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Climate change and health

27 March 2018

The increasing intensity of human activity has damaged the natural world in many ways. Huge areas of forests, woodlands and wetlands have been destroyed to create farmland and extract resources such as fuel. Plastic rubbish litters the shores of distant polar islands and chokes marine life, driving many species into extinction. Scientists agree that humans have also damaged Earth’s atmosphere, including creating holes in the ozone layer through use of chlorofluorocarbons (CFCs), halons and other ozone-depleting chemicals .

Happily, in much of the world deforestation is slowing; nations are taking steps to limit creation of plastic waste; and the ozone layer is expected to recover substantially by mid-century thanks to continued regulation and substitution worldwide of pollutants.

In contrast, it is difficult to be optimistic about the most significant environmental concern of recent decades – climate change – and our response to it. Human-induced climate change is already causing serious environmental damage, and inevitably much of that damage also affects humans.

This article provides a brief overview of the current and predicted effects of climate change and how they relate to human health.

Climate change – genesis and effects

The release of massive volumes of carbon dioxide, methane and other greenhouse gases (GHGs) into the atmosphere as by-products of human activity, mainly since the mid-20th century, is warming the atmosphere and the planet. This occurs because GHGs exacerbate the Earth’s natural greenhouse effect, reducing the outflow of infrared energy, with multiple consequences for all living organisms.

Global warming
The Earth’s average surface temperature has risen about 1.1 degrees Celsius (° C) since the late 19th century . Most of the warming occurred in the past 35 years, with 16 of the 17 warmest years on record occurring since 2001 . The year 2016 was the warmest to date, 0.99 C hotter than the 20th-century average. Current warming is about 10 times as rapid as the average during recovery from any ice age .

In Australia, mean (average) surface air temperature has increased by around 1.0° C since 1910 . Australia’s top five warmest years were 2013, 2014 and 2015. The year 2013 was Australia’s warmest on record (with 2016 fourth, and 2017 third). Sea surface temperatures around Australia have warmed by nearly 1.0° C since 1900, with 2013–15 recorded as the region’s five warmest years on record .

Glaciers are melting and sea levels are rising
Greenland lost about 300 cubic kilometres of ice per year between 2002 and 2016, and Antarctica lost about 125 cubic km of ice per year in the same period . Partly as a consequence, global sea level rise is accelerating, with the rate in the past two decades nearly double that of the 20th century. Global mean sea level was 225 mm higher in 2012 than in 1880.

Extreme weather is more frequent and intense
Extremely hot days in Australia are getting hotter, with the number of very hot (>40° C) daytime temperatures per year increasing since the 1990s. The number of days per year over 35° C has increased and extreme temperatures have increased on average at 7 per cent per decade. Very warm monthly maximum temperatures occurred on about 2 per cent of days in 1951–80; this happened on more than 11 per cent of days in 2001–15.

Ocean acidification
Oceans absorbs about a quarter of the carbon dioxide released into the atmosphere every year . Since the beginning of the Industrial Revolution, the mass of carbon dioxide absorbed by the upper layer of the oceans has increased by about 2 billion tonnes per year, causing a 30 per cent rise in the acidity of surface waters.

Effects of climate change on health

Climate change affects the social and environmental determinants of health – our access to clean air, safe drinking water, sufficient food and secure shelter. Changes to the physical environment cause changes in the conditions to which humans and other organisms have adapted over millions of years, affecting the distribution of food sources and biological health threats.

Heat stress and bushfires
Extreme air temperatures cause increases in deaths associated with cardiovascular, kidney and respiratory diseases, particularly among elderly people. More than 70 000 excess deaths were recorded in the European heat waves of 2003.

Weather associated with high fire danger has become more prevalent in many locations in south-eastern Australia – one of the most fire-prone regions of the planet. By exacerbating bushfire frequency and intensity, climate change poses direct risks to people’s safety.

Respiratory problems
Pollen and other aeroallergens that can trigger asthma – which affects about 300 million people worldwide, or 4 per cent of the global population – are at higher concentrations in extreme heat. The health burden associated with asthma will increase as climate change continues to drive temperatures higher.

Infectious diseases
Climate change is increasing the duration of seasons when major insect-borne diseases are transmitted and altering their geographical spread. The disease of most concern with respect to climate change is malaria, which already kills over 400 000 people every year in the developing world. Mosquitoes thrive in warm and humid conditions, and global warming combined with changed rainfall patterns will extend their range substantially over coming decades. In 1996, Joan Bryan, Desmond Foley and Robert Sutherst published an article in the Medical Journal of Australia  stating that:

Although endemic malaria was eradicated from Australia by 1981, the vectors remain and transmission from imported cases still occurs. Climate modelling shows that global warming will enlarge the potential range of the main vector [the Anopheles mosquito]; by the year 2030 it could extend along the Queensland coast to Gladstone, 800 km south of its present limit.

