Millions of people are being exposed to heatwaves, which can lead to heart problems, renal disease, and death.
The number of people vulnerable to heatwaves is going up; 157 million more people were exposed to heatwaves last year compared to 2000.
People who have diabetes, cardiovascular problems, or respiratory issues are more vulnerable to heatwaves. Heatwaves can also harm people indirectly by increasing livestock mortality, which in turn can lead to food shortages.
Those in Europe and the East Mediterranean are more vulnerable than people in Africa and southeast Asia, the report said. This is likely because the former two locations have more elderly residents and people who live in urban areas — factors that increase risk.
Floods, which are becoming more common, can kill people, exacerbate mental health issues, and spread infectious diseases.
The number of people exposed to floods could increase by 2 billion by 2100, according to the report.
Already, about 15% of all natural disaster-related deaths are due to floods.
South America and southeast Asia have seen the greatest increases in extreme rainfall, though the floods have become more frequent globally since 1990.
Some parts of the world already experience deadly droughts all year long.
Droughts are dangerous because they can lower crop yields and reduce access to clean water, making it more likely that people will be infected by waterborne diseases.
Parts of South America, Africa, and southeast Asia already experience droughts all year long. By 2100, the number of people exposed to droughts annually could rise by 1.4 billion.
Deaths due to climate-related diseases, including skin cancer and dengue fever, have gone up despite many improvements in global health.
Climate change has played a role in expanding the reach of dengue fever, the report said. Deaths from the disease are going up quickly, particularly in southeast Asia and the Americas.
Though skin cancer is rising in some areas as well, the connection to climate change is more behavioral than environmental. People are likely to spend more time outside during warmer, drier temperatures, which increases their exposure to ultraviolet radiation that causes skin cancer.
Malignant skin cancer rates have gone up in Europe, the Western Pacific, and the Americas.
Diseases caused by the waterborne Vibrio bacteria — like wound infections, sepsis, and the stomach flu — are also going up globally.
According to the report, the percentage of coastal areas susceptible to these infections has gone up in northern latitudes over the last few decades. The northeastern US and the Baltic region are particularly vulnerable.
At the same time, some climate-related diseases' mortality rates have gone down. Diarrheal diseases, for example, are on the decline in Africa. A study in the New England Journal of Medicine says greater access to safe water and sanitation has likely contributed to this decline.
Some countries are seeing decreases in crop yields, making malnutrition much more likely.
While there is enough food to feed the global population, extreme weather is already causing crop yields to go down in many countries.
For some areas, falling yields mean that climate change is hurting crops faster than any new technology is trying to save food supplies. Without enough food, people will start showing symptoms of malnutrition, such as reduced muscle mass, lower stamina, and breathing difficulties.
Air pollution is too high in most cities, and it can lead to both cardiovascular and respiratory problems.
People in more than 90% of cities are breathing air with pollution levels above recommended World Health Organization guidelines.
Concentrations of air pollution have risen in nearly 70% of cities worldwide between 2010 and 2016, according to the report. About 7 million people die due to air pollution each year.
Phasing out fossil fuels could help lower these deaths, as coal use is responsible for about 16% of premature deaths related to air pollution. An average of more than 460,000 people die prematurely in connection with the burning of coal for electricity.
Climate change has already forced thousands of people to migrate in recent years, and millions more could be pushed to leave their homes.
Health risks can cause people to leave their homes, but migration itself can also pose health risks.
Some of the most common health problems associated with migration and being a refugee are hypothermia, burns, cardiovascular issues, pregnancy-related complications, and hypertension.
According to the report, climate change is the primary reason behind thousands of people's decisions to migrate in recent years.
People can develop psychological problems due to trauma from extreme weather events, and heatwaves are particularly concerning.
Mental health can be affected by the frequency, intensity, and duration of weather-related events.
Heatwaves are especially concerning because they have been linked to rises in hospital psychiatric admissions and suicides, the report said. The authors cited a study in Australia that linked higher suicide rates to hot years.
Weather-related events can also harm people's mental health in indirect ways — if an event causes food shortages, homelessness, or damages sacred places, it could tear down sources of support that improve well-being.
As a whole, though, the effects of climate change on mental health are under-researched.
