The most extensive research into tree mortality since the AR5 has been in the western USA, where anthropogenic climate change accounted for half the magnitude of a drought in the period 2000-2020 that has been the most severe since the 1500s,  and for one-tenth to one-quarter of the magnitude of the 2012-2014 period of the severe drought in California that lasted from 2012 to 2016 . Across the western USA, anthropogenic climate change doubled tree mortality between 1955 and 2007 . Lodgepole pine  mortality increased 700% from 2000 to 2013  and piñon pine  experienced >50% mortality from 2002 to 2014 . In montane conifer forest in California, anthropogenic climate change has increased tree mortality by one-quarter . One-quarter of the trees died in some areas, with mortality rates of ponderosa pine  and sugar pine  increasing to up to 700% of pre-drought rates . Substantial field evidence shows that anthropogenic climate change has caused extensive tree mortality in North America .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report