Health risks increasing slowly

For health professionals such as nurses the real challenges of climate change go well beyond theoretical debates. By Louise Williams

Within the cool confines of the Australian National University’s supercomputer laboratory, biostatistician Keith Dear (above) couldn’t be further removed from the simplistic and bitterly polarised climate change debate.

But, while Australia’s politicians, vested interest groups, advocates and sceptics bang heads over the carbon tax, international and local research communities are moving steadily forward in their understanding of the extraordinary complexities of climate science, and the equally daunting new areas of research and knowledge we must urgently build if we are to adapt, and survive, in a warmer world.

Dr Dear’s most high profile contribution to date is his estimates of the likely changes in mortality and morbidity across Australia due to heat and cold to the end of this century for the 2008 Garnaut Climate Change Review. He is also a contributing author of the upcoming fifth report of the Intergovernmental Panel on Climate Change (IPCC). It turns out our climate “comfort zone” is actually very narrow; as soon as you deviate away by only a few degrees mortality shifts upwards.

By combining weather pattern projections with both demographic and health data, Dear has concluded Australia could be facing over 800,000 more cases of gastroenteritis, a sharp and rapidly accelerating increase in heat related deaths into the tens of thousands from mid century, and a significant movement south of the serious mosquito-borne disease, dengue fever.

Now with access to Australia’s fastest supercomputer facility – which opened, fortuitously, at ANU in 2009 – these initial models of three specific health risks look “quite simple”, he says.

Dear and his team are continuing to build increasingly sophisticated models, taking into account multiple future weather scenarios – down to daily conditions – plus “de-personalised” cause of death data, hospital admissions, geographic location and local characteristics affecting health such as proximity to medical care and air pollution; which already adds up to millions of rows of data.

And, that’s really just a beginning.

“Climate change doesn’t kill people in a novel way. A very large number of risks increase a little bit....we have to start thinking in mathematically subtle ways about probabilities.

“The truth is not simple,” he says of the disappointing tone and level of Australia’s current public debate.

By way of illustration, consider the potential impacts of heat and drought in rural Australia. Direct heat-related deaths are one thing, but we also know rural suicide rates and depression, for example, increase during severe drought. There is also a well documented link between depression and cardiovascular disease, for example. So far, the health risks for Australia of extreme heat, gastroenteritis and dengue fever have only been modelled separately.

“But, if we are really going to understand the impact of climate change on health we have to put a myriad of risks together,” he says. That way everything from emerging infectious diseases to underlying, subtle changes to existing health threats can be cross referenced with “adaptations”, like air conditioning in our homes and workplaces, heat wave alarms, even mass planting of trees to combat urban heat generated by vast areas of concrete, as well as issues such as access to medical care.

One way to do this is to set up a “virtual Australia” with every citizen represented (but not identified) as a distinct unit, and a large range of data summaries from this month’s census mapped on. On top of this “population simulator” any number of variables can be overlaid, he says. His own team, part of Australia’s Climate Change Adaptation Research Network for Human Health includes a mathematician, a climate scientist, and epidemiologist, an emergency physician and a GP to ensure the widest range of inputs.

For a biostatistician accustomed to working with solid, real world data – initially in clinical trials and then in epidemiology – Dear says the single biggest challenge is modelling into a range of possible future climate scenarios

Dear came to the ANU via Cambridge, Reading, Harvard and Newcastle Universities and the five years he has been working on the health risks posed by climate change is a natural extension of his early work in epidemiology, he says. Nevertheless, this is relatively new field.

Globally, climate change and health risks were definitively linked by the World Health Organisation in 2000, which then attributed 2.4 per cent of worldwide diarrhoea and 6 per cent of malaria to climate change. The first large scale, quantifiable impacts on human health are likely to be changes to the geographic range and seasonality of some infectious diseases – including malaria and dengue fever and food-borne infections such as salmonellosis which peak in warmer months. Climate sensitive diseases are already among the largest global killers; diarrhoea, malaria and protein-energy malnutrition.

However, the future public health consequences loom even larger. Although much attention has been focused on rising sea levels and the areas facing inundation and the immediate death and injuries caused by severe weather events; wider, large scale disruption to food-production with changing rainfall patterns, including longer droughts and more intense floods, will put intense pressure on the world’s health. Developing countries have been identified as especially vulnerable by international agencies; “rain-fed” agriculture, for example, employs 70 per cent of Africa’s entire working population. While Australia has considerably more resources to “adapt” – and a national climate change adaptation research network is already in place – we are also facing considerable health challenges.

Despite Australia’s vocal climate change sceptics, Dear has no doubt about the urgency of his task. A new global collaboration, led by the London School of Hygiene and Tropical Medicine, was established last year, through which researchers from all over the world, including Dear, will share their “models” and methods; a positive development which should inform national models everywhere.

Personally, Dear says he does “whatever my teenage daughter tells me to” when it comes to his own “green” credentials; riding a bike to work, harvesting water in the family’s Canberra home and planning to buy the first electric cars to come onto the market.

But, personal behaviour isn’t really what he is worried about.

Firstly, he’s dismayed by the divisive public debate over whether or not climate change caused, for example, the recent Queensland floods or the deadly Black Saturday bushfires in Victoria.

“The essential point is we keep asking the wrong question.

“Floods and fires are caused by extreme weather events and no single weather event is caused, or will ever be caused, by climate change,” he says.

What the Australian public is apparently so reluctant to grasp is that climate change increases the frequency of extreme events – so that what we need to be considering is changing probabilities and risks, not looking for simplistic ways to lay blame.

And he believes Australia’s failure to act to date is both an “embarrassment and a disgrace”.

“For Australia action on climate change is a moral issue, it isn’t even about whether or not the small amount of CO2 we put out makes a difference. We can’t expect to stand up on the world stage and criticise China and India when we have no moral authority ourselves,” he says.

From a scientific point of view much, much more can be done to pre-warn us about the health risks ahead.

Just as climate scientists started with simple models just looking at the atmosphere, then added interactions with oceans, the same kinds of sophisticated model can be developed for health – with enough funding, he says. For Australia, the most urgent issues are likely to be dengue fever and the impact of shifting agricultural to new regions, and the likely dismantling entire rural communities, as weather patterns change. However, only with sophisticated projections can we build policies and strategies to adapt.

But, watching the politics of climate change in Australia and worldwide, he says, is a different matter.

“When you stare the facts in the face they are scary. The magnitude of the disaster has not been recognised, even if we act now things will get worse because CO2 levels cause slow change with a long “lag” effect – personally, I am very frightened about the future.”