Global Warming Impacted by Brake Friction

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Research into the environmental impact of brakes has been concentrating on particulate emissions – brake dust – and how this affects air quality. A post on, “Rubbing Earth the Wrong Way,’ takes a look at another impact braking might have on the atmosphere: contributing to global warming. The article, excerpted below, examines the impact friction-producing heat might have on global warming, indicating there are two major sources of this: friction from aircraft moving through the air and braking.

Earth’s atmosphere is heating up faster than predicted by climate change models.  Those models assume that greenhouse gas accumulation is the sole cause of global warming. 

The discrepancy between predictions and reality raises the question:  are greenhouse gases really the only cause of global warming?  There may be at least one additional, important, and as yet unrecognized contributing factor:  our old thermodynamic friend, the law of conservation of energy.  Or, in more simplistic terms, heat from friction. 

Related post:
Particulate Emissions from EV Brakes, Tires a Pending Problem

The role of heat from friction hasn’t previously been considered.  The first law of thermodynamics dictates that the energy used to propel and stop vehicles will eventually be converted to heat. 

At least two sources of anthropogenic frictional heat may be significant contributors to climate change.  One is aircraft.  Airliners cruise pan-globally at high subsonic speeds.  Right now there are roughly 10,000+ planes airborne.  How many contrails can you see right now? 

An even more significant source of frictional heat may be brakes.  Brakes use friction to decelerate and stop wheeled vehicles:  bikes, cars, trucks, trains, even landing aircraft.  In doing so, the vehicle’s kinetic energy is converted to heat.  Depending on frequency and duration of braking, discs reach temperatures of 200 – 600°C.  (Please never touch a brake disc on a vehicle shortly after it’s stopped!) 

There are well over a billion cars on the planet.  How many times per day do you use your brakes?  Without doing the detailed math, you get the idea:  brakes put a lot of heat into the atmosphere! 

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Consider stopping a 10,000 metric ton train travelling at 20 m / s.  Remember conservation of energy:  the moving train’s kinetic energy equals 2000 MJ.  All of this gets converted to heat during stopping.  Also, since most vehicular braking occurs in large urban areas, this heat source would be concentrated in those areas. 

The entire post, with further links to research sites, can be viewed by clicking HERE.

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