On LinkedIn last week, I was asked my definition of "climate change." In case you are interested, here it is: Our climate continually changes. Clearly, the mean atmospheric and oceanic temperatures of earth are warmer than 100 years ago. This is due to a mix of natural (volcanic, solar, internal variability) and human-driven factors including greenhouse gas concentrations, land use changes, instrument relocations and numerous other factors. Unfortunately, we don't know the exact contribution of each of these factors.