Impacts on human health
“Climate change is a medical emergency, it thus demands an emergency response.”Professor Hugh Montgomery, director of the University College London Institute for Human Health and Performance
In a 2018 report from one of the world’s leading medical journals, The Lancet, doctors, academics and policy experts from 27 organizations around the world, warned that “a rapidly changing climate has dire implications for every aspect of human life, exposing vulnerable populations to extremes of weather, altering patterns of infectious disease and compromising food security, safe drinking water and clean air.” It stated that the rising heat and wilder weather linked to global warming make climate change the biggest global health threat of the 21st century, with hundreds of millions more people already suffering over the last two decades. Indeed, 800 million people (11% percent of the world’s population) are currently vulnerable to climate change impacts such as droughts, floods, heat waves, extreme weather events and sea-level rise. The authors of The Lancet’s report called for fast action to curb climate change and prepare global health systems for growing challenges.
It has been estimated that if all countries met the Paris Agreement to stay below 2°C heating, we could avoid 138,000 premature deaths a year across the entire European region of the World Health Organisation. Mental health threats are also on the rise, from children worried about their future in an overheating world to families stressed by disaster losses.
It is estimated that the direct damage costs of climate change to health will be between USD 2-4 billion per year by 2030.
Health threats from extreme weather
The authors of the Lancet Countdown Report said that climate change impacts – from heatwaves to worsening storms, floods and fires – were surging and threatened to overwhelm health systems.
Heatwaves can cause heat stress and lead to premature deaths – see section on heatwaves for some facts and figures about the health impacts we are already seeing. In addition, extreme weather, such as storms and floods, not only cause injuries and loss of life directly but can also shut down hospitals, spur disease outbreaks and produce lingering mental health problems as people lose their homes and livelihoods. Wildfires also dramatically worsen air pollution in some areas (see section on health threats from air pollution).
Extreme weather, along with soil degradation, is also impacting food production and water availability, leading to increased risks of health impacts through starvation, dehydration and malnutrition – for some facts and figures see sections on impacts on global food production and impacts on water availability. Indeed, global heating is not only already reducing crop yields, but is also shrinking the amount of nutrients in cereal crops, increasing the risk of malnutrition even for those who do manage to get enough to eat.
Increased spread of diseases
“Climate change is disrupting natural ecosystems in a way that is making life better for infectious diseases.”Andrew Dobson, department of Ecology and Evolutionary Biology, Princeton University
Higher temperatures help the bacteria that cause deadly diarrhoea (and wound infections) to thrive, leading to increased spread of infectious diseases such as cholera. Since 1950, the Baltic region has seen a 24% increase in coastal areas suitable for cholera outbreaks. Indeed, the second most suitable year on record for the spread of the cholera bacteria was in 2018.
In addition, hotter temperatures increase the frequency with which mosquitoes feed off humans, whilst increased rainfall creates more stagnant water sources for these deadly insects to breed in. Mosquitoes are considered to be one of the most dangerous species on the planet, due to their ability to spread many deadly diseases such as Zika virus, West Nile virus, chikungunya virus infections, dengue fever and malaria. Indeed, almost 700 million people contract a mosquito-borne illness every year resulting in more than one million deaths. A growing number of scientists are concerned that global warming could lead to an explosive growth of the mosquito-borne diseases worldwide – a problem that will be exacerbated by the fact that mosquitoes are becoming increasingly resistant to insecticides.
Indeed, in recent years the rate of infection spread of malaria has increased dramatically and in sub-Saharan Africa’s highlands, zones where malaria-carrying mosquitoes can survive have expanded by 27%. The global incidence of the dengue fever has grown dramatically in recent decades, and it is now the most rapidly expanding infection around the world, with about half of the world’s population now at risk. Nine of the ten most suitable years for the ability of mosquitoes to transmit this deadly disease have happened since 2000, with 2017 having the second highest level recorded since 1950.
Rising temperatures are also creating conditions for tropical diseases – which already have devastating health impacts to people who live in the tropics – to spread to other parts of the world where they are not usually seen (see section on future impacts of global heating on human health). There is potential spread of the Asian tiger mosquito – carrier of dengue fever, chikungunya fever, Zika, encephalitis and canine heartworm – which has already been found at isolated spots in Southern England and threatens to become established. Cases of the Zika virus, which causes horrific birth defects, have recently occurred via local transmission in France – enabled by increased temperatures – and there are fears it could spread to the UK soon. A few years ago Italy had a number of cases of malaria in people who had not travelled abroad, whilst in recent years there have been a number of cases of mosquito-transmitted dengue fever in France and Spain.
