Hi Mike et al.,
I can't get involved in a back-and-forth -- we are in the process
of moving back to NYC, to live in a Columbia apartment to avoid
time wasted in commuting and taking care of a house/property.
However, I'm surprised by your comment, Mike. Most GCM groups
make hundreds, if not more, GCM runs between one IPCC report and
the next, and there are hundreds, if not more, model parameters.
There is a widespread, if not universal, tendency to prefer those
model configurations that yield a magnitude of warming in the
past 200 years that is consistent with observations. In this way,
wittingly or not, the 3C sensitivity is "baked into" the models
-- because, as we showed in our "Acceleration" the usual aerosol
forcing employed is close to the IPCC best estimate for aerosol
forcing. As shown by a graph in the Supplementary Information of
our paper, the change of the IPCC aerosol forcing during the
period of rapid warming is negligible. In such case, the climate
sensitivity required to match the observed warming rate is ~3C
for 2xCO2. However, if the aerosol forcing increased by ~0.5 W/m2
(became more negative) during 1970-2005, as simulated by Bauer et
al. and as independently inferred in our paper, then a climate
sensitivity of ~4.5C is required to match the observed warming.
However, the temperature change in the last 200 years is only one
of the three independent ways that we obtain the 4.5C
sensitivity, and the other two are much cleaner, independent of
the GCM issues.
High climate sensitivity demanded by large cloud feedback,
clearly shown by Earth's darkening in the past 25 years, is
summarized in the recent communication to my email list.
The third method is described in our "Global warming in the
pipeline" paper: comparison of equilibrium glacial and
interglacial climates. For several decades, based largely on
CLIMAP and "confirmed" by MARGO, it was believed that the LGM was
only 3-4C colder than the Holocene. Thanks especially to Alan
Seltzer, we now know that the LGM was 6-7C colder, which demands
the higher ECS -- several new paleo studies confirm the high ECS.
Best, Jim
On Mon, May 19, 2025 at 3:39 PM 'Michael MacCracken' via
geoengineering <[email protected]> wrote:
Ron et al.--Just a note that the 3 C sensitivity is not
"embedded" in the climate models. That is the value that
emerges from the representations of the various physical
processes that play out against each other. So, assuming the
observations and resulting analyses are accurate, for there
to be a higher sensitivity, it might be that some of the
processes are not parameterized in a way that fully
represents possibilities and realities (observations to
calibrate parameterizations can be drawn from only the
conditions we are experiencing), some processes are not
represented at all (viewed as long-term such as isostatic
rebound, etc.), the resolution of the models is not fine
enough to treat aspects of the processes, etc. In any case,
however, the 3 C sensitivity is not built into the models.
Mike
On 5/19/25 1:49 PM, Ron Baiman wrote:
Thank you LDM and Dan,
@LDM:
(IMO) Thanks for sharing! IMO this recent Hansen and
Kharecha Newsletter with further evidence supporting a
climate sensitivity of 4.5 rather than the established IPCC
value of 3.0 that is (as I understand it) embedded in most
current climate models, is excellent and should be widely
distributed, per these last two paragraphs:
"Criticisms of the Acceleration paper in the media did not
address the physics in our three assessments of
climate sensitivity. Instead, criticisms were largely ad hoc
opinions, even ad hominem attacks. How can
science reporting have descended to this level? Climate
science is now so complex, with many sub-
disciplines, that the media must rely on opinions of climate
experts. Although there are thousands of
capable scientists in these disciplines, the media have come
to depend on a handful of scientists, a clique
of climate scientists who are willing, or even eager, to be
the voice of the climate science community.
But are they representative of the total community, of
capable scientists who focus on climate science?
We have lamented9 the absence of scientists with the breadth
of understanding of say Jule Charney or
Francis Bretherton,10 or our beloved, sometimes crotchety,
former colleague, Wally Broecker. However,
the truth is that there are many scientists out there with a
depth of understanding at least as great as the
clique of scientists that the media rely on. Given the
success of this clique in painting us as outliers, we
are dependent on the larger community being willing to help
educate the media about the current climate
situation. For that purpose, we will discuss – one-by-one in
upcoming communications – several of the
matters that are raised in our papers. Thanks for your
attention."
