'Malaria is creeping up the mountains'
Interview: Rudi Slooff

Only 13,000 years ago, much of northern Europe groaned under the weight of glaciers. Human life was virtually impossible there, and only over the following centuries did our ancient ancestors feel able to edge northwards into lands that had been abandoned to the ice for some 10,000 years. If today the temperatures everywhere are rising, ice-caps are melting and sea-levels rising, may this not be merely a further swing of the geophysical pendulum towards a Tropic Age. Or is it All Man's Fault? I put this question first to Dr Rudi Slooff.

Dr Rudi Slooff
© WHO

Dr Slooff: Meteorologists who in recent years have studied the interaction of greenhouse gases with global climates have of course taken into account the natural fluctuations in global temperature and atmospheric composition. We know, for instance, from fossil ice core analysis that temperatures and carbon dioxide levels fluctuated wildly, but always in tandem, during part of the previous interglacial period, about 100,000 years ago. Nevertheless, not many scientists in this field still believe that the projected changes � in other words, towards a steady rise in temperature worldwide � are simply the result of natural causes.

To what degree is global warming actually happening?

Let us first agree that we define global warming as that part of the greenhouse effect that is attributable to human actions. The Intergovernmental Panel on Climate Change (IPCC) took some seven years � from 1988 to 1995 � to be able to say in its Plenary Session that there is discernible human influence on the climate. Today, based on anticipated future trends in greenhouse gas (GHG) emissions, the IPCC estimates that the global mean temperature will rise by 1.4 to 5.8 degrees Centigrade over the next hundred years.

Levels of carbon dioxide in the atmosphere have been increasing ever since the beginning of the Industrial Revolution, roughly from the start of the last century. The rate of increase in those levels during the past decades is accelerating, and humans are clearly releasing into the atmosphere more greenhouse gases, that is, carbon dioxide, carbon monoxide, nitrous oxide, ozone and methane than natural processes can absorb. Not only do we fell the forests which act as a natural sink for carbon dioxide through photosynthesis, but we add to the gases through burning or processing that timber. So the effect of deforestation is doubly harmful.

Of course, contamination of local environments with noxious industrial, agricultural and automotive wastes poses a direct and tangible toxic threat to human biology. In contrast, the emission of most GHGs has no direct toxic consequence for humans but the resulting climate change may alter various ecological relationships that may then impinge on human health.

The warming is brought about by gases accumulating in the troposphere. But suppose there were two volcanic eruptions on the scale of Mount Pinatubo in the Philippines in 1992. Might they not counterbalance everything that mankind has managed to do to the atmosphere?

Well, it's true that particulate matter creates cooling. In Al Gore's book Earth in the Balance, he says there was an enormous volcanic eruption in Indonesia in early 1816, and in Europe that year was described as "the year without a summer," when peasants wandered throughout Europe in search of food. But such natural effects don�t last. The effect of GHGs is much more permanent.

So what are the likely direct impacts on human health of global warming?

We see, as one main category, heatwaves and extreme weather events. Heatwaves bring in their wake a mortality increase in both the very young and the very old, while there are also psychosocial effects. Some years ago, heatwaves in Los Angeles were accompanied by a very steep rise in violence and mindless looting.

Extreme events, such as storms and floods, are obviously more difficult to predict in terms of effects. Some climatologists believe we shall see more of them! Insurance statistics show that more extreme events are already happening. Cyclones wipe out huge numbers of people and millions of acres of crops; yet people live in low-lying delta areas, such as Bangladesh and Mozambique, precisely because the huge river silt deposits are very fertile. People sometimes have nowhere else to go.

What are the likely indirect effects of climate change?

The main indirect effects will be the spread of infectious diseases, including those carried by insects and other vectors, damage caused by aggravated air-pollution and by exposure to more ultraviolet radiation (UVR), and the loss of food security. Malaria is already a huge problem, and we see clearly that it is creeping up into mountain areas in such countries as Kenya, Papua New Guinea, Ethiopia. The mosquitoes are now transmitting disease above 2,000 metres, where people have hitherto not been taking precautions against malaria nor against dengue fever, so both diseases are evidently spreading.

Malaria bacterium
© CNRI/Science Photo Library

Tuberculosis and water-borne diseases like cholera are less influenced by climate change, and more by interhuman contact and polluted water supplies. We have come across a hypothesis that cholera distribution depends in part on Vibrio cholerae attaching itself to plankton. And since satellite observations show that algal blooms are exploding all over the world as sea surface temperatures rise, they and the related plankton can contribute to cholera epidemics. Emerging diseases too may be favoured. For instance, hantavirus pulmonary syndrome appears to be transmitted from rodents. The Midwest United States suffered an outbreak when the rat population boomed after a wet year followed six very dry years which had virtually killed off vegetation and rodent predators.