According to Professor James Logan, head of the department of disease control at London School of Hygiene and Tropical Medicine: “We are seeing mosquito populations move and change and that is likely to bring more malaria. There is evidence that this has already started to happen. It’s not just malaria but other vector-borne diseases, such as dengue, which is now in Europe and we are also seeing in the UK. Some places in the UK are warm enough in summer to sustain a potential malaria outbreak.”
Hotter conditions may also be giving some disease-causing microbes greater resistance to antibiotics.
The threat of new diseases
It’s not just known diseases that might spread to new areas with increasing temperatures. Some scientists think that the Spanish flu virus or other unknown pathogens might be buried in permafrost and as the climate changes they may be released.
In addition, the number of animal diseases newly appearing in humans is increasing. Currently about 60% of human infectious diseases have an animal origin yet this number is going up, with 75% of new human diseases having jumped from animals to humans.
The UN reported that the rising number of new diseases from wildlife is driven in part by degradation of natural habitats, exploitation of wildlife and climate change. For example, deforestation in Malaysia and Singapore caused fruit bats carrying Nipah virus to move from the forest to fruit plantations, where they came into close contact with pigs. Pigs then got the virus from the bats, and then passed it on to humans. Exploitation of wildlife brings humans into closer contact with animal diseases they may not have been exposed to before, whilst climate change increases the chance of transmission of animal diseases to humans because the microbes causing such diseases will thrive in a warmer, wetter, more disaster-prone world. Whilst the exact origins of COVID-19 are not yet certain, it has certainly spread from animals to humans.
Speaking about COVID-19 in March 2020, former United Nations’ Climate Chief Christiana Figueres said we should expect more disease outbreaks “if we continue to deny, delude and delay on climate change”.
Health threats from air pollution
Air pollutants are produced through the uncontrolled burning of fossil fuels. Air pollution is already the world’s largest environmental cause of disease and premature death, being responsible for an estimated 7 million premature deaths each year with 4.8 million dying from outdoor pollution, and the remainder from household pollution. Overall, air pollution kills more people each year than smoking.
Air pollution is further exacerbated by increased numbers of forest fires. California’s wildfires in 2018, spurred by drought, not only cost more than 80 lives but also polluted air as far east as Massachusetts.
Exposure to air pollutants has been linked to a huge range of diseases, from lung cancer and respiratory infections to stroke, dementia and even diabetes. Indeed, pollution is the world’s largest environmental cause of human disease and premature death, either directly or increasing the risks of dying from a variety of diseases. About half of the early deaths from air pollution are related to heart disease and stroke. The next most common causes are lung cancer and pneumonia. For more information on the increasing numbers of deaths from air pollution, see section on air pollution.
In the 15 countries that emit the most greenhouse gas emissions, the health impacts of air pollution are estimated to cost more than 4% of their GDP.
Health threats from intensive agriculture
Intensive agriculture is also a source of human diseases due humans coming into close contact with large numbers of highly-bred animals. Indeed, since the 1940s, intensive agriculture, such as factory farming, has been associated with the emergence of 25% of new human diseases.
Certain pesticides used in intensive farming are also thought to cause harm to humans, for example, organophosphates have been linked to cardiovascular diseases and damage to the nervous system. In addition, the risk of the meat we eat containing bacteria that cause food poisoning (such as Campylobacter) is increased by intensive farming, as stressed animals become more susceptible to infection – a matter made worse by the fact that antibiotics given to livestock have led to antibiotic resistance in the bacteria. Such overuse of antibiotics in the farming industry – leading to resistance – is also severely limiting our ability to be able to use antibiotics to treat human diseases.
Children and the elderly are especially vulnerable
Children and the elderly are particularly vulnerable to the health impacts of climate change. Nick Watts, executive director of the 2019 Lancet Countdown Report, warned: “Children’s bodies and immune systems are still developing, leaving them more susceptible to disease and environmental pollutants. The damage done in early childhood lasts a lifetime. Without immediate action from all countries climate change will come to define the health of an entire generation.” As Stella Hartinger at The Lancet put it: “The path that the world chooses today will irreversibly mark our children’s futures. We must listen to the millions of young people who have led the wave of school strikes for urgent action.”
Impacts on global food production
“It really becomes difficult to see at such levels of warming how we’re going to maintain our agriculture such that the population of the world can actually feed itself.”Dr Peter Stott, Head of the Met Office Climate Monitoring and Attribution Team
Soil degradation, rising temperatures, the spread of new pests and diseases, and increases in extreme weather events – such as heat waves, floods and droughts – are already having a huge impact on food production across the globe. Indeed, over 124 million people across 51 countries and territories are already facing crisis levels of acute food insecurity or worse, requiring immediate emergency action.
