Global Warming in the Pipeline will be published in Oxford Open Climate Change
of Oxford University Press next week. The paper describes an
alternative perspective on global climate change – alternative to that
of the Intergovernmental Panel on Climate Change (IPCC), which provides
scientific advice on climate change to the United Nations.
Our paper may be read as being critical of IPCC. But we have no
criticism of individual scientists, who include world-leading
researchers volunteering their time to produce IPCC reports. Rather we
are questioning whether the IPCC procedure and product yield the advice
that the public, especially young people, need to understand and protect
their home planet.
Discussion of our paper will likely focus on differences between our
conclusions and those of IPCC. I hope, however, that it may lead to
consideration of some basic underlying matters.
Three-pronged analysis. IPCC
climate analysis leans heavily on GCMs (global climate models), too
heavily in my opinion. We prefer a comparable weight on (1) information
from Earth’s paleoclimate history, (2) GCMs, and (3) observations of
ongoing climate processes and climate change. This 3-pronged approach
can result in rather complex papers, but, so, too, is the real-world
complex. We use this 3-pronged approach in both the heavily
peer-reviewed paper, “Ice Melt, Sea Level Rise, and Superstorms,”
published in 2016 and in our present “Global Warming in the Pipeline”
(these papers hereinafter abbreviated as Ice Melt and Pipeline, respectively). Below I note specific travails and consequences for the Ice Melt
paper that resulted from the fact that our 3-pronged approach differed
from that of IPCC. I hope that some explanation here may help avoid a
similar fate for Pipeline, as the world is running short on
time to develop a strategy to preserve a propitious climate for today’s
young people and their children.
Guidance for observations.
Climate change today is driven by two large human-made climate forcings:
greenhouse gases (GHGs) and aerosols (fine airborne particles, which
result in visible air pollution when present in sufficient amount).
Aerosol climate forcing results in part from the effect of aerosols
themselves on incoming solar radiation, but mainly from the effect of
aerosols as condensation nuclei for cloud drops. Increased aerosols
result in smaller cloud drops (because the supply of water vapor is
limited), which in turn causes clouds to be brighter (higher
reflectivity) and longer lived (thus increasing global cloud cover).
Measurement of aerosol climate forcing thus requires precise global
monitoring of cloud and aerosol microphysics. Whether NASA would measure
the aerosol climate forcing was a contentious issue beginning in the
late 1980s, primarily because the observations required sampling of the
seasonal and diurnal cycles of cloud cover that could best be achieved
from a pair of relatively inexpensive small satellites, which we dubbed
Climsat. This proposal was deemed by some to be competitive with NASA
plans for its Earth Observing System, which was focused on large
platforms in near-polar orbit. As a result, the aerosol climate forcing
has not been monitored and aerosol forcing is, in effect, a free
parameter in climate models.
Absent accurate knowledge of the aerosol forcing, a wide range of
climate sensitivities are consistent with observed global warming during
the past century. A small climate sensitivity requires rather little
aerosol cooling to match observed warming. However, a larger climate
sensitivity combined with greater aerosol cooling is also consistent
with observed global warming. In Pipeline, we obtain an
indirect inference on aerosol climate forcing via well-defined knowledge
of climate sensitivity (from paleoclimate) and accurate satellite
measurements of Earth’s energy balance. Especially because of the
absence of monitoring of the aerosol climate forcing, it is crucial that
the precise measuring of Earth’s radiation budget continue. If NASA is
not going to make such plans, it is crucial that ESA (the European Space
Agency) take up the challenge. Otherwise, today’s young people truly
will be “up sxxt crick without a paddle,” in any efforts to understand
continued global temperature change and guide climate and energy
policies.
Pipeline, via paleoclimate analyses, reveals that climate sensitivity is higher than IPCC’s best estimate of 3°C for doubled CO2.
This is a double whammy, because the higher sensitivity implies that
the aerosol effect is underestimated by IPCC. Thus, in addition to
higher climate sensitivity, the Faustian payments that come due as we
clean up air pollution are greater. In the absence of measurements of
aerosol climate forcing, the magnitude of the observed change of Earth’s
radiation budget in the regions of heavy ship traffic indicates that
aerosol models are likely underestimating the effect of aerosols on
clouds.
Guidance for climate policy. Guidance
for global energy and climate policies is also hindered by
over-reliance on models. As a result, science has not informed
policymakers well about the prospects for ongoing climate change, as
evidenced by claims that targets for limiting global warming can still
be achieved via realistic phasedown of emissions. This fiction is
maintained via the combination of unrealistic assumptions in Integrated
Assessment Models and low-sensitivity climate models. The conclusions of
that approach are falsified in Pipeline by comparison of results from those models with ongoing real-world observations.
The reluctance of IPCC, the body providing scientific guidance to the
United Nations, to provide technical advice is disappointing. As one
example, note that, buried in the thousands of pages of IPCC reports is
the conclusion that nuclear power has the smallest carbon and
environmental footprint among the major sources of energy. It has long
been understood by energy experts that, in the absence of nuclear power,
fossil fuels will provide the 24/7 dispatchable electricity generation
essential to complement intermittent renewable energy. The hesitance to
offer such technical advice may be related to scientific reticence.
Scientific Reticence. This topic is discussed in Pipeline. I must finish this communication this morning, so I conclude with the example provided by the Ice Melt paper. The concluding words of the title of the Ice Melt
paper were “…2°C global warming is highly dangerous.” The paper had
been heavily peer-reviewed by four referees and by the wider community
via the open review process. One of the four referees – an IPCC lead
author – had strong objections to the paper, but he was overruled by the
other three referees and the editor. However, the editorial board
intervened, insisting that the paper could not be published unless we
changed the last words of the title from “…2°C global warming is highly
dangerous” to “…2°C global warming could be dangerous,” an almost
meaningless conclusion.
The editor – an exceptional scientist – agreed with our position, but
was unable to prevail. I wrote an explanation of the public’s
understanding of the word “dangerous”: if a person looked down a dark
street and saw a bunch of guys loitering and seeming to hold weapons,
would that person consider that street to be dangerous and take a
different route home, even though there was not 100 percent proof that
he would be assaulted if he went down that street? The editor then
reported to me, in disappointment, that, if I included that explanation
in a letter to the journal, we would not be able to publish Ice Melt
in the journal (all correspondence between an author and the journal is
publicly available). We decided to submit to this demand (omitting the
discussion of what “dangerous” means to the public in our official
communication) because of a prior similar experience with another
journal (which resulted in a one-year delay of publication, as we had to
start the review process over with a different journal). Such is the
nature of the scientific reticence that has infected our scientific
community.
In Ice Melt, we used the three-prong analysis to show that
continued high emissions would cause shutdown of the North Atlantic
Overturning Circulation (AMOC) and the Southern Ocean Overturning
Circulation (SMOC) this century, possibly by mid-century, and sea level
rise of several meters on the 50-150 year time scale. In Pipeline we
reveal how the reticent community, with full reliance on models (that
tend to be unrealistically insensitive to freshwater injection) alone,
could manage to dismiss this result, and, instead, conclude that there
was less than 1 percent chance of shutting down AMOC, even with high GHG
emissions. | |
No comments:
Post a Comment