Have you seen the videos? August 29th 2022 9,858 Retweets14,788 LikesWhen the Pakistani minister for climate change said that “literally, a third of the country was underwater”, I thought she didn’t mean “literally” literally. But she did. It’s affecting a whopping 50 million people. How come such a mountainous country as Pakistan is submerged under water? We hear this is due to climate change, and that Pakistan is one of the countries most affected by climate change. But why? Meanwhile, not too far away, China is having one of the worst droughts in history. August 23rd 2022 8,662 Retweets19,565 LikesSatellites give us both Pakistan’s floods and China’s drought. August 26th 2022 422 Retweets811 LikesThese events are two sides of the same coin. To understand, we need to go to China first. China’s HeatwaveIt’s unprecedented. August 20th 2022 6,847 Retweets12,279 LikesThe heat is causing a drought, which also reduces hydropower, which in turns reduces the energy available to seek relief from the heat with AC. Unsurprisingly, this heatwave is caused by climate change. It’s no surprise that the rest of the Northern Hemisphere is suffering from the same heatwave. Records have been reached in the US, India, the UK, Spain, France… Why this dramatic increase, when we’ve only increased global temperatures by 1.2°C since the beginning of the Industrial Era? It’s a matter of distributions. This is the normal distribution of temperatures, which humans have evolved with, with somewhat equal events of extreme heat and cold. But if you shift it just a little towards hotter temperatures: You increase heatwave events manifold. This is what’s happening across the Northern Hemisphere. But then why is it causing these floods in Pakistan? And why not in China? Pakistan’s FloodsWe’re hearing the cause is a historic monsoon. August 30th 2022 5,688 Retweets13,462 LikesAre monsoons the only culprit? To understand this, we need to understand Pakistan’s geography. Pakistan has two things: very high mountains, and a very flat plain. The plain, in turn, is either desert or the Indus Valley. The Indus Valley is where the population is most concentrated. You can easily tell by just looking at the map of nightlights: So when the Indus floods, it does so on the most fertile areas of its valley. The most fertile areas are also the most populous, and so a big share of Pakistan’s 220 million people is affected. So why the floods? Why is the monsoon so aggressive this year? The Monsoon in the Indian SubcontinentThe monsoon rains start in June and cover the entire Indian Subcontinent by August. These are winds coming from the Indian Ocean, from the southwest, loaded with humidity, which then condensates and falls on land. Later, during the winter, the direction is inverted: Winds go from the land towards the sea, from the northeast towards the southwest. But why do these winds exist? They don’t correspond to the wind patterns of the rest of the Earth. It’s because, unlike most of the rest of the Earth, the Indian Ocean only occupies the southern hemisphere, while the Eurasian continent is on the north. During summer in the northern hemisphere, the Indian Ocean heats up close to India, which causes water to evaporate. But the land heats up much more than the water. Hot air goes up. That empties the air at the bottom, and the colder, more humid air from the sea then goes on the land. The humid air enters the land, rises as it’s heated, and there it meets colder air that condenses the water and it falls. So when Eurasia burns with a heatwave, all of its hot, dry air travels up, which leaves an emptiness¹ that sucks up massive amounts of humid air from the Indian Ocean onto the continent. The hotter the heatwave:
So that’s why a historic heatwave in the region leads to a historic monsoon. But that’s not all. There are two more factors at play, both linked to this: The HimalayasThe Himalayas², of course, are created by the Indian Tectonic Plate hitting the Eurasian Plate. The Himalayas are massive, so they stop the water due to the rainshadow effect we’ve discussed multiple times in this newsletter: Here’s a video that gives an intuitive sense of the effect: August 23rd 2022 13 Retweets35 LikesIn the Himalayas, most of the humid air drops its water on the Indian Subcontinent side of the Himalayas, not on the Tibet side, which is why China is seeing a drought and Pakistan a flood³. There’s one last element: the glaciers. Pakistan has 7,000 glaciers, the most of any country outside of the polar regions. Historic heatwave means historic glacier melting, which means historic floods. Uncharted Territories is a reader-supported publication. To receive new posts and support my work, consider becoming a free or paid subscriber. Takeaways
Thank you for reading Uncharted Territories. This post is public so feel free to share it. 1 AKA “low pressure”. 2 It’s not just the Himalayas. It’s all the mountain ranges around Pakistan: Mainly the Hindu Kush, but also the Tibet area behind the Himalayas. I just call it the Himalayas for simplicity: It doesn’t change the idea, and most people don’t make the difference in their brains. 3 China does get a lot of water from Tibet. Most of its rivers, including the crucial Yellow and Yangtze Rivers, are born there. But it’s substantially less than on the Himalayas side. Also, that water doesn’t come as much from the southern monsoon winds and rains, but rather from the monsoons that come from the Pacific and drop their water through the continent, including Tibet. Thanks for subscribing to Uncharted Territories. This post is public, so feel free to share it. © 2022 Tomas Pueyo |