(Part of the How to Talk to a Global Warming Skeptic guide)
Objection: The alarmists were predicting the onset of an ice age in the ’70s. Now it’s too much warming! Why should we believe them this time?
Answer: It is true that there were some predictions of an “imminent ice age” in the 1970s, but a cursory comparison of those warnings and today’s reveals a huge difference.
Today, you have a widespread scientific consensus, supported by national academies and all the major scientific institutions, solidly behind the warning that the temperature is rising, anthropogenic CO2 is the primary cause, and it will worsen unless we reduce emissions.
In the 1970s, there was a book in the popular press, a few articles in popular magazines, and a small amount of scientific speculation based on the recently discovered glacial cycles and the recent slight cooling trend from air pollution blocking the sunlight. There were no daily headlines. There was no avalanche of scientific articles. There were no United Nations treaties or commissions. No G8 summits on the dangers and possible solutions. No institutional pronouncements. You could find broader “consensus” on a coming alien invasion.
Quite simply, there is no comparison.
If you want some additional detail, Real Climate has discussed this, and William Connelly has made a hobby of gathering everything that was written about global cooling at the time.