ALBERTO SALVO Today Online 16 Jan 19;
News reports of a study I authored, published in Nature Communications last month, have put the spotlight on how different segments of society may be affected by climate change.
What can we infer from the findings given that the global climate is changing and researchers and policymakers are trying to understand the impacts of rising temperatures on societies around the world?
Scientists use unseasonal weather fluctuations — say a warmer versus cooler summer — to examine how heat affects a range of socioeconomic variables that we care about, such as public health, worker productivity, industrial output, commuter behaviour, school test scores, and so on.
Specifically, consider the ways in which people protect themselves from excess heat.
Earlier studies have credited the energy-hungry air-conditioner with a decline in heat mortality in the United States over the past century, as well as lower heat mortality in the US than in poorer India, where adoption of air-conditioning remains low.
In Europe, fewer excess deaths during 2018's hot summer compared to an earlier heat wave in 2003 may be due to increased adoption of air-conditioners during the 15 interim years.
Another study by my colleagues, published this month in the Proceedings of the National Academy of Sciences, quantifies a large response to heat by residential electricity consumers in Shanghai, China.
On warm days (above 25°C), a 1°C increase in daily temperature raises household electricity use by a staggering 15 per cent.
Shanghai is one of China’s richest cities, with a near 100 per cent penetration rate of air conditioners in residences, comparable to 90 per cent in the US and Japan.
The price of buying and operating an air-conditioner has fallen so fast relative to incomes that Shanghai households do not hesitate to turn their appliances on when temperatures rise.
Households need to protect themselves from environmental stress as best they can, yet it is ironic that increased electricity demand to cope with heat often leads to more burning of fossil fuels to supply the electricity, which in turn leads to greater greenhouse gas emissions and higher temperatures in the future.
In contrast to rich areas in Asia and the US, only 8 per cent of the three billion people living in the tropics currently have access to air conditioning.
This brings us to the question, absent air conditioners, how do households seek relief from heat?
To study this question, I examined the combined electricity, water and town gas bills of about 130,000 anonymous households in Singapore over more than three years.
Daily temperatures in Singapore range between 24°C and 31°C, depending on the time of the year, and relative humidity averages 76 per cent.
Tropical Singapore is unique in that, despite its overall wealth, not everyone has an air-conditioner at home.
For example, less than 20 per cent of households in one-room and two-room flats had an air-conditioner during the period of study.
I found that households in one-room and two-room flats — which tend to have lower per-capita incomes compared with households in other types of dwelling — significantly increase their water consumption when temperatures rise.
A 1°C increase in daily temperature raises these households’ water use by 1-4 per cent. Specifically, a +1°C heat shock induces an increase in water use equivalent to one more daily shower for every 2.3 households living in one-room flats.
In comparison, households in dwelling types with higher mean per-capita incomes, such as five-room flats and condominiums, do not respond to heat stress by raising water demand.
As in the Shanghai study, it is their electricity consumption that shows a steep response to temperature. Needless to say, air conditioners are prevalent among more affluent households.
To complement the evidence from the billing data, I conducted an online 300-person survey on heat relief behaviour in Singapore.
From that, 39 per cent of respondents stated that on a very hot day, they would shower more often and longer.
This is comparable to 36 per cent who indicated that they would turn on the air-conditioner. The survey also found that washing one’s face as well as one’s (sweaty) clothes are common water-based cooling behaviours.
What does all of this mean?
If energy and water-based cooling patterns in Singapore are predictive of heat-relief behaviours elsewhere in the urbanising tropics, heat may increase water consumption in less developed cities where most households have yet to adopt air conditioning.
This is worrisome in that, besides temperature extremes, precipitation patterns are also shifting due to climate change, with some regions set to experience extended periods of low rainfall and reduced water availability.
Improved demand forecasting for interconnected water and energy systems is highly relevant in a tropical landscape undergoing both climatic and human transitions.
A policymaker in a region that is water-stressed may prefer that households conserve water when it is hot and dry, even if that means consuming more electricity and indirectly increasing greenhouse gas emissions to generate that electricity.
It is hard to blame the policymaker from turning a blind eye to climate change if the immediate concern is getting his/her constituency through a period of draught.
More broadly, we should heed the warning revealed in Singapore’s household utility bills across different income groups.
That is, heat creates disutility and households try to seek relief by expending their limited resources and money that they could otherwise use for other meaningful purposes, such as education.
We will do well to take note of what the Meteorological Service Singapore said in a statement on Tuesday (Jan 15): The last month of 2018 was the second warmest December since 1929, while the past decade is the warmest on record.
"These are signs of the long-term warming trend in Singapore," it added.
As temperatures continue climbing in the next decades, households are set to consume growing amounts of utilities and stay less outside.
And the greater consumption of utilities will lead to greater warming, unless societies can move away from fossil fuels to renewable types of energy.
A better understanding of the consequences of climate change may compel policymakers to enact, and voters to accept, policies to mitigate carbon emissions and shift the economy away from its dependency on fossil fuels toward renewable energy.
Climate change is a problem we need to address. People here are already feeling the heat, so to speak.
ABOUT THE AUTHOR:
Alberto Salvo is an associate professor at the department of economics from the Faculty of Arts and Social Sciences in the National University of Singapore.
