Andean Glaciation in South America During the Holocene
Rodbell, D.T., Smith, J.A. and Mark, B.G. 2009. Glaciation in the Andes during the Lateglacial and Holocene. Quaternary Science Reviews 28: 2165-2212.
The temporal correspondence of the Little Ice Age in essentially all of (1a) the glacierized portions of the Northern Hemisphere and (1b) the great meriodional expanse of most of Andean South America, as well as (2) the similar glacial activity of both parts of the planet during this time period, provide strong support for the proposition that much of the world commenced its return to its current more milder climatic state from the very bottom of what we could call the Holocene's "thermal basement." And this evident truth suggests that the 20th-century warming of the planet should have been rather dramatic, starting (as it did) from such a cold initial temperature.
Considered in this light, the significant warming that followed the Little Ice Age is readily recognized to not have been all that unusual, as it was only what should have been expected to occur, in light of the warming's unusual (extremely low) thermal point of origin. And recognizing that fact helps one to understand why there is no compelling reason to assume that the concurrent historical increase in the atmosphere's CO2 content had anything at all to do with the post-Little Ice Age warming. The time for the latter had simply come, based on the specific state of the prior millennial-scale warming-and-cooling cycle of the planet; and that state (record global cold) just happened to coincide with the start of the historical increase in the air's CO2 content that was caused by the historical increase in mankind's industrial activity, which has had essentially no impact on either the rate or magnitude of global warming over the last hundred or so years.