From the graph of the data, every day for the past 365 days has indeed been an all time high, higher than any previously recorded temperature recorded by the same method since records began in 1979. So does not appear to be misleading.
I see what you're saying. You're reading it as "every day is hotter than the previous day". The way I said it is open to misinterpretation but the article is better. It says "record-breaking year of heat" and "broken temperature records every single day over the past year," the record being the highest sea temperature for that day. Every day is an all time high for that day. The oceans are seasonally affected, so not constant temperature even averaged across the globe.
This is ignoring seasonality, of course Winter temperature can not be as high as summer temperatures but still break historic records (just as an example)
This is somehow a given when talking about seasonal data.
It's expected that a warmer year would be warmer at the majority of points in time. Variance should normally result in there being both warmer and colder points.
To be warmer at every point in time, the year needs to be significantly warmer.
