Climate Change: A Natural Hazard?: Book Launch Address
Peter Walsh, John Zillman, Ladies and Gentlemen
Before talking about the book, Climate Change: A Natural Hazard,
there are a number of people that I must thank. Without their
support there would not have been a book to launch.
Firstly, I must thank my family who have been supportive in
this and many previous ventures associated with my indulgences
in climate. Over the years my wife, Elaine, has been very understanding,
as I have travelled the world increasing my knowledge of the global
climate. More recently I have disappeared into my study for long
periods to research and write. The task would never have been
completed without her support and consideration.
The Lavoisier Group provides a forum for discussion and debate
in Australia on the climate change issue, even when the public
has been led to believe that the science of climate change has
been settled. I sincerely thank the Lavoisier Group for having
arranged this launch of the book, and also for the assistance
and encouragement that has been provided, especially by Ray Evans.
I particularly thank John Zillman for taking on the role of
formally launching the book. Our professional association in the
Bureau of Meteorology goes back three decades but it was about
15 years ago that we were actively working towards achieving a
National Climate Program for Australia. Seventy percent of natural
disasters are associated with weather and climate extremes. As
Director of Meteorology, John took the lead to ensure that the
climate observing infrastructure, climate research and the range
of services available to this country met our national needs.
Unfortunately, at the same time as the sober National Climate
Program initiative was being prepared the prospect of dangerous
anthropogenic global warming became an international environmental
issue. Alas, greenhouse global warming became the prominent climate
issue and a National Climate Program was never formally considered.
John Zillman, as Vice-President of the World Meteorological
Organization, played a key role in establishing the Intergovernmental
Panel on Climate Change (the IPCC) that was created within the
UN system to provide an authoritative international statement
of scientific opinion on climate change.
Nearly two decades later, we are still debating the science
of climate change. This only underscores the complexity of the
climate system. The book that I have written, Climate Change:
A Natural Hazard, describes the important processes that are relevant
to variability of the climate system on all timescales. It addresses
controversial issues and I will briefly discuss a few of these
The Radiation Forcing Hypothesis is
For the IPCC, the concept of radiative forcing is central to
climate change. Radiative forcing emerges from a one-dimensional
radiation-convective model of the climate system. Radiative forcing
assumes that there was radiation balance at the top of the atmosphere
before industrialisation commenced.
Radiative forcing is a simple, seductive hypothesis for how
emissions of carbon dioxide, especially burning of fossil fuels,
will lead to global warming. If the concentration of carbon dioxide
in the atmosphere continues to increase it is suggested that dangerous
climate change will occur.
The simple radiation forcing hypothesis cannot be sustained,
except in the most qualitative terms. It ignores the energy reservoir
of the tropical oceans and the need for deep convection to distribute
excess energy of the tropical oceans through the atmosphere. It
ignores that the earth is essentially two different regions---the
tropics, over which solar radiation is accumulating, and the polar
regions, where radiation loss to space is dominating.
If we were to only consider radiation and convection as the
dominant processes of the atmosphere then we should expect to
observe the tropics getting warmer and warmer and the polar regions
getting colder and colder. We know this is not the case.
Ongoing poleward transport of energy by the atmospheric and
ocean circulations is vital for a stable climate and global radiation
balance. Variations of poleward transport of energy will lead
to variations in global temperature.
Variability of the poleward transport of energy can cause major
climate change. For example, during the last glacial cycle that
lasted about 100 thousand years, the sea level dropped about 130
metres as mountain glaciers and polar ice sheets expanded. Then
the sea level returned to its present level as mountain glaciers
and polar ice sheets retreated. There is no evidence that the
glacial cycle was forced by solar radiation because the annual
total of solar radiation received by the earth did not change
appreciably on these timescales.
A sustained change in poleward energy transport will cause
a temperature change over middle and high latitudes. However,
it is not necessarily true that radiation forcing will produce
significant climate change.
Rudimentary Computer Models have Gross Inadequacies
The projections of the magnitude of global warming due to increases
in atmospheric carbon dioxide concentration are based on computer
model simulations. The veracity of those projections depends on
the ability of the computer models to simulate the climate system.
