=+16. Climate change. The Earth has been getting warmer.

Most climate scientists agree that one important cause of the warming is the increase in atmospheric levels of carbon dioxide 1CO22, a greenhouse gas. Here is part of a regression analysis of the mean annual CO2 concentration in the atmosphere, measured in parts per thousand (ppt), at the top of Mauna Loa in Hawaii and the mean annual air temperature over both land and sea across the globe, in degrees Celsius. The scatterplots and residuals plots indicated that the data were appropriate for inference and the response variable is Temp.

Variable Coeff SE(Coeff)

Intercept 10.707 0.4810 CO2 0.010 0.0013 R-squared = 67.8%

s = 0.0985 with 29 - 2 = 27 degrees of freedom M15_SHAR8696_03_SE_C15.indd 529 14/07/14 7:30 AM 530 CHAPTER 15 Inference for Regression