Urban Transformations Research Centre                                                                                                  HRSC0015

Written evidence submitted by Urban Transformations Research Centre

Prepared for:              Environmental Audit Committee

Purpose:              Submission to a short inquiry into Heat resilience and sustainable cooling

Contact:              Thomas Longden

Senior Researcher – Urban Transformations Research Centre

Overview              Western Sydney University.

Response              What evidence exists on the relationship between heat and human health (mortality and morbidity), and which communities are worst affected?

There is notable evidence of an association between extreme heat and adverse human health.

While there are studies that find that the cold kills more people than the heat, careful review of these papers is needed to understand how they control for the usual rate of mortality (via a reference temperature to estimate relative risk), whether they focus on the entire range of temperature (or just extreme events), and factors such as seasonality (which are correlated with issues such as flu and pneumonia).

Some of my research has focused on temperature-related mortality and how that has impacted Australia. There are three papers that have relevant findings for the United Kingdom and elsewhere.

Relative differences in temperatures can predict deadly heatwaves and explain how dangerous heatwaves can occur in more temperate areas. The difference between the 3-day average and the 30-day average (which has been called the Extreme Heat Index – Acclimatisation, EHI-A) is part of the Australian Bureau of Meteorology Heatwave Service for Australia. In my research paper, I found that heat-related mortality tends to be associated with heatwaves that do not allow for sufficient acclimatisation to hot temperatures. This helps explain why cities with cooler temperatures can have deadly heatwaves.

When the 3-day average is 7°C hotter than the prevailing summer period (30-day average), then there is a statistically significant increase in deaths associated with temperature. Few heatwave emergency response plans use a measure that accounts for acclimatisation, but it could lead to a better response in more temperate climate zones.

For more information refer to Longden, T. Measuring temperature-related mortality using endogenously determined thresholds. Climatic Change 150, 343–375 (2018). https://rdcu.be/djqDm

Measuring temperature-related mortality needs a justifiable reference temperature that is suitable for that climate zone. While studies having found that there are more cold deaths than heat deaths, a reassessment of how to set the reference temperature and a larger national dataset found the opposite result for Australia. For example, a study published in The Lancet found that the cold kills more people in Sydney, Melbourne and Brisbane than the heat.

Using a similar methodology as that used in the study published in The Lancet, I found the majority of deaths related to temperature in Australia are caused by heat. In my study, I estimated 2% of deaths in Australia between 2006 and 2017 were due to the heat. In the three warmer climate zones this number was higher, ranging from 4.5% to 9.1% of deaths. In the coldest climate zone, 3.6% of deaths were due to the cold and the heat was less dangerous.

These estimates are notably different to those in The Lancet study where the total for Sydney, Melbourne and Brisbane had 6.5% of deaths associated with cold temperatures, but only 0.5% of deaths due to the heat.

A key difference is the location of the reference point where relative risk equals one. For Melbourne, The Lancet had a reference temperature of 22.4°C, which meant almost 90% of Melbourne’s historical daily average temperatures were classified as cold. This could be equivalent to a day with a maximum of 31.4°C and a night minimum of 13.4°C.

For more information refer to Longden, T. The impact of temperature on mortality across different climate zones. Climatic Change 157, 221–242 (2019). https://rdcu.be/djqJN

National mortality records in Australia suggest substantial under-reporting of heat-related mortality on death certificates. Less than 0.1% of 1.7 million deaths between 2006 and 2017 were attributed directly or indirectly to excessive natural heat on death certificates. However, empirical studies indicate that these official records underestimate the association at least 50-fold.

For more information refer to Thomas Longden, Simon Quilty, Philip Haywood, Arnagretta Hunter, Russell Gruen, Heat-related mortality: an urgent need to recognise and record, The Lancet Planetary Health, Volume 4, Issue 5, 2020. https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(20)30100-5/fulltext

What actions can be taken to protect those most vulnerable to the impacts of extreme heat?

Australia provides an extreme example of temperature-related energy insecurity that leaves people without cooling/heating and compromises the other functioning of the home, including refrigeration, lighting and life support medical equipment (for example, oxygen concentrators, sleep apnoea machines, home renal dialysis equipment).

Poor quality housing, low incomes, poor health, and energy insecurity associated with prepayment all exacerbate the risk of temperature-related harm. For example, households with high electricity use located in the central climate zones had a one in three chance of a same-day disconnection on very hot or very cold days.

In Australia, the Essential Service Commission (for Victoria) observes that “customers who are disconnected from electricity or gas can face significant risks to their welfare… disconnection for non-payment reasons should only ever be a last resort”. Australia’s National Energy Retail Rules require that the retailer not arrange for the de-energization of premises having life support equipment or during an extreme weather event, but this is not comprehensively applied in remote NT communities where prepayment for electricity applies.

For more information on this research refer to: Longden, T., Quilty, S., Riley, B. et al. Energy insecurity during temperature extremes in remote Australia. Nature Energy 7, 43–54 (2022). https://rdcu.be/djqS8

In the UK, increased use of air-conditioning and other cooling devices (fans etc.) will increase the rate of disconnection for prepayment customers.

Post-pay customers may also be placed under greater stress. High temperatures and electricity disconnections for low-income homes have been linked in California. For more information on this research refer to: Barreca, A., Park, R.J. & Stainier, P. High temperatures and electricity disconnections for low-income homes in California. Nature Energy 7, 1052–1064 (2022). https://rdcu.be/djqTM

What can be done to protect the UK’s existing public and private sector housing stock from the impacts of extreme heat while ensuring that homes are sufficiently warm in the winter months?

There is a wide literature on the benefits of retrofits for poor housing and low income families. The Healthy Homes literature is wide, but this review article is a good starting point: Philippa Howden-Chapman, Julie Bennett, Richard Edwards, David Jacobs, Kim Nathan, David Ormandy, Review of the Impact of Housing Quality on Inequalities in Health and Well-Being, Annual Review of Public Health 2023 44:1, 233-254. https://www.annualreviews.org/doi/full/10.1146/annurev-publhealth-071521-111836

Does the UK need a dedicated Heat Resilience Strategy? What lessons can be learned from other nations when it comes to national strategies for heat resilience?

One key example of a policy that aims at improving thermal comfort is the New Zealand healthy homes standards that have introduced specific and minimum standards for heating, insulation, ventilation, moisture ingress and drainage, and draught stopping in rental properties. Between 1 July 2021 and 1 July 2025, all private rentals must comply with the healthy homes standards within certain timeframes from the start of any new, or renewed, tenancy. These standards change by climate zone. These standards will improve thermal comfort during both cold and heat events.

https://www.tenancy.govt.nz/healthy-homes/about-the-healthy-homes-standards/

August 2023