The Short Version
The claimed warming rate is broadly supported, but the exact framing overstates precision. A station record from Twee Rivieren shows mean annual maximum temperature rising by about 1.95°C from 1960 to 2009, or roughly 0.040°C per year, which is very close to 0.039°C per year. The “about 1.6°C over 40 years” wording is an approximation rather than a directly reported park-wide 40-year result.