## Reading layer `arctic_fires' from data source 
##   `/home/rstudio/shiny/Applied_Biogography/canada/data/arctic_fires.shp' 
##   using driver `ESRI Shapefile'
## Simple feature collection with 363073 features and 6 fields
## Geometry type: POINT
## Dimension:     XY
## Bounding box:  xmin: -179.7813 ymin: 66.5001 xmax: 179.9466 ymax: 85.2332
## Geodetic CRS:  WGS 84

Introduction

With COP26 coming up I thought it might be interesting to check the empirical data on temperature anomalies above the arctic circle (~ >66.5 degrees N). The climate records are available in R through the rnoaa package. The data set is documented here. https://www.ncei.noaa.gov/metadata/geoportal/rest/metadata/item/gov.noaa.ncdc:C00861/html

The data is used in multiple publications, and is subject to good quality controls.

Method

The following steps were used to produce a single plot of temperature anomalies from multiple stations.

  1. Extract only the stations with more than 50 years of records of average temperature
  2. Group the data by station id and month of the year
  3. Subtract the overall monthly mean for that station from the observed daily value.
  4. Take the mean of these anomalies for each day of the records over all the stations included.
  5. Simplify to a single value per month by taking the mean of these daily values
  6. Plot this single time series as a dynamic graph with a ten year (120 month) rolling average. Note this value can be changed by the user.

Stations included in the analysis

Dygraph with ten year rolling average

Number of fires above the arctic circle

Fires in 2020

## Classes 'sf' and 'data.frame':   648 obs. of  1 variable:
##  $ geometry:sfc_POLYGON of length 648; first list element: List of 1
##   ..$ : num [1:23, 1:2] -145 -145 -145 -145 -145 ...
##   ..- attr(*, "class")= chr [1:3] "XY" "POLYGON" "sfg"
##  - attr(*, "sf_column")= chr "geometry"
##  - attr(*, "agr")= Factor w/ 3 levels "constant","aggregate",..: 
##   ..- attr(*, "names")= chr(0)

Interpretation

The current warming trend in the ten year mean began to be noticeable around 2000, which implies that the change initiated in 1990. This coincides with analyses shown in IPCC reports . However there was a clear cooling trend between the 1940s and the 1970s. So over the time period analysed the amount of observed warming depends on the reference point used. If the current trend is analysed alone then the warming is around 3 degrees C. If current temperatures are compared with the peak in the 1940s the warming is around 1.5 degrees. One possible explanation for the cooling observed in the 1970s is the impact of aerosols. Clean air legislation was widely adopted in the 1980s and households switched from burning coal to burning gas. (CESS 1976; Krishnan and Ramanathan 2002; Fleming 1998; Chylek and Wong 1995; Zhou and Savijärvi 2014). However, the data alone are open to many different interpretations, including some more alarmist takes (Tollefson 2018). In particular the almost 1.5 degrees C increase in the last decade could be extrapolated to suggest that the target of restricting warming to below 1.5 C would not be feasible for the area above the arctic circle.

References

CESS, R. D. 1976. “Stratospheric Aerosols: Effect Upon Atmospheric Temperature and Global Climate.” Tellus 28 (1): 1–10. https://doi.org/10.1111/j.2153-3490.1976.tb00645.x.
Chylek, Petr, and J. Wong. 1995. “Effect of Absorbing Aerosols on Global Radiation Budget.” Geophysical Research Letters 22 (8): 929–31. https://doi.org/10.1029/95gl00800.
Fleming, James R. 1998. “Global Cooling, Global Warming: Historical Dimensions.” In. Oxford University Press. https://doi.org/10.1093/oso/9780195078701.003.0015.
Krishnan, R., and V. Ramanathan. 2002. “Evidence of Surface Cooling from Absorbing Aerosols.” Geophysical Research Letters 29 (9). https://doi.org/10.1029/2002gl014687.
Tollefson, Jeff. 2018. “IPCC Says Limiting Global Warming to 1.5 °C Will Require Drastic Action.” Nature 562 (7726): 172–73. https://doi.org/10.1038/d41586-018-06876-2.
Zhou, Y., and H. Savijärvi. 2014. “The Effect of Aerosols on Long Wave Radiation and Global Warming.” Atmospheric Research 135-136 (January): 102–11. https://doi.org/10.1016/j.atmosres.2013.08.009.