Final answer:
In the late 1980s, scientists and the public began to widely recognize the trend of increasing average temperatures on Earth, a phenomenon closely linked to human activity and industrialization. The concept of global warming entered mainstream scientific discussion during this decade.
Step-by-step explanation:
Scientists began to notice that the average temperature of the earth was increasing in the late 1980s, when the concept of global warming gained broader recognition. Data shows the average annual temperature on Earth has been rising over the past 100 years, largely attributed to human activities such as the burning of fossil fuels since the Industrial Revolution, leading to a rise in greenhouse gas levels.
The consensus among climate researchers is that these activities are the primary cause of the observed warming. It's worth noting that in 1896, Swedish physicist Arrhenius helped lay the groundwork for understanding the greenhouse effect, but it was not until nearly a century later that the broader scientific community and public began to grasp the implications of climate change.