Global warming, health warning

Although the following comments relate to Australia, they have broad application to most other countries.

Let there be no doubt, global warming is a killer. It is likely to contribute to or be the direct cause of your premature death because of the way in which it causes:

• loss of human habitat;
• greater incidence of disease; and
• increased ozone production.

Loss of human habitat

Humans can only live in a habitat where very limited climate conditions prevail, where for most of the time it is not too cold (above 0C) and not too hot (below 40C). Habitat that is wet enough to cultivate food, and dry enough to avoid prolonged high humidity. Outside these conditions, we struggle to survive and do not live for very long. Loss of habitat due to the effects of global warming poses serious threats to our survival.

Humans, and no less importantly the animal and plant species they depend on for food, can only cope with anything outside these parameters for a relatively short period. The effects of global warming and the increasing speed with which it is happening are therefore of immediate and longer term importance to humans.

Global warming produces climate extremes resulting in longer, more frequent periods of severe heat, draught, high winds, tidal surges and flooding. Such conditions pose a threat to our health and wellbeing, as evidenced by the 2009 extreme heat conditions in southeast Australia when temperatures exceeded 40C and remained above that level for almost a week. The resulting bush fires killed 173 people and destroyed thousands of houses and other property.

Less well known is that the heat during this short period caused the premature death of an estimated 200 people in southeast Australia. The very young and the old are particularly vulnerable to atmospheric temperatures in excess of normal body temperature. Had heatwave conditions lasted longer, the death toll would have been much higher.

Heatwave conditions result in a greater incidence of bushfires, accompanied by very dry conditions and high winds. These contribute to a contraction of the human habitat since they prevent reliable food production and water supply needed to sustain a population of any size, particularly very large urban populations. The latter then become dependent on food imported from more distant areas where it can be produced and on water saved and stored from recycling, infrequent rainfall and desalination.

Examples of this are already evident in areas of dense population such as Perth, Melbourne and the Brisbane - Gold Coast region. All are areas trying to cope with populations growing at such a rate that increased demand is placed on dwindling water and food supplies. The Goulburn Valley and other irrigation areas of Victoria, once aptly known as the food-basket of Australia, are faced with drying river basins unable to provide the water needed to sustain food production.

Global warming is already causing land based snow and ice to melt much faster than it is being formed with the result that, apart from the remnants of the Greenland and Antarctic Ice caps, the planet is likely to be ice free by 2100. The consequences of this have been described elsewhere.

Suffice it to say that this will result in sea level rises inundating low lying coastal lands where 70 per cent of the population live - and result in loss of land currently used for production of the food on which they depend. It will only be possible to maintain food security by reducing exports or by importing more.

If population growth is not curtailed, the presently low incidence of malnutrition will increase significantly. This will reduce resistance to diseases, particularly vector borne diseases, which either do not occur or are rare at present.

Greater incidence of disease

Global temperatures are already rising so fast that some species of plant and animal life have no time to adapt. They face extinction or, at best, much reduced habitat able to support fewer numbers. For other life forms, rising temperature increases their habitat and this is the case for mosquitoes and ticks, both of which carry diseases and infect humans with them.

These vectors are currently limited to habitat in hotter, more humid parts of Australia mostly in and north of Townsville on the east coast. They are rare or do not occur further south where winter temperatures fall to levels which kill them. However, as ambient temperatures increase, mosquitoes and ticks will move further south and survive winter in places such as Brisbane and the more densely populated southeast corner.

In a few decades from now disease carrying ticks and that harbinger of so many ills, the Anopheles mosquito, may even spread as far south as Sydney and bring with them serious diseases at present rare or unheard of in those places.

As mosquitoes and ticks spread further south, they will bring diseases for which, at present, there is limited treatment. Many of these diseases either kill or permanently and adversely affect humans, particularly those with impaired resistance to them.

Encephalitis, dengue fever and some forms of malaria and tuberculosis are particularly difficult to cure and can prove fatal. Others, such as asthma are rarely fatal if well managed but are exacerbated, becoming much more serious due to the presence of micro particles in the air caused by bushfires and dust-storms or worse, by an increase of atmospheric ozone.

While diseases causing diarrhea can be successfully treated, they weaken and disable those who contract them, usually from inadequately treated water but also from food. For example, rising sea surface temperatures can increase the presence of vibrio cholerae found in fish and increase the likelihood of contamination in imported food. Children are more susceptible to cholera than adults and more likely to die without timely treatment.

The World Health Organisation estimates that global warming is already responsible for 150,000 deaths annually and that half of these occur in the Asia-Pacific region. Mortality will increase as temperatures rise and vectors spread to more populated areas.

Increased ozone

Ozone is a molecular form of oxygen occurring at very low levels in the lower atmosphere. It is produced from oxides of nitrogen (NO and NO2) and other volatile substances emitted into the air by vehicles, fuel stations and power stations every day of the week. At present temperatures and in the presence of sunlight some of these are transformed into ozone, though seldom in such quantity that the ozone produced exceeds 40 parts per billion (ppb) for more than a few hours.

As global warming raises ambient temperatures, more of these substances are converted into ozone and its concentration in the lower atmosphere or troposphere rises. This is one of the major reasons why we need to avoid an increase of more than 2C in global temperatures. However, unless there is agreement at the Copenhagen Conference on significant reduction of greenhouse gas emissions the amount of ozone produced from these substances will increase to dangerous levels.

We can not live without oxygen (O2) but we can not live with ozone (O3). The presence of ozone in the troposphere in concentrations above 40 parts per billion near the earths’ surface is corrosive and toxic to humans, other air breathing animals and many food plants.

Ozone attacks the cells of the airway and lungs causing them to swell, produce fluid and fail in their ability to provide us with sufficient oxygen or protect us from diseases such as asthma caused by allergy and emphysema caused by smoking cigarettes.

If global temperatures rise more than 2C, ozone concentration in the lower atmosphere is likely to rise above 100 ppb, a level dangerous to health. The effects on humans of ozone at various concentrations for short periods of up to eight hours exposure are known and these are listed below:

• 0-40 ppb. No ill effects evident but may contribute to asthmatics being somewhat less well;
• 40-80 ppb. Those sensitive to ozone may experience slight breathing difficulty with increased rate of respiration, possibly slight pain caused by inflammation of lung cells. May cause healthy people to become asthmatic or experience longer recovery times from influenza;
• 80-150 ppb. Healthy individuals may experience the above. Those sensitive to ozone will experience reduced lung function evidenced by the need to take deeper breaths more frequently, some pain arising from inflammation of lung cells and more frequent coughing. Asthmatics are likely to experience an increase in breathing problems;
• 150-300 ppb. Healthy individuals will experience pain from inflammation and other damage of lungs, be limited in level of physical activity, frequent coughing and soreness, congestion with phlegm and other fluids emitted by damaged cells. Those with pulmonary complaints (emphysema, asthma, tuberculosis, etc) or heart problems at increasing risk of dying. Those without them are at increased risk of developing them. Children and young adults at highest risk of lung damage and dying.

What is not known for certain is the effect of exposure to higher levels of ozone on a permanent basis. It is reasonable to assume that those effects would be more severe than indicated above and possibly fatal.

Increased concentration of ozone in the atmosphere must and can be avoided by reducing emissions from which it is made and curbing global warming.

Conclusion

Global warming is a very real health risk and one which is already beginning to affect us. It can kill us all and will do so if it is allowed to go unchecked. We know the risks, we know the measures required to limit them. The choice is ours.