The different computer models developed in the various research
centres around the world have differences in their construction
and specification of internal processes. They produce a range
of estimates of future global warming. The performance characteristics
of the various computer models have been examined within the framework
of the Coupled Model Intercomparison Project (CMIP).
IPCC has drawn on the model intercomparison in its Third Assessment
Report. The apparent ability of the computer models to simulate
many of the characteristics of the current climate system is the
basis for the IPCC confidence in their use.
However, the intercomparison also identifies some significant
weakness in the computer simulations. On average, the rate of
mass overturning of the tropical atmosphere is more than 20 percent
less than observed for the atmosphere. This means that there are
gross errors in the poleward transport of energy by the computer
The peak poleward transport of energy by the atmosphere is
known with confidence from satellite and other direct observations.
A decrease in the transport by only one percent would allow the
volume of Arctic sea ice to more than double in ten years. It
is surprising, therefore, that the gross underestimation of poleward
energy transport by the computer models is not reflected as cooling
and expansion of the ice sheets over the polar regions.
The computer models have compensating gross errors in the latitudinal
distribution of net longwave radiation at the surface. There is
too much radiation loss over the tropics, thus cooling the surface,
and not enough radiation loss over polar regions, thus retaining
energy in the surface. The magnitude of the radiation errors in
the computer models is up to five times the expected radiation
forcing from doubling carbon dioxide concentration.
The magnitude of global warming projected by the computer models
cannot be considered reliable because of the errors in poleward
energy transport and net surface longwave radiation.
Recent Global Warming
The IPCC claims that the global warming observed over the past
50 years has been due to human activities. This claim is based
on the apparent ability of computer models, when forced by natural
and anthropogenic factors, to simulate the global surface temperature
record of the 20th century.
There is, however, an essential discrepancy between the computer
simulations and observations. The computer models project warming
of the atmosphere, especially over the tropics. Contrary to what
the computer models project, over the past two and a half decades
there is no evidence of warming of the tropical atmosphere. This
is a period when accurate satellite observations have been available
and we can directly compare the simulations by the computer models
The projection of atmospheric warming is the basis for claims
of a positive feedback through water vapour, a natural greenhouse
gas. Overall, the effect of water vapour feedback in the computer
models is to amplify the direct effect of carbon dioxide several
times over. By this mechanism, the computer models exaggerate
the magnitude of anthropogenic greenhouse warming.
The IPCC conclusion that most of the warming of the past 50
years is attributable to human activities is not soundly based.
The Mythology of Runaway Global Warming
One of the fears raised in relation to continued burning of
fossil fuels is that it will lead to runaway global warming. Sir
David King, Chief Science Adviser to the British Government, has
been quoted as saying that human induced climate change is a bigger
danger than global terrorism. That is a big call.
We can be confident that the prospect of runaway global warming
is a mirage conjured up by activists and propagandists. It is
based on the spurious idea of positive feedbacks.
Bill Priestley, a former Chief of the CSIRO Division of Atmospheric
Research, published a paper in 1966 on the limitation of temperature
by evaporation in hot climates. From a study of worldwide surface
temperature data he showed an upper limit of 33 ºC over well-watered
vegetation. The study and its findings were in the context of
agriculture and irrigation planning but the physics has universal
application. In a passing comment, Priestley noted that 30 ºC
represented a practical upper limit to surface temperatures over
Observations of sea surface temperatures from the equatorial
western Pacific Ocean, extending over the past two decades, confirm
that the warmest ocean waters have fluctuated in a narrow temperature
range about 30 ºC. At this temperature it is evaporation
that dominates the energy exchange between the ocean and the atmosphere.
Any reduction in net longwave radiation at the surface due to
enhanced greenhouse gas concentration will be compensated by increased
evaporation without an increase in surface temperature.
There has been no observed trend in the temperature of either
the warmest ocean surface or the tropical troposphere. Nor should
we expect any trend in the future. Temperatures of the warmest
ocean surface and the tropical troposphere are constrained by
natural upper bounds.
