RISK p3-14 CLIMATE CHANGE ... Hansen et al predictions 2015 150814

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RISK
CLIMATE CHANGE
HANSEN etal PREDICTIONS

Dr. James Hansen - formerly NASA's head climate scientist,
now Adjunct Professor at Columbia University

INTRODUCTION
In July 2015, Dr. James Hansen and others released a
report that concludes that climate change is a far more
serious problem and bigger risk than we have been
thinking about up to this time. This slideset contains
some highlights of the report which should be taken into
consideration by everyone as a matter of considerable
urgency. The conclusions of the Hansen report should be
taken very seriously.

The purpose of this slideset is to help make the content
of the Hansen etal report more easy to digest … simply by
pulling out bits of the report … from the ABSTRACT, the
INTRODUCTION and the SUMMARY IMPLICATION.
The full report may be accessed here:
http://www.atmos-chem-phys-discuss.net/15/20059/2015/acpd-15-20059-2015.pdf
or here:
http://www.truevaluemetrics.org/DBpdfs/People/JamesHansen/James-Hansen-ACPD-Climate-Change-Impacts-15-2

This is the REPORT TITLE:
Ice melt, sea level rise and superstorms, plus evidence
from paleoclimate data, climate modeling, and modern
observations show that 2◦C global warming is highly
dangerous.

AUTHORS …
J. Hansen
1
, M. Sato
1
, P. Hearty
2
, R. Ruedy
3,4
, M. Kelley
3,4
,
V. Masson-Delmotte
5
, G. Russell
4
, G. Tselioudis
4
, J. Cao
6
,
E. Rignot
7,8
, I. Velicogna
8,7
, E. Kandiano
9
,
K. von Schuckmann
10
, P. Kharecha
1,4
, A. N. Legrande
4
,
M. Bauer
11
, and K.-W. Lo
3
,

INSTITUTIONS …
1 Climate Science, Awareness and Solutions, Columbia University Earth Institute, New York,
NY 10115, USA
2 Department of Environmental Studies, University of North Carolina at Wilmington, North
Carolina 28403, USA
3 Trinnovium LLC, New York, NY 10025, USA
4 NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA
5 Institut Pierre Simon Laplace, Laboratoire des Sciences du Climat et de l’Environnement
(CEA-CNRS-UVSQ), Gif-sur-Yvette, France
6 Key Lab of Aerosol Chemistry & Physics, Institute of Earth Environment, Chinese Academy
of Sciences, Xi’an 710075, China
7 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, 91109,
USA
8 Department of Earth System Science, University of California, Irvine, California, 92697, USA
9 GEOMAR, Helmholtz Centre for Ocean Research, Wischhofstrasse 1–3, Kiel 24148, Germany
10 Mediterranean Institute of Oceanography, University of Toulon, La Garde, France
11 Department of Applied Physics and Applied Mathematics, Columbia University, New York,
NY, 10027, USA

From the ABSTRACT …

There is evidence of ice melt, sea level rise to +5-9 m, and
extreme storms in the prior interglacial period that was
less than 1 ◦C warmer than today.

Human-made climate forcing is stronger and more rapid
than paleo forcings, but much can be learned by
combining insights from paleoclimate, climate modeling,
and on-going observations.

We argue that ice sheets in contact with the ocean are
vulnerable to non-linear disintegration in response to
ocean warming, and we posit that ice sheet mass loss
can be approximated by a doubling time up to sea level
rise of at least several meters.

Our climate model exposes amplifying feedbacks in the
Southern Ocean that slow Antarctic bottom water
formation and increase ocean temperature near ice shelf
grounding lines, while cooling the surface ocean and
increasing sea ice cover and water column stability.

Ocean surface cooling, in the North Atlantic as well as the
Southern Ocean, increases tropospheric horizontal
temperature gradients, eddy kinetic energy and
baroclinicity, which drive more powerful storms.

