Scientists presumably intending to report unusual modern warming in response to anthropogenic activities indicate all or nearly all modern warming and treeline advances at a Rocky Mountain ice patch site occurred from the 1910s to the 1940s. [emphasis, links added]
An interesting observation found in the body of a new study (Pederson et al., 2025) is that 30% of the globe’s forests have not even warmed in the modern era (1900s-present), and just 50% of the globe’s forests have not advanced upslope.
This would appear to challenge claims of global-scale warming.
“Variations in local conditions likely explain why recent warming documented at approximately 70% of treelines globally only resulted in ~50% exhibiting upslope advances.”
The study documents a millennia-scale treeline and temperature record from a high-elevation site (>3,000m [9,843 feet] above sea level) in the USA’s Rocky Mountains (Yellowstone region).
A melting ice patch reveals a pine forest grew at this elevation, which is ~180 m [591 feet] above today’s treeline limit, approximately 6,500 to 4,200 years ago.
Higher treelines are indicative of warmer Holocene temperatures.
Volcanically-induced cooling after 4,200 years ago led to the decline in treeline elevation to modern levels in the Late Holocene.
The authors point out that the 21st-century warming in this region has now equaled the warm-season temperatures of the mid-Holocene.
Interestingly, the observed (instrumental) and reconstructed modern warming trends shown in the paper indicate all or nearly all accomplished in the decades between the 1910s and 1940s.
The modern treeline advance was also achieved by the 1940s.
This would appear to indicate there has been no obvious net warming trend or net treeline advance since the 1940s despite the abrupt increase in greenhouse gas emissions from fossil fuel burning after 1945.
Read more at No Tricks Zone
