Earlier this year I attended a meeting in France where some of the most experienced and knowledgeable outdoor gear designers got together to discuss future clothing ideas. Whilst there I cornered one of them and asked him to explain to me exactly why we get cold.
I knew the basics of conduction, convection and radiation, but I wanted to know more. The guy just looked at me and said: “Andy, all you have to remember is that there is no such thing as cold - only the absence of heat” and that was it.
Now I’m quite a dunce when it comes to the sciences, in fact, I never even turned up for my physics exam but this strange statement sparked an interest that led to me searching out textbooks I never thought I’d ever read of my own choosing. What I learnt in my studies forms a big part of this article.
This statement came at a time when I was trying to get to grips with understanding how my body is affected by the cold, as twice this year I’ve attempted major winter climbs that proved to be, for me at least, very close to my physical limit. The challenge of these two routes - the West Face of the Petit Dru and the East Face of Mermoz - lay not in the climbing itself, but in surviving the environment in which I found myself forced to climb.
Unlike most Alpine wall routes, on these climbs the focus was not on loose rock, run out pitches or poor belays, but in staving off exhaustion, frostbite and the increasing mental and physical fatigue involved in just making it from day to day.
What I learnt on those routes was that the art of climbing these major Alpine challenges - and many walls, faces and mountains like them - lay not in having the ability to crank up grade VII ground, or copperhead A4 seams, but about knowing how to look after oneself in a tough environment. This is the ‘art of suffering’.
In reality this art lies not in putting up with pain, but in knowing how not to suffer in the first place and, when it hurts, understanding why. And so these two factors, the science and the experience, came together to explain the mechanics of suffering and how to apply it to myself.
This article has been, for me, a very difficult one to write as it attempts to mesh several very complicated elements together (some of which I still don’t fully understand), both scientific and unscientific, in order to explain why we suffer.
As usual this article is based on a mishmash of cobbled together biology, physics and my own experiences and I apologize in advance to any doctors or physicists who see faults in what I say in this article. This article is not dedicated to extreme Alpinism, but to all climbing, at any level, wherever a chill wind may blow, because as Desmaison once said: “The storm doesn’t care how experienced you are.”
The cold makes us colder and heat makes us hotter, right? If we only lived a life of centrally heated leisure this would be all we’d ever need to understand. For those of us who step beyond the door in bad weather we soon learn that if we get wet, or it’s windy, we get colder faster. This may seem like common sense and the knowledge taken as granted, but many novices don’t know this, often resulting in a cruel lesson. As we learn more we begin to understand the science behind the shivers and so learn more about conduction and convection, the two main causes of our suffering. If we are to cover this topic and understand what’s going on, then I think it’s crucial we step further into the science, as only then can we look at each layer of understanding and truly know why we
Every atom contains energy. These atoms wiggle around and the higher their energy the faster they wiggle. This movement is measured as heat and so the faster the wiggle the greater the heat.
Energy will always try to achieve equilibrium, but it will only flow from high energy density toward lower energy density (hot to cold). What is actually happening is that the higher charged atom is drawn toward the lower charged atom and when they strike each other some energy is transferred over to the lower energy particle, which in turn moves off towards other lower energy atoms. This way some energy (heat) is transferred from one atom to another as it tries to achieve equilibrium. So in layperson’s terms cold means a lack of energy and hot is an abundance of energy.
The steeper the temperature gradient the faster this flow of energy and this is why if you were suddenly transported from your comfortable, centrally heated living room to the North Pole you wouldn’t last long, as the energy would flood out of you at high speed.
Although it doesn’t affect you the climber (hopefully), atoms only stop wriggling when they have almost no more energy left. This would be measured at -273.15°C (or 0° Kelvin), otherwise known as absolute zero.
The core temperature of your body is 37°C, but the outer layer is only 34°C, so atomic energy is transferred across this temperature gradient, moving energy (heat) out towards your skin. This energy is then passed on to your clothing, the rate of which depends on its insulation value. Finally, the energy will be passed beyond your clothing into the atmosphere; this is conduction.
