Climate change is contributing to the inequitable suffering of billions of people around the world. Driven by human greenhouse gas emissions, climate-related hazards -- including heat waves, floods, wildfires, and disease outbreaks -- are accelerating more rapidly and having more direct effects than previously anticipated. Indeed, health is increasingly an important lens through which to measure the effects of climate change -- making climate change more salient and tangible to the public and policymakers.
The health crisis posed by climate change is enormous. But how big exactly? According to the World Health Organization's (WHO) webpage, "Between 2030 and 2050, climate change is expected to cause approximately 250,000 additional deaths per year." This number is one of the first you'll encounter if you research online the impact of climate change on health, yet, it seems wholly inconsistent with the Lancet's of climate change as the greatest global health threat of the 21st century.
The problem, and the explanation for this discrepancy, is fourfold. First, the WHO statistic accounts for only four health impacts known to be related to climate change -- malnutrition, malaria, diarrhea, and heat stress -- whereas many other pathways to health harms are known. Second, the number is widely considered to be a by most climate and health experts. Third, the estimate is now nearly a decade old and likely out of date. Finally, the "250,000 additional deaths per year" estimate represents a projection for the future and not an assessment of the harm already being caused by climate change.
Indeed, relatively little is known about the real-time impacts of climate change on human health. This knowledge gap has cascading consequences and leads to the suboptimal development of interventions and solutions designed to support the provision of care in many healthcare settings.
The consequences for this gap in knowledge are considerable. Is climate change just another public health challenge or is it the greatest existential threat to health we have ever faced, as so many experts continue to claim? The uncertainty engendered by our lack of understanding of the real-time harms caused by climate change results in the health sector being under-prioritized time and time again.
Globally, between 0.5% and 5% of all climate supports the health sector, and none of the 203 projects funded by the United Nations Framework Convention on Climate Change Adaptation Fund since 2015 have been primarily dedicated to adaptation in the health sector.
A recent call to commission a attempts to address this problem. Such a global effort to take stock of the impact would close data gaps for groups like the Lancet Countdown and the Intergovernmental Panel on Climate Change by providing a real-time, standardized, and complete accounting of climate change health consequences around the world. However, such an undertaking requires improved methods of attribution for climate health harms.
The International Classification of Diseases (ICD) system is a global collaborative led by the WHO that is used to classify and track morbidity and mortality. It is one of the primary inputs for surveillance systems utilized by public health professionals attempting to estimate climate change-related health harms. Unfortunately, when it comes to climate-sensitive health conditions, there is no ICD code for "hottest day of the year," "unprecedented extreme weather," or "patient harmed by climate change."
Recent has highlighted how clinicians are uniquely positioned to help identify and map the true extent of the crisis through improved medical coding. This research also identifies gaps in the current iteration of the ICD system for climate-sensitive health harms, and points to how the system can be improved. The development of new climate-sensitive ICD codes, such as "sequela from heatwave" and "exposure to wildfire smoke," would help medical professionals and patients understand the scope of the health threats posed by climate change and inform policies to keep people safe.
Making the tremendous human suffering fueled by climate change more visible through improved medical coding can also inform action to keep more people out of harm's way. Moreover, using real-time data derived from point-of-care clinician insight has the potential to both improve health system climate resilience and help allocate scarce resources to particularly vulnerable populations.
Jeni Miller, PhD, executive director of the Global Climate and Health Alliance, recently , "Declaring an official health day at COP28 is welcome proof of the growing political realization that the climate crisis is also a health crisis."
As the immense risks of climate change to our health become even more obvious, the voices of health professionals are critical for helping to make the case for policies that protect people. Healthcare providers are at the vanguard of this movement and we need to equip them and local, state, and federal policy makers with better data that can inform smarter responses to threats posed by climate change.
is an assistant professor of emergency medicine at the University of Washington in Seattle. He is the first author on a climate change and health informatics . is clinical assistant professor of pediatrics at Stanford in California, with a background in clinical informatics. He has published multiple on climate change and health informatics. , is an associate professor of nursing at Monash University in Melbourne, Australia, and first author on multiple health informatics in peer-reviewed journals.