Physics & Climate
e) Solar Influence
The
Fifth
and
Sixth
Assessment
Report
(
AR5
and
AR6
)
[1,
2])
of
the
Intergovernmental
Panel
on
Climate
Change
(IPCC)
announced
new
evidence
of
an
anthropogenic
climate
change
based
on
many
independent
scientific
analyses
from
observations
of
the
climate
system,
paleoclimate
archives,
theoretical
studies
of
climate
processes,
and
simulations
using
climate
models.
In
these
reports
the
IPCC
classifies
the
hu
man
influence
as
extremely
likely
to
be
the
dominant
cause
of
the
observed
warming
since
the
mid-20th
century
(e.g.,
AR5-WG1-SPM
-D3),
while
contributions
from
natural
forcings
and
internal
variability
would
only
likely
be
in
the
range
of
−0.1°C
to
0.1°C.
Particularly
increasing
emissions
of
carbon
dioxide
over
the
last
century
are
made
responsible
for
this
change,
and
the
Equilibrium
Climate
Sensitivity
(ECS)
as
a
measure
for
the
Earth’s
temperature
increase
at
doubled
CO
2
concentration
in
the
atmosphere
is
specified
with
an
assessed
best
estimate
of
3°C
and
a
likely
range
of
2.5°C
to
4°C
(high
con
fi
-
dence,
AR6-WG1-SPM
, A.4.4).
However,
anthropogenic
contributions
to
this
warming
are
still
quite
contradictorily
discussed,
and
because
of
the
far
reaching
consequences
for
future
climate
predictions,
above
all,
it
is
important
to
scrutinize,
how
far
such
an
assertion
of
a
pure
anthropogenic
climate
change
can
really
be
confirmed
by
the
increasing
GH-gas
concentrations,
or
how
far
also
native
effects
like
variations
of
the
solar
activity
can
explain
the
observed
rising
temperature.
Also
the
impact
of
thermally
and
solar
induced
cloud
cover
changes,
which
affect
our
climate,
but
which
are
not
always
well
understood,
have
to
be
considered
with
its
implications
on
the
observed
tem
-
perature changes.
Recently
a
researcher
team
of
23
experts
in
the
fields
of
solar
physics
and
climate
science
from
14
different
countries
published
an
extensive
scientific
study,
in
which
they
analyzed
quite
controversial
datasets
(
Connolly
et
al.
2021
[3]).
From
these
data
they
could
explain
global
warming
as
anything
from
“
mostly
human-caused
”
to
“
mostly
natural
”,
and
they
infer
that
the
IPCC
may
have
been
premature
in
their
conclusion
that
recent
climate
change
is
mostly
caused by human greenhouse gas emissions.
In
another
actual
study
(
Harde
2022
[4])
we
compare
composed
rural
land
and
sea
surface
tem
perature
measurements
of
the
Northern
Hemisphere
(
Soon
et
al.
2015
[5])
with
simula
-
tions
performed
by
an
ad
vanced
2-Lay
-
er-Climate-Model
(2LCM)
(
Harde
2014
[6],
Harde
2017
[7]),
which
allows
to
calculate
the
global
tempera
ture
trend
under
the
simultaneous
im
pact
of
in
-
creasing
CO
2
concentrations
and
solar
variability.
This
model
with
its
main
features
is
briefly
discussed
together
with
the
CO
2
radiative
forcing,
the
solar
radiative
forcing
and their specific feedbacks (see also:
b) Climate Sensitivity
, 2-Layer Model).
This
study
covers
simulations
under
quite
contrasting
conditions,
on
the
one
hand
based
on
the
model
means
of
the
Coupled
Model
Intercomparison
Project
Phase
5
(CMIP5)
and
Phase
6
(CMIP6),
characterized
by
Equilibrium
Climate
Sensitivities
of
ECS
=
3.2°C
for
CMIP5
and
ECS
=
3.78°C
for
CMIP6,
on
the
other
hand
based
on
our
own
calculations
of
CO
2
radiative
forcing
with
an
ECS
=
0.68°C.
For
the
solar
radiative
forcing
we
consider
six
different
Total
Solar
Irradiance
(TSI)
time
series
with
significantly
different
trends,
which
with
respect
to
their
impact
on
global
warming
are
subject
of
a
further
amplification
by
thermally
induced
feed
-
backs
as
well
as
solar
induced
cloud
feedbacks
(see
diagram
above).
