Chapter 1.4, Problem 24E

Greenhouse Gases Although greenhouse gases are essential to maintaining the temperature of the Earth, an excess of greenhouse gases can raise the temperature to dangerous levels. One of the most threatening greenhouse gases is carbon dioxide $\left({\text{CO}}_{\text{2}}\right)$. The Mauna Loa atmospheric ${\text{CO}}_{\text{2}}$ measurements constitute the longest continuous record of atmospheric ${\text{CO}}_{\text{2}}$ concentrations available in the world. The following table shows the concentration of ${\text{CO}}_{\text{2}}$ (in parts per million) at Mauna Loa, Hawaii, for three years. (Source: noaa.gov.)

Year	$C{O}_2$ (ppm)
1968	323
1999	368
2015	401

(a) Obtain the least-squares line that fits these data. (Let $x=0$ corresponds to 1968.)

(b) Estimate the concentration of CO₂ in the year 2008. How does this compare with the actual reading of 386?

(c) If the trend continues, in what year will the concentration of CO₂ reach 408 ppm?