We focus attention on the Southern Ocean’s role in
affecting atmospheric CO2 amount, which in turn is a
tight control knob on global climate.

The millennial (500–2000 year) time scale of deep ocean
ventilation affects the time scale for natural CO2 change,
thus the time scale for paleo global climate, ice sheet and
sea level changes.

This millennial carbon cycle time scale should not be
misinterpreted as the ice sheet time scale for response to
a rapid human-made climate forcing. Recent ice sheet
melt rates have a doubling time near the lower end of the
10–40 year range.

We conclude that 2◦C global warming above the
preindustrial level, which would spur more ice shelf melt,
is highly dangerous.

Earth’s energy imbalance, which must be eliminated to
stabilize climate, provides a crucial metric.

From the INTRODUCTION …

Humanity is rapidly extracting and burning fossil fuels
without a full understanding of the consequences.
Current assessments place emphasis on practical effects
such as increasing extremes of heat waves, droughts,
heavy rainfall, floods, and encroaching seas (IPCC, 2014;
USNCA, 2014). These assessments and our recent study
(Hansen et al., 2013a) conclude that there is an urgency to
slow carbon dioxide (CO2) emissions, because the
longevity of the carbon in the climate system (Archer,
2005) and persistence of the induced warming (Solomon
et al., 2010) may lock in unavoidable highly undesirable
consequences.

Despite these warnings, global CO2 emissions continue
to increase as fossil fuels remain the primary energy
source. The argument is made that it is economically and
morally responsible to continue fossil fuel use for the
sake of raising living standards, with expectation that
humanity can adapt to climate change and find ways to
minimize effects via advanced technologies. We suggest
that this viewpoint fails to appreciate the nature of the
threat posed by ice sheet instability and sea level rise.

If the ocean continues to accumulate heat and increase
melting of marine-terminating ice shelves of Antarctica
and Greenland, a point will be reached at which it is
impossible to avoid large scale ice sheet disintegration
with sea level rise of at least several meters. The
economic and social cost of losing functionality of all
coastal cities is practically incalculable. We suggest that
a strategic approach relying on adaptation to such
consequences is unacceptable to most of humanity, so it
is important to understand this threat as soon as
possible.

NOTE WELL THIS PHRASE …
“The economic and social cost of losing functionality of
all coastal cities is practically incalculable.”

We examine events late in the last interglacial period
warmer than today, called Marine Isotope Stage (MIS) 5e
in studies of ocean sediment cores, Eemian in European
climate studies, and sometimes Sangamonian in
American literature (see Sect. 5 for timescale diagram of
Marine Isotope Stages).

Accurately known changes of Earth’s astronomical
configuration altered the seasonal and geographical
distribution of incoming radiation during the Eemian.
Resulting global warming was due to feedbacks that
amplified the orbital forcing. While the Eemian is not an
analog of future warming, it is useful for investigating
climate feedbacks, the response of polar ice sheets to
polar warming, and the interplay between ocean
circulation and ice sheet melt.

Our study relies on a large body of research by the
scientific community. After introducing evidence
concerning late Eemian climate change, we analyze
relevant climate processes in three stages. First we carry
our IPCC-like climate simulations, but with growing
freshwater sources in the North Atlantic and Southern
Oceans. Second we use paleoclimate data to extract
information on key processes identified by the modeling.
Third we use modern data to show that these processes
are already spurring climate change today.

From SUMMARY IMPLICATIONS:

Humanity faces near certainty of eventual sea level rise of
at least Eemian proportions, 5–9 m, if fossil fuel
emissions continue on a business-as-usual course, e.g.,
IPCC scenario A1B that has CO2 700 ppm in 2100 (Fig.∼
S21). It is unlikely that coastal cities or low-lying areas
such as Bangladesh, European lowlands, and large
portions of the United States eastern coast and northeast
China plains (Fig. S22) could be protected against such
large sea level rise.

