The first part of this series explained how it is almost certain that the average global temperature will be the warmest ever this year. However, what is normally known as temperature is air temperature two metres above the earth’s surface. Another set of temperature numbers which deserve close attention are sea surface temperatures (SSTs). Although strongly correlated with air temperatures, SSTs do not always move exactly the way air temperatures do. For example, air temperatures in 2015 would only be
Sea surface mercury set for record highs2024 is almost certain to be the warmest year by SSTs
According to NOAA’s dataset, the average SST this year up to November is 21.07°C, the warmest ever, and surpassing the previous record held by 2023 by 0.08°C. Can 2024 SSTs end up behind 2023 value given such a small difference? For that to happen, December SSTs will have to average 20.08°C or lower, a level last seen in December 1992 in NOAA’s data. To put it another way, December will have to be at least 0.72°C cooler than November for average 2024 SST to be ranked second. The most SSTs have changed from one month to the next in NOAA’s data beginning January 1854 is by 0.33°C (between January and February 1868). This means that only a Black Swan event can prevent 2024 from being the warmest ever year by SSTs.
To be sure, SSTs turned cooler than 2023 from July
2024 is expected to be the warmest year by SSTs on average because of the first half of the year. From July onwards, SSTs have been cooler than in 2023. This is unlike air temperatures, which were nearly tied with 2023 also in August and October in NOAA’s data. None of this, however, diminishes the scale of the warming in SSTs. As the accompanying chart shows, SSTs are still trending far above normal (taken as 1971-2000 average in NOAA’s data) and previous records. The reason why SSTs have not been the highest ever for the month from July is because a cyclical factor -- the periodic warming of the equatorial Pacific Ocean called El Nino – has gone away. The El Nino that began in June 2023 ended in April 2024, allowing the world’s average SST to come down below 2024 levels.
North Atlantic is the reason for the record warming…
Just as in 2023, most of the warming seen in average SST in 2024 can be explained by one specific region: the North Atlantic ocean. Up to November, the North Atlantic averaged a warming of 1.22°C compared to normal. In comparison, the North Pacific, which experienced the next highest level of warming, was only 0.81°C warmer than normal. As previously reported, scientists believe that the relatively bigger spike in warming in the North Atlantic could be because of both natural cycles specific to the Atlantic and some man-made factors – such as a change in maritime shipping laws in 2020, which reduced sulphur emissions in a busy shipping route. Sulphur emissions temporarily mask global warming by reflecting sunlight.
…but it is the Indian Ocean that has broken its records beyond July
While the North Atlantic contributed the most to the warming in world’s average SST, it is the Indian Ocean where record warming has persisted in the second half of 2024. Except March and October, all months up to November were the warmest ever for the Indian Ocean. For the North Atlantic, only the months up to June were the warmest ever this year. No other ocean has experienced record-breaking SSTs for more than three months this year.
{{^htLoading}}{{/htLoading}}{{#usCountry}}{{/usCountry}} 