Huang, J., Ou, T., Chen, D.,
Lun, Y. and Zhao, Z.
2019
The amplified
Arctic warming
in recent decades
may have been
overestimated
by CMIP5 models.
Geophysical Research
Letters 46: 13,338-12,345.
NOTE:
Policies aimed
at protecting
the environment
from CO2-induced
global warming
rely almost entirely
upon models.
What if those
predictions
are wrong?
SUMMARY:
The model-predicted
secular rate of warming
was 67% higher
than that
determined from
observations
(0.21 °C).
The chart shows an
increasing disparity
between modeled
and
observed warming
rates, that starts
around the middle
of the record,
and grows to
+0.14 °C
per decade
by the mid-2010s.
Huang et al. state that
"anthropogenically
(man made)
induced secular warming
has been overestimated
by the CMIP5 GCMs
during the most recent
warming period, and
the overestimation
is aggravated
with time."
Given the error bars
shown on the chart,
in the very near future
the observed warming rate
will likely fall outside
'the significance levels
of the ensemble
model mean,
removing
any remaining
credibility
left in the
model
projections
of future
Arctic warming.
The five researchers say
"it is hard to figure out
whether the overestimation
of the secular Arctic warming rate
mainly comes from inaccurately
simulated change of Arctic
sea ice extent or effects of
associated physical processes
under increasing anthropogenic
emissions."
DETAILS
In their study,
five researchers
set out to examine
how well
model projections
of Arctic temperatures
( poleward of 60°N )
compared with good
old-fashioned
measurements.
They used a
statistical procedure
suitable for nonlinear analysis
(ensemble empirical mode
decomposition) to examine
secular Arctic warming
over the period 1880-2017.
Observational data
utilized in the study
were obtained from
the HadCRUT4.6
temperature database,
whereas model-based
temperature projections
were derived from simulations
from 36 Coupled Model
Inter-comparison
Project Phase 5
( CMIP5 )
global climate models
( GCMs ).
The model-estimated
rate of secular warming
(the solid red line)
increased quite sharply
across the 138-year period,
rising from a value of around
0 °C per decade
at the beginning
of the record to a value
of 0.35 °C per decade
at the end.
Observations started off
with a higher warming rate
than that of the models
(a rate of 0.13 °C per decade;
the solid black line.
Then dipped below
the rate of warming
predicted by the models
around the middle
of the record.
Then experiencing
a lower rate of warming
relative to the models
through the end of the record.
CHART BELOW:
Observed and model-predicted
rates of nonlinear, secular warming
in the Arctic (60-90°N)
over the period 1880-2017.
The black and red dashed lines
indicate the 10th and 90th
percentiles for temperature means.
