Freeman Dyson's views on climate in the Independent
Eminent theoretical physicist and climate sceptic Freeman Dyson
interviewed by emailin last Friday's Independent by their
science editor Steve Connor.
Dyson is famous for his work in the field of quantum
electrodynamics, in which he made a
major advance in 1948. Now retired, he is a member of the
academic advisory board of the climate sceptic thinktank the Global Warming Policy
In an occasionally testy email exchange, The Independent sought
to tease out Dyson's position on climate change. We took a look at
what he said.
"the computer models are very good at
solving the equations of fluid dynamics but very bad at describing
the real world. The real world is full of things like clouds and
vegetation and soil and dust which the models describe very
This statement implies that computer models do not take into
account the impact of clouds, vegetation, soil and dust on
temperature trends. This is
Climate models are mathematical representations of the
interactions between the atmosphere, oceans, land, ice and sun.
This is a complex task, which means that there are limitations to
the certainty that scientists give to model predictions. These
uncertainties are factored into the predictions made
by the IPCC, and are made obvious in their reports.
recent report suggests that complex feedbacks in the climate
system will always introduce some error into the predictions of
climate models. These limitations make the magnitude and timing of
predicted climate change uncertain, but they do not change
confidence in identifying the overall warming trend.
"we do not know whether the recent
changes in climate are on balance doing more harm than good. The
strongest warming is in cold places like Greenland. More people die
from cold in winter than die from heat in summer."
This statement focuses on just one effect of temperature rise -
the number of deaths from excessive heat or cold. It also focuses
on just one part of the world.
true that in Europe, North America and other temperate regions
there are more deaths related to cold winters than hot summers.
However, climate change will impact on human societies in
many ways, affecting for example agricultural yields, water
supplies, sea levels and the health of the oceans. It is in
poorer countries, many of which are in the tropics, that the
worst effects on human health will be experienced. A
World Health Organisation (WHO) report estimates that 3% of
malaria and 3% of diarrhoea deaths worldwide in 2004 were
attributable to climate change. Of these deaths, the majority were
children. A further 12,000 deaths were thought to be hastened by
"there are many other causes of climate
change besides human activities, as we know from studying the
Yes, the world's climate has varied in the past, for many
different reasons, some better understood than others. Over
geological timescales, factors such as sun brightness, changes in
the Earth's orbit, and greenhouse gas levels have all altered our
However, noting that something happened before without human
influence does not demonstrate that humans are not causing it
today. The climate change we are currently experiencing is well
Dyson himself admits, atmospheric
CO2 and other greenhouse gases prevent heat energy from leaving the
Earth's climate, increasing its temperature. Human activity has
dramatically increased the amount of CO2 in the atmosphere, and is
dominant factor affecting Earth's climate on a human timescale
IPCC's FAQ section for more detail).
"the carbon dioxide in the atmosphere is
strongly coupled with other carbon reservoirs in the biosphere,
vegetation and top-soil, which are as large or larger. It is
misleading to consider only the atmosphere and ocean, as the
climate models do, and ignore the other reservoirs"
Whilst it might have been true that climate models only
considered the atmosphere and ocean in the 1960s, today's climate
models are far more sophisticated. Terrestrial vegetation, sea-ice,
the effects of dust and aerosols, and even chemical cycles
(including the carbon cycle) are now
routinely incorporated in modern climate models.
"the biological effects of CO2 in the
atmosphere are beneficial, both to food crops and to natural
vegetation. The biological effects are better known and probably
more important than the climatic effects."
The last report produced by the
IPCC, in 2007, predicts that more C02 in the atmosphere could
positively impact on plant growth and yields. But climate change
also means higher temperatures and the likelihood of more extreme
weather events - both of which are likely to have a negative impact
on plant growth. Again, the impacts are likely to be worse in
tropical regions. The IPCC says
"Climate change increases
the number of people at risk of hunger (high confidence)… Climate
change alone is estimated to increase the number of undernourished
people to between 40 million and 170 million."
"the climate of the earth is an
immensely complicated system and nobody is close to understanding
As (presumably) every climate scientist will attest, the climate
of the Earth is an "immensely complicated system". But
sophisticated research methods have been developed to examine the
Earth's climate. As with any other scientific field, there are some
parts of it that are well understood, and others less so
Climate models are tested using a method known as "hindcasting"
- testing the models' reconstructions of past climates against what
actually happened. The models have
been shown to successfully predict past and current climate
conditions, indicating that the modellers have a pretty good
understanding of Earth's climate.
"If it happens that I am wrong and the
climate experts are right, it is still true that the remedies are
far worse than the disease that they claim to cure."
While not strictly a scientific claim, this is clearly a matter