Government climate scientists typically start their graphs in 1979 – the year of peak Arctic sea ice, which was up two million km² from 1974.
1979 was the coldest year on record in the eastern Arctic. By cherry picking 1979, they turn a long term cooling trend into a sharp warming trend.
1979 was also the coldest winter on record in the US
Scientists use 1979 satellite launches as an excuse, but there was plenty of other data available.