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| Journal of the New Zealand Medical Association,
11-December-2009, Vol 122 No 1307
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Climate science, denial and the Declaration of Delhi
George Laking, Alistair Woodward, Scott Metcalfe, Alexandra
Macmillan, Graeme Lindsay, Joanna Santa Barbara, Anne MacLennan, Imogen
Thompson, Susan Wells; for OraTaiao: New Zealand Climate and Health
Ten years into the third millennium, climate change looms as
the central issue facing humanity’s collective future. It should be no
surprise that climate change now appears in our professional
domain.1,2
Most of us will have attested at the start of our career to
something like the World Medical Association (WMA) Declaration of
Geneva,3 which begins
“I SOLEMNLY PLEDGE to
consecrate my life to the service of humanity”.
Although our day-to-day focus as clinicians is more on
individual humanity, the pledge requires us to also consider the collective
wellbeing of populations over time. That wellbeing strongly depends on climate
and the environment, and so in October 2009 the World Medical Association
adopted the Declaration of Delhi, “to provide a response ... to the
challenges imposed on health and healthcare systems by climate
change”.4
The Delhi Declaration begins by noting the most likely
effects predicted by the Intergovernmental Panel on Climate Change (IPCC,
AR4).5 The IPCC has “very high
confidence” (its code for “at least a 9 out of 10 chance of being
correct”) that climate change currently contributes to the global burden
of disease and premature death. These and related effects are “projected
to progressively increase in all countries and
regions”.4
With this in mind, the WMA has committed the medical
profession to actions to mitigate and adapt to the effects of climate change.
These are summarised as advocacy, leadership, education and capacity building,
surveillance and research, and collaboration. The WMA Declaration of Delhi is a
global call to action for the entire medical community, and our colleagues are
responding internationally.6–9
Most readers of this Journal devoted their
education to what was viewed as ‘the Health Sector’. We did not
anticipate our interest in human welfare would require a good understanding of
geophysics and politics. So it is understandable if many of us feel outside our
professional comfort zone when we consider how the medical profession should
respond to climate change.
Many times in the past the profession has engaged with
issues outside the health sector when the stakes for health were high. Road
safety, tobacco and nuclear weapons are three recent examples.
But climate is new territory, and many doctors will seek to
increase their understanding of the background, particularly when dissenting
voices are heard in the public media. Here we explore the scientific basis to
the Declaration of Delhi, with reference to commonly used contrary arguments.
Due personal verificationThe first challenge to the Declaration of Delhi is whether
we should accept it. After all, the earlier Geneva Declaration on the Duties of
Physicians enjoins that:
“A PHYSICIAN SHALL
certify only that which he/she has personally
verified”,3
and consequently we have had scepticism and resistance to
ex-cathedra statements drummed into us from Day One of medical school.
Scepticism means asking questions, not taking matters on face value, and not
being swayed by authority unless we decide independently there is good reason to
act.
But true scepticism does not mean refusing to act in the
absence of certainty. Doctors are well aware that decisions must be taken on the
evidence to hand, weighing up the risks, on the basis that complete knowledge is
seldom available and time is precious. Our patients’ well-being often
demands we act on the basis of incomplete and emerging information.
What applies at the bedside is true also in the public
domain. Our experience of medical controversy reminds us that science is
frequently disputed, particularly when commercial interests are at stake. Think
back, for example, to the arguments over the effects of lead on child health.
For the better part of a century a few prominent scientists, supported by
industry, advanced doubt as reason to delay removal of lead from paint and
petrol.10,11 In recent history, we as a
profession have taken a stand on similar controversial issues, on the grounds
that the evidence may not be perfect, but still sufficient for action. Examples
include passive smoking, immunisations, and cardiovascular risk. The Declaration
of Delhi puts the profession in such a position now with climate change.
It is fair to ask how we as doctors might personally
verify3 anthropogenic global warming,
especially in the absence of our preferred evidentiary tool, the randomised
controlled trial. The evidence mainly resides in a single incomplete case
report, the geophysical history of planet Earth. A very short supporting case
series is suggested by our neighbours Venus and Mars. Clearly verification must
take a different form to how we would approach a controversy over drug therapy
or food supplements.
Some contrary argumentsArguments commonly cited against climate change were mooted
in an open letter written in 2007 by “100 Prominent Scientists” to
the Secretary-General of the United Nations.12
This group claimed that recent observations of phenomena such as glacial
retreats, sea-level rise and the migration of temperature-sensitive species are
not evidence for abnormal climate change, “for none of these changes has
been shown to lie outside the bounds of known natural variability”.
