BEIJING (REUTERS) - China's coastal sea waters have risen by 3.4mm per annum over the 1980-2020 period and hit their third-highest level on record last year, the country's environment ministry said on Wednesday (May 26).

In its annual bulletin on the state of the country's environment, the Ministry of Ecology and Environment said that China's coastal waters were now 73mm higher than "normal", defined as the average over the 1993-2011 period.

The ministry also said that average national temperatures stood at 10.25 deg C last year, slightly lower than the year before but still 0.7 deg C higher than the 1981-2010 average.

Global sea levels have risen as a result of warmer water temperatures as well as melting glaciers and ice sheets.

According to a report from the Ministry of Natural Resources published last month, average coastal sea temperatures in China have risen by an average of 0.27 deg C per decade since 1980, while coastal air temperatures have risen 0.39 deg C.

The ministry also forecast that coastal water levels could rise by another 55mm to 170mm in the next 30 years, requiring China to adapt more thoroughly in order to protect its coastlines.

Cities on China's eastern coast have already been making contingency plans to cope with rising sea levels, with the major financial hub of Shanghai already looking into building new drainage tunnels and tidal gates.