Climate is a complex system,
composed of many different
processes, showing non-linear
relations between variables.
Earth's atmosphere
can be considered
as a closed non-linear
thermodynamic system.
The thermodynamic
state is maintained by
a balance between
incoming solar radiation,
heating the planet,
and outgoing shortwave
and longwave radiation,
cooling the planet.
The energy
balance is
affected by
the incoming
and outgoing
radiation.
Changes in the
energy balance
of the atmosphere
are the drivers
of climate change.
It is believed
that Earth absorbs
slightly more energy
from the Sun, than is
emitted back to space,
thanks to increasing
amounts of CO2
in the atmosphere,
creating an energy
imbalance.
Energy
imbalance
has been
investigated
using satellites
and models,
and it seems
to be increasing
in the last decades.
Those changes
have been argued
to be due to human
activities.
When reaching
the Earth, part of
the incoming
solar radiation
is reflected
off the clouds,
and the surface,
as shortwave
radiation (SW).
Changes in the
cloud distribution,
or surface albedo
( reflectivity),
will change the
energy balance.
In the last
four decades,
changes in
cloud distribution
of low-level clouds,
such as subtropical
stratocumulus,
have been important.
They have the ability
to reflect large
amounts of radiation
back to space,
but do not
significantly
reduce outgoing
radiation cooling
our planet.
The rest
of the radiation
is absorbed
by the atmosphere,
or passes through
to the Earth’s surface.
Shortwave and
longwave radiation
are strongly related,
and changes in one,
influence the behavior
of the other.
When analyzing
both together,
measures
of correlation
do not give
us information
about causality
( which variable is
driving the system? ).
Changes in
the incoming
or outgoing
radiation can
generate an
energy imbalance
which drives
climate change.
Clouds and
surface albedo
HAVE changed
in the last four
decades.
SW radiation has
more influence
on the system.
So clouds
and albedo,
which ultimately
determine the
SW radiation, are
important variables
for climate change
The Decadal Survey
for Earth Science and
Applications from Space
(2018) lists as one of the
key science questions
“How changing
cloud cover
and precipitation
will affect climate,
weather and Earth’s
energy balance
n the future”.
It is not possible
to guarantee
that clouds
are the only
climate change
factor, because
climate is a
complex, highly
interconnected
system.
As usual, with
real science,
there are many
unanswered
questions
-- the science
is far from
being "settled".