More than 95% of what we eat is dependent on the presence of healthy soil, yet a third of our soils are now classified as being moderately or highly degraded and we are currently losing soil 10-100 times faster than it can be regenerated (see section on soil degradation). Indeed, The Lancet reported that rising temperatures over the past 30 years have already led to a decline in the capability of many global cereal crops to deliver full yields. In fact, the crop-yield potential of all major crops tracked, in all regions of the world, have fallen as temperatures have risen. Over the past 30 years, there have been declines in average global yield potential of maize (-4%), winter wheat (-6%), soybean (-3%) and rice (-4%). Many natural versions of our favourite foods such as chocolate, coffee and avocados are already threatened to the point of extinction.
Rising temperatures are also shrinking nutrient levels in cereal crops, increasing the chances of malnutrition. In addition, the combination of hotter temperatures and increasingly globalised trade enables crop pests and diseases to spread to new parts of the world. For example, the Xylella bacterium, considered to be one of the most dangerous plant diseases worldwide, kills olive, almond, and citrus trees – as well as grapevines. Xylella was once restricted to the Americas, but it has now spread to Europe, the Middle East and Asia. Many of our staple foods, such as wheat, sorghum, potatoes and rice, are also under threat from emerging crop diseases. For example, a fungus called ‘wheat blast’ has recently emerged and spread in Brazil and the USA, and climate change is making places like Bangladesh more susceptible to this disease. Ocean warming has caused up to a 35% decline in North Atlantic fish yields.
We live in a globally interconnected society, so a reduction in crop yields on one side of the globe is likely to have impacts on food prices on the other. When harvests fail, countries often ban their food exports, leading to a ‘domino effect’ that can cause price raises across the globe.
Massive price hikes can lead to families struggling to put food on the table, which is what happened in Egypt and other Middle Eastern countries in 2010-2011 during the Arab Spring uprisings. These Middle Eastern countries were the world’s top grain importers and were therefore the most severely affected by a spike in grain prices related to a major drought in China, and also an export embargo in Russia following a record heatwave which destroyed 40% of the grain harvest there. This 2010 Russian heatwave was made considerably more likely by climate change and contributed to a global wheat shortage, as well as a 90% increase in international grain prices.
The climate change-linked heatwave that struck Europe in 2003 resulted in the worst crop decline in 100 years with plants growing 30% less in the heat. Livestock farmers were particularly affected in France – fodder was reduced by 60% and almost 4 million broilers died due to the heat. In Spain the poultry flock was reduced by between 15% and 20%. The exceptional drought in California at the beginning of the last decade (the worst on record, its severity connected to global heating) led to billions of dollars in losses in the agricultural sector. The drought forced farmers to leave over one million acres of farmland fallow and many lakes and reservoirs hit historic lows forcing farmers to pay engineers to drill ever deeper wells and deplete aquifers, however this then leads to increasing soil salinity which further degrades the farmland adding to further future losses.
In a more recent example, the Murray-Darling Basin, known as the breadbasket of Australia, has just experienced its worst two year drought on record, prompting Credit Suisse to warn investors that “whole swathes of what has been the food bowl of Australia is at risk”. Rice outputs slumped by 90% and grain harvests in New South Wales were 60% below their ten year average. Many dairy farms went out of business entirely with a third closing in just 6 years. Abstraction of water from rivers for irrigation exacerbated the low water levels and led to over one million fish dying in mass kills. According to a report by the Interim Inspector General of the Murray-Darling Basin Water Resource: “The past two decades or so have seen a marked change in the volume of water available in the system. Analysis shows that the median annual inflow over the past 20 years is approximately half that of the preceding century. More significantly, the frequency of drier years is also much greater”. Another report by the Australian Bureau for agriculture found that this change in climate has led cropping farmers to see their annual farm profits fall by 35%.
Another dramatic impact of climate change on food availability is demonstrated by the recent plagues of locusts that wreaked havoc across the Horn of Africa and the Middle East and into East Asia, destroying hundreds of kilometers of crops. The UN warned that “25 million people in the East Africa region will face acute food insecurity in the latter half of the year.” It was the largest such outbreak in at least 70 years, and it followed a prolonged period of exceptional rainfall: from October to mid November 2019, the region saw 300% of its average rainfall. This is connected to the Indian Dipole being in a ‘positive phase’, which, according to a new paper, is becoming more frequent as the climate warms. This led researchers at the Food and Agriculture Organisation of the United Nations (FAO) to warn that “if this trend of increased frequency of cyclones in [the] Indian Ocean continues, then certainly, that’s going to translate to an increase in locust swarms in the Horn of Africa”.
