1. Extend your linear modelling of CET in data set atldjf.txt by performing a multiple regression that includes the mean wintertime sea-level pressure at Iceland. Comment on whether this improves the fit ?
2. Use the sea-level pressures in data set atldjf.txt to explain the CET response by performing a multivariate regression excluding time. Which pressure observations are most important in explaining the CET ?
3. Test the sensitivity of the above multivariate regression to
the inclusion of time as an explanatory factor. Are pressures alone
sufficient for explaining the long-term trend in CET since 1950 ?