Explanation:

• The Keeling Curve is a graph showing the concentration of CO₂ in Earth’s atmosphere since 1958, based on continuous measurements taken at the Mauna Loa Observatory in Hawaii by Dr. Charles David Keeling.
• It is considered a reliable measure of CO₂ in the middle troposphere and has been instrumental in raising awareness about global warming and climate change.
• The curve shows both a long-term upward trend (due to fossil fuel burning) and seasonal fluctuations (due to plant growth and decay cycles).