We could improve this by adding a small offset to the linear term which is what we originally showed as the best linear fit. (rabett.blogspot.ru)
Because of the «noise», relatively minor variations in temperatures between different data bases can lead to significant differences between linear fits for short time frames. (skepticalscience.com)
Remove the filter from your data and then tell us what your R ^ 2 linear fit reveals. (judithcurry.com)