Climate 'science'

The definition of ‘climate’ adopted by the World Meteorological Organisation is the average of a particular weather parameter over 30 years. It was introduced at the 1934 Wiesbaden conference of the International Meteorological Organisation (WMO’s precursor) because data sets were only held to be reliable after 1900, so 1901 – 1930 was used as an initial basis for assessing climate. It has a certain arbitrariness, it could have been 25 years.

For its recent 1.5°C report the IPCC has changed the definition of climate to what has been loosely called “the climate we are in.” It still uses 30 years for its estimate of global warming and hence climate – but now it is the 30 years centred on the present.
...
Global warming is now defined by the IPCC as a speculative 30-year global average temperature that is based, on one hand, on the observed global temperature data from the past 15 years and, on the other hand, on assumed global temperatures for the next 15 years. This proposition was put before the recent IPCC meeting at Incheon, in the Republic of Korea and agreed as a reasonable thing to do to better communicate climate trends. Astonishingly, this new IPCC definition mixes real and empirical data with non-exiting and speculative data and simply assumes that a short-term 15-year trend won’t change for another 15 years in the future.
Just think of the opportunities to jigger the 'data' for political purposes in that mess.