Scientists are now sure of the correlation between global warming and human health, but big knowledge gaps remain, not least because climate and health researchers are rarely in touch with one another

Entire India is vulnerable to dengue transmission due to higher temperatures, according to a study. (Image by coniferconifer)

Entire India is vulnerable to dengue transmission due to higher temperatures, according to a study. (Image by coniferconifer)

India needs to address the huge gap between climate forecasters and health experts to be better prepared for the health impacts of warming temperatures, and devise sound mitigation and adaptation strategies, experts say.

Of late India has begun to take some steps in this direction. India’s national climate targets or Intended Nationally Determined Contributions (INDCs), submitted to the UN Framework Convention on Climate Change (UNFCCC) in October, say the country is now adding a “health mission” to the National Action Plan on Climate Change (NAPCC) that was first announced with eight missions in 2008.

The proposed health mission will evolve strategies for mitigating, containing and managing the adverse impacts of climate change on health. It aims to analyse epidemiological data, identify vulnerable population and regions, build knowledge base and expertise, and increase awareness and community participation, according to the INDC document.

The Indian Council of Medical Research (ICMR) too has set up a Global Environmental Change and Health High Powered Group, Ramesh Dhiman, scientist at the National Institute of Malaria Research (NIMR), recently said at a workshop on climate and health in New Delhi. Based in the Indian capital, NIMR is one of the institutes under the ICMR umbrella.

Madhavan Nair Rajeevan, director of the Pune-based Indian Institute of Tropical Meteorology (IITM), said, “There is a gap between health managers and climate managers, and between climate forecasters and health experts. We should try our best to form a bridge between the two groups, especially in view of post-disaster health hazards.”

Dushmanta Ranjan Pattanaik, a scientist at the numerical weather prediction division India Meteorological Department (IMD), said, “Climate and health is a complex problem and scientists need to work together.”

Some climate change impacts such as heat stress act directly and can be estimated. When scientists at the Gandhinagar-based Indian Institute of Public Health looked for the relationship between maximum temperatures and mortality rates during a 2010 heat wave in Ahmedabad, they found an almost perfect correlation, as seen in this graph

Source: Dileep Mavalankar, Director, Indian Institute of Public Health, Gandhinagar

Source: Dileep Mavalankar, Director, Indian Institute of Public Health, Gandhinagar

But other impacts of climate change are not so direct. Examples include water-borne diseases such as cholera and vector-borne diseases such as malaria and dengue, which require complex models to estimate future changes.

Estimating indirect impacts

Methods of estimation vary. Some observational studies focus on seasonal patterns of diarrhoeal illnesses or vector-borne diseases. Others focus on the area of spread of diseases such as malaria and dengue, which requires extensive data on disease occurrence over space and time. Prediction of future health risks and potential benefits of intervention measures require complex models.

Climate information including extended range climate forecasts – such as heat index, cold wave and heavy rainfall – can offer guidance on minimising health-related illness by taking appropriate measures and surveillance systems and keeping up-to-date information on diseases, Pattanaik said.

A recent World Health Organisation report also warns about the potential health risks of black carbon – tiny soot particles formed due to incomplete burning of fuels. The report says that black carbon, ozone and methane – frequently described as short-lived climate pollutants (SLCPs) – not only cause global warming but also “contribute significantly to the more than seven million premature deaths annually linked to air pollution.”

Several of the projected impacts of climate change on health are avoidable and simply an exacerbation of existing health issues, rather than emergence of new and unfamiliar diseases. Researchers need to strengthen existing disease monitoring and surveillance programmes, as such information is vital for devising appropriate adaptation strategies.

Scattered studies

Some examples of studies linking climate and health are available from India. An example is a study led by Dhiman in 2011 on projection of changes in malaria transmission. The study, which used the UK-based Hadley centre’s regional modelling system PRECIS for 2030, indicated the appearance of new foci of malaria transmission in the western Himalayan states of Uttarakhand and Jammu and Kashmir, plus a rise in the intensity of malaria in India’s north-eastern states that form part of the eastern Himalayas. The scientists found malaria transmission even in colder months in hilly areas of Uttarakhand.

The entire country is vulnerable to dengue transmission due to higher temperatures, according to the study, which was published in Current Science by the Indian Academy of Sciences.

NIMR has set up three field sites in India’s Himalayan region to study the impact of changing climate on vector-borne diseases, Dhiman said. Observations and past records indicate that Bhimtal in Uttarakhand has started recording 8-9 months of transmission of the malaria vector since 2006, compared to six months previously.

Similarly scientists have found malaria ‘sporozites’ – the tiny, mobile individuals released by a mosquito into humans – even in the cold month of November; and a shift in mosquito density from April to May; and from the plains to the hills. The malaria vector has also invaded more areas in Assam following deforestation.

Another key study was done in 2013 by the World Health Organisation South East Asia Regional Office in collaboration with NIMR and the University of Michigan. In this, researchers found that sea surface temperature in the South Atlantic impacts the monsoon rainfall and malaria epidemics in Kutch region of Gujarat. The information can be used to develop a model that uses climate change to predict malaria risk. The results have significance in other regions of the world where sea surface temperatures are the dominant drivers of rainfall and subsequent malaria outbreaks.

Indian scientists have also developed tools for early warning of malaria, using rainfall, vegetation index, sea surface temperature, and temperature condition index over the last five years, Dhiman said.

Challenges remain

The country faces an uphill task in integrating the climate and health sectors. For one, there is little information of precise climatic factors that determine vector distribution at local level.

Scientists still need to fine-tune some variables fed into models to predict changes in vector transmission. For example, ‘vegetation index’ or a numerical indicator of the greenery works correctly for predicting vector density in desert areas where changes in vegetation are more apparent, but not in well-irrigated, densely vegetated areas. Another indicator that monitors drought at a regional level, the ‘temperature condition index’, works only if the temperature is less than 40 degrees Celsius in March and April.

A big challenge is that while scientists have developed early warning systems for malaria and dengue, these have not been integrated with policy. Planners need to work out changes in timing of anti-mosquito sprays in view of changes in transmission cycles.

“In order to encourage more researchers entering the field of climate change and health, there is a need to build capacity in handling climate data, and training in GIS (geographical information system) for creating baselines and resultant maps,” Dhiman added.

The need for extensive national and international data has been highlighted by international experts too. A study led by Townsend Peterson, Biodiversity Institute and Department of Ecology and Evolutionary Biology, University of Kansas, published in Philosophical Transactions, examined the global potential distributions of the dengue vectors Aedes aegypti and Aedes albopictus in relation to changing climate worldwide.

The results indicated complex global rearrangements of potential distributional areas, and “also signalled a crucial priority: digitisation and sharing of existing distributional data so that models of this sort can be developed more rigorously,” it concluded.

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