The atmosphere of the Anthropocene is quite unlike any atmosphere the planet has known, and the effects of humanity’s impacts on our aerial ocean will leave their mark on the world for millennia to come. The chemicals we are introducing into the air will find their way into the oceans, rocks and living parts of our world. Corals and trees are ingesting a different ratio of isotopes (forms) of carbon from the one they took in during the Holocene, because they are now absorbing carbon dioxide emitted from fossil fuels. But despite this, our changes to the atmosphere itself are as transient or permanent as we make them. If, tomorrow, we stopped releasing gases into the atmosphere, switched off our millions of signalling devices, ceased all aerial transport, within a matter of years most of our atmosphere would return to Holocene-like conditions. Within a few centuries, even the carbon dioxide levels would drop down to pre-industrial norms.
We are of course not going to stop releasing chemicals tomorrow, though. The amount of almost every pollutant humans emit is increasing, and will continue to change the climate. Despite being told repeatedly that our climate is changing, by numerous scientists, agencies and media, it is nevertheless hard to fully appreciate how significant this is – we may intellectually believe the change, but to emotionally understand and realise what it means is a different matter.
Our climate is one of humankind’s most powerful reference points. It fundamentally describes where and how we live, our culture, environment and even our place in time. Climate is what defines the Holocene geological epoch. The climate is what determines biodiversity regionally and globally, it decides the ecology, the hydrology (how much water there is) and weather. It determines, for example, whether malaria is more likely and whether wheat can grow.
Living in a changed climate is like living in a different world – or rather, our world in a different geological time. Instead of the climatically stable Holocene, we are entering the uncharted territory of anthropogenic, or human-caused, climate change. We will feel its effects even as we try to insulate ourselves from the changes and adapt to them. Climate change will increasingly affect our food production, the integrity of our cities, energy production, global politics, and the way we interact with other people and other species.
Human behaviour and the way nations develop will decide the atmospheric conditions as the Anthropocene unfurls. And the atmosphere of the Anthropocene will also play a deciding role in how humans develop. Poverty-stricken, backward Nepal is teetering on the edge of a bright new future: it has the promise of a functioning democracy, and the benefits of a decade of NGO experimentation in projects from micro-hydro to clean-cook stoves, even while it battles the legacy of atmospheric warming from industrialisation elsewhere. Whichever way it teeters, the children of Nangi have in many ways escaped the destiny of most of their contemporaries. Because they are already a part of the great human conversation, theirs will be a more assured Anthropocene, with opportunities to overcome the limitations imposed by geography.
The effects of our transformation of the atmosphere will crop up frequently in this book – I’ll show how they are intertwined with other changes we’re making to our planet. Many of humanity’s solutions rest on our innovative technological invasion of the skies, innovations just like Mahabir Pun’s in Nangi. As Google’s Larry Brilliant said about world-changing: ‘It starts with ordinary people. Ordinary people do extraordinary things, and then we lionise them. We make heroes out of them. And that’s a problem, because it makes other ordinary people look at these heroes and think that they can’t achieve the same things. But that path is open to everybody. Anybody at any time.’
When early Earth’s shifting sludge of molten rock hardened into a crust, some 4.3 billion years ago, our planet got its first land cover. As this crust cooled atop the churning lava, like the skin on a pan of custard, it contracted and twisted, leaving some parts higher and thicker than others: the first mountains were created.
But the earth is never still. This solid ground, this apparently permanent land is imperceptibly shifting. Over the billions of years, the planet’s bubbling-custard turbulence has shattered the crust into scattered fragments, or sent its many islands crashing together to form huge continents. Several of these vast, coalesced supercontinents have merged and separated, each time creating an entirely reconfigured planet – the most recent and best known of these is Pangaea (‘all-earth’), which formed 300 million years ago before splitting up. Each time the drifting plates of crust have crashed into each other, the collision sends one edge above the other, creating a mountain. When the plates have drifted apart, the wrinkles are pulled smoother and the mountains sink. So some mountains on the planet are on the up, like the still-growing Himalayas, and others are dropping.
Mountains can also appear suddenly, through the process that gave birth to the original land masses, volcanism. Every so often, a bubble of molten rock spews out of a crack between the plates, and piles up on the surface of the land or seabed, creating a new mountain. Kilimanjaro in Tanzania and Kinabalu in Borneo appeared in this way.
When mountains first arise, they are sharp and jagged like the Himalayas, but over time, they round down as their surfaces erode, crumbling gradually away through glacial or river flows, or in the sudden slips of a landslide. Exposure to the air, wind, sun, munching microorganisms, and rain, also wear away mountain rocks in a process called ‘weathering’, which locks away carbon dioxide from the air as it reacts with dissolved minerals in the rocks.
Mountains are unusual because they have multiple climates. Usually, in order to experience a different temperature or weather system, you need to travel hundreds of kilometres north or south, but heading just a hundred metres up or down a mountain can have a similar effect. That’s because the air molecules in our atmosphere are not evenly spread out – they are far denser in a blanket near the ground. The higher you rise, the fewer molecules there are in the air to radiate back the sun’s heat, so it’s colder. That’s why mountains – even those on the equator, like Mount Kenya – have snow and ice on the top. When the altitude is combined with latitude, such as in Antarctica, the entire range can be hidden under deep snow and ice.
This change in climate produces interesting island-like ecosystems, with some species found only on specific altitude-defined spots on certain mountains where they have been isolated from their cousins for thousands of years.
The relative coldness up a mountain also generates the world’s largest source of fresh water, as moisture-laden air condenses against the peaks, relinquishing its load as rain or snow. And much of this remains where it accumulates, in mountain caches. For perspective, consider this: 97.5% of the Earth’s water is ocean or salty groundwater; of the remainder, just 0.01% is held in the clouds and rain, 0.08% is in all the world’s lakes, rivers and wetlands, 0.75% is in groundwater, while 1.66% is in glaciers and snow-packs. That means well over half of the world’s fresh water is stored in glaciers.
That’s how it was in the Holocene. But, as humans heat the planet in the Anthropocene, mountains are changing dramatically. Species seeking their usual living temperatures are climbing up the slopes at an