Together
these
amplifi
-
cations
are
denoted
by
the
Equilibrium
Solar
Sensitivity
ESS
(temperature
change
at
TSI
=
0.1%)
with
values
varying
between
0.19°C
and
0.9°C
depending
on
the
prevailing
feedbacks.
The
amplification
due
to
cloud
changes
was
derived
from
observations
within
the
Internatio
-
nal
Satellite
Cloud
Climatology
Project
over
the
1980s
and
1990s
(see:
b)
Climate
Sensitivity
,
Clouds).
From
these
simulations
we
see
that
under
CMIP5/6
conditions
with
large
thermal
feedbacks
but
very
flat
solar
variability
the
calculated
temperature
increase
over
the
Industrial
Era
is
di
-
stinctly
larger
than
found
from
obser
-
vations.
The
left
plot
shows
the
calcu
-
lated
temperature
anomaly
(Ma
genta
Diamonds)
for
the
model
mean
of
the
CMIP6
ESMs
based
on
the
TSI-
time
series
of
Matthes
et
al.
(2017)
[8]
(Green
Squares),
which
after
averaging
over
the
11-yrs
Schwabe
cycles
is
characterized
by
a
very
flat
trend.
The
composed
temperature
time
series
as
a
weighting
of
30%
rural
land
data
(
Soon
et
al.
2015
[5])
and
70%
sea
surface
data
(
Kennedy
et
al. 2019
[9]) is displayed as Blue Triangles.
Even
CO
2
forcing
alone
contributes
to
a
too
large
warming,
in
particular
the
observed
domi
-
nant
temperature
variations
over
the
last
century
with
a
broader
dip
over
the
50s
to
80s
cannot
be
traced
back
only
to
CO
2
,
which
was
only
monotonically
increasing
over
the
considered period and mistakenly is assumed to be only of anthropogenic origin.
On
the
other
hand
calculations
relying
on
our
own
CO
2
radiative
forcing
data
(
Harde
2017
[7])
with
significantly
smaller
thermal
feedback
but
larger
solar
variability
show
excellent
agree
-
ment
with
the
land-ocean
tempera
ture
composite
(30%
rural,
70%
sea
surface).
So
a
si
mu
-
lation
based
on
the
TSI
time
series
of
Hoyt
&
Schatten
(1993)
[10]
repro
duces
the
stronger
temperature
drop
over
the
50s
till
80s
and
also
the
total
warming
of
about
0.9°C
over
the
Industrial
Era
with
a
correlation fac
tor of r = 0.95.
A
larger
deviation
is
only
found
for
the
late
19th
and
early
20th
century.
Assuming
a
composed
temperature
series
of
only
10%
land
and
90%
ocean
weighting
(left
plot,
Blue
Tri
-
angles)
and
starting
the
comparison
with
the
calculation
(Magenta
Dia
-
monds)
at
1908,
this
correlation
is
almost
perfect
(r
=
0.99),
indicating
a
slightly
larger
sen
-
sitivity of our simulation to the sea surface temperature data.
Consideration
of
additional
forcings
like
the
Atlantic
Multi-Decadal
Oscillation
with
its
maximum
phase
at
the
end
of
the
19th
century
and
a
period
of
about
60
yrs
as
well
as
other
native
oscillations
can
further
improve
this
agreement,
but
as
long
as
their
size
and
origin
cannot
better
be
identified,
is
solar
radiative
forcing
and
its
amplification
by
induced
cloud
changes
the
most
plausible
explanation
for
the
observed
temperature
changes,
all
the
more
also
the
other
forcings
more
or
less
are
expected
to
be
controlled
by
the
solar
wind
and
super
-
posed planetary gravitational impacts (
Mörner et al. 2020
[11]).
From
our
calculations
we
derive
a
CO
2
affected
portion
to
global
warming
over
the
Industrial
Era
of
not
more
than
0.34°C
and
over
the
last
century
of
only
0.24°C,
which
is
30%
of
the
total
warming,
while
apparently
two
thirds
are
caused
by
the
solar
impact.
As
human
CO
2
emissions
should
not
have
contributed
more
than
15%
to
the
increase
over
the
Industrial
Era
(see:
d) Carbon Cycle
), the anthropogenic fraction to global warming is expected to be only 0.05°C.
References
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