the Keeling Curve shows that ...

a.
atmospheric carbon dioxide concentrations have risen steadily over the last 60 years.

b.
the biosphere has no impact on atmospheric composition.

c.
Hawaii's temperature has risen steadily over the last century.

d.
atmospheric carbon dioxide concentrations were higher in 1960 than they are today.

The Keeling Curve named after Charles David Keeling is a type of graph that shows the concentrations of carbon dioxide in the atmosphere. This was stated by Charles David Keeling and includes annual measurements since 1958 taken in Hawaii and other zones around the world. Due to these measurements it has been determined the concentration of carbon dioxide varies slightly during the year and also, in the last decades the total concentration has steadily increased which shows the impact of human activities on the atmosphere composition as in 1958 there were 313 ppmv and 60 yeas later in 2018 the measure registered was around 450 ppmv. Thus, the Keeling Curve shows "atmospheric carbon dioxide concentrations have risen steadily over the last 60 years".