The Climate System does have Internal
IPCC has claimed, based on analyses of computer models, that
recent global warming is unlikely to be due to internal variability
of the climate system. That is, the warming of the past 50 years
is due to human activities.
More recent ocean research suggests that the global warming
of recent decades can be directly linked to natural interactions
between the oceans and the atmosphere.
A change in the surface wind field over the tropical Pacific
Ocean has reduced the shallow overturning in the ocean surface
layer since the mid-1970s. Reduced upwelling of cold water has
altered the surface energy balance and caused the area with surface
temperatures near 30 ºC to expand and for ocean surface temperatures
elsewhere to warm. Overall, evaporation of water vapour from the
oceans and the supply of latent energy to the atmosphere have
An observed increase in the overturning tropical circulation
during the past two decades can be directly attributable to the
enhanced latent energy supply from the warmer tropical ocean.
The more vigorous atmospheric circulation has increased the poleward
transport of energy. Warming middle and high latitude temperatures
and contracting ice mass are to be expected.
Satellite observations confirm that there has been an increase
in the emission of longwave radiation to space from the tropics,
consistent with warmer ocean surface temperatures. The increased
radiation to space, however, is contrary to IPCC's radiation forcing
hypothesis, which predicts that increased concentrations of carbon
dioxide will reduce the emission of longwave radiation to space.
The oceans are the flywheels of the climate system as they
have large thermal capacities and relatively long inertial periods.
Each ocean circulation has characteristic inertial periods whose
timescales reflect basin topography. The inertial periods range
from the decadal to the millennial and are excited by changing
surface wind stress.
The surface temperature patterns and energy exchanges from
the oceans drive the atmospheric circulation. The atmospheric
circulation responds rapidly to changing energy input from the
oceans. This is clear from El Niño events and the more
persistent tropical forcing since the middle 1970s. We should
expect variations of local and regional climate that have timescales
that are characteristic of the inertial periods of the ocean circulations.
Fluctuations of climate on a range of timescales are consistent
with internal variability of the climate system.
Climate Change and Future Policy
The spectre of dangerous anthropogenic climate change has come
to dominate government and business policy, especially across
the energy and environment sectors. Decisions are being formulated
and implemented based on the climate change projections endorsed
by the IPCC. In particular, the Kyoto Protocol and its impending
ratification mean that reduction of greenhouse gas emissions is
an objective that takes priority over economic efficiency, international
competitiveness and, in a number of sectors, job creation.
The science underpinning climate change projections is not
settled. The book, Climate Change: A Natural Hazard, exposes serious
defects in the IPCC Third Assessment Report and its climate change
- The radiation-forcing hypothesis is a poor construct for
the climate system. Its simplicity focuses unduly on radiation
processes and ignores the natural interactions of the ocean and
atmospheric circulations that also affect climate.
- The computer models of the climate system are seriously flawed
and the projections of anthropogenic global warming are exaggerated.
The prospect of runaway global warming is a mirage.
- The past climate has fluctuated because of natural internal
variability and external forcing. Global temperature patterns,
rainfall distributions, ice volumes and sea level have varied
on a range of timescales. We must anticipate and be prepared
for such variability continuing into the future. The twentieth
century was probably neither the warmest century nor the 1990s
the warmest decade of the last millennium.
Weather and climate extremes are hazards that continue to threaten
life and property and will not go away by reducing greenhouse
gas emissions. It is important that scarce resources are applied
to the development of community infrastructures that are resilient
and provide protection against weather and climate extremes.
Climate Change: A Natural Hazard challenges widely held assumptions
and highlights uncertainties of the science that tend to be conveniently
ignored. I have also tried to ensure that the scientific arguments
are clearly described and free from jargon to enable policymakers
to participate in the important debate. It is not a debate that
should be confined to the circles of the scientific elite. We
must ensure a strong connect between the science and the dependent
I thank everyone who has come to this occasion and, again,
to John Zillman for doing me the honour of its launch.
The book is available for purchase tonight from my lovely daughters-in-law
who are assisting The Avenue Book Store of Middle Park.
To read Dr John Zillman's's launching speech for Climate Change: A Natural Hazard,
please click here
For details of how to order Climate
Change: A Natural Hazard, please click here