rottndog, why was Greenland green? It certainly wasn’t because the ice shelf had melted. The study just mentioned shows the ice shelf has been around for half a million years. The reason is because Erik the Red was a great real estate agent. He figured out that persuading all his friends to migrate to “Freezingcoldiceshelfland” was hardly going to attract big buyers. :-)
Okay, I’m being slightly facetious (although there is a myth that Erik the Red did over-exagerate Greenland’s lushness). There was a warm medieval period back around 900 years ago. Climate does change naturally - the sun was warmer back then, it got colder during the 1800’s when the little ice age hit us, then got warmer in the early 20th century. The sun has been the major driver of temperature over the past 1000 years.
But the correlation between solar activity and temperature ended in 1975 when temperatures started rising - solar levels have been steady since the 1950’s. So the question isn’t ‘has climate changed naturally in the past?’ but ‘what’s causing global warming now?’ The usual suspects - solar variations, volcanoes, Milankovitch cycles - are conspicuously absent.