Jim Haywood, an expert on brown haze at the UK Met Office Hadley Centre for Climate Research, has carried out modelling studies on the Chile–Peru stratocumulus clouds, which indicate that modifying the cloud would produce a significant cooling effect. However, modelling also reveals other potential consequences: spraying the West African clouds appears to reduce rainfall over the Amazon, which would be bad; spraying salt into the clouds off Chile seems to increase rainfall over arid Australia, which could be useful. British engineer and inventor Stephen Salter, who pioneered wave-energy technology, thinks that rather than focusing on the three main clouds, it would be better to monitor oceanic warming zones in strategic locations around the world and spray salty nuclei into the air above them to create cooling reflective clouds and help modify dangerous weather. ‘Typhoons like Haiyan [which devastated the Philippines in November 2013] could have been significantly dampened before it made landfall by spraying the cloud,’ Salter says. He has designed a fleet of floating towers that could pump seaspray into clouds to whiten them, and he calculates the total cost of deployment on a scale that reduced global temperatures by half a degree per year would be less than that of a single international climate conference.
Meanwhile, other scientists are looking at what effect sulphur particles would have if they were pumped tens of kilometres into the stratosphere, mimicking a volcanic eruption but on a lesser, though more long-term, scale. Their experiments, restricted so far to laboratories, are looking at how reflective of the sun’s heat different particles would be, and whether the cooling particles would have any unwanted side effects, such as destroying the ozone layer.
The changes humans have made to mountains in the Anthropocene have largely been driven by temperature or precipitation – both of which we still have the power to alter, whether by reducing our greenhouse gas emissions or by reducing the sun’s power to heat us. The Anthropocene could become a time of more nuanced climate change, where temperature and precipitation are modulated to humanity’s needs, where weather is planned. It’s an extraordinary idea.
Humans have always modified their environment – it is only because of our exquisitely adapted brain that we thrive worldwide, essentially by insulating ourselves against the natural environment. Whether we raise average global temperatures by two, four or even six degrees, enterprising members of our species will no doubt adapt successfully. Given centuries, the entire human population would likely manage to live comfortably under such conditions. The problem is that the rate at which we are warming the atmosphere is too rapid for humans to adapt. Nevertheless, the concept of artificially cooling the atmosphere is highly controversial, given the atmosphere is a global commons. Perhaps it is because the intent is so explicit; although humans are artificially warming the atmosphere with greenhouse gas emissions, the intent behind burning fossil fuels has always been to produce energy, not to warm the planet. Some argue that even research in this area should be banned because it implies intent to carry out the practice; others say that it draws effort away from climate-change mitigation – from decarbonising our energy production. But surely freedom of inquiry should be preserved – carrying out scientific research into whether something would work and what its consequences might be does not make a scientist an advocate for deployment, and there are scientific questions that need to be answered, such as the impact on rainfall, and whether or not it would even be technologically possible, before society can start to decide whether or not to deploy such techniques.
This new, Anthropocene field of geoengineering is a fascinating area of research and the scientists working in it are some of the most remarkable and thoughtful people I’ve encountered. It is eerily reminiscent of the atomic research carried out in the 1940s – today’s geoengineers are working at the cutting edge in an exciting, entirely new science, spending their lives making discoveries and designing amazingly powerful technologies that they fervently hope will never be deployed. Each speaks sincerely about the risks involved with deployment, and reiterates that slashing emissions of warming gases is the best way of dealing with the problem. There may be very real and serious consequences of using reflectors. Models indicate that cooling the northern hemisphere (to slow catastrophic ice melt in the Arctic) would slash rainfall in poor countries in the southern tropics; one solution would be to simultaneously deploy reflective coolants above the southern hemisphere. Another problem is the so-called ‘termination’ issue. In order to keep global temperatures down and counteract future warming, these reflectors would need to be sprayed continuously and perhaps in greater amounts. If the spraying programme was terminated, global temperatures would rise very suddenly by whole degrees – this would be much more dangerous for humanity than gradual global warming caused by our rise in emissions.
However, the predicament that humans currently find themselves in – facing catastrophic climate change and yet increasingly reliant on the fuels that exacerbate the problem – means that planetary cooling techniques are likely to be seriously considered. It is, after all, what humans have always done when presented with a challenge – engineer a way through it. Proponents of solar radiation management, such as Paul Crutzen, point out that they are simply mimicking volcanic activity and have the potential to quickly and cheaply reverse the warming effect of a doubled carbon dioxide concentration. And, since we already know what happens when a volcano erupts, it is arguably one of the safest methods – safer than the impacts of global warming, for example. The technique could be used continually to avoid catastrophic climate change, or in times of severe drought or heatwaves, hopefully under the auspices of an internationally agreed treaty. And, carefully deployed, such techniques could potentially maintain or bring back glaciers over entire mountain ranges. But, while the world ponders the feasibility, ethics and wisdom of global-scale cooling, Norphel and other architects of the mountains are devising practical and effective local solutions to a warming planet.
Water that falls from the sky, leaks from a lake, rises from a spring or melts out of a glacier will make its way from land to ocean in a river. These freshwater conduits are life-giving. They irrigate forests and meadows, create wetlands and deltas, transport nutrients and sediments, and nurture entire ecosystems – self-contained watery worlds of animals, plants and microorganisms.
And yet, rivers owe their very existence to life forms. For billions of years, terrestrial fresh water flowed to the oceans in vastly broad, shallow sheets – like floods – across the planet’s hard barren surface. It took the arrival on land of root-based plants, around 420 million years ago, for rivers to evolve. Plant roots weakened the surface of rocks, making them crumble, producing mud that eroded channels through which water then coursed. The plants’ strong root systems then further channelled the water, strengthening the muddy banks and creating a deeper, meandering path that we would recognise as a river. As these proto-rivers flooded and receded, sediments were periodically dumped, creating deeper, richer soils where huge woody plants took root. Forests diversified and enhanced the channels, helping produce the vital network of wetlands that exists today.
The world’s rivers drain nearly 75% of Earth’s land surface, from the icy polar regions to the steamy tropics. Although they hold only about 0.0001% of the world’s water (and less than one-third of all fresh water), rivers are a key part of the global hydrological cycle, describing the geography of accessible fresh water for plants and animals. Hundreds of thousands of species have evolved to rely for all or part of their lifecycles on freshwater bodies, from the trickling source of a mountain stream, the torrential violence of waterfalls and rapids, the calm deep waters that flow between riparian forests, to the wide-open, sediment-flooded wetlands and deltas.
The rejuvenating flow of Earth’s powerful arteries appears timeless. Dinosaurs lived and died on riverbanks that exist today. They fed on fish, some of which – such as sturgeon and gars, and the arowana and arapaima of the Amazon – still swim the rivers. These ancient creatures are joined by a vast array of newer fish, reptiles, mammals, birds and insects