The claim did not specify a time-scale, which means that the
“bounds of natural variability” were potentially very wide. For
example, the characteristic sea level for the planet, based on evidence from the
last 500 million years, is about 100 metres higher than the present
day.13 Just because something falls within the
bounds of known natural variability, does not mean it is desirable.
In clinical practice, variation of physiological parameters
within a reference range may often be cause for concern. For example, in the
case of human temperature, 700 recordings from 148 healthy subjects varied
between 35.6°C and 38.2°C,14 being a
2.6°C (7%) variation with a mean of 36.8°C and 37.7°C an upper
limit of normal. Doctors commonly see rising temperatures within the normal
range, and must judge whether this is “natural variability” or the
first flicker of something more serious.
Another example is weight change. A 5 kg fall in a
patient’s weight might be within the bounds of normal, if it occurred over
the course of a year. If the weight were lost over a month, we would tend to
consider a potentially serious explanation. It is often the rate as
much as the magnitude of change that is important.
The 100 Scientists also noted a recent apparent lull in
global warming, saying that despite computer projections of temperature rises,
there has been no net global warming since 1998. “That the current
temperature plateau follows a late 20th-century period of warming is consistent
with the continuation today of natural multi-decadal or millennial climate
cycling.”12
Such arguments fail to see the wood for the trees, in this
case by picking an arbitrary short series of just the last 10 years and an
abnormally warm single year (1998) as the starting reference point. Clinically
this is akin to taking false reassurance from an isolated set of
‘good’ laboratory values (a false-negative), when looking at all
results over time would show a more serious evolving pattern. The climate change
deniers have used data selectively,15 where the
IPCC has assiduously used all available data to properly compare pre- and
post-industrial trends.16 The most recent
global data, released by the World Meteorological Organisation, show that
2000-2009 has been the warmest decade ever since direct measurements
began.17
The 100 Scientists concluded that “it is not possible
to stop climate change, a natural phenomenon that has affected humanity through
the ages.” This insistence on an explanation in terms of natural phenomena
is akin to ‘diagnostic anchoring’, in which data not compatible with
a starting diagnostic assumption are systematically excluded from
consideration.18 We know in medicine that signs
of pathology may often be modified or masked, so that ‘natural
appearances’ become misleading. For example, factors such as age or
treatment with corticosteroids or partially effective antibiotics may attenuate
the fever response.
The same applies to the short-term climate trend, which may
be damped down or reinforced by factors such as the El Nino Southern Oscillation
(the periodic change in atmospheric conditions around the Pacific affecting
rainfall patterns and temperatures
world-wide.19 Longer-term temperature increases
are also being artificially masked by aerosols in the atmosphere.
In medicine, we have to recognise the underlying true
febrile process even when it may be modified by other factors. Similarly, we
have to recognise the climate's complexity when interpreting apparent lulls in
global warming and likely future warming trends.
In the end, the most decisive tool for interpreting change
tends not to be rate or magnitude but rather context. If the person
whose temperature has just been recorded as 37.7°C is a possibly
neutropenic oncology patient with malaise, the temperature should at the very
least be rechecked within an hour. It would be a brave doctor who failed to act
on a rising temperature in this context, simply on the grounds that it was still
within the normal range.
If a person lost 5kg of weight over a month in the setting
of an intensive diet and exercise programme, this might be explicable. But if
that weight were lost in the context of fevers and night sweats, there would be
a strong suspicion of something more sinister.
Although the analogy between clinical practice and planetary
climate is necessarily imperfect, it reminds us to look for context. The
relevant context for scientific observations on climate is the world’s
approximate 50 gigatonne annual CO2-equivalent
greenhouse gas emissions.16
Airborne aetiologyAt the heart of the 100 Scientists’ position lies a
very simple idea, that “... carbon dioxide
(CO2), [is] a non-polluting gas that is essential
to plant photosynthesis.” This blanket claim (that
CO2 is non-polluting) must raise a red flag to
doctors, conditioned as we are by Paracelsus’ dictum that
“All substances are
poisons; there is none which is not a poison. The right dose differentiates a
poison and a remedy”.20
CO2 and other greenhouse
gases become increasingly polluting at elevated concentrations. By analogy, in
the clinical setting, electrolytes such as potassium are vital at normal
concentrations, but quickly become life-threatening when concentrations rise
above normal.