As regards food security, 350 million people are already dependent on permanent food aid. Their lands are becoming demographically denser, the amount of arable land is declining, and with climate change and shifting rainfall patters, there is a high risk of even more frequent crop failures. But let me make it clear that I don�t believe the climate can be blamed for everything. Human mobility and the mobility of food � foodstuffs transported all over the world � all contribute to the spread of diseases.

Are certain populations likely to be more affected than others?

In poor or densely populated developing countries, people will to some extent get "more of the same" � infectious diseases, food insecurity. Other countries may expect new problems from emerging diseases, ecological changes, chronic flooding and increased UVR. There may be an increased influx of refugees in some places. Low-lying islands in the Pacific and Indian Oceans and coastal cities are exposed to sea-level rise; a rise of 10 to 12 centimetres has been recorded for this century.

Then there is the risk of the permafrost melting or moving deeper, as in Siberia or Alaska where high buildings have been planted on it. Moreover, the permafrost contains great quantities of methane gas which, as a greenhouse gas, could spark off a positive feedback if it were to be released. There may be some benefits from climate change too � winters that are less severe, greater food harvests at higher latitudes or altitudes.

Are there dangers of increased conflict as a result of dwindling resources and population displacement?

We are already seeing this happening today and there is no reason to suppose such problems will go away. Climate change, however, is only one contributory factor. Rwanda and Sierre Leone are cases in point.

What can be done to combat existing and future public health problems arising from climate change?

We should first think of strengthening our capacity to deal with present-day problems; that will take care of many future problems too. It will be fatal to do nothing. We should do whatever is possible to prevent climate change by bringing GHG emissions down. The United Nations Framework Convention on Climate Change (UNFCCC) which originated at the UN Conference on Environment and Development in Rio de Janeiro in 1992 and has been ratified by a great many countries, called for the reduction of all national GHG emissions to 1990 levels by the year 2000. That target was not reached. In any case, if it was simply done country by country, that would merely perpetuate the inequitable poor-rich gap. On a per capita basis, the United States uses 10 to 20 times as much fossil fuel as most Third World countries, which cannot afford the cost of installing GHG-free technologies overnight. There has to be 'redistribution', meaning that the developed world must reduce GHG emissions more while accepting that developing countries will reduce less, or are even allowed to increase them. The European Union has proposed a GHG reduction scheme based on those principles.

What else is the international community doing about all this?

WHO, the World Meteorological Organization (WMO) and the UN Environment Programme (UNEP) published Climate Change and Human Health in 1996, a 300-page comprehensive assessment of the current situation and of future projections. Its purpose was "to assist and promote further international collaboration aimed at improving our understanding of how climate variability and climate change affect human health so that preventive and protective action can be taken."

In particular it examined: the potential adverse health impacts of summertime heat stress, the beneficial effects of milder winters upon cold-related mortality; the complex ways in which climatic change would affect the potential transmission of vector-borne diseases, and the likely increased occurrence of water-borne and foodborne infections; the potential impacts of climate change upon agricultural productivity: possible changes in extreme weather events, such as heat waves, floods, storms and droughts, and how these would affect human health; the impacts of sea level rise on the health of vulnerable populations; and potential health effects of increased ground-level exposure to UVR.

That book proved to be a source of inspiration for negotiations taking place under the UNFCCC, but member states still need concrete advice on the handling of public health issues associated with global climate change. Scientists need data from other countries and guidance on research priorities.

We subsequently proposed the setting up of an Interagency Network on Climate and Health. Embracing WHO, WMO and UNEP, its aim was to help countries to find ways of making national assessments of the climate-health relationship through training, raising awareness and pilot studies. It also aimed to create a database as the address to which all member states could turn for information and to act as consultants in a fast-moving scene which still needs a great deal of applied research in a huge number of fields.

Providing such services is very much in line with WHO's role in environmental health, which is to help to monitor trends, to support research activities, to set standards, to facilitate data exchange and to offer training in health risk assessment and environmental epidemiology.

John H. Bland is former Editor-in-Chief of WHO's illustrated magazine World Health. Climate Change and Human Health is available from Distribution and Sales, WHO, CH-1211 Geneva 27, Switzerland, price Sw.fr.30 (in developing countries Sw. fr. 21)

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