@Dan: Thanks for sharing! I will definitely give this a
listen!
Best,
Ron
On Sun, May 18, 2025 at 4:04 PM LDM <[email protected]> wrote:
https://www.columbia.edu/~jeh1/mailings/2025/CloudFeedback.13May2025.pdf
Large Cloud Feedback Confirms High Climate Sensitivity
James Hansen and Pushker Kharecha
13 May 2025
Abstract.
Earth’s albedo (reflectivity) declined over the 25 years
of precise satellite data, with the decline so large
that this change must be mainly reduced reflection of
sunlight by clouds. Part of the cloud change is caused
by reduction of human-made atmospheric aerosols, which
act as condensation nuclei for cloud formation, but most
of the cloud change is cloud feedback that occurs with
global warming. The observed albedo change proves that
clouds provide a large, amplifying, climate feedback.
This large cloud feedback confirms high climate
sensitivity, consistent with paleoclimate data and with
the rate of global warming in the past century.
https://youtu.be/NxV1IbHt7fU
When Will We Go Over 2ºC? & Hansen's Cloud Update
<https://www.youtube.com/@climatechat>
On Sun, May 18, 2025 at 9:09 PM Ron Baiman
<[email protected]> wrote:
Wow! Thanks for sharing Renaud. I haven't read it
but from the abstract it (very unfortunate for all
of us humans and most other species, but not really
surprising for many of us humans) looks like
forecasts of Hansen et al. 2024 are being vindicated!
Best,
Ron
On Wed, May 14, 2025 at 9:51 AM Renaud de RICHTER
<[email protected]> wrote:
Earth's Energy Imbalance More Than Doubled in
Recent Decades
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024AV001636
Abstract
Global warming results from anthropogenic
greenhouse gas emissions which upset the
delicate balance between the incoming sunlight,
and the reflected and emitted radiation from
Earth. The imbalance leads to energy
accumulation in the atmosphere, oceans and land,
and melting of the cryosphere, resulting in
increasing temperatures, rising sea levels, and
more extreme weather around the globe. Despite
the fundamental role of the energy imbalance in
regulating the climate system, as known to
humanity for more than two centuries, our
capacity to observe it is rapidly deteriorating
as satellites are being decommissioned.
Key Points
*
Earth's energy imbalance more than doubled
in recent decades
*
The large trend has taken us by surprise,
and as a community we should strive to
understand the underlying causes
*
Our capability to observe the Earth's energy
imbalance and budget terms is threatened as
satellites are decommissioned
Plain Language Summary
Global warming is caused by the imbalance
between the incoming radiation from the Sun and
the reflected and outgoing infrared radiation
from the Earth. The imbalance leads to energy
accumulation in the atmosphere, oceans and land,
and melting of the cryosphere, resulting in
increasing temperatures, rising sea levels, and
more extreme weather around the globe according
the the United Nations Intergovernmental Panel
on Climate Change (IPCC). Observations from
space of the energy imbalance shows that it is
rising much faster than expected, and in 2023 it
reached values two times higher than the best
estimate from IPCC. We argue that we must strive
to better understand this fundamental change in
Earth's climate state, and ensure our capacity
to monitor it in the future.
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Addressing the Urgent Need for Direct Climate Cooling:
Rationale and Options
<https://academic.oup.com/oocc/article/4/1/kgae014/7731760>
Baiman et al. 2024. /Oxford Open Climate Change/
An Open Letter to the IMO Supporting Maritime Transport that
Cools the Atmosphere While Preserving Air Quality Benefits
<https://academic.oup.com/oocc/article/4/1/kgae008/7706251>.
Baiman et al. 2024. /Oxford Open Climate Change/
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