Jay Jacob,
You're misquoting and misreading them.
They say, "Experts are certain 2023 will be 'the warmest year in recorded history." History means, written down; documented. If you read their website, NASA’s Goddard Institute for Space Studies, the National Oceanic and Atmospheric Administration’s National Climactic Data Center and the UK Meteorological Office’s Hadley Centre, you will see they all mean readings taken from instruments since 1880. This means the warmest year since 1880.
The fundamental difference is that the Paleocene–Eocene Thermal Maximum was caused by natural processes. These changes are caused by human activity.