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Carbon Brief Staff

28.02.2011 | 7:00pm
ScienceFreeman Dyson’s views on climate in the Independent
SCIENCE | February 28. 2011. 19:00
Freeman Dyson’s views on climate in the Independent

Eminent theoretical physicist and climate sceptic Freeman Dyson was 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 Foundation.

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.

Claim 1:

“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 poorly.”

This statement implies that computer models do not take into account the impact of clouds, vegetation, soil and dust on temperature trends. This is not true.

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.

A 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.

Claim 2:

“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.

It is 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 climate change.

Claim 3:

“there are many other causes of climate change besides human activities, as we know from studying the past.”

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 climate.

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 understood. As 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 currently the dominant factor affecting Earth’s climate on a human timescale (see the IPCC’s FAQ section for more detail).

Claim 4:

“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.

Claim 5:

“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)â?¦ Climate change alone is estimated to increase the number of undernourished people to between 40 million and 170 million.”

Claim 6:

“the climate of the earth is an immensely complicated system and nobody is close to understanding it.”

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.

Claim 7:

“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 of opinion…


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