-15°C, 80lb load, snow up to your armpits, 100kph winds, how do you avoid hypothermia without dying of heat exhaustion? Knowing how to dress will dictate whether you’re comfortable or suffering.
This process of energy transfer (conduction) will continue until the energy level (temperature) is equal in both materials, as only then will energy transfer stop between the atoms. This is called thermal equilibrium and is an important principle to understand as it relates directly to your survival in the mountains.
If you place an ice cube in the palm of your hand then energy will be transferred until thermal equilibrium is achieved. Your skin gets cold not because cold energy is being absorbed by your atoms, but because your hot atoms are losing their heat to the ice’s colder atoms. Unfortunately for the ice cube equilibrium will only take place once its frozen low energy water molecules have warmed to 34°C. The atoms in your skin bombard the ice’s atoms until they are wriggling like crazy, causing them to lose their connectivity, turning the ice from a solid to a fluid state (water). Your body wins this battle as your body’s supply of energy vastly outnumbers that of the ice cube.
If on the other hand you were dropped naked into a glacier, the ice would have the upper hand and so equilibrium will be achieved in its favour i.e. your body temperature will eventually match that of the glacier (the liquid within you would turn into a solid). And so survival depends on either winning the thermal equilibrium battle, which is unlikely as your body is out gunned by the environment around you, or in having the resources to fight an unwinnable battle. In this battle you will always be losing, but fortunately you can retreat for more ammo in order to continue the fight (food and warmth). The thing to remember is that when you have no ammo left and you are unable to retreat, the battle will be lost and you’ll become a victim of thermal equilibrium.
Humans are considered tropical animals and naked we require an ambient temperature of 37°C, plus or minus perhaps one degree in order to survive.
The reason we are here now in the cold northern hemisphere, far from the warmth of Africa - the cradle of the human race - is due to our ancestors’ ability to adapt and protect this core temperature. Prehistoric people found that by exploiting the skins of other animals, along with the feathers of birds and natural materials like bark, plants and grasses, they could create a mobile micro climate that allowed them to venture beyond the safety of their safe ambient habitat.
This allowed them to move further north, or into the high mountains, in search of food. This ability to adapt to ‘protect and survive’ is one of the reasons the Homo sapiens became so successful, driving the Neanderthals further and further north as their clothing became more and more sophisticated.
Man’s ability to protect its core is the foundation of all exploration and colonization, the reason we have been able to travel far beyond our perfect ambient habitat, to explore our planet’s arctic wastes, deserts, high mountains and even the emptiness of space.
Below: Night number 15 and minus a lot but still smiling. Several layers of Powerstretch, nylon and hollow fibre keeping Ian Parnell’s morale up.
As most climbers know, your body has an internal temperature of 37°C, a temperature you must maintain with very little deviation if you are to stay mobile and healthy. This core makes up about 90% of the your body’s mass and is mainly concerned with the heart, lungs and brain. The shell of the body comprises of 1.65mm layer of skin, which has an average area of 1.8 square metres and a temperature of 34°C - a fact worth remembering when it comes to understanding how important it is to reduce heat loss via convection.
The first response to a downward variation in body temperature is shivering and goose bumps. Goose bumps are the body’s attempt to raise its hairs in order to increase their loft. Unfortunately, unless you’re Robin Williams or that guy from The Joy of Sex, this will have no effect as the human race shed most of it’s thick ‘monkey hair’ hair millions of years ago. Shivering is the body’s attempt to generate heat by involuntary contraction and expansion of the muscles in order to create friction.
If your core temperature continues to fall then your body will begin to restrict blood flow in order to safeguard the core. This is done by reducing the size of blood capillaries and thereby reducing heat loss by the conduction of heat energy from your blood. Like an army retreating into its citadel, the body will fight its way back towards the brain, sacrificing fingers and toes, arms, legs and so on until there’s nowhere left to run. Frostbite can often be caused in this period.
Your body will also begin to pump out chemicals like thyroxine, used to increase metabolic rate and norepinephrine, which increases the heart rate as well as blood pressure, plus, increase the conversion of glycogen to glucose and the conversion of fats to fatty acids.