Climate change is likely to also increase the incidence of dengue virus infection. Dengue is already present in northern Queensland. Recent research shows that large areas of Europe, the United States, east Asia and northern and eastern Australia could become suitable breeding grounds for mosquitoes that transmit dengue.

Food and water shortages
Ocean acidification reduces the concentrations of calcium carbonate minerals, hindering the ability of some organisms – including oysters, clams, sea urchins, corals and calcareous plankton – to produce and maintain their skeletons and shells. Ocean fish and shellfish are the primary sources of protein for more than a billion people worldwide, so ocean acidification represents a direct threat to human nutrition and health.

Increasingly erratic rainfall patterns are expected to affect the supply of fresh water, thereby compromising hygiene and increasing the risk of diarrhoeal diseases in developing countries. Water scarcity can lead to drought and famine. Climate change is predicted to increase the intensity and frequency of droughts worldwide by the late 21st century. Altered precipitation means floods are also becoming more frequent and intense, and this is expected to continue throughout the this century, causing further contamination of water supplies.

An estimated 625 million people lived in low-elevation coastal zones in the year 2000 (10 per cent of the global population), and this number is expected to grow to 879–949 million by 2030. Low-lying coastal areas are highly vulnerable to sea-level rise, which can increase salinity in agricultural land and render it unproductive. Salinity problems in Bangladesh are predicted to cause significant shortages of drinking and irrigation water by 2050 and a decline in rice yield of 15.6 per cent.

What is being done to try to reduce the impact of climate change on human health?

The Kyoto Protocol, an international agreement linked to the United Nations Framework Convention on Climate Change, set binding targets internationally for reduction of emissions. Thirty-seven industrialised countries and the European Community committed to reducing GHG emissions to an average of 5 per cent below 1990 levels in the period 2008–12, and at least 18 per cent below 1990 levels for the period 2013–20. Subsequently, in 2015, the Paris Climate Accord bound signatory countries to holding temperature rises by the year 2100 to ‘well below 2° C above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5° C’.


Many countries are making progress on these commitments, largely by replacing technologies that produce large amounts of GHGs in the generation of energy with low-emission, renewable sources. New solar photovoltaic capacity grew by 50 per cent worldwide in 2016, rising faster than any other fuel. Although coal-fired capacity continued to grow, about half as much coal-fired capacity was retired as was added. China accounts for over 40 per cent of global growth in renewable energy, largely driven by concerns about air pollution and energy capacity.

When the Australian Government ratified the Paris Agreement in November 2016, it formally agreed to consider the ‘right to health’ of citizens in the context of the nation’s climate change response, and to recognise the additional benefits for health in developing mitigation strategies. To promote human health as a priority in Australia’s policies, the Climate and Health Alliance (CAHA – a coalition of over 30 health and medical organisations) developed a Framework for a National Strategy on Climate, Health and Well-being for Australia, released in June 2017. The CAHA framework recognises that the determinants of health and wellbeing lie largely outside the health sector. Its key recommendations are to:

  • Establish national emissions-reduction targets consistent with the recommendations of the Climate Change Authority and based on Australia’s fair share of the global task to reduce emissions.
  • Evaluate through a national study the economic savings from additional health benefits associated with a range of emissions-reductions strategies.
  • Reduce deaths from air pollution by phasing out coal and strengthening national emissions standards for motor vehicles.
  • Prevent poor health associated with inadequate building standards by including climate-resilience measures in the National Construction Code.
  • Avoid adverse health effects contributed by industry and infrastructure projects by incorporating health impact assessments in the evaluation of project applications.
  • Promote healthy, low-emissions diets and lifestyles through provision of funding for public education programs.
  • Ensure health professionals are able to recognise, prepare for and respond to the health impacts of climate change through establishing a national education and training framework.
  • Monitor health impacts through the establishment of a national environmental health surveillance system that includes climate-related indicators.
  • Provide national leadership through the establishment of a Ministerial Health and Climate Change Forum, consisting of federal and state/territory ministerial responsibility for health, environment and energy.

State governments are beginning to incorporate climate change into health planning. Under the Climate Change Act 2010 (Vic.), local government is required to consider climate change when preparing municipal public health and wellbeing plans. Western Australia’s Department of Health recently published its Health impacts of climate change: Adaptation strategies for Western Australia, which is ‘being used to inform Government and community policy and decision-making for community adaptations’.


The trend in global emissions suggests a 4° C increase in global average temperature by 2100. Limiting emissions to ensure a 2° C goal above pre-industrial levels is technologically and economically feasible, but to achieve it all countries – especially the major emitting economies – need to take immediate and comprehensive action.

Unfortunately, tardy and insufficient global action to date means that the Paris Climate Accord’s 2° C goal is very unlikely to be met. This, in turn, suggests that the health effects of climate change described above are mostly underestimates. To reduce their severity, we need to act quickly and decisively to limit GHG emissions and plan our health system responses carefully.