2022 Lancet Report Warns of the Effects of Climate Change on Human Health

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Climate change has already damaged human health, food supplies, and the environment. Rapid, decisive, coordinated action is needed to avert catastrophic health impacts.
Climate change increases the risk of emerging diseases and co-epidemics.

Climate change is undermining global health and food security and is exacerbating the effects of the COVID-19 pandemic, according to the Lancet Countdown 2022 report, published in The Lancet.

“After 30 years of United Nations Framework Convention on Climate Change negotiations, the Lancet Countdown indicators show that countries and companies continue to make choices that threaten the health and survival of people in every part of the world,” stated the report authors, who include international experts from 51 academic institutions and UN agencies monitoring the impact of climate change on health. “As countries devise ways to recover from the coexisting crises, the evidence is unequivocal. At this critical juncture, an immediate, health-centered response can still secure a future in which world populations can not only survive, but thrive.”

The new edition of Lancet Countdown was developed to improve the monitoring of associations between climate change and health. New and reintroduced metrics include:

  1. the effects of extreme temperature on food insecurity;
  2. exposure to wildfire smoke;
  3. household air pollution;
  4. the alignment of the fossil fuel industry with a healthy future; and
  5. health considerations in each country’s Nationally Determined Contributions.

Recent and Potential Health Effects of Climate Change

Extreme weather events in 2021 and 2022 such as floods, wildfires, and record temperatures caused destruction throughout the world and increased the burden on health services already coping with the effects of the COVID-19 pandemic. Heat-related deaths increased globally by 68% from 2000 to 2004 to 2017 to 2021, a rate that was significantly worsened during the pandemic.

At this critical juncture, an immediate, health-centered response can still secure a future in which world populations can not only survive, but thrive.

Climate change increases the risk of emerging diseases and co-epidemics. The number of months for potential malaria transmission increased by 31.3% in the highland areas of the Americas and 13.8% in the highland areas of Africa between 1951 to 1960 and 2012 to 2021. The risk of dengue transmission increased by 12% in the same period.

The global mean surface temperature is estimated to be 2.4°C to 3.5°C above pre-industrial times by 2100, with a 48% chance that the 1.5°C threshold proposed in the Paris Agreement will be exceeded within 5 years. The average temperatures that humans were exposed to during the summer of 2021 were 0.6°C higher than the average temperatures in 1986 to 2005, which was twice the global mean temperature increase in the same period (0.3°C).

Exposure to extreme heat is associated with acute kidney injury, heatstroke, adverse pregnancy outcomes, worsened sleep patterns, adverse effects on mental health, worsening of underlying cardiovascular and respiratory disease, and increases in nonaccidental and injury-related deaths.

The number of annual hours of moderate risk of heat stress during light outdoor physical activity increased globally from 2012 to 2021 by an average of 281 (33% increase) hours per person, and high-risk heat stress increased by 238 (42%) hours per person, compared with the baseline average in 1991 to 2000. The greatest increase was in medium-Human Development Index (HDI) countries.

Wildfires, Droughts, and Flooding

Health-related effects of wildfires include thermal injuries, exposure to smoke, loss of physical infrastructure, and effects on mental health and well-being. The global population had an average of 9 more days of very high or extremely high meteorologic wildfire danger in 2018 to 2021 vs 2001 to 2104, with 110 (61%) of 181 countries having an increase.

Droughts have adverse effects on food and water security, threaten sanitation, affect livelihoods, and increase the risk of wildfires and infectious disease transmission. From 2012 to 2021, nearly 47% of global land area on average was affected by at least 1 month of extreme drought each year, which was an increase of 29% over the period of 1951 to 1960.

The risk of flooding is also of concern. Between 2006 and 2018, the global mean sea level increased by 3.7 mm per year, and is estimated to be 0.28 to 1.01 m or more by 2100 depending on mitigation efforts on climate change, ice sheet collapse, and local factors. About 149.6 million persons were living less than 1 meter above sea level in 2020 vs 145.2 million in 2010. Persons living in these areas are at risk of flooding, coastal and riverbank erosion, severe storms, soil and water salinization, spread of infectious diseases, and permanent inundation.

Food Production and Malnutrition

Climate change is adversely affecting food production, supply chains, and food access, and increased temperatures are reducing the duration of crop growth. Changing environmental conditions affect the spread of crop and livestock pests and diseases and lead to production losses. Increasing water temperatures and ocean acidification threaten fish stocks.

“Shifting to low-carbon, plant-forward diets would have the multiple benefits of reducing agricultural greenhouse gas emissions, improving health outcomes, reducing the diversion of grains to livestock and the demand of land for crop production, water demand, and the risk of agriculture-related zoonotic disease outbreaks,” stated the study authors. “Interventions to increase the resilience of food systems, and improve sanitation and health care can minimize climate-related nutritional risks.”

