Climate change is increasing the frequency and intensity of some
extreme weather events. Extreme heat and cold events are the most likely to increase and worsen followed by more frequent heavy rain or snow and increases in the intensity of droughts. Extreme weather events, such as floods, hurricanes, heatwaves, droughts and wildfires can result in injuries, death and the spread of
infectious diseases. For example, local
epidemics can occur due to loss of infrastructure, such as hospitals and
sanitation services, but also because of climate changes creating a more suitable weather for disease-carrying organisms.
Heat Since the 1970s, temperature on the surface of Earth has become warmer each decade. This increase happened faster than in any other 50-year period over at least the last 2000 years. Compared to the second half of the 19th century, temperature in the 21st century show a warming of 1.09 °C. Extreme heat is a direct threat to health, especially for people over 65 years, children, people living in cities and those who have already existing health conditions. Rising
global temperatures impact the health and well being of people in multiple ways. In the last few decades, people all over the world have become more vulnerable to heat and experienced an increasing number of life-threatening
heatwave events. Physical exercise is beneficial for reducing the risk the many illnesses and for mental health. At the same time the number of hours per day when the temperature is dangerously high for outdoor exercise has been increasing. The rising heat also impacts people's ability to work and the number of hours when it is not safe to work outdoors (construction, agriculture, etc.) has also increased. Unless
greenhouse gas emissions are reduced, regions inhabited by a third of the human population could become as hot as the hottest parts of the
Sahara within 50 years. The projected annual average temperature of above 29 °C for these regions would be outside the biologically suitable temperature range for humans.
Heat-related health effects for vulnerable people Exposure to extreme heat poses an acute health hazard, especially for people deemed as vulnerable. Vulnerable people with regard to
heat illnesses include people with low incomes, minority groups, women (in particular pregnant women), children, older adults (over 65 years old), people with chronic diseases, disabilities and
multiple long-term health conditions. Human responses to heat stress can include
heat stroke and overheating (
hyperthermia). Extreme heat is also linked to
acute kidney injury, low quality
sleep, and complications with
pregnancy. The human body requires evaporation of sweat to cool down and prevent overheating, even with a low activity level. With excessive heat and humidity human bodies would no longer be able to adequately cool the skin. A
wet-bulb temperature of 35 °C is regarded as the limit for humans (called the "physiological threshold for human adaptability" to heat and humidity). As of 2020, only two weather stations had recorded 35 °C wet-bulb temperatures, and only very briefly, but the frequency and duration of these events is expected to rise with ongoing climate change. Global warming above 1.5 degrees risks making parts of the
tropics uninhabitable because the threshold for the wet bulb temperature may be passed. People with cognitive health issues (e.g.
depression,
dementia,
Parkinson's disease) are more at risk when faced with high temperatures and ought to be extra careful as cognitive performance has been shown to be differentially affected by heat. People with diabetes and those who are overweight, have sleep deprivation, or have cardiovascular/cerebrovascular conditions should avoid too much heat exposure. The risk of dying from chronic lung disease during a heat wave has been estimated at 1.8–8.2% higher compared to average summer temperatures. An 8% increase in hospitalization rate for people with
chronic obstructive pulmonary disease (COPD) has been estimated for every 1 °C increase in temperatures above 29 °C. This results from the way many cities are built. For example, they often have extensive areas of asphalt, reduced greenery along with many large heat-retaining buildings that physically block cooling breezes and ventilation. It increased by about 50% when the population growth in these cities is not taken into account. Also more than 2,000 people died in
Karachi, Pakistan in June 2015 due to a severe heat wave with temperatures as high as . Due to climate change temperatures rose in Europe and heat mortality increased. From 2003–12 to 2013–22 alone, it increased by 17 deaths per 100,000 people, while women are more vulnerable than men. Increasing access to indoor cooling (
air conditioning) will help prevent heat-related mortality but current air conditioning technology is generally unsustainable as it contributes to
greenhouse gas emissions,
air pollution,
peak electricity demand, and urban heat islands. Heatwave early warning and response systems are important elements of heat action plans.
Reduced labour capacity Heat exposure can affect people's ability to work. Working in extreme heat can lead to labor force productivity decreases as well as participation because employees' health may be weaker due to heat related health problems, such as dehydration, fatigue, dizziness, and confusion. It is also well established that regular physical activity is beneficial for human health, including mental health. Many of the
consequences of droughts have effects on human health. But these effects go beyond direct physiological effects. Prolonged drought and environmental degradation can undermine livelihoods, especially in areas that depend on agriculture, and lead to the displacement of large populations seeking resources and economic opportunity. In the Lake Chad Basin, for example, the loss of water resources, desertification and reduced rainfall have displaced millions and decimated traditional livelihoods. Such large movements put pressure on the areas that receive them, increasing competition for scarce resources and possibly aggravating existing social and ethnic tensions.. Such conditions create environments of economic despair, political exclusion, and social unrest that violent extremist groups can exploit. For example, in northern Nigeria, declining agricultural productivity and widespread poverty associated with drought have increased the vulnerability of populations, especially young men, to recruitment by groups like Boko Haram that provide financial incentives, food security, or a sense of community . Drought, thus, functions as an environmental and public health stressor and an indirect driver of conflict and terrorism by changing population dynamics and increasing structural vulnerabilities.
Floods Due to an increase in heavy rainfall events,
floods are expected to become more severe in the future when they do occur. From a mid-term perspective, floods can seriously impact infrastructure, thereby disrupting emergency services and access to medical facilities such as hospitals. This disruption can even affect hospitals located far from the epicenter of the extreme event. For example, the
2022 Pakistan floods (which were likely more severe because of climate change) affected people's health directly and indirectly. There were outbreaks of diseases like malaria, dengue, and other skin diseases. from a surface fire in the western desert of
Utah.
Wildfires become more frequent and intense due to climate change.
Wildfires Climate change increases
wildfire potential and activity. Climate change leads to a warmer ground temperature and its effects include earlier snowmelt dates, drier than expected
vegetation, increased number of potential fire days, increased occurrence of summer
droughts, and a prolonged
dry season. Wood smoke from wildfires produces
particulate matter that has damaging effects to human health. The health effects of wildfire smoke exposure include exacerbation and development of respiratory illness such as
asthma and
chronic obstructive pulmonary disorder; increased risk of
lung cancer,
mesothelioma and
tuberculosis; increased airway hyper-responsiveness; changes in levels of inflammatory mediators and coagulation factors; and
respiratory tract infection. Furthermore, tropical cyclones and storm tracks are moving towards the poles. This means some regions will see large changes in maximum wind speeds. Scientists expect there will be fewer tropical cyclones. But they expect their strength to increase. == Health risks from climate-sensitive infectious diseases ==