Polvani, L.M., Previdi, M.,
England, M.R., Chiodo, G.
and Smith, K.L.
2020
Substantial twentieth-century
Arctic warming caused by
ozone-depleting substances.
Nature Climate Change 10: 130-133.
NOTE:
Polvani et al. (2020) state that ozone-depleting substances (ODS), e.g. chlorofluorocarbons, have increased substantially in the atmosphere since the late 1950s.
Much remains to be learned about their climate impact, considering ODS have radiative forcing efficiencies up to several thousand-fold larger than atmospheric CO2.
Polvani et al. note that over the period 1955-2005, the radiative forcing from ODS is estimated at 0.31 W m-2, which
"amounts to nearly one-third of the radiative forcing from CO2 (1.02 W m-2), making ODS, collectively, the second most important greenhouse gas in the latter half of the twentieth century."
Their objective was to estimate how much global warming might be attributable to direct radiative warming from increased ODS concentrations over the period 1955-2005.
SUMMARY:
Polvani et al. say their work reveals
"a substantial contribution of ODS to recent Arctic warming."
That would indicate a reduced role for atmospheric CO2.
Huang et al. (2019) found that climate models are presently overestimating the Arctic's warming rate by 67%, overstating the role CO2 is playing in Arctic temperature.
A similar finding was observed when focusing on temperatures within the Arctic region (60-90°N; Figure 1b).
There, average annual mean warming between 1955 and 2005 was 1.59°C when ODS were included in the model, but only 0.82°C when it was not.
Polvani et al. say that "ODS contributed almost 0.8°C to forced Arctic surface warming in the latter half of the twentieth century."
It was determined that ODS was also responsible for approximately half of the loss in September Arctic sea ice over the period 1955-2005
DETAILS:
To accomplish their design, the team of five researchers analyzed ensembles of climate model integrations for this 50-year interval with (designates the historical ensemble) and without (designated FixODSO3 ensemble) ODS present as a forcing factor.
Chart Below:
The climatic impact of ODS on (a) global temperature, (b) Arctic temperature and (c) September sea ice extent over the period 1955-2005 as determined by a ten-member CAM5LE ensemble both with (labelled historical) and without (labelled FixODSO3) ODS present in the model.
The boxes extend from the lower to upper quartile of the data, with a line at the median and whiskers showing the entire range across each ensemble; individual members are denoted by small black dots.
Arctic temperatures are averaged for latitudes 60-90°N). Red dots denote the observed values obtained from GISTEMP27 v.3 for surface temperature and HadISST28 v.2.2.0 for sea ice.
Reference
Huang, J., Ou, T., Chen, D.,
Lun, Y. and Zhao, Z.
2019
The amplified Arctic warming in the recent decades may have been overestimated by CMIP5 models.
Geophysical Research Letters 46: 13,338-12,345.