The health of millions of people across the world is already being significantly harmed by climate change, a major new report finds
November 1, 2017 — From driving up the number of people exposed to heatwaves to increasing the risk of infectious diseases, such as dengue fever, climate change has had far-reaching effects on many aspects of human health in last few decades, the authors say.
In fact, the effect of climate change on human health is now so severe that it should be considered “the major threat of the 21st century”, scientists said at a press briefing held in London.
The report is the first from the Lancet Countdown on Health and Climate Change, a project involving 24 academic institutions and intergovernmental organisations from across the world. The project plans to release a report tracking progress on climate change and global health every year.
Feeling the heat
The report uses a set of 40 indicators to track the effects of climate change on global health. The first of these indicators assesses the “direct impacts” of climate change on human health, including the effects of exposure to extreme heat and natural disasters.
One of the report’s findings is that, from 2000 to 2016, the rise in the average temperatures that humans were exposed to was around three times higher than the rise of average global temperatures worldwide.
This is shown on the graph below, where the rise in the global average surface temperature from 2000 to 2016, when compared to the average from 1986 to 2008 (red), is shown alongside the rise in the temperatures that humans are typically exposed to (blue).
The average temperatures that humans are exposed to are significantly higher than the global surface average because most people live on land, where warming happens most quickly, explains Prof Peter Cox, an author of the new report and a climate scientist at the University of Exeter. He tells Carbon Brief:
The report also finds the number of “vulnerable” people exposed to “heatwave” events increased by around 125 million between 2000 and 2016. “Vulnerable” is here defined as being over the age of 65, while a “heatwave” is defined as three consecutive nights where temperatures are in the top 1% of the 1986-2006 average for the region.
In 2015, a record 175 million more people were exposed to heatwaves, when compared to the average for 1986-2008, the report finds. You can see this in the chart below, which shows the change in the number of people exposed to heatwaves from 2000 to 2016, relative to 1986-2008.
These spikes in exposure are a result of an increase in heatwave events, as well as other environmental and social factors, including population growth, Cox says.
Heatwave exposure has previously been linked to an increased risk of premature death in many parts of the world, he explains:
The report finds that the number of weather-related disasters from 2007 to 2016 increased by 46%, when compared with the average for 1990-1999.
Asia is the continent most affected by weather-related disasters, the report says – particularly because of its size and population. Between 1990 and 2016, 2,843 weather-related disasters were recorded in Asia, affecting 4.8 billion people and causing more than 500,000 deaths.
Despite a rise in the number of natural disasters, there has been no discernable rise in the global number of deaths or in the number of people affected by natural disasters, when compared to data from 1990 to 1999, the report finds.
This could indicate that countries are beginning to invest in adaptation strategies to cope with natural disasters, Cox says. However, the mismatch could also reflect a lack of data on deaths from climate-related disasters in the developing world, he adds:
Losses to the global workforce
Another set of indicators explored by the report look at the “human-mediated” impacts of climate change. These are impacts that are intrinsically linked to human society, but often exacerbated by climate change.
The first of these indicators explores how climate change has affected the productivity of the global workforce, particularly in the less economically-developed parts of the world. The report finds that the global productivity in rural labour capacity – defined as those who work in outdoor manual labour in rural areas, but excluding agricultural workers – has fallen by 5.3% from 2000 to 2016.
The chart below shows how this global loss in productivity is spread across the world, with red indicating a percentage loss in productivity and blue showing a percentage gain in labour capacity.
In 2016, this drop in productivity effectively took more than 920,000 people globally out of the workforce, the report finds, with 418,000 of these workers being “lost” from India.
One way that higher temperatures threaten labour capacity is by making manual work more physically challenging, the report finds:
An additional “human-mediated” impact of climate change is undernutrition, the report finds. It reports that the number of undernourished people in the top 30 undernourished countries of the world has increased from 398 million in 1990 to 422 million in 2016.
This is at least in part driven by the effect of climate change of yields of staple crops such as wheat, rice and maize, the report says. Climate change affects crop yields through increasing local temperatures, changes to rainfall patterns and more cases of drought. The report says:
The report also investigates the “environment-mediated” impacts of climate change. These are impacts on human health that are caused by environmental factors but can be worsened by climate change.
One such impact is the spread of infectious diseases around the globe. Rising temperatures can increase the spread of infectious diseases by allowing pests to conquer new parts of the world, as well as by creating ideal conditions for reproduction and virus replication.
Climate change has affected the prevalence of many infectious diseases, the report notes. However, as an example, the report focuses on how climate change has impacted the spread of dengue fever, a disease spread by mosquitoes native to much of southeast Asia, central and south America, and Africa.
The research shows that the rate of the spread of dengue fever has increased from between 3% and 5.9% globally, when compared to levels from 1990.
The chart below shows how the rate of the spread of dengue fever (vectorial capacity) has increased in the world’s most affected countries from 1950 to 2015. The chart shows results from two species of mosquito, including yellow fever mosquito (Aedes aegypti; left) and Asian tiger mosquito (Aedes albopictus; right).
On the heat map, each block represents one year, with red showing an increase in spread and blue showing a decrease in spread. The chart shows that, since 1995, the vast majority of countries have experienced an increase in the rate of the spread of dengue fever.
The increase in the rate of the spread of dengue fever could be driven by changes in environmental conditions as a result of climate change, says Prof Hugh Montgomery, co-chair of The Lancet Countdown and a professor at University College London. He told the press conference:
Looking to the future, the report also explores how climate change could bring new health-related woes, including an increase in the displacement of people as a result of sea level rise.
It is clear that both the current and potential future impacts of climate change on health demand immediate action on tackling fossil fuel use, says Cox, adding that it is not too late to stem some of the effects of climate change on human health. He tells Carbon Brief:
Montgomery echoed the call for immediate action to tackle climate change for the good of human health. He told the press conference:
However, there are reasons to be hopeful, he adds, pointing to progress on climate action within the last decade, including a shift away from electricity produced from coal and an increase in the investment into electric cars. He adds: