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Global warming isn’t just a parlour discussion anymore; it’s here and happening right now, and it’s a serious threat to human health.

Summer, particularly in South Africa when the thermometer shoots way into the 30s and seems to get stuck there, is the best time for an environmentalist to start arguments at dinner parties about the reality of global warming. For one thing, it’s getting easier and easier to win. You don’t even have to try to remember those complicated climate change stats – just let the heat speak for you.

And besides, you've got Science on your side. The climate change experts are finally starting to get to grips with their vast, amorphous subject, and what they’re saying, with growing conviction and consensus, is:

Things are definitely hotting up.

'So what?' quip the dinner-party dissenters. 'Summer always was my favourite season.'

Even so, there’s no getting round the fact that the planet’s temperature has never risen so alarmingly before, that it’s still rising, and that it’s almost entirely our own fault.

Small temperature increase = huge global impact
According to the United Nations’ Intergovernmental Panel on Climate Change (IPCC), primarily because of the release of greenhouse gases from fossil fuels, over the past 100 years or so the earth’s average surface temperature has risen by about 0.6°C.

Which, admittedly, doesn’t seem like much. Even when we hear that the IPCC expects the temperature to rise by between 1.4°C and 5.8°C by 2100, this still doesn’t seem like anything a notch more air conditioning and a well-iced gin-and-tonic couldn’t handle.

The trouble is that even a small rise in temperature can have huge impacts – if that small rise is planet-wide and permanent. A useful analogy is the human body: your temperature fluctuates throughout the day, and at any one time, different parts of your body will have different temperatures. But, rather as it would be physiologically worrisome if your average temperature suddenly went up by a degree or two and stayed there, similarly it’s a big deal when this happens to the entire planet.

And, according to health and climate scientists at the World Health Organization, it’s a big deal for human health. They say: never mind the future, the estimates are that global warming already contributes to more than 150,000 deaths and 5 million cases of illness annually. The symptoms of a feverish planet likely to have the greatest potential impact on human health, are as follows:

More heat
We’re in for more hot days and heat waves. This is particularly bad news for urbanites, as heat waves are generally worst in cities, whose heat-retaining tarred and concrete surfaces, and heat-generating motor vehicles and industries turn them into “urban heat islands”.

And heat kills. The 2003 heat wave in Europe, for example, one of the worst in 150 years, caused deaths in the tens of thousands – and showed that even the developed world is poorly equipped to deal with such events. We can expect many more heat-related deaths, mainly through cardiovascular and respiratory disease, and mainly in the most vulnerable: the elderly and chronically ill.

More wild weather
Global warming isn’t just a matter of heat; rising temperatures are likely to trigger more and worse “extreme” weather events, like floods, droughts and storms. In this wilder world, weather patterns will be less predictable, which means it’ll be harder to plan for disasters, stretching public health budgets to the limit.

In addition to physical injury and death, natural disasters have several other negative health impacts. Flooding can cause drinking water contamination and the spread of diarrheal diseases like cholera. Respiratory infections may also increase from crowding (as happens in disaster relief shelters: think Katrina); molds, which flourish in the damp left by floodwaters, may cause respiratory symptoms.

Survivors of natural disasters have higher rates of psychiatric disorders like anxiety and depression, and behavioural disorders in children. Developing nations would be particularly vulnerable to rising waters, because many of their inhabitants live on flood plains and coastal plains.

Droughts mean less water for food production, which would lead to more malnutrition, with long-term health consequences - especially for children. Again, developing countries, whose food security is already threatened, would bear the brunt. Water scarcity may force people to use poorer quality sources of water, resulting in an increased incidence of diarrheal diseases.

More disease
Animals that carry infectious diseases, like mosquitoes and rats, generally thrive in warm, moist climates. A warmer world could give them a boost, allowing them to spread from the tropics and subtropics, and low-lying areas, into more temperate zones and higher altitudes, carrying with them scourges like malaria, dengue fever, yellow fever and encephalitis. They’d spread in time too – longer summers would prolong transmission seasons. One estimate suggests that 260 to 320 million more people could be at risk for malaria by 2080.

More dirty air
The impact of certain air pollutants, like tropospheric ozone (the “bad” ozone in the lower atmosphere), tends to be more severe at higher temperatures. Climate change is also likely to increase the risk for forest fires, which are associated with an increased incidence in respiratory disease, and acute attacks of asthma, bronchitis and chest pain.

Warmer winters may mean an earlier start to the grass pollen season, and raised levels of certain tree pollens. Rising levels of carbon dioxide, the main greenhouse gas, also appears to stimulate the release of allergenic pollens and spores in some plants. Hay fever sufferers should brace themselves for more frequent, persistent and severe attacks.

So what’s to be done?

Tackle the symptoms: keep your cool

See Easy ways to beat the summer heat, and don’t underestimate the dark side of Summer. Check up on elderly or ill friends and relatives when the temperature soars, and help out with stressful chores so they don’t need to get hot and bothered.

Tackle the cause: reduce your emissions

It’s not just industry and big business that’s responsible for the problem; we all are: those of us who drive cars and live in electrified houses contribute handsomely to greenhouse gas emissions. There are multiple ways to reduce emissions; here are the basics:

  • Get a little less dependent on motorised transport. Walk, cycle, use public transport or share rides whenever you can.
  • Think of ways you can use household electrical appliances less. Keep heating and cooling appliances at lower settings, and turn off lights when not in use.
  • Reduce, reuse, recycle. Any manufacturing of new products takes energy, produces greenhouse gases, and makes us all sweat that little bit more.
  • Support companies and politicians who show genuine commitment to reducing dependence on fossil fuels (through instituting programmes of more efficient energy use, for example, or making the switch to “green” energy alternatives) – and put pressure on others to follow suit.
  • Finally, get people thinking and talking about global warming. A heated debate livens up many a languid summer dinner party...

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