GLOBAL WARMING : ''PANAMA CANAL STRUGGLES''

A SEVERE drought in Panama has resulted in lower water levels in the Panama Canal, forcing more shippers to limit the amount of cargo their largest ships carry so they can safely navigate the waterway.

''The last five months have been the driest dry season in the history of the canal,'' said Carlos Vargas, the Panama Canal Authority's executive vice president for environment, water and energy.

The canal - an engineering master work that provides a shortcut between the Atlantic and Pacific   -handles about 5 percent of the world's maritime trade. Any hiccup in its operation can ripple through the  global economy and affect the United States , the origin-or-destination for much of the canal's traffic.

And these problems may become more commonplace as the as the climate changes.

Earlier this year, the authority imposed draft limits on ships, forcing some to limit and lighten their loads to ride higher in the water so they would not run aground.

Although the dry season has ended and rains have returned  some restrictions will remain through the summer, Mr Vargas said. Such restrictions may have to be imposed more frequently if, as scientists expect, climate change leads to more extreme storms and dry periods.

The drought is linked to an EI Nino that developed early this year and is expected to continue into the fall. During an EI Nino, warmer-than-normal  surface waters in the equatorial Pacific can affect weather patterns in many parts of the world, including rainfall in Central America.

EI Nino events occur every two to seven years , on average, and have been noticed for centuries. They have led to canal restrictions in the past.

Already,  four of the most intense storms and several of the worst droughts since the canal opened 105 years ago have occurred in the past decade, said Robert F. Stallard, a hydrologist with the United States Geological Survey and the Smithsonian Tropical Research Institute who has studied water issues in Panama for decades.

''Planning for more extreme weather in the future is the way things have to go,'' Dr. Stallard said.

The authority imposed the limits in February, as the drought took hold and levels in the two lakes that supply water to the canal begin to fail. The limits affected only very large ships using the canal's newest locks, which opened in 2016.

An average of about seven ships a day use those locks.

The World Students Society thanks author Henry Fountain.