I just bought X-rite calibration kit but one thing makes me curious. Should I set colder white point (6500K) for summertime and warmer (5000K) for winter? Will global warming affect my settings?
For color calibration to be of any real use, it is important that you work in a controlled, stable-light environment - meaning that your light quality does not change. This does mean avoiding natural light as it changes due to time of day and, as your question also notes, the time of year.
So circling back around to your question - the white-point setting depends on your lighting environment and how you'd like your colors to be perceived in that environment. Global warming should not effect colors except in putting particulates into the air that may impact light quality. Again, by working in a controlled, stable-light environment, this should not be an issue.