Our current system of death certification makes it difficult to monitor climate-related deaths, often leading to underestimates. Given that the impacts of climate change are only set to worsen, some suggest it is time to explicitly include
‘climate change’ on death certificates.
Environmental conditions have always impacted human mortality, but understanding the statistics around this mortality can be challenging. As the impacts of climate change worsen, we are sadly going to see an uptick in mortality in response
to extreme environmental conditions.
This has led to calls for ‘climate change’ to be included on death certificates, with those in favour arguing it will improve the reporting and attribution required for evidence-based responses and local, regional and national adaptation
Too often, the impact of climate change on mortality is simplified to immediate deaths in the aftermath of natural disasters such as floods, wildfires, or hurricanes. The issue of underreporting climate-related deaths has similarities with
cases of lightning strikes, where the direct cause (e.g. a falling tree branch or the collapse of a building on fire) is reported without any reference to the indirect cause (i.e. the initial lightning strike that triggered the events
culminating in death).
Calculating climate-induced mortality using death certificates alone risks significantly underestimating total mortality. Official statistics suggest a mere 66 people were officially killed by Hurricane Maria in 2017, while the true value
is thought to be at least 70 times higher. Similarly, researchers in Australia found that the true number of heat-related deaths was 36,765 across the country between 2006 and 2017, approximately 36 times higher than official statistics of
‘The true number of heat-related deaths was 36,765 across the country between 2006 and 2017, approximately 36 times higher than official statistics of 993.’
The above figures demonstrate the inadequacy of death certificates’ ability to account for environmental conditions; the committal of non-biomedical factors results in substantial inaccuracies in cause-of-death estimations in many
Arnagretta Hunter, a cardiologist at Australian National University—co-author of the study looking at heat-related deaths in Australia—argues that to better understand the health impacts of climate change, it is critical we understand it
from a data-driven perspective, rather than solely considering it from a biological perspective.
She desperately advocates for the modernisation of death certification and the inclusion of indirect causes, with all death certificates prompting any external environmental factors that contributed to the death.
This mortality data can then be combined with large-scale environmental datasets to conduct more robust impact assessments that will improve our ability to track heat-related mortality, and could provide key information needed to develop
interventions to help the most vulnerable.
Due to the exclusion of environmental data from death certificates, epidemiologists currently rely on calculations of ‘excess deaths’ to estimate the impact of climate change. While excess deaths can provide a relatively complete overview
of the mortality rates at a given time, they can reflect multiple factors and are heavily dependent on assumptions around how many people were likely to die if an event did not happen.
While many agree that including environmental information on death certificates would be useful, they are more sceptical regarding its effectiveness. Principally, disease epidemiologists say ‘climate change’ simply is not a medical
diagnosis; its inclusion on a death certificate would solely be a reflection of the physician's opinion, although more simple environmental conditions could still be recorded.
‘Epidemiologists currently rely on calculations of ‘excess deaths’ to estimate the impact of climate change.’
Furthermore, many countries do not issue death certificates or struggle to certify all their deaths, a problem encountered throughout the COVID-19 pandemic. Few countries in the tropics have the required resources for accurately collating
These caveats mean including climate-related data on death certificates is unlikely to prove significantly more insightful than simply using excess deaths and should not be prioritised over ensuring infrastructure is put in place that
allows vulnerable countries to record all their deaths.
Some argue that rather than focusing on certification, we should be working towards identifying key climate-risk factors that drive mortality, although without robust mortality data this is challenging.
A more feasible alternative is improving how we record climate-related excess deaths. Climate health scientists are increasingly adopting the principles of detection and attribution studies (common within climate science more broadly) to
measure the health effects of climate change.
Such studies require the creation of two counterfactuals, one where they calculate how many deaths would have occurred if the event had not happened, and another on the event’s severity in the absence of climate change. Combining these two
scenarios allows researchers to calculate the proportion of deaths from a disaster that can be attributed to climate change.
Apportioning a certain fraction of excess deaths to climate change will reduce any space for political manoeuvring aiming to downplay the impacts of climate change, and will give us a more robust picture of the number of deaths directly
attributable to human-induced climate change. Obviously, such studies would take time—by which political attention may have shifted—and are again subject to certain assumptions that could be disputed.
‘Apportioning a certain fraction of excess deaths to climate change will reduce any space for political manoeuvring aiming to downplay the impacts of climate change.’
However, said issues could be minimised by legislating for independent official national statistical bodies to be given funding and responsibility for such studies. This should enhance transparency, speed and repeatability when compared to
current university-conducted studies.
So while including ‘climate change’ specifically on death certificates is not immediately practical (and likely never will be), merely asking the question raises critical discussions around how we best record the true human cost of climate
Given that climate change is set to be the defining problem of the 21st century, it seems implausible that we do not have robust, repeatable and transparent mechanisms to track its impact on mortality. This simply has to change.
Featured Image: World Bank | Flickr
Arnold C. (2022) Death by climate change. Nature Climate Change. Volume 12, issue 7, pages 607-609.
Kishore N., Marqués D., Mahmud A., et al (2018) Mortality in Puerto Rico after Hurricane Maria. New England Journal of Medicine. Volume 379, issue 2, pages 162-170.
Longden T., Quilty S., Haywood P., et al (2020) Heat-related mortality: an urgent need to recognise and record. The Lancet Planetary Health. Volume 4, issue 5, page 171.