Hot impacts

Rise in temperature could lead to: Submerging of small islands like Tuvalu and Lakshwadeep 290 million additional cases of malaria1 Increase in allergies due to increase in the pollen count per plant2 More of asthma cases Increased incidences of diarrhoea and cholera More deaths due to heat stress More of droughts and floods Melting of glaciers Increase in average number of tropic disturbance days from 17 to 293 Increase El Nino effects — the periodic warming of Pacific waters More of skin cancer cases due to exposure to UV light

References 1. A McMicheal and S Kovats 1999, The impacts of climate change, in http://www.met-office.gov.uk/ research/hadleycentre/pubs/brochures/B1999/i mp_human_health.html, as viewed on March 20, 2003. 2. Anon 2000, A problem with pollen, in Down To Earth, Vol 9, No 9, published by Society for Environmental Communications, New Delhi, September 30, p 49. 3. N Singh and M Nadkarni 2001, Health holocaust, in Down To Earth, Vol 10, No 11, published by Society for Environmental Communications, New Delhi, October 31, p 34.

Deluge and disease
The increase in the frequency and intensity of floods, storms, droughts and cyclones affects health through loss of shelter, migration of people, contamination of water supplies, loss of agricultural yield (thus leading to hunger and malnutrition), thereby increasing the risk of diarrhoea and also causing damage to health care infrastructure set up in a particular area. The reduction in fresh water supplies affects water resources and sanitation. This in turn reduces the water available for drinking and washing. With the lowering efficiency of local sewer systems, the end result is a higher concentration of bacteria and other microorganisms in raw water supplies. Water scarcity may force people to use river water for their essential needs, which is often contaminated, leading to an increased incidence of diarrhoeal diseases. Many Pacific Island countries report high incidences of diarrhoea during high temperatures and extremes of rainfall.¹⁹

With water becoming scarce and populations increasing, there is an increased pressure on water availability and water quality. Deep digging of bore wells for groundwater makes the contamination levels of arsenic and fluoride rise considerably. Already 26 states of India report incidences of fluorosis, and arsenic affects nearly 6 million people in West Bengal alone.

Increase in temperature correlate with increased populations of some microorganisms that cause waterborne diseases, such as Vibrio cholerae bacterium, which causes cholera. Higher ambient temperatures foster the growth of pathogens that thrive in or on food, such as Salmonella.²⁰ The cholera organism is known to live in sea-borne plankton that blooms as the sea surface warms. The 1991 outbreaks in Peru is cited as circumstantial evidence for this chain of events, because it spread extremely quickly and took place when an EL Nino (warming of Pacific waters) had warmed Peru’s coastal waters.²¹ Changes in the El Nino Southern Oscillation (ENSO), a major source of climate variability is known to influence cholera cycles. Increasing temperatures make ENSO stronger and more variable. Since the cholera virus thrives in brackish water and warm temperatures, it becomes more sensitive to climate patterns, leading to more frequent outbreaks.²²

Vector borne diseases
Driving the predicted rise in infectious diseases are changes in temperature, rainfall, and humidity, which give bugs a boost. Hot climates make pathogens spread over a wider range, and increase their survival rate. Heavy rainfall increases the mosquito population, which triggers an epidemic of malaria. Most of the vector-borne diseases occur in populations, which are unprotected, lacking basic public health measures and adequate sanitation facilities. An increase of 3-5°C in the temperature translates to about an extra 50–80 million cases of malaria in a year.²³ In India, Rajasthan and Gujarat have reported high incidences of malaria during heavy rains.²⁴ Similar relationship has been reported in the years following El Nino and during La Nina (the cooling of the Pacific waters) after the El Nino phenomenon.²⁵

Shorter incubation periods result in a threefold higher transmission rate of malaria. Smaller adult mosquitoes are born in higher temperatures and they need to feed more often to develop into eggs, which, in turn, increase the chances of disease transmission. What is more disturbing is that this may result in a break down of prey-predator relationship like that of frogs and mosquitoes, leading to an increase in vector numbers.²⁶ The scenario is grim in East Africa where the temperatures have increased by 0.15°C per decade from 1970 to 1998, and a rising trend in malaria is being noticed.²⁷ With a vast percentage of the Indian population living in areas prone to malaria and a limited public health infrastructure, increased temperatures is going to create havoc with malaria transmission increasing to higher latitudes and altitudes. The World Health Organisation (WHO) has already recorded "quantitative leaps" in malaria incidences in the recent years.²⁸ High temperatures speed up the life cycles of the mosquito as well as the disease organisms that the mosquitoes harbour and make the adult mosquitoes bite more.

In a temperature of 32°C, the dengue virus takes just seven days to incubate in the Aedes aegypti mosquito, whereas in a temperature of 30°C it would have normally taken 12 days to incubate. In 1996, New Delhi, India witnessed a major dengue outbreak , with over 10,000 cases and 400 deaths.²⁹ Another epidemic was reported from Ludhiana, India in the same year, the first of its kind in that region.30 The vector of dengue has also started moving towards the mountain regions with cases coming in from Jammu. This clearly shows that dengue as a disease is spreading to new areas within the country thus posing a public health hazard.

Climatologists at the US National Aeronautical Space Administration (NASA) are now linking the breakouts of Bartonellosis, an insect-borne highly fatal disease to El Nino. Bartonellosis causes life-threatening anaemia and manifests itself in blood-filled, wart-like skin lesions. Cusco, in Peru, which witnessed the strongest El Nino event in 1997-98, also reported an outbreak of this disease during the same period, making scientists believe that El Nino was the dominant factor in the epidemic.³⁰