Ever since human-caused climate change emerged into public consciousness around the late 1980s, news stories and public awareness campaigns surrounding the topic have predominantly been accompanied by images of polar bears and melting ice, reinforcing common misconceptions that the impacts are far away in space and time and removed from our daily lives. Recent national surveys showed that 58 percent of Americans believe that they themselves will not be harmed by climate change, while 61 percent had given little or no thought to how climate change might affect people’s health.
Yet mounting scientific evidence has led experts to conclude that climate change presents “the biggest global health threat of the 21st century”. A recent study demonstrated that there are 467 different pathways by which human health, water, food, economy, infrastructure and security have already been impacted by climate hazards. Here are 8 major ways that climate change harms our health today and threatens it tomorrow:
1. The frequency, intensity, and duration of heatwaves, droughts, wildfires, floods and storms are increasing due to climate change.
The most well-known and visible manifestation of climate change to date is probably the increasing volatility of extreme weather events worldwide, causing deaths, injuries, debilitating and fatal diseases, and displacement. Researchers have estimated that climate-related disasters caused 2.52 million deaths globally between 1980 and 2013. Besides the growing research field of attribution studies, in which scientists can tease out the role climate change played in increasing the likelihood and/or severity of an extreme event, some have gone even further to make a direct connection to the human death toll. For example, researchers estimatedthat during the 2003 European heat wave, which claimed over 70,000 lives in 12 countries, climate change increased the likelihood of heat-related deaths by 70 percent in Paris and 20 percent in London.
2. As average temperatures continue to rise, so will heat-related disorders.
In addition to heat waves, climate change is generally causingtemperatures to rise, hot days to become more common, and summers to last longer. In cities, this problem is being compounded by the “urban heat island” effect, which can lead to temperatures being 1–5°C higher than surrounding rural areas. Exposure to extreme heat can lead toserious illness and even death, with the most vulnerable groups including children, the elderly, and those performing outdoor work or activities.
An unforeseen example of human “climate canaries” has emerged in Central America and southern Mexico, where more than 20,000 sugarcane workers have died from chronic kidney disease most likely caused by extreme temperature and employment conditions that prevent adequate hydration and rest. Similar patterns are appearing in workers halfway round the world in India, Sri Lanka and Thailand.
3. Climate change can exacerbate air pollution.
Besides the fact that climate change and air pollution share many major common sources (fossil fuel and biomass burning), climate-driven changes in weather patterns and higher carbon dioxide levels could also worsen air quality in many regions of the world. Effects include higher frequency of stagnation events, elevated ozone concentrations, increased wildfire activity and higher levels of wind-blown dust and pollen.
The harmful health effects of air pollution include a myriad of acute and chronic heart and lung diseases that will lead to lost school and work days, hospital visits, and even premature death. There is also emerging evidence that air pollution can reduce fertility and is harmful to our brains—causing development delays and autism in children, as well as reduced IQ and increased Alzheimer’s disease in adults.
4. Elevated carbon dioxide (CO2) concentrations are associated with decreased human cognitive performance.
Elevated CO2 levels in occupied buildings are a well-known indoor air quality concern, with studies reporting associations with declines in cognitive performance and increased risk of sick building syndrome in office workers and schoolchildren. Thanks to human activities, today’s atmospheric CO2 levels (approximately 410 parts per million) are the highest they’ve been in the past 15 million years, and will likely exceed 1,000 ppm by 2100 on our current trajectory. As outdoor CO2 levels rises, background indoor levels are likely to rise too. The ramifications of this effect on public health and economic productivity are not yet well understood, but it’s worth bearing in mind that current guidelines typically recommend keeping indoor CO2 levels below 1000–1500 ppm.
5. Climate change influences the transmission of vector-, food-, and water-borne diseases.
Rising temperatures, changes in precipitation patterns, and sea-level rise can affect the abundance and distribution of vectors and the pathogens they transmit in both time (duration of transmission seasons) and space (extents in latitude and elevation). For example, warming temperatures have influenced the invasion of North America by West Nile virus and the spread of malaria to higher elevations in the East African Highlands. There are also growing concerns that ancient or unknown microbes may emerge from the thawing Arctic permafrost.
Additionally, changes in weather patterns and infrastructure damage following extreme weather events can enhance the spread of water- and food-borne diseases, including cholera and diarrheal diseases.
6. Climate change threatens food and nutrition security.
While rising temperatures and CO2 levels might initially help some crops in certain regions, the overall outlook is negative. Global food demand is expected to increase by 14 percent per decade to 2050 whereas global crop yields are expected to decrease by 1–2 percent per decade, potentially leading to food scarcity, price shocks and social unrest.
The climate impacts on our food systems are multifold. For example, warming temperatures, drought and extreme weather events will cause declines in staple crops including wheat, maize, sorghum and millet (global wheat and maize yields are already beginning to decline). Rising CO2 levels and warming ocean temperatures lead to ocean acidification and collapse of coral reef ecosystems, which will exacerbate declining fish yields from overfishing and pollution. Higher atmospheric CO2 levels have been found to reduce the nutritional value of crops such as wheat, rice, barley and potato by depleting their protein and mineral contents.
7. Climate change will cause mass migration and most likely increase collective violence.
Military experts warn that climate impacts are “threat multipliers” that will aggravate stressors such as environmental degradation and political instability in vulnerable regions, thereby catalyzing conflict. Historically, water shortages and temperature/precipitation extremes are associated with increased conflict and sociopolitical instability; climate change may have been one of many factors that triggered the devastating Syrian civil war. In addition to civil unrest, sea level rise and extreme weather events will make certain regions become uninhabitable. By 2050, 50–250 million people could be at risk of displacement due to climate change.
8. Climate change poses threats to our mental health and well-being.
These impacts can occur through multiple direct and indirect pathways. For example, extreme weather events are associated with a wide range of mental health problems, including acute and post-traumatic stress disorders, depression, drug and alcohol abuse, suicide, and child or spousal abuse. The destruction and loss of homelands due to climate impacts may diminish the sense of belonging and solace that people derive from their connectedness to the land (an effect that has been termed “solastalgia”). In addition, indirect mental health effects may occur following declines in personal physical health or community wellbeing.
Despite all of this, it is also important to realize that tackling climate change presents “the greatest global health opportunity of the 21st century” and that the barriers to achieving this are primarily sociopolitical (rather than economic or technical). Actions to mitigate climate change offer a wealth of immediate and local health benefits that include reducing air and water pollution from fossil fuel combustion, designing cities to include more green spaces and with active commuters in mind, avoiding massive costs in health care and emergency relief, and ensuring energy, food and water security.