Rapid large sea level rise may begin sooner than
generally assumed. Amplifying feedbacks, including
slowdown of SMOC and cooling of the near-Antarctic
ocean surface with increasing sea ice, may spur
nonlinear growth of Antarctic ice sheet mass loss. Deep
submarine valleys in West Antarctica and the Wilkes
Basin of East Antarctica, each with access to ice
amounting to several meters of sea level, provide
gateways to the ocean. If the Southern Ocean forcing
(subsurface warming) of the Antarctic ice sheets
continues to grow, it likely will become impossible to
avoid sea level rise of several meters, with the largest
uncertainty being how rapidly it will occur

The Greenland ice sheet does not have as much ice
subject to rapid nonlinear disintegration, so the speed at
which it adds to 21st century sea level rise may be
limited. However, even a slower Greenland ice sheet
response is expected to be faster than carbon cycle or
ocean thermal recovery times. Therefore, if climate
forcing continues to grow rapidly, amplifying feedbacks
will assure large eventual mass loss. Also with present
growth of freshwater injection from Greenland, in
combination with increasing North Atlantic precipitation,
we already may be on the verge of substantial North
Atlantic climate disruption.

Storms conjoin with sea level rise to cause the most
devastating coastal damage. End-Eemian and projected
21st century conditions are similar in having warm
tropics and increased freshwater injection. Our
simulations imply increasing storm strengths for such
situations, as a stronger temperature gradient caused by
ice melt increases baroclinicity and provides energy for
more severe weather events. A strengthened Bermuda
High in the warm season increases prevailing
northeasterlies that can help account for stronger end-
Eemian storms. Weakened cold season sea level
pressure south of Greenland favors occurrence of
atmospheric blocking that can increase wintertime Arctic
cold air intrusions into northern midlatitudes.

Effects of freshwater injection and resulting ocean
stratification are occurring sooner in the real world than
in our model. We suggest that this is an effect of
excessive small scale mixing in our model that limits
stratification, a problem that may exist in other models
(Hansen et al., 2011). We encourage similar simulations
with other models, with special attention to the model’s
ability to maintain realistic stratification and
perturbations. This issue may be addressed in our model
with increased vertical resolution, more accurate finite
differencing method in ocean dynamics that reduces
noise, and use of a smaller background diffusivity.

There are many other practical impacts of continued high
fossil fuel emissions via climate change and ocean
acidification, including irreplaceable loss of many
species, as reviewed elsewhere (IPCC, 2013, 2014;
Hansen et al., 2013a). However, sea level rise sets the
lowest limit on allowable human-made climate forcing
and CO2, because of the extreme sensitivity of sea level
to ocean warming and the devastating economic and
humanitarian impacts of a multi-meter sea level rise. Ice
sheet response time is shorter than the time for natural
geologic processes to remove CO2 from the climate
system, so there is no morally defensible excuse to delay
phase-out of fossil fuel emissions as rapidly as possible.

We conclude that the 2◦C global warming “guardrail”,
affirmed in the Copenhagen Accord (2009), does not
provide safety, as such warming would likely yield sea
level rise of several meters along with numerous other
severely disruptive consequences for human society and
ecosystems. The Eemian, less than 2 ◦C warmer than pre-
industrial Earth, itself provides a clear indication of the
danger, even though the orbital drive for Eemian warming
differed from today’s human-made climate forcing.

Ongoing changes in the Southern Ocean, while global
warming is less than 1◦C, provide a strong warning, as
observed changes tend to confirm the mechanisms
amplifying change. Predicted effects, such as cooling of
the surface ocean around Antarctica, are occurring even
faster than modeled.

Our finding of global cooling from ice melt calls into
question whether global temperature is the most
fundamental metric for global climate in the 21st century.
The first order requirement to stabilize climate is to
remove Earth’s energy imbalance, which is now about
+0.6 W m−2, more energy coming in than going out. If
other forcings are unchanged, removing this imbalance
requires reducing atmospheric CO2 from 400 to 350∼ ∼
ppm (Hansen et al., 2008, 2013a).

