Please keep in mind that most (nearly all?) of our climate models only include rising carbon emissions from human sources. Thawing permafrost and warming swamps and burning forests and such will (very likely) produce additional carbon(-equivalent greenhouse gases).
They use the beautiful term "Unrepresented Earth system feedback mechanisms" in this 2019 paper: https://www.nature.com/articles/s41586-019-1368-z.pdf
Keep on alarming, doomer!