If none of this is able to stop cooling and your core temperature falls by 2°C then you will begin to feel the effects of hypothermia. You will quickly become confused, loose fine motor co-ordination and become lethargic, much of which is caused by your brain prioritizing its own survival. This period may compound your exposure, as you may not be in a fit state to defend yourself, or be mentally competent enough to recognize how much danger you’re in and retreat. It’s for this reason that partners should always be aware of the first signs of hypothermia, so that they can intervene.
If your body temperature continues to fall then your muscles will begin to cease to work and your body’s internal thermostat will no longer function. Once this happens your chances of survival in the mountains is almost zilch unless the mountain rescue helicopter is flying by or your partners act extremely quickly. Unfortunately in many circumstances (stuck on a belay high on a mountain, or staggering through a storm), there is very little that can be done.
By the time your body has slipped a further 5°C you’ll be deeply and severely hypothermic and will appear dead. Blood flow (cardiac output and arterial pressure) will be reduced, along with cardiovascular and brain function. Victims of hypothermia have been resuscitated with core temperatures as low as 15°C, but in mountaineering accidents severe hypothermia is generally fatal.
So what does all this mean to you, the storm-bound climber in the real world? Well the relationship between this molecular transfer of ‘hot’ energy to ‘cold’ energy directly relates to understanding how to maintain your core temperature, as only by slowing this energy transference can you operate and stay alive in the cold. To do this you must build a wall to slow down heat transference between the warm particles of your body and the cold heat-robbing particles outside it. This requires you to understand insulation and how to maximize its effectiveness.
The main ally you have in this battle against the mightier low-density environments is insulation. Insulators slow the transference of this atomic energy and in the case of clothing is formed by some form of sponge that stabilizes the air (liquid). Air is comprised of atoms that have totally lost connectivity with their surrounding atoms, meaning they are just bouncing around wildly. Unharnessed liquid is a poor insulator (be it air or water), but once stabilized it is one of the most effective, as this stops low energy liquid coming into contact with you and cooling you off. It’s for this reason that non-porous insulators work best in windy conditions (windproofs).
The thicker the insulation the slower the conduction, but no matter how thick your clothing is conduction will continue. This is why you can throw on a down jacket that will keep you warm for a few hours of non-movement, but you will still become cold as the heat drips out.
If you were a house then this would simply be a case of fitting some cavity wall foam and a bit of fibreglass wadding. Unfortunately you’re not a house, but a living breathing animal who not only wants to run around, but also has the urge to go to places far too cold for your own good, often heavily burdened and with a finite supply of energy to defend yourself with.
This analogy is worth remembering, as many climbers seem to dress as if they were insulating a loft rather than a human being, failing to understand that increasing your insulation doesn’t necessarily make you more comfortable.
It often only requires a few millimetres of the right insulation to create a comfortable micro climate around the wearer, something that can be seen in animals that live successfully in the cold, like wolves, polar bears and foxes.
Due to the fact that trapped air is the prime insulator in performance clothing, it is crucial that a stable atmosphere is achieved, otherwise the body will waste energy trying to maintain this ever cooling micro climate. It’s for this reason that windproofs from Ventile to Pertex have always been so important for mountaineering.
The expected heat output of the user should be taken into account when working out what to wear, not just the necessary thickness of the actual insulation required to insulate the user from the cold. A human at work can produce 1,600% more energy (heat) than a non-active human. This is why we see arctic explorers pulling sleds in just their thermals at -25°C and Everest summit climbers in down suits at -15°C. Once insulation is understood, then the most important fact to understand is that…
If you’re exercising hard, or there is an ambient temperature over 37°C, or both, your body temperature will rise. When your skin reaches 37°C your body begins to sweat. This is your body’s attempt to cool itself via evaporative heat loss. As we all know, as your skin becomes wet, water begins to evaporate from it making your skin colder. This is due to the fact that movement of air across your skin prevents any build-up of humid air near its surface and more water molecules leave your skin than return to it, increasing conduction dramatically. The faster the air speed the faster the evaporation and the more rapid the heat loss. For a water molecule to leave the surface of liquid water, it needs a substantial amount of energy due to the fact it must break several hydrogen bonds. The speed of this loss is primarily effected by wind speed and ambient temperature, commonly known as wind chill, with the actual amount of energy lost being dependent on the surface area of flesh being exposed i.e. the more skin that’s covered the less effective evaporation. This process is extremely effective at controlling your core temperature and keeping you cool.