Even in the UK heavy rainfall and floods in the north of England in 2019 caused widespread damage to winter vegetables such as potatoes, cauliflowers and cabbages. Some wholesalers have said that the supply of some domestically grown vegetables, such as Savoy cabbage, are already tightening, whilst the price for potatoes in the UK was already about 8% higher in the first week of November 2019 than in the previous month, and conditions for growers remained difficult in the early part of 2020. In August 2020, the National Farmers’ Union announced that the UK was facing the worst wheat harvest since the 1980s due to consecutive seasons of extreme weather – with yields likely to be down by up to 40%. As a result, some millers have already increased the price of flour by 10%.
Impacts on water availability
“Global freshwater security – and therefore global food security – is at far greater risk than we ever imagined.”Professor Jay Famiglietti, senior water scientist at NASA’s jet propulsion laboratory
According to the United Nations World Water Development Report in 2018, an estimated 3.6 billion people (nearly half the global population) already live in areas that are potentially water-scarce at least one month per year. This situation is being exacerbated by hotter, drier conditions and more frequent and more extreme droughts.
In 2017 a drought in East Africa, made up to twice as likely by climate change, displaced around 800,000 people in Somalia. In 2018 an intense drought in Cape Town, made three times more likely by climate change, led to severe water restrictions being put in place and the city came to within days of turning off its water supply, a day that is known as Day Zero (the day when a city’s taps dry out and people have to stand in line to collect a daily quota of water). Climate scientists have calculated that climate change has already made a drought this severe go from a ‘once every 300 years’ event to being a ‘once every 100 years’ event. At 2°C of heating, a drought of this severity will happen roughly ’once every 33 years’. In 2019, after a harsh drought followed by a searing heatwave, Chennai in India was left nearly out of water as its reservoirs ran dry. For some more examples of how extreme weather events linked to climate change have already impacted fresh water supplies see section on impacts on global food production.
Water availability is also impacted by the melting of mountain glaciers. Today, around 1.9 billion people live in catchment areas downstream of glaciated mountain ranges and depend on glaciers for clean water. Yet these glaciers are rapidly melting. See section on melting ice and rising seas.
Pollution also has large impacts on availability of clean water. In fact, poor water quality due to poor sanitation and poor nutrient management is one of the most widespread problems affecting water supplies. In the United States alone, the annual cost of damage caused by contamination of water by nutrients is approximately US$2.2 billion.
Mass displacement and threats to safety, human rights and our global economy
“Climate crisis is the greatest ever threat to human rights. The economies of all nations, the institutional, political, social and cultural fabric of every state, and the rights of all your people, and future generations, will be impacted.”Michelle Bachelet, United Nations Rights Chief
In the first six months of 2019, extreme weather events displaced a record seven million people from their homes.
The latest Ministry of Defence Global Strategic Trends report identified climate change and resource use as among the highest risks to global defence and security – with a potential impact (and certainty of occuring) far higher than weapons of mass destruction.
It has been argued climate change has already led to a rise in global inequality.
Extreme weather events (made more likely by climate change) already cause huge financial losses and threaten to make our world “systemically uninsurable” – for more information see section on extreme weather.
According to the World Economic Forum’s (WEF) 2020 Global Risk Report, climate action failure, biodiversity loss and extreme weather were considered the biggest threats to the global economy. The report also stated: “Climate related issues dominated all of the top-five long-term risks in terms of likelihood”. A separate study found that when over 200 global change scientists were asked about their perception of the same risks they assessed likelihood of the risks as even greater then the WEF report.
Average survey responses from experts on the likelihood and impact of particular global risks, on a scale from 1 to 5. Environmental risks are shown in green
The McKinsey Global Institute Climate Risk and Response Report 2020 warned: “Greater awareness of climate risk could make long-duration borrowing more expensive or unavailable, impact insurance cost and availability, and reduce terminal values. This could trigger capital reallocation and asset repricing. This recognition could happen quickly, with the possibility of cascading consequences.”
On Channel 4 News in July 2019, Mark Carney, Former Governor of the Bank of England, said that efforts to reverse global warming will lead to “major changes” in the UK economy. Companies that fail to respond to climate change “will go bankrupt without question.” Carney has also warned that “Once climate change becomes a defining issue for financial stability, it may already be too late.”
Follow the links to read about how mass displacement, poverty and financial instability and social instability and conflict are expected to be impacting our world by 2050 or by the end of the century.