Climate change and health

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Climate change has introduced a new set of risks and concerns for human health. Though it is a global phenomenon; its impact and implications on health however are local. Though health outcomes in response to climate change have not been measured but initial data shows that it affects the population living in the developing world and those living in the poorer sections of the developed countries more.

Existing information suggests a range of negative health impacts. Some positive health outcomes, notably reduced cold-weather mortality, are also possible, but the negative outcomes far outweigh the expected positives.


Why should I be aware of this?

  • Climate change is a significant and emerging threat to public health.
  • It impacts vulnerable populations and vulnerable sections of the society more.
  • Climate variability and change cause death and disease through natural disasters, such as heat waves, floods and droughts.
  • In addition, many important diseases are highly sensitive to changing temperatures and precipitation. These include common vector- borne diseases such as malaria and dengue; as well as other major killers such as malnutrition and diarrhoea.

All about climate change and health

The link between changes in surrounding atmosphere and human health is not new. It was first reported by Plinius, the Younger, in 73 AD. He documented the fatal respiratory consequences of natural air pollution caused by the eruption of Mount Vesuvius.

Climate change refers to large and irreversible changes in the earth’s climate. The inconsistencies in environment-- a result of variations in temperature, pressure and climate-- impact lifestyle, physical environment, infrastructure, disease and health patterns.

The danger of climate change could be simplistically classified into two groups:

  1. Greater extremes of weather and climate;
  2. Unforeseen weather in areas of the world (i.e. extreme heat in cold areas and vice versa).

The Fourth Assessment Report by the World Health Organisation has identified three areas in which human health has already been affected by climate change. These are

  1. Alteration of distribution of some infectious disease vectors
  2. Seasonal distribution of some allergenic pollen species
  3. Increased heat wave related deaths

Climate change and health effects some facts

  • Study shows that global mean surface temperature will rise by 1.4°-5.8° C. Warming will be greatest over land areas, and at high latitudes.
  • The projected rate of global warming is greater than anything humans have experienced in the last 10,000 years;
  • The frequency of weather extremes is likely to change leading to an increased risk of floods and drought. There will be fewer cold spells but more heat waves.
  • The frequency and intensity of El Niño may be affected.
  • Global mean sea level is projected to rise by 9--88 cm by the year 2100.

Some of the health effects include:

  • Increasing frequencies of heat waves: recent analyses show that human-induced climate change significantly increased the likelihood of the European summer heat wave of 2003.
  • More variable precipitation patterns are likely to compromise the supply of fresh water, increasing risks of water-borne disease.
  • Rising temperatures and variable precipitation are likely to decrease the production of staple foods in many of the poorest regions, increasing risks of malnutrition.
  • Rising sea levels increase the risk of coastal flooding, and may necessitate population displacement. More than half of the world's population now lives within 60km of the sea. Some of the most vulnerable regions are the Nile delta in Egypt, the Ganges-Brahmaputra delta in Bangladesh, and many small islands, such as the Maldives, the Marshall Islands and Tuvalu.
  • Changes in climate are likely to lengthen the transmission seasons of important vector-borne diseases, and to alter their geographic range, potentially bringing them to regions which lack either population immunity or a strong public health infrastructure.

Infectious diseases

Both land temperature and temperature of surface water have important influence on the insect responsible for vector-borne infectious disease -especially mosquitoes, which spread malaria and viral diseases such as dengue and yellow fever. Changes in temperature and rainfall patterns have been linked with the outbreak of infections in new areas or in areas where their incidence was low. Between 1970 and 1995, the annual number of dengue epidemics in the South Pacific was positively correlated with La Niña conditions.

Extereme whether

Temperature extremes such as heat waves and cold spells have been causing greater number of deaths. In many temperate countries, death rates during the winter season are 10-25% higher than those in the summer. In July 1995, a heat wave in Chicago, US, caused 514 heat related deaths (12 per 100,000 population) and 3300 excess emergency admissions.

Most of the excess deaths during times of thermal extreme are in persons with preexisting disease, especially cardiovascular and respiratory disease. The very old, the very young and the frail are most susceptible

Natural disasters

The effects of weather disasters such as droughts, floods, storms and bushfires on health are difficult to quantify. Globally, natural disasters and their impacts have been increasing.

Who is more at risk?

The impacts of climate on human health will not be evenly distributed around the world. Developing country populations, particularly in Small Island States, arid and high mountain zones, and in densely populated coastal areas, are considered to be particularly vulnerable.

What can we do?

  • Opt for short-range climatic forecasts to reduce health impacts.
  • Introduce early warning systems to minimise loss from natural disasters.
  • A humanist approach needs to climate change related health issues needs to be developed accompanied by equity and social justice.
  • Reduce personal carbon footprint.
  • Protect carbon sinks.


  • The WHO has estimated that climate change is responsible for around 150,000 deaths annually and 5million Disability Adjusted Life Years (DALY), mainly in developing countries.
  • Abnormally high temperatures in Europe in the summer of 2003 were associated with at least 27,000 more deaths than the equivalent period in previous years.
  • Other weather extremes, such as heavy rains, floods, and hurricanes, also have severe impacts on health.
  • Approximately 600,000 deaths occurred world-wide as a result of weather-related natural disasters in the 1990s; and some 95% of these were in poor countries.
  • In October 1999, a cyclone in Orissa, India, caused 10,000 deaths. The total number of people affected was estimated at 10-15 million
  • In December 1999, floods in and around Caracas, Venezuela, killed approximately 30,000 people, many in shanty towns on exposed slopes.
  • In addition to changing weather patterns, climatic conditions affect diseases transmitted through water, and via vectors such as mosquitoes. Climate-sensitive diseases are among the largest global killers.
  • Diarrhoea, malaria and protein-energy malnutrition alone caused more than 3.3 million deaths globally in 2002, with 29 % of these deaths occurring in the Region of Africa.
  • Evidence to suggest that climate change could have caused an early onset of spring pollen season in the northern hemisphere, leading to an increase in the duration of the pollen season.
  • With 11 of the last 12 years (1995-2006) being the warmest years since the commencement of the temperature records, the average global surface temperature would increase by 1.1 oC to 6.4 oC causing alteration of planetary ecosystem.


  • Global Warming, Climate Change, Air Pollution and Allergic Asthma
  • Learn more about Health impacts of climate extremes
  • Climate Change and Health linkages WHO
  • Climate change and health:Research Chalanges for vulnerable populations