Herein lies the problem with the whole sweat thing. It was fine when we were being chased naked through the jungle by sabre tooth tigers, but not that effective a couple of million years later when we’re stomping up towards the CIC Hut in the rain wearing all our winter clobber. The problem is that when the climber sweats, the insulation becomes saturated with moisture, making the air a less efficient insulator, as energy is now able to be conducted faster via the water now bouncing around within it. Initially this insulation will match that of the overheated body as thermal equilibrium is achieved with your overheating skin, compounding the problem.
The only way to cool the body will either be by the ambient temperature being lowered (weather or altitude), slowing of muscular energy production (stopping), or by removing insulation in order for evaporation to take place more effectively.
With the clothing saturated, cooling effect may be increased, especially so if windproofing is removed from these layers and eventually your body will bring its skin temperature back to 34°C. This is when the problems start. If you were naked the sweat would just evaporate away now you’ve cooled down, but this isn’t the case if you’re wrapped up in a suit of sweat-drenched fleece.
Although your body’s thermostat has switched off the air conditioning, now it’s re-establishing a comfortable skin temperature, your body’s still losing heat, meaning that very quickly it will need to work in order to raise the body temperature. If this coincides with a slowing of internal heat generation (lunch break, summit photo, broken pelvis etc), your body is suddenly in a very precarious position and very exposed to the cold. This is chilling and it is one of the most common causes of hypothermia, being the ‘storm within’ not the ‘storm without’ that can kill. A great example of this in nature is how animals who are chased in harsh arctic temperatures often die of hypothermia once they have escaped the predator due to sweat that has built up in their fur.
Due to the fact that only a very thin layer of dry insulation is actually needed to create an ‘active’ micro climate, if you can understand chilling, and you learn how to avoid it as much as is possible, then you will be able to remain comfortable - if suitably equipped - in just about any temperature.
To begin with don’t hang your hopes on wonder wicking fabrics and highly breathable shells. The fabric and outdoor companies will try and persuade you they have the technology to keep you warm and dry whatever the weather or rate of perspiration, but this is impossible because YOU’RE the problem, not the fabric.
Even a string vest, the most breathable thing you can wear, will become sweaty and raise your body temperature over 37°C if you’re pushing it, so how can a layer of polypropylene or polyester ever hope to keep you from chilling? No, the first defence against overheating and chilling is to use these super fabrics correctly so they are not called on to do the impossible.
Your first priority is to stay cool by controlling the ventilation and thickness of insulation you wear, so as to reduce the likelihood of your skin temperature reaching that thermostat triggering temperature of 37°C.
If you look at an experienced climber approaching a route they will often wear very little, or if they are forced to wear a lot of clothing by bad weather, they will move slow enough to limit energy production. This way they regulate their perspiration level so as not to overpower their clothing system. Fitness also plays a major part in this, as a fit climber is less pushed than an unfit climber and so sweats less.
Novices on the other hand can often be found wearing every piece of clothing they own, sweating their proverbials off all the way. This is why novices are often the first to stop for a rest, the first to get dehydrated (drinking loads of cold water also lowers your body temperature as the heat is transferred from your belly) and the first to chill.
Novices or the inexperienced (or those that never learn) put all their clothes on from the start because they don’t realize how much heat their muscles will generate once they set off. I’ve walked into the Northern Corries with first timers who’ve worn full thermals, fleece, shell jacket and salopettes, hats and gloves when I’ve just had a thin layer of shelled polyester (Dri-Clime, Zyphur, Tempest etc). When we’d stop I’d throw on my belay thick jacket and be toasty, while they’d be sweating and hot, yet be chilled and eager to move on after a few minutes.
