Actually the sun had below average activity in the early 70's and very weak activity in the mid 70's to about 1978. Activity did climb however in 1979. So the cold 70's occurred with weak solar activity. Exactly what one would expect.
The Sun was pretty active in the late 1970s, when all the pre-moon bats
were worried about "nuclear Winter", led by the dishonest Carl Sagan.
We were in a Sunspot Maximum in the mid 1970’s. Talk about wonderful HF radio propogation. Every day I drove through the high desert in NM with a 550 watt HF transceiver under my dashboard. WOW was that fun.
Worked all over the world driving down the road. Hope I live to see that again.
Actually the sun had below average activity in the early 70's and very weak activity in the mid 70's to about 1978. Activity did climb however in 1979. So the cold 70's occurred with weak solar activity. Exactly what one would expect.