The suggestion that humans are changing the climate tends to evoke two main responses. It's also highly politicized and contentious. To help the average citizen navigate this debate, here are some frequently asked questions. We experience weather locally, at one place and at one time.
Climatology studies the average weather of the entire globe over centuries.
Climate's natural variation has been large. Paleoclimatologists, who attempt to reconstruct the climate's of past eras, have evidence that at times the Earth's average temperature has been 10 degrees cooler than today and at other times 20 degrees warmer than today. It's been very difficult. Climatologists only have comprehensive global temperature and rain fall measurements going back a century. Over this period, the last 100 years appears to stand out.