In summary, the mid-Holocene, roughly 6,000 years ago, was generally warmer than today, but only in summer and only in the northern hemisphere. More over, we clearly know the cause of this natural warming, and know without doubt that this proven “astronomical” climate forcing mechanism cannot be responsible for the warming over the last 100 years.
ncdc.noaa.gov

Koch compared the kill dates of the trees in the southern and northern Coast Mountains of British Columbia and those in the mid- and southern Rocky Mountains in Canada to similar records from the Yukon Territory, the European Alps, New Zealand and South America. He also looked at the age of Oetzi, the prehistoric mummified alpine "Iceman" found at Niederjoch Glacier, and similarly well-preserved wood from glaciers and snowfields in Scandinavia. The radiocarbon dates seem to be the same around the world, according to Koch. It's important to note that there have been many advances and retreats of these glaciers over the past 7000 years, but no retreats that have pushed them back so far upstream as to expose these trees.

Read more at: phys.org