Have a Question about Climate Science? #askclimate : Earth Matters : Blogs
The answer is in fingerprints of change – each kind of climate change (driven by orbital change, greenhouse gases, aerosols, volcanoes, ocean variability etc.) has a different fingerprint – the regional and temporal pattern of temperatures/rainfall etc. We look for each of the fingerprints for plausible factors and see which ones fit all the observations best. For trends over the last 50 years, it is clearly the fingerprint of greenhouse gases (particularly carbon dioxide) that fit best.