The message that the climate science delivers to
policymakers, instead of defining a safe “guardrail”, is
that fossil fuel CO2 emissions must be reduced as rapidly
as practical. Hansen et al. (2013a) conclude that this
implies a need for a rising carbon fee or tax, an approach
that has the potential to be near-global, as opposed to
national caps or goals for emission reductions. Although
a carbon fee is the sine qua non for phasing out
emissions, the urgency of slowing emissions also implies
other needs including widespread technical cooperation
in clean energy technologies (Hansen et al., 2013a).

The task of achieving a reduction of atmospheric CO2
is formidable, but not impossible. Rapid transition to
abundant affordable carbon-free electricity is the core
requirement, as that would also permit production of net-
zero-carbon liquid fuels from electricity. The rate at which
CO2 emissions must be reduced is about 6 % per yr to
reach 350 ppm atmospheric CO2 by about 2100, under the
assumption that improved agricultural and forestry
practices could sequester 100 GtC (Hansen et al., 2013a).

The amount of CO2 fossil fuel emissions taken up by the
ocean, soil and biosphere has continued to increase (Fig.
S23), thus providing hope that it may be possible to
sequester more than 100 GtC. Improved understanding of
the carbon cycle and non-CO2 forcings are needed, but it
is clear that the essential requirement is to begin to phase
down fossil fuel CO2 emissions rapidly.

It is also clear that continued high emissions are likely to
lock-in continued global energy imbalance, ocean
warming, ice sheet disintegration, and large sea level rise,
which young people and future generations would not be
able to avoid.

Given the inertia of the climate and energy systems, and
the grave threat posed by continued high emissions, the
matter is urgent and calls for emergency cooperation
among nations.

SunSun
BOP
Financial
Capital
Human
Capital
Man Built
Capital
Natural
Capital
Sun SunSun
EOP
Financial
Capital
Human
Capital
Man Built
Capital
Natural
Capital
Sun
Greenland's Melting Ice

SunSun
BOP
Financial
Capital
Human
Capital
Man Built
Capital
Natural
Capital
Sun SunSun
EOP
Financial
Capital
Human
Capital
Man Built
Capital
Natural
Capital
Sun
Antarctica

LAST THOUGHT
I went to a lecture by a Cambridge scientist visiting New
York more than 25 years ago. The takeaway from his talk
was that the ocean currents would change as a result of
ice melt, maybe in ways that would be catastrophic. He
also made it clear that there would be change, but that
exactly what that change would be was difficult to
predict. Hansen et al are confirming the hypothesis of this
old talk … and I for one, think we should take Hansen's
message very seriously.

A copy of the James Hansen etal
report is available here:
http://www.atmos-chem-phys-discuss.net/15/20059/2015/acpd-15-20059-2015.pdf
or
http://www.truevaluemetrics.org/DBpdfs/People/JamesHansen/James-Hansen-ACPD-Climate-Change-Impacts-15-2

EXPLANATION
This slideset is A WORK-IN-PROGRESS. It will be
upgraded periodically. It is part of a series of more than
50 slidesets. Navigation to all of these is available here:
http://www.truevaluemetrics.org/DBadmin/DBtxt001.php?vv1=N1-Slidesets-p3
FEEDBACK is welcome. Please email to Peter Burgess …
peterbnyc@gmail.com … with a catchy phrase in the
subject line so that it gets attention, and please identify
the specific slideset(s) involved.

THANK YOU
Some links and contact information:
Peter Burgess … peterbnyc@gmail.com
Peter Burgess LinkedIn profile
https://www.linkedin.com/in/peterburgess1
Link to TrueValueMetrics.org website
http://www.truevaluemetrics.org/
Link to navigation to other slides in this series:
http://www.truevaluemetrics.org/DBadmin/DBtxt001.php?vv1=N1-Slidesets-p3

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