Can we blame climate change for thunderstorm asthma?

Australians have been left unsettled by the recent thunderstorm asthma event that claimed eight lives in Melbourne. As with previous extreme weather events, we are left to wonder whether it was climate change at work, if it will happen again and if it will be worse next time.

We can’t say for sure if the thunderstorm asthma event was caused directly by climate change. But modelling each extreme event is neither feasible nor necessary. All weather events should now be considered in the context of climate change and general climate projections are sufficiently alarming to justify the need for governments to prepare for, and adapt to, new risks these pose to our health.

How climate change affects Australia

Updated projections from the Bureau of Meteorology and the national science body, CSIRO, outline Australia has warmed 0.9℃ since 1910 and can be expected to warm a further 0.6℃ to 5.1℃ by 2090, depending on reductions in greenhouse gases.

Hotter days will be more common and more severe. Rainfall during the cooler seasons will decrease in southern Australia while extreme rain events will become more common, particularly in the tropics. Ocean acidification and sea level rise will continue, wind speeds may decrease and tropical cyclones may become more intense but less frequent.

Severe thunderstorms are projected to be more common in eastern Australia; about 14% more frequent in Brisbane and 30% in Sydney. Unlike heat and rainfall projections, links between climate change and thunderstorms in Australia are less well understood due to uncertainty around the physical processes that underpin them.

Thunderstorms can be dangerous due to accompanying winds, lightning and flash floods, as well as their potential to rupture pollen into tiny particles that can be inhaled into the lungs. In general, global warming can trigger asthma, and other illnesses, through increased baseline pollen and ground-level pollutants such as ozone.

Climate change also poses a health risk beyond asthma and thunderstorms that is critical to prepare for.

How our health will be affected

Climate change poses a threat to health directly through extreme weather events, warmer average temperatures and sea level rise. Indirectly it can destabilise the systems that keep our air clean, produce our food, provide us with fresh drinking water and enable economies to thrive. These shifts pose a threat to livelihoods, food and water security, and social and political stability.

Heatwaves and reduced rainfall pose the greatest threat to Australians’ health and livelihoods. Indirectly, these changes will increase the severity of bushfires and droughts. These and other extreme events are a significant risk to physical and mental health.

Extreme prolonged heat can trigger acute heat stroke and dehydration or exacerbate underlying illnesses such as heart and kidney disease. Rates of injury, crime and domestic violence also increase in heatwaves. Melbourne’s 2009 heatwave was associated with a 62% increase in deaths and 46% increase in ambulance emergencies.

The elderly, the young, those with chronic disease and those engaged in physical outdoor work are especially vulnerable.

Infectious diseases pose a different challenge. In warmer climates, the transmission potential of mosquito-borne diseases such as malaria is increased. As warmer climates expand southwards, malaria, dengue and Ross River virus will occur in new regions of Australia.

Although thunderstorm asthma has been well documented and has previously occurred in Melbourne, the recent storm revealed that public and health services were unprepared.

In explaining the difficulty of adequately responding to the crisis, Victoria’s health minister Jill Hennessy likened it to 150 bombs going off in different places at once. With current climate change projections, governments need better planning for the likelihood of similar crises.

Getting prepared

There are increasing demands from the health sector for a national strategy to address climate change and the related health concerns. Such action would also address Australia’s international obligations to develop and report on national climate change adaptation strategies, and to achieve strong greenhouse gas emissions reductions.

Key elements of health sector adaptation include early warning systems and more adequate preparation of the workforce. Health professionals need to learn about climate change and related risks to be able to identify vulnerable people, such as the elderly and those with pre-existing conditions, participate in emergency responses and contribute to health system stewardship.

Similar adaptation strategies can often be implemented for different climate risks. For example, the risk from heatwaves and thunderstorms could both be reduced by early warning systems, vulnerability mapping and public health education.

However, while predicting a thunderstorm may be relatively straightforward, predicting acute asthma epidemics requires a detailed understanding of the process and sensitive monitoring of allergens in the air.

Irrespective of whether climate change contributed to the thunderstorm in Melbourne last week, we can be sure that Australia’s climate projections herald new risks to health that cannot be ignored.