres said.

Asia was the hardest hit region last year, with the largest number of displaced people seen in countries such as India, the Philippines, Bangladesh, Indonesia, China and Pakistan.

In China alone, more than 15 million people were forced to leave their homes after floods, while 11 million people were displaced in Pakistan, the report said. The large floods in India in 2009 also continued to force people to leave their homes in 2010.

“This report provides us with evidence of the extent and urgency of the problem that we cannot ignore. We must increase collaborative efforts to prevent displacement by natural disasters, and do a better job of protecting those displaced,” Rasmusson said.

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Malin Rising in Stockholm contributed to this report.