The earth’s climate is getting warmer. The most common theory attributes the increase to an increase in atmospheric levels of carbon dioxide (CO2), a greenhouse gas. Here is a scatterplot showing the mean annual temperature anomaly (the difference between the mean global temperature and a base period of 1981 to 2010 in C) and the CO2 concentration in the atmosphere in parts per million (ppm) at the top of Mauna Loa in Hawaii for the years 1959 to 2016.

a) What is the correlation between CO2 and Temperature?
b) Explain the meaning of R-squared in this context.
c) Give the regression equation.
d) What is the meaning of the slope in this equation?
e) What is the meaning of the y-intercept of this equation?
f) Here is a scatterplot of the residuals vs. predicted values.
Does this plot show evidence of the violation of any assumptions behind the regression? If so, which ones?

g) CO₂ levels will probably reach 450 ppm by 2050. What mean temperature anomaly does the regression predict for that concentration of CO₂?
h) Does the answer in part g mean that when the CO₂ level hits 450 ppm, the temperature anomaly will reach the predicted level? Explain briefly.

Transcribed Image Text:

Global_temp_anomaly 0.75 0.50 0.25 0.00 325 350 375 Variable Intercept CO2(ppm) CO₂ (ppm) A regression predicting Temperature anomaly from CO₂ pro- duces the following output table: Response variable is: Global_temp_anomaly R-squared = 89.7% s = 0.0885 Coefficient -3.17933 400 0.0099179