> The average worldwide temperature was 17C (63F), just above the previous record of 16.9C reached in August 2016, according to data from the National Centers for Environmental Prediction.
There are a lot of different factors at work. One of the most prominent is El Niño, which brings warm water up from the depths of the Pacific ocean.
The number reported here is the surface temperature, which doesn't account for the heat absorbed by the deep ocean. Some years, the additional heat of climate change is captured by the oceans and hidden from the surface temperature measurement -- those are La Niña years, and the surface is comparatively cool. This year El Niño is bringing all of that heat back up, contributing to setting records.
All of this is driven by the chaotic 3D motion of oceans, taking the temperature up and down on years-long scales. Climate change operates on decades-long scales, but goes monotonically up. This year we also have an increase in the short-term scale, leading to record temperatures.
El Niño isn't the only factor; it's just one of many. Together, it means we don't set record temperatures every single year. But it will happen more and more often because of the longer-term scale which only goes in one direction.
And this is an average global temperature:
> The average worldwide temperature was 17C (63F), just above the previous record of 16.9C reached in August 2016, according to data from the National Centers for Environmental Prediction.
https://climatereanalyzer.org/clim/t2_daily/
Information from the first couple of paragraphs of TFA