Figure 2. The level of hourly downward total solar irradiance at BRW, 1 Jan 2014 – 31 Dec 2014
The average annual temperature at BRW has increased significantly since 1985 (Figure 3). Specifically, the average annual temperature over the 2015-2020 time period was about 3.37 oC higher than in 1985-1990. The temperature data reported by the PABR weather station at the nearby Barrow Airport from 1985 through 2020 are consistent with the trend at BRW (Figure 4). The PABR data also indicates that the four warmest years since 1921 occurred in 2016, 2017, 2018, and 2019. In these four years, the average annual temperature was about 5.03o C higher than the average annual temperature from 1921 through 1939. These findings do not support the assertion by Lindzen that the recent warming is about the same as before the 1940s (2020, pp. 12-13). In terms of the magnitudes of the recent warming, the increases are consistent with Arctic amplification, as explained by Pithan & Mauritsen (2014) and Winton (2006).
The upward trend in temperature at both BRW and PABR is consistent with the temperature trend for the Arctic noted by Post et al. (2019), Markon et al. (2018, p 1190-1192), and Thoman et al. (2020, p. 4). Box et al. (2019) have reported significant changes in nine key measures of the Arctic climate system over 1971 through 2017. The qualitative story is clear: “the transformation of the Arctic to a warmer, less frozen, and biologically changed region is well underway.” (Thoman et al., 2020, p. 1). Consistent with these changes, the annual mean permafrost temperatures have increased at many locations throughout the Arctic (Romanovsky et al., 2017, p. 69). For example, based on data reported by EPA, the average annual permafrost temperature at the Deadhorse Permafrost Observatory ( https://permafrost.gi.alaska.edu) over the years 2015 through 2020 was about 2.81 oC higher than during the years 1985 through 1990 (EPA, 2021). In four of the 11 permafrost observatories whose 2020 annual temperatures are reported by EPA, the 2020 average temperatures were between -1 and 0oC. There is evidence that thawing has adverse implications for carbon emissions because of stimulated microbial decomposition (Schuur et al., 2021).
According to AMAP, “Arctic warming can also have effects far beyond the region: for example, the recent rapid warming of the Arctic appears to have created conditions favoring a persistent pattern in the jet stream that provokes unusual extreme temperature events in the Northern Hemisphere.” (AMAP, 2019, p. 4). Taylor et al. (2017, p. 303) have indicated it is very likely that human activities have contributed to these trends. While the literature supports this finding, it has also been suggested that the significant natural weather and climate variability in the Arctic poses an attribution challenge (Taylor et al., 2017, p. 319). Consistent with this reported variability, both downward total solar irradiance and temperature at the hourly level are highly variable (Figures 5 and 6). Concerning the hourly CO2 concentration levels, there is a significant upward trend in the hourly CO2 concentration levels over the sample (Figure 7). Despite the upward trend in both CO2concentrations and temperature, there is no visually obvious relationship between the two variables (Figure 8). While some climate deniers may be tempted to claim that the data in this figure vindicates their position, the view here is that a lack of correlation between two variables only rules out causality when the hypothesized relationship is quite simple.