Golden Oldie #1: The IPCC used to admit the truth: Long term climate forecasting is impossible

What the IPCC used to say

 presented in an easier to read format:

"14.2.2
Predictability in
a Chaotic System"

The climate system
is particularly challenging
since it is known that
components in the system
are inherently chaotic;
there are feedbacks
that could potentially
switch sign,
and there are
central processes
that affect the system
in a complicated,
non-linear manner.

These complex, chaotic,
non-linear dynamics
are an inherent aspect
of the climate system.

As the
IPCC WGI Second
Assessment Report
(IPCC, 1996)
(hereafter SAR)
has previously
noted,
“future unexpected,
large and rapid climate
system changes
(as have occurred
in the past) are,
by their nature,
difficult to predict.

This implies that
future climate
changes may also
involve ‘surprises’.

In particular,
these arise from
the non-linear,
chaotic nature
of the climate
system

... Progress
can be made
by investigating
non-linear
processes and
sub-components
of the climatic system.”

These thoughts
are expanded
upon in this report:
“Reducing uncertainty
in climate projections
also requires a better
understanding of these
non-linear processes
which give rise
to thresholds
that are present
in the climate system.

Observations,
palaeoclimatic data,
and models suggest
that such thresholds
exist and that transitions
have occurred in the past
 ... Comprehensive
climate models
in conjunction
with sustained
observational systems,
both in situ and remote,
are the only tool to decide
whether the evolving
climate system
is approaching
such thresholds.

Our knowledge
about the processes,
and
feedback mechanisms
determining them,
must be
significantly improved
in order to extract
early signs
of such changes
from model simulations
and observations.”
(See Chapter 7, Section 7.7).



14.2.2.1
Initialization and
flux adjustments

" ... Models,
 by definition, are
reduced  descriptions
of reality
and hence incomplete
and with error.

Missing pieces
and small errors
can pose difficulties
when models
of sub-systems
such as the ocean
and the atmosphere
are coupled.

As noted in Chapter 8,
Section 8.4.2,
at the time of the SAR
most coupled models
had difficulty
in reproducing
a stable climate with
current atmospheric
concentrations of
greenhouse gases,
and therefore
non-physical
“flux adjustment terms”
were added. "


This sounds like
what I have known
since the late 1990s
-- the climate models
are all fluxed up !