The BBC asked an Oxford University Climate Scientist about the wet-bulb temperatures the UK is experiencing and whether they are dangerous. Climate scientists are notoriously conservative; they are not prone to presenting worst-case scenarios or playing up risks.
22°C Twb was the worst she expected, and yet here I am in my Oxfordshire South-facing garden measuring dangerous temperatures. Micro-climates are rarely taken into account when we try to understand heat stress. Activity is rarely understood in relation to wet bulb temperatures, apart from the UK military:
“Heat illness is a spectrum of illness which includes heat exhaustion and heat stroke. In practice, it is difficult to distinguish between the conditions, and they may coexist. For the purposes of this policy the term heat illness refers to those individuals who become incapacitated as a result of a rise in core body temperature. In the military environment,
the vast majority of cases of heat illness or injury are exertional in nature, rather than the classical heat illness or injury seen in the general population.” https://cgo.mod.uk/media/1upge0rc/role1-jsp539-1-ab.pdf
The problem with underplaying the risks is that people will push themselves and overdo physical exertion (sport) under dangerous weather conditions. What most people, and especially people who lead outdoor activities is that you cannot “push through” heat stress.
“Heat illness is a serious problem for the Armed Forces. The incidence of heat illness depends on numbers exposed to the risk and how well that risk is managed. The overall incidence rate of heat illness cases has not changed over the past five years and 3 soldiers died from heat illness on exercise in the UK in 2013. There were 333 UK Armed Forces personnel who were identified as having a heat illness during the period October 2015 – September 2016 (86 of which were in the UK winter). Rates are higher in the untrained and the young (16-19 years). Exertional heat illness is frequently diagnosed in temperate climates outside of summer months. Many of these cases can be prevented by greater awareness of the risk by commanders at all levels. The severity of cases can be reduced with good management, effective first aid measures and evacuation to medical care, however, prevention is the main aim.” https://cgo.mod.uk/media/1upge0rc/role1-jsp539-1-ab.pdf
UKs summer wet bulb temperatures are a risk to anyone doing outdoor recreational activities. It is not uncommon for poorly trained activity leaders to not understand heat stress with tragic consequences.
These Charts were produced by Ariel’s parents following their son’s death from heat stress: An avoidable death caused by untrained walking leaders. This type of tragedy is not uncommon.
Chart A
Chart B
- Chart B was developed by Professor Yoram Epstein to be used in Ariel’s Checklist for hikers in Israel.
- Environmental heat stress categories are given in Wet Bulb Globe Temperature values.
- These are minimum rest periods. You may plan for more rest but not less.
- Fluid recommendations are just general guidelines and may vary based on many factors. People should monitor individual fluid needs.
- Warning!! Do not read Chart B in isolation. These guidelines are for healthy, relatively fit hikers. For novice, less fit, unacclimated, sleep-deprived, or overweight individuals, the tour leader should refer to Moderate Work as Hard Work.
“Ariel had been on a supervised hike in the Judean Desert with other young men. The hike was part of an overall educational experience when he collapsed due to exertional heat stroke.
The circumstances surrounding his death are particularly distressing and heart-wrenching given that Ariel’s death was preventable. Ariel did not die of an underlying heart defect or other congenital anomaly. There were no drugs or alcohol involved.”
He died because the people leading the hike
- Did not recognise the risk factors of heat-related illnesses
- Or the signs and symptoms of an extreme heat crisis.
In memory of Ariel, his parents hope heat stress is preventable https://arielschecklist.com/
The Above Charts are applicable anywhere. They are not about understating or overstating risk. For climate change-affected British heatwaves at 1.5-3C global temperatures, they are an accurate guide to how heat kills.
Expedition leaders, amateur athletes, wilderness practitioners, bushcrafters, preppers (most preppers have nothing to say about wet bulb temperatures), campers, walkers.
People who work outside, or in hot indoor environments are at risk
Core body temperature = heat gained – heat lost = cooling or overheating
Solidarity Prepping: Preparing For Climate Change 