Travel ''For most runners and outdoor folk, the largest slice of their individual emissions will be caused by travel, which accounts for one fifth of global emissions. Flying is the most carbon-intensive thing we can do. A flight from London to Berlin creates three times the emissions saved by a year of recycling, and only the US and China generate more emissions via boarding passes than us here in the UK. ''In most cases, a train journey will create around a quarter to a third of CO2e of a flight. Fossil fuel-powered cars aren''t much better than flights; the bigger they are and the fewer passengers they transport, the worse the greenhouse gas (if SUVs were a nation, they would rank seventh in the world for emissions and have wiped out all gains made by electric and hybrid vehicles). However, four in a car can be similar emissions as a train journey, so lift-sharing and car-pooling for races is a genuine CO2e saver. ''Running is carbon neutral transport of course, as is cycling (unless your pedal power is fuelled by beef, in which case it''s about as bad as a car). I''ve found I can get to races I used to fly to (such as UTMB) via train.

However, now that I know more about the environmental cost of travel, I simply don''t want to race abroad so often any more.'' Kit ''The running shoe industry is responsible for approximately the same annual emissions as the entire United Kingdom. That''s worth saying again out loud. Those shoes are almost all made from plastic (i.e., fossil fuels), almost all are non-recyclable and brands tell us we should bin our daps after 300 miles in case they injure us (which no studies prove). ''The clothing industry as a whole is responsible for many times more pollution again, possibly as much as 10% of global CO2e (although that figure is disputed). And then there''s the large range of environmental and ethical issues around the production process: massive water usage and pollution, toxic dyes and forever chemicals, slave labour, child labour, the fact 69% of our clothes are made from fossil fuels - the very thing scientist warn us we need to stop using right away - and the millions of microfibres released into the oceans, harming wildlife and maybe us too.

With clothing (but not footwear), plenty of CO2e is emitted by us, the consumer, every time we wash and dry items (with more microfibres released). ''The industry excels at greenwash, bandying phrases like "eco-friendly" about while pumping out an endless stream of products in what constitutes an overconsumption crisis. If we care about the planet, should we only buy from Patagonia, wear t-shirts made from bamboo and daps made from mushrooms? Well, those materials all still cause CO2e in production and may not be as durable. The most sustainable kit is the stuff we''re already wearing. We need to buy less and make it last longer.'' Diet ''We already know red meat is linked to most of the worst diseases and clearly isn''t very kind to animals. It''s also terrible for the planet. Meat and dairy alone are responsible for 18% of global CO2e, more than travel.

Beef is by far the worst offender, costing the planet 99kg CO2e just to produce 1kg of meat, which is crazily inefficient. This graph turned me vegan. A quarter of our footprint comes from food and it can be reduced by over 70% by cutting out animal flesh and juices. ''Yes, there''s far too much plastic packaging in the world, but it''s the food in the packaging that''s the most important thing - with almost all meat and dairy being worse for the planet than plants. Sadly, "sustainably"-reared beef is actually worse and eating local isn''t usually better environmentally (90% of international food is shipped, which is really efficient). Food waste is an epic, er, waste too, and is far more significant than where the food came from and what it''s wrapped in.'' What can we do? ''We''re not yet at the point where we should consider completely giving up doing the things we love, and we needn''t feel guilty for existing. Almost none of this stuff is our fault.

It was BP who invented the idea of a personal carbon footprint; the idea individuals are to blame for the climate and ecological emergency, not huge multi-billion-pound corporations plundering the planet. ''To me it''s fairly simple: do your best with the Big Three of travel, kit and diet. No one is or can be perfect. We''re just seeking progress. But above that, we need to push for systemic change and be a little bit activist. Join in with protests, civil disobedience, online campaigns; email your MP, your favourite brands and companies; talk to anyone who''ll listen but especially friends and family; join The Green Runners, Protect Our Winters, Extinction Rebellion, Greenpeace, Just Stop Oil. That will have more impact. Greta Thunberg wouldn''t have had the profound impact she has if she''d stayed at home to wash her hummus pots for recycling instead of getting out on the streets to protest.

'' What can brands do? ''Make less. Make things that will last. Help us extend the life of kit. Take responsibility for kit after we''ve used it all we can. Brands should have their carbon footprint independently audited and a transparent plan to aggressively reduce it. Transparent supply chains should also be the norm so that we can eradicate unethical practises. And just stop the BS.'' What can events do? ''Cutting right down/out plastic waste and all those terrible t-shirts is worthwhile, but that''s just a tiny part of an event''s footprint.

In many cases, 90% of emissions will be from participant travel. We need to spread awareness, but also incentivise better decisions for runners with low-carbon travel options. Maybe change race start times so that they''re compatible with public transport or give discounts for low-carbon travel with small punishments for a higher-carbon one. ''Though I guess it''s turned out that way a bit, this wasn''t meant to be pious, preachy or finger-pointy. I''m not perfect. This stuff is complex and not always easy to fix. Spearing awareness is the first step. ''Also remember that running is well brill.

It brings real happiness, health benefits, meaning and Strava kudos to millions. It has a relatively low impact compared to some sports and activities. But it could definitely be better. Thanks for making it this far. For the climate change jokes, you''ll have to read the book though.''.