Moving on to the CO2 data for the next section of the data lab.

The next several questions anticipate your having followed the slides through the process of creatingfive groups based on date(created using the commandxtile) and run regressions just on the data in those groups. Use yourifstatements with regression carefully!***

Regress adjusted CO2 on dec_date for group 1, i.e. the first about 12+ years of the data.

How much does the CO2 level increase per year during this period?