With this in mind we review in detail the global
‘greenhouse effect’, and the part played by
CO2. (We are indebted in the following account to
the work of Held and Soden, who have documented progress in understanding of
greenhouse gases over the last
century.21)
In 1827, Fourier described the heat-trapping ability of the
atmosphere, which functions in essence as a one-way filter. Visible frequencies
of sunlight are transmitted freely and warm the Earth. The return journey as
radiated heat is blocked because the atmosphere at these frequencies is highly
absorbent.
In 1861, Tyndall discovered that atmospheric heat is
absorbed mainly by water vapour and CO2, trace
gases making up less than 1% by weight. From his laboratory observations, he
concluded that water vapour acted as “a blanket, more necessary to the
vegetable life of England than clothing is to man”. At the levels
described by Tyndall, CO2 is indeed a
non-polluting gas essential to photosynthesis (albeit that when plants are
stressed, including by heat, they photosynthesise less and move more to
respiratory metabolism;22 such a potential
further positive feedback mechanism bodes poorly for the future climate).
Observational data suggesting that the climate could warm in
response to atmospheric CO2 were first published
by Arrhenius at the end of the 19th century. The effect does not need to be
strong; like compound interest on a loan it simply needs to persist over time.
In 1905, Chamberlin made a key interpretative advance in
writing that water vapour,
“... confessedly the
greatest thermal absorbent in the atmosphere, is dependent on temperature for
its amount, and if another agent, as CO2, not so
dependent, raises the temperature of the surface, it calls into function a
certain amount of water vapour which further absorbs heat, raises the
temperature and calls forth more vapour ...”.
Simply put, warm air holds more water as vapour before it
starts to rain. In the early 1960s, data from the first Venus probes suggested
that a water-mediated greenhouse effect had overtaken that planet’s
atmosphere.23 Since that time, positive
feedback between water and greenhouse gases such as
CO2 has been a central element in models of
global warming.21,24-25 More recent experiments
from NASA’s Aqua satellite have confirmed this link. The observed increase
in atmospheric heat absorption per degree rise in temperature is approximately
2.04 W/m2/K.26
Predictive models workIt is true that greenhouse gases such as
CO2 and water are but one part of a much larger
and complex global system. Climate modellers face a significant technical
challenge when they attempt to estimate greenhouse gas-mediated temperature
gains in the future. But it is important to note the modellers do not claim to
foretell what will happen in the future. Instead, they offer models as a guide
to what may happen, based on best efforts to understand causal relations and
complexity.
The climate models used in the IPCC AR4 were tested against
the conditions of the last 40 years and produced backcasts that fitted closely
with observations at global and regional
levels.16 As Held and Soden wrote in 2000,
“... it is useful to watch
an animation of the output of such a model, starting from an isothermal state of
rest with no water vapour in the atmosphere and then ‘turning on the
sun,’ seeing the jet stream develop and spin off cyclones and anticyclones
with statistics that closely resemble those observed, watching the Southeast
Asian monsoon form in the summer, and in more recent models, seeing El
Niño events develop spontaneously in the Pacific
Ocean.”21
Doctors are familiar with this kind of uncertainty. We are
constantly required to make forecasts, judging risk and prognosis on a daily
basis. We regularly use algorithms,27 imperfect
as they may be, to assess risk and individualise clinical decision-making.
Cardiovascular risk is one such example. Quantitative risk
models cannot of course predict the date on which an individual patient will
suffer a heart attack or stroke. But an algorithm based on age, gender, current
blood pressure, lipid profiles, diabetes, and smoking history, expressed as a
simple colour chart or computer programme, provides an invaluable guide to
decisions about treatment. This has been validated in New Zealand through a back
casting exercise, demonstrating how well the model could
‘predict’28 results from previous
epidemiological studies.28-30
But unsurprisingly, if your starting position is to
categorically deny that CO2 or other greenhouse
gases can trap heat in the atmosphere, it is unlikely your models will predict
human-induced global warming.
The science demands actionDue scepticism has an important role to play, particularly
in fields such as evidence based medicine that are complex and contested. It is
essential though to distinguish between appropriate scepticism and
counterproductive ‘denialism’. Denialism includes the use of
rhetorical arguments, at times selective and influenced by economic interests
beyond the science, inter alia,15 to
give the impression of legitimate argument where there is none. There are common
patterns in the tactics employed by the tobacco industry in its beat-up of
‘the smoking controversy’, those who deny that HIV causes AIDS, and
the climate change ‘sceptics’ (see Diethelm & McKee
200915 for more detail). This kind of denial is
dangerous, and must be questioned diligently.