The second most important thing is to use the fabrics that give you the best advantage, both in reducing chilling by their material and construction and in giving you an advantage if they do become saturated if sweating can’t be avoided. By doing so you can achieve much higher performance and greatly increase both your comfort and survivability. Cotton is the worst fabric you could ever wear for cold conditions because it has to be totally saturated before it will begin to transfer water molecules on to the next layer on, meaning you chill and will continue to chill. It’s for this reason that cotton is the best tropical fabric as it greatly increases heat transfer, which aids cooling.
The three most important features of an anti chill fabric are:
The moisture must be transferred away from your skin so that conduction and evaporation is reduced to a minimum. This can be achieved in several ways but is most commonly achieved by hydrophilic coatings or by the construction of the fabric (capillary action). My favourite fabrics are those which cover the maximum area of skin yet have the lowest surface contact and have a dense outer layer. The fabric close to the skin absorbs moisture and moves it away towards the more dense jersey surface, being pushed away by the heat of the body. Once there it’s spread over a much larger surface area as it’s the denser face, where it can be more easily evaporated or moved towards the next layer. The moisture trapped in the tips of the fabric can also be heated extremely quickly, reducing rapid conduction as thermal equilibrium may be achieved and the air between the contact points can be dried out faster. These fabrics are generally known to be ‘warm when wet’ and include pile, fleece and brushed micro fibres.
A thick dense fabric will hold less air and more moisture than a less dense loftier fabric and because air is a very poor conductor it’s the central feature when it comes to warmth. It’s also much easier to remove moisture from the air than it is from a fabric, so drying time and wet warmth are also tied in with the fabric’s density. Modern piles and fleeces, down and synthetic fills are good examples of this.
The closer the fabric the better the transfer of heat. Isn’t that a bad thing? No the faster you can achieve thermal equilibrium with your base layers the less swift conduction will take place and a perfect micro climate can be achieved. This close layer will be highly efficient at stabilizing and re-establishing equilibrium if the user gets too hot or too cold and, gram for gram, will outperform a thicker but baggier inefficient layer. This is why a tight wetsuit is better than a baggy wet suit, even though both are full of potentially heat-sapping moisture. Stretch base layers are best, but most modern base layers are undermined by being too loose, being cut in order to pass as casual pieces.
Layering, be it conventional or in modified ‘Soft Shell’ system, is the most effective way of maintaining your comfort level over varying temperatures and heat outputs. By using a primary base layer that is close fitting, low density and thin (NOT expedition weight), you can achieve a good micro climate that will allow perspiration to be moved away by conduction and convection (the wind). If this proves a bit too cold (if it’s windy), then a thin windproof layer on your top should create a good working micro climate in even the coldest conditions, as a stable micro climate can be achieved that the wind can’t steal (you don’t need thick fleeces to create a micro climate). This why you often see climbers in the Himalaya wearing just their base layer or a base layer under their shells.
Ventilation is also crucial and this is the reason why many soft shell systems work well (Buffalo, Montane etc), because they give the user one layer that does three jobs (base, insulation and shell), which allows them to fully ventilate when heat output is at its max.
This thin active layer can very often be regulated purely by increasing or decreasing heat output (speed), or by putting on or taking off of hats or gloves (6% of heat is lost out of your noggin remember). If you feel your core temperature slipping add another thin layer on your top. The best thing is you will not be sweating tons, so you’re less likely to suffer from dehydration, another cause of coldness. Even if you’re feeling chilly by the time you are nearly at your objective, any insulating layers you put on will be totally dry, so you’ll gain maximum advantage of their insulation.
Lastly functionality is crucial. Make sure each piece of your clothing system is compatible and allows you to put on and remove easily. Don’t just focus on whether or not you can just remove your shell trousers easily, as insulation needs to be equally flexible.
So there you have it, a mishmash of information that personally I’ve found has changed the way I’ve viewed the cold worlds I sometimes visit. I’m sure there is a lot here that is confusing, or even downright wrong, but I hope it’ll spur you on, like me, to give protecting your core a little bit more thought.
As usual there are no fleeces or jackets reviewed here, but if you get to grips with what I’m trying to say then you won’t need reviews as you should have a better grip on what you need to know.
And so, hopefully, this article will help to understand how you stay more comfortable in the future and if you’re unlucky or just masochistic, learn the art of suffering yourself.