Temperatures are already breaking records this year: Last month was the warmest May for the world’s oceans since record-keeping began in 1850, according to the National Oceanic and Atmospheric Administration.
The average ocean temperature throughout May was 0.85 degree Celsius higher than normal for the month.
For the planet as a whole, May was the third warmest on record, the agency said Thursday in its monthly climate update. North America and South America had their warmest May on record.
In the United States, rising temperatures hit Washington state and northern Idaho especially hard. Two cities in Washington — Bellingham and Spokane — as well as smaller communities in the region, set records for their warmest May.
Warmer water tends to hold less oxygen, and large-scale fish dieoffs may happen earlier in the year as the climate continues to warm. Last week, thousands of dead fish washed up on Texas beaches from unusually warm waters and lack of oxygen in the Gulf of Mexico. Across the ocean, higher temperatures contribute to coral reefs dying. The ocean also expands as it warms, raising sea levels even further on top of the added water from melting ice sheets.