British mountaineer Kenton Cool has reached the summit of Mount Everest for the 20th time, becoming the first non-Sherpa climber in history to achieve the milestone. The 52-year-old mountain guide first climbed Everest in 2004 and has spent the past two decades guiding clients to the summit of the worlds highest mountain. While the achievement marks a significant moment in British mountaineering, it also gives Cool a rare perspective on how Everest itself has changed during that time.Cool has witnessed the rapid growth of commercial expeditions, record numbers of climbers and increasingly visible signs of climate change. When I look back at my first climb compared to today, they are worlds apart. Due to disturbing amounts of glacial loss from the Khumbu glacier over the years, there is now a river running through Base Camp. Back in 2004 this only appeared at the end of the season, now it flows constantly. The changes I see every time I return leave me humbled.Scientific research supports those observations. Professor Duncan Quincey, a glaciologist at the University of Leeds where Cool studied Earth Sciences is currently working on the Losing their Cool research project which examines how mountain glaciers are warming under intense solar radiation, accelerating melt rates and making them more sensitive to global warming than previously understood.The glaciers here are melting at a rate beyond historic precedence, says Quincey. Were seeing surface lowering of several metres a year in places. Satellite data from the 1960s to today shows the area around Everest Base Camp has lowered by more than 50 metres, which is staggering.In recent years Everest has seen an unprecedented surge in climbers. Over the last 25 years 15,781 people have climbed above Everest Base Camp, nearly three times as many as in the previous 80 years combined. In total, more than 13,700 summits have been recorded on Everest, achieved by around 7,500 individual climbers. The growth in expeditions has increased mountain congestion. Busy seasons can see close to a thousand people on the mountain at once, with more than 200 climbers attempting the summit on peak days.Cool believes the future of Everest will require both experience and adaptation as conditions continue to evolve. He supports a proposal currently under discussion in Nepal that would require climbers to first summit a 7,000-metre Himalayan peak before being eligible for an Everest permit. Everest is an extraordinary mountain, but it demands respect and experience, says Cool, as the mountain changes, and as more people come here, we need to make sure climbers are properly prepared.Whilst Cools livelihood is closely tied to Everest, he is conscious of the impact his expeditions have on the mountain and has taken steps to minimise it. Cools company, In Cool Company, is a member of 1% for the Planet, an initiative that sees 1% of annual revenue donated to environmental charities and projects. His travel emissions are offset in line with the principles of the Gold Standard, supporting verified climate and sustainability initiatives. Cool also uses his expeditions as an opportunity to highlight the visible effects of climate change in high mountain environments, including glacial retreat. He regularly engages with scientists like Professor Duncan Quincey and environmental experts to better understand the actions individuals and organisations can take to reduce emissions. On a personal level, he follows a plant-based diet whenever possible, helping to further reduce his environmental footprint.Despite two decades on the worlds highest peak, Cool says the mountain never becomes routine. It never gets any easier or any less frightening. Its the tallest mountain in the world and with it comes an incredible sense of majesty. I rely on every bit of experience I have to move safely in this environment. Standing on the summit for the twentieth time is incredibly special.Kenton has successfully guided several high-profile public figures, celebrities and explorers on expeditions across the globe including Ben Fogle and Sir Ranulph Fiennes.