Notably, during the COVID-19 pandemic, government restrictions led to worsened global malnutrition, with the number of undernourished people increasing by 161 million to 720 to 811 million between 2019 and 2020. A greater number of heatwave days led to an increase of 3.7 percentage points in self-reported moderate to severe food insecurity in 2020 vs 1981 to 2010, which is equivalent to an additional 98 million persons reporting moderate or severe food insecurity. Russia’s war on Ukraine is also worsening food insecurity and may lead to an additional 7.6 to 13.1 million persons undernourished globally in 2022.

Greenhouse Gas Emissions

Owing to responses to COVID-19, anthropogenic CO2 emissions decreased by 5.4% in 2020, the largest decrease in the past 25 years. But with inadequate structural change to limit fossil fuel use, emissions increased by 6% in 2021, an all-time high level. “The grossly insufficient decarbonization, compounded by geopolitical conflict, has made it vastly more challenging to limit the temperature rise to 1.5°C, and the window of opportunity to limit the temperature rise is rapidly closing,” the researchers commented.

The largest single source of greenhouse gas emissions is energy systems, which are significant contributors to air pollution. Phasing out coal is particularly urgent owing to its high greenhouse gas emissions and air pollution intensity, according to the report, although coal provides 26.7% of global energy supply, 2.8 percentage points more than in 1992. However, increased use of renewable electricity reached record levels in 2020.

About 770 million persons do not have access to electricity in their homes, and the use of dirty fuels is increasing exposure to air pollution. For the first time in 6 years, the number of people without access to electricity increased in 2020, with changes to the use of biomass and other unreliable fuels increasing exposure to household air pollution. According to the World Health Organization, the use of solid fuels for cooking led to 3.8 million deaths attributable to household air pollution in 2016.

The global food system is responsible for one-third of all greenhouse gas emissions. In 2019, 55% of global agricultural emissions resulted from red meat and dairy products, and 11.5 million deaths were attributable to imbalanced diets. Of these deaths, 17% (2 million) were related to red and processed meat and dairy consumption, of which 93% were in high and very high HDI countries. For low and medium HDI countries, low consumption of fresh fruit and vegetables was the primary contributor to diet-related mortality — 44% of all diet-related deaths in low HDI countries and 37% in medium HDI countries.

In 2019, the health care field contributed to about 5.2% of global greenhouse gas emissions, an increase of more than 5% from 2018. Among the 37 health systems that were assessed individually, the United States had the most emissions per person, although it has the sixth-lowest healthy life expectancy at birth (66.2 years).

Among the 8 largest publicly listed international oil and gas companies (IOCs) by production volume and the 7 largest state-owned national oil and gas companies (NOCs), production strategies generate substantial greenhouse gas emissions. These companies’ share of greenhouse gas emissions is currently expected to exceed their ability to be consistent with the goal of limiting the global average surface temperature rise to 1.5°C — by an average of 39% for the IOCs and 37% for the NOCs in 2030. These excess emissions are expected to increase in 2040 to 87% for IOCs and 111% for NOCs.

Increased Focus on Solutions and Health Planning

Individual, scientific, and governmental engagement in health and climate change reached their highest recorded levels in 2021, with climate change solutions an increasing focus. Renewable electricity and use of electric vehicles also had record growth, and investments and employment in clean energy are increasing.

The Lancet Countdown found that total of 49 of 95 countries reported having a national health and climate change plan in place. In 2021, 30 (39%) of 78 countries reported having climate-informed health surveillance systems for vector-borne diseases, 25 (32%) of 78 countries for waterborne diseases, 23 (35%) of 65 countries for airborne diseases, and 14 (21%) of 66 countries for diseases that can be transmitted to human from animals (ie, zoonoses). Among 47 countries, 6 (13%) had surveillance for mental health risks and 8 (11%) of 70 countries had surveillance for food-borne diseases. Among cities, 33% of those in very high-HDI countries and 39% of those in medium-HDI countries had at least moderate levels of greenness compared with 16% in high and low-HDI countries.

In 2021, 112 (63%) of 177 countries reported high to very high health emergency management implementation. In HDI countries large disparities occurred, with 35% of low- or medium-HDI countries having high to very high implementation rates of health emergency management vs 88% of very high-HDI countries.

A health-centered response to the climate crisis would create an opportunity for a low-carbon, resilient future but also improve global health and well-being, according to the report authors.

“Such response would see countries promptly shifting away from fossil fuels, reducing their dependence on fragile international oil and gas markets, and accelerating a just transition to clean energy sources,” noted the study group. “A health-centered response would reduce the likelihood of the most catastrophic climate change impacts, while improving energy security, creating an opportunity for economic recovery, and offering immediate health benefits.”

The 2022 Lancet Countdown is the seventh iteration of its report on health and climate change. The Countdown is an international, transdisciplinary collaboration of 51 academic institutions and UN agencies that monitors the changing health profile of climate change.


Romanello M, Di Napoli C, Drummond P, et al. The 2022 report of the Lancet Countdown on health and climate change: health at the mercy of fossil fuels. Lancet. 2022;400(10363):1619-1654. doi:10.1016/S0140-6736(22)01540-9