Over the next 30 years, China's coastal sea levels will rise between 6.8 to 17 centimeters, according to the China Sea Level Bulletin issued by the marine early warning and monitoring department of the Ministry of Natural Resources.

The bulletin, released in May, called for areas, including Tianjin and Shanghai, to enhance their coastal protection measures. It said that last year the sea level in the country's coastal areas was 8.4 cm higher than normal, the highest level since 1980.

Over the past 40 years, China's coastal sea levels rose at an average rate of 3.4 millimeters per year, higher than the global average during that period.

According to the bulletin, high sea levels increase the impact of marine disasters. Last year, storm surges in China and city floods mainly occurred from July to October, when sea levels were high.

The Bulletin of China Marine Disaster released by the department in April said that storm surges had caused about 2.5 billion yuan ($373 million) in losses last year. Of that figure, the losses in Zhejiang province accounted for 38 percent.

Rising seawater eroded more coastal areas in Liaoning, Hebei, Fujian and Hainan provinces last year than in 2020, the bulletin said.

Erosion can coarsen sand, damage soil, destroy infrastructure and cause economic losses, according to an essay published by the ministry.

Higher sea levels also mean that salt water can threaten freshwater supplies, and affect agricultural and industrial production, the bulletin said.

"Our crops and drinking water will be ruined immediately if they get soaked by saltwater," said Zhai Panmao, a Chinese climatologist.

"We can't reverse some of the changes, such as an increase in sea levels, but by reducing emissions of greenhouse gases, we can slow the process in some respects while controlling the level of warming. It is not the responsibility of any particular country, but of all the countries around the globe, which should work together to cope with climate change."

Reduction measures include replacing fossil fuels with clean energy and using energy more efficiently, he said.

The bulletin quoted last year's report by the Intergovernmental Panel on Climate Change as saying that the heating of the climate system has caused global average sea levels to rise, mainly through ice loss on land and thermal expansion from ocean warming.

Sea temperature, air temperature, wind and precipitation can all cause abnormal changes in coastal sea levels, it said.

In coastal areas that are vulnerable to rises in sea levels, authorities should improve infrastructure to prevent floods and enhance defensive facilities. They also need to use groundwater resources in reasonable amounts to keep land from subsiding and lessen the impact of rising sea levels, the bulletin suggested.

"Authorities should especially prevent land subsidence in Shanghai and Tianjin by improving monitoring and embankment projects," it said.