Heatwaves and their consequences


File photo taken on Jan 27, 2023, shows residential and high-rise buildings in smog as the sun rises over Bangkok. — AFP photo

WHAT is a heatwave by definition? This is a difficult question to answer for the actual temperatures of such and its length varies worldwide. I shall look at various places on the globe where I have dear relatives and friends living: the United Kingdom, Greece, Malaysia, and Adelaide in South Australia.

Certainly, we can declare that heatwaves produce abnormally hot weather exacerbated by humidity. We know that the daily maximum temperatures recorded in any place in the world are taken from shade temperatures in a Stevenson screen, but these temperatures do not reflect the actual temperatures felt by humans. The latter temperatures are usually much higher and are affected by the relative humidity of the air. These temperatures are often recorded on apps as the ‘feel by temperature’.

The Malaysian Meteorological Department (MetMalaysia) has defined a heatwave when average daily temperatures exceed 37 degrees Celsius for three consecutive days. The threshold temperature set by the UK’s Met Office is when at least there are three consecutive days above 25 degrees Celsius across much of the country but London’s threshold, because of its ‘heat island’ effect, is set at 28 degrees Celsius. In Greece, the Hellenic National Meteorological Service defines the threshold at three consecutive days at 30 degrees Celsius or more over the whole of the country. In the South Australian city of Adelaide, the definition of a heatwave is five consecutive days in excess of 35 degrees Celsius with four of these exceeding 40 degrees Celsius.

Causes of heatwaves

These vary from place to place in our world but usually they form when high pressure, at altitudes of between 3,000 metres and 7,600 metres, strengthen and remain over an area for several days or weeks. With climate change, this is now a common occurrence in both the northern and southern hemispheres as the jet streams follow the sun. In both hemispheres, the high pressure is on the Equator side of the jet streams in the upper atmosphere layers

As the high pressure sinks or subsides downwards it warms and dries adiabatically, thus preventing convectional uplift of air from the Earth’s surface and hence the lack of clouds. This exclusion of cloud-cover increases short wave radiation and a rise in the UV index for humans. Should global warming, currently at 1.5 degrees Celsius reach 2 degrees Celsius, it is highly likely that heatwaves once occurring every 10 years will occur every other year! Usually, heatwaves are accompanied by drought, thus compounding the problem for many countries.

On March 26 this year, forecasts suggested that heatwaves in Malaysia and Singapore would last until mid-April. Exactly a month later, MetMalaysia reported that Kota Marudu, Sabah and in Mukah and Selangau in Sarawak were witnessing heatwaves with temperatures between 35 degrees Celsius and 37 degrees Celsius.

Many cities in the world lack vegetation in the form of parklands and trees in wooded enclaves or along roads. Kuching is very fortunate in this aspect for the trees here help to lower the city temperature and mitigate the heat island effect, as well as provide welcome shade.

Recently, I spent 89 days in this city with many of these days coping with feel-like temperatures of 37 degrees Celsius to 39 degrees Celsius. The present El Nino event has increased drier weather and could last for another six months. The west coast of Sabah has certainly received scorching temperatures with little or no rain.

Longer exposure to extreme temperatures

On March 31, thesundaypost reported ‘Climate change is slowing heatwaves and prolonging misery’. A research paper released from Utah State University looked at heatwaves as ‘distinct weather patterns that are more like air currents and not unlike storms’. By measuring the movements of heatwaves over time, the researchers determined how fast the hot air was moving.

They discovered that for every decade from 1971 to 2020, heatwaves slowed down by an average daily rate of 8km, resulting in the heatwaves staying in an area for much longer. From 1971 the duration of heatwaves also increased by an average from eight to 12 days for the last five years of the study. Professor Wei Zhang, the senior author of this report, expressed his worries on cities that lacked green infrastructure with disadvantaged populations suffering disastrous effects.

Effects of heatwaves on people

There are many disorders which can affect us when exposed to extreme heat leading to increased body temperatures occasioned by the environment in which we live or through over exertion. Common illnesses are heat stroke, exhaustion, oedema, cramp, and rashes.

A regular intake of water and electrolytes can reduce such. Usually, the risk of death from exposure to extreme heat is caused by cardiovascular, cerebrovascular, and respiratory conditions. The frequent occurrence of haze as pollution is trapped in cities by descending high pressure can cause a surge in respiratory conditions. Prolonged heatwaves, however, create their own environmental problems for as greenhouse gas emissions rise, air pollution increases, as does electricity demand leading to outages in electricity supply caused by increased and longer use of air conditioning and electric fans.

A man carries a plastic bucket across the cracked bed of a dried-up pond in Vietnam’s southern Ben Tre Province, in this photo taken on March 19 this year. — AFP photo

Civil disruptions, wildfires, infrastructural damage

Often heat stress leads to violent crimes and it has been proven that crime rates increase under heatwave conditions. Rioting and looting of shops has been experienced in Croydon, South London, in a heatwave of August 2011, and Detroit, USA suffered such in the sweltering heat of July 1967. Wildfires abound in heatwaves as the ground is dry and plants wilt.

Many thousands of acres of forests and homes were destroyed in heatwaves affecting California, Portugal, Spain, and Greece in 2023 together with bushfires threatening major cities in Australia.

More locally, in Miri, constant surveillance by the Fire and Rescue Department (Bomba) of the peat areas nearby has now become a frequent event. Roads can melt as can railway tracks buckle leading to the cancellation of journeys and long detours. Heatwaves certainly cost us huge sums of money!

Economic effects

Heatwaves accompanied by drought can severely lower crop yields (unless irrigation is constantly present) by preventing plant growth through dehydration and disruption of normal planting times. Labour productivity is disrupted through heat exhaustion in both agriculture and industry.

The United Nations (UN) Climate Bank holds a Green Climate Fund for use in countries and regions affected by emissions mitigation, water security, agriculture, infrastructure, and public health to deal more often than not with rainfall deficits and threatened crop failures owing to heat waves. Small scale farmers most benefit from this fund although not many are aware of it.

Heatwaves accompanied by drought can severely lower crop yields. — Photo from Pexels

Wildlife suffers too

The impacts of intense heatwaves in Malaysia affect mostly those animals most in need of conservation for high temperatures alter ecosystems and habitats. Prolonged heatwaves cause water sources to dry up leading to dehydration and ultimate death. Diurnal animals seek shade and birds, reptiles and small mammals are particularly vulnerable, suffering from heat stress as their bodily thermoregulation systems become disrupted.

Reproduction levels are reduced as eggs and embryos fail to develop. Food sources are also threatened as plants wilt, thus affecting herbivores, and insect activity is also reduced. Much like humans, animals also suffer from heat stress and heatstroke and with parasites and diseases thriving in such hot conditions they could face eventual deaths. Wild animals will instinctively migrate to human settlements in search of food and water in times of heat stress, thus the increased numbers of snakes found in houses and gardens and animal raids on vegetable farms. Coping with such is easier said than done.

It looks most likely that heat waves will become more frequent and a climatic norm but let us not lose heart for we should have the capacity to cope with them psychologically, physiologically, and technically and with heat resistant developed crops to provide our daily food but at what price?