A new scientific study says surface temperatures in the Northeastern U.S. (Appalachian Mountains) have undergone a significant long-term cooling trend since the early 20th century, complicating the detection of a clear anthropogenic global warming (AGW) signal for the region.
According to Eck (2018), the two coldest Appalachian winters since 1910 were recorded in recent years (2009-’10 and 2010-’11), and 9 of the 10 warmest winters occurred prior to 1960.
In the early 1930s, Appalachian winters were 4.7°C warmer than they have been during the last 30 years (1987-2017).
Several other recently-published papers also reveal a long-term cooling trend not only for the Northeastern U.S. (Eck, 2018), but the Southeastern U.S. (Rogers, 2013; Christy and McNider, 2016), the Central U.S. (Alter et al., 2017), and the Southwestern and Northwestern U.S. (Loisel et al., 2017; Steinman et al., 2016).
In other words, the regions in the continental United States that are less affected by urbanization biases and artificial instrumental heating may not be responding to “global” warming or to the rise in anthropogenic CO2 emissions as climate models have suggested.
“[A] majority (12/14) of the regions within the SAM [Southern Appalachian Mountains] have experienced a long-term decline in mean winter temperatures since 1910. Even after removing the highly anomalous 2009-2010 winter season, which was more than two standard deviations away from the long-term mean, the cooling of mean winter temperatures is still evident.”
“Higher winter temperatures dominated the early 20th century in the SAM [Southern Appalachian Mountains] with nine of the ten warmest winter seasons on record in the region having occurred before 1960.”
“The 1931-1932 winter season, the warmest on record, averaged 8.0°C for DJF [December-February], nearly 4.7°C higher than the 1987-2017 normal mean winter temperature of 3.3°C.”
“Despite the 2016-2017 winter season finishing with the highest mean temperatures (5.7ºC) observed in the SAM [Southern Appalachian Mountains] since 1956-1957, there have been several years of anomalous negative temperature anomalies, with the 2009-2010 (0.3ºC) and 2010-2011 (1.2ºC) winter seasons finishing as two of the coldest on record for all regions.”
Central U.S. Cooling (-0.35°C) Since 1910
“In the central United States … observational data indicate that rainfall increased, surface air temperature decreased, and surface humidity increased during the summer over the course of the 20th century concurrently with increases in both agricultural production and global GHG emissions.”
“From 1910- 1949 (pre-agricultural development, pre-DEV) to 1970-2009 (full agricultural development, full-DEV), the central United States experienced large-scale increases in rainfall of up to 35% and decreases in surface air temperature of up to 1°C during the boreal summer months of July and August … which conflicts with expectations from climate change projections for the end of the 21st century (i.e., warming and decreasing rainfall) (Melillo et al., 2014).”
“Thus, it seems that GHG emissions do not contribute greatly to the regional changes in summer climate that have been observed in the central United States.”
Southeastern U.S. Cooling Since 1890s
Long-Term Cooling Trend In The Western U.S.