Diligent questioning has also been leading scientists to
update the latest IPCC assessment, which is now more than two years old. The
science in this area is fast-moving. There is mounting evidence the IPCC
predictions may have been too conservative, where more recent
comprehensive reviews31–33 indicate that
climate change is proceeding at or beyond the upper projections of the 2007 IPCC
assessment.
This is not a criticism of IPCC models, so much as an
ongoing refinement process, similar to updating a medical diagnosis and
prognosis as evidence accumulates. The purpose of climate models is not to
foretell the future, but to inform and guide present-day decision-making in
light of future possibilities.
The climate observations, IPCC models, and physical
mechanisms are consistent; the mechanisms mooted are plausible and can be
demonstrated experimentally at the correct scale; and the process can be
observed in real life and reproduced by models. There is no plausible
alternative explanation that passes these basic tests.
In summary, there are more than sufficient grounds to reject
the arguments of the 100 Scientists12 and
kindred Climate Change Deniers.15 Change is not
necessarily normal: small changes can matter especially when they are rapid and
cumulative, and variation within normal ranges (e.g. variation in either
absolute temperature or rates of change of temperature) is not always benign;
the context of greenhouse gases makes such variation alarming. There is ample
evidence the climate models perform well. CO2 and
other greenhouse gases are causing substantial climate change at current
industrial atmospheric concentrations, and will continue to harm unless these
concentrations are reduced.
Good medicine recognises risk and urgency and is willing to
act on presumptive diagnoses and emerging yet incomplete information. The
warnings of the IPCC are stark, and have serious implications for health workers
throughout the world.2
As Sir Austin Bradford-Hill pointed
out,2 scientific work is inherently incomplete
and uncertain, and yet we are required to use such knowledge as we have and to
act now in the face of uncertainty. Uncertainty is not in itself a reason to
postpone or avoid action.
New Zealand adopted this precautionary principle when we
signed up to the Rio Convention after the Earth Summit of 1992. In the health
arena, New Zealand has acted on this principle in its response to epidemic Group
B meningococcal disease. In the absence of trials of vaccine efficacy, we
undertook safety trials and implemented a vaccination programme, as the most
ethical option.34 In contrast, we have watched
helplessly while HIV-AIDS deniers seriously retarded work on that illness in
Africa, causing much increased mortality and
morbidity.15,35
The same principles hold true whether the scale of action be
clinical or global. As Peter Doherty (the Nobel Prize-winning Australian
immunologist) says, paralleling climate science with biomedical research:
“This experiment, which
involves 6.8 billion human beings, as well as every other complex life form on
our small planet, can only be done once. Can we afford to explore the extent of
its possibilities? I fail to comprehend how any competent scientist could argue
that our current strategies are sustainable. Comparable intimations of disaster
during for instance the testing of a new drug would lead to the immediate
termination of the trial.”
As a profession and as global citizens, we need to move
beyond dissent and denial. We were able to do this for lead, tobacco and
immunisations. As reasonable as it is to verify the evidence on climate change,
circumstances now require us all to take
action.1,2,4,6–9,37–47
Competing interests: This paper is
authored by individual health professionals belonging to, and on behalf of,
OraTaiao: New Zealand Climate and Health1 (www.nzchg.webs.com). Professor Alistair
Woodward was a member of the writing teams that prepared the fourth
(AR4)48 and earlier assessment reports for the
IPCC (2004–07 and before).
Author information: George Laking, Medical
Oncologist/Health Economist, Auckland; Alistair Woodward, Public Health
Physician/Professor of Public Health, Auckland, Scott Metcalfe, Public Health
Physician, Wellington; Alexandra Macmillan, Public Health Physician, Auckland;
Graeme Lindsay, Public Health Physician, Auckland; Joanna Santa Barbara,
Associate Professor of Psychiatry (retired), Motueka; Anne MacLennan, Palliative
Medicine Specialist, Wellington; Imogen Thompson, Public Health Medicine
Registrar, Wellington; Susan Wells, Public Health Physician, Auckland
Acknowledgments: Dr Andy Reisinger,
Associate Professor Ralph Chapman and Dr Jim Salinger reviewed material relating
to climate science for factual accuracy, and provided content and advice. The
authors alone are responsible for the content of this paper, including any
errors or omissions.
Correspondence: Dr George Laking, Auckland
Regional Cancer and Blood Service, Auckland DHB, Auckland, New Zealand. Email:
GeorgeL@adhb.govt.nz;
OraTaiao: New Zealand Climate and Health website (interim): www.nzchg.webs.com References:
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