>In order to relate global mean temperature derived from the C3S dataset (ERA5) to the pre-industrial era, we use the estimate that the 1981-2010 reference period is approximately 0.69°C and that the 1991-2020 reference period is approximately 0.88°C warmer than the period 1850-1900, the time period typically referred to as the pre-industrial level for temperatures by the Intergovernmental Panel on Climate Change (IPCC).
>Note that these estimates were updated during Autumn 2021, due to new findings published in AR6 WGI report “Climate Change 2021: The Physical Science Basis”. See more here under “Reference periods and anomalies”.
I’m sure this is all fine and valid, but they really need to work on their messaging. To a skeptic, this is gonna sound a lot like “oh yeah we pretty much just made the numbers up.”