Much scientific work attributes global warming to man-made emissions, though some dispute a connection.
The panel, known by the initials IPCC, is a group of scientists convened by the U.N. to review scientific, economic and other data on climate change and issue a technical baseline that policy makers can draw upon.
The panel members reviewed scientific studies as well as research from governments and industry.
Last October, the panel urged governments to step up efforts, including meeting voluntary carbon-reduction goals laid out in the 2015 Paris climate accord, to avoid the destruction of ecosystems and rising sea levels that would lead to flooding. The Trump administration pulled the U.S. out of the accord.
In August, the U.N. panel recommended people eat more vegetables and less meat to help slow emissions of greenhouse gases because livestock production releases more of the heat-trapping gases.
The new report, called the “Special Report on the Ocean and Cryosphere in a Changing Climate,” was prepared by more than 100 scientists from more than 30 countries who assessed about 7,000 studies concerning the effect of climate change on the oceans and global ice sheets, assuming carbon emissions continue at the current pace.
As the atmosphere has warmed over recent decades, the oceans have absorbed heat unevenly, creating patches with unusually warm sea temperatures that can encompass thousands of square miles and persist for months, affecting fisheries, wildlife and weather patterns, the U.N. panel scientists said.
“This is an emerging issue,” said IPCC vice chair Ko Barrett, deputy assistant administrator for research at the National Oceanic and Atmospheric Administration. “These heat waves have doubled in frequency and are increasing in intensity.”
Since 2003, vast pools of water up to 9 degrees Fahrenheit or so above normal have been detected repeatedly in the Pacific around Australia, in the Mediterranean, from Southern California up to Alaska, and in the Atlantic off New England, the scientists said.
This year, one of the largest such warm pools so far has appeared in the Pacific stretching from Alaska to Hawaii, the National Oceanic and Atmospheric Administration said this month.
As sea and air temperatures warm world-wide, ice sheets at opposite ends of the planet are melting, the U.N. panel said.
Between 2006 and 2015, the Greenland Ice Sheet lost ice at an average rate of about 278 billion tons every year, while ice sheets in Antarctica during the same period melted at a rate of about 155 billion tons every year, the U.N. panel said. Snow cover and mountain snow packs also are declining, the U.N. panel said.