By Gavin Schmidt & Michael Mann, RealClimate
Extending the instrumental record of climate beyond the late 19th Century when many of the national weather centers were first started is an important, difficult and undervalued task. It often is more akin to historical detective work than to climatology and can involve long searches in dusty archives, the ability to read archaic scripts and handwriting, and even Latin translations (for instance, when going through the archives of the Paris Observatory) (sounds like a recent bestseller, only less lucrative, no?).
Why bother? Well, it is unfortunate, though probably not coincidental, that the modern record starts at the same time that significant modifications of atmopsheric composition (greenhouse gases, aerosols etc.) were occuring on a global scale. Thus this period is not ideal for assessing the magnitude of natural changes (both intrinsic and forced by natural processes like solar variability or volcanic eruptions) since there is likely a contamination from human-related causes. So extending instrumental records back as far as possible is an important approach to providing a context for modern changes.
