The Rising Sea

A quarter of a century has passed since the impact of human activity on the global climate was formally recognised by the United Nations. The latest IPCC report, published on 8 October, calls for the average global temperature to rise no more than 1.5ºC above pre-industrial levels, but climate change has already and irreversibly altered the physical world in ways that are fundamentally altering the human world: extreme droughts, a rising frequency of intense storms and wildfires, the geographic expansion of vector-borne diseases. The collective implication of these changes is uniform: a rising level of risk to your health and stability, regardless of who you are or where you live.

For anyone under the age of 30 – more than half the world’s population – the experience of a stable climate is entirely unknown. That is to say, not a single month in their lifetime has fallen within the limited range of temperature, precipitation or storm activity that governed the planet for the previous 10,000 years. Climate change is as much about our lived experience as our distant fate, despite its popular characterisation as a future threat only.

No biological community observed by science has been untouched by the changed chemistry of the atmosphere and oceans, by the repositioning of global wind patterns and currents, or by the rapidly migrating seasons. The residue of our species is detectable in a spadeful of soil collected from anywhere on Earth, revealed as a distinct horizon in the stratigraphic record, rich with coal dust and radionuclides, and securing our place alongside meteor strikes in the deep history of the planet. A single species has now ushered the planet from one geologic epoch to another, an occurrence without precedent in the paleoclimatic record, and unlikely to occur again.

Across the Earth’s biomes, the oceans wear the mark of the Anthropocene most plainly, with their steady, relentless rise – their contrapuntal response to the Earth’s disappearing ice. The oceans are a persistent, easily measured and inarguable record of our effect on the global ecosystem. About 40 per cent of the global population lives in coastal zones; the inexorable inland shift of the seas foretells a migration unseen in human history. Prior migrations brought about by human-driven ecological change – such as the Dust Bowl in the American West – were localised in space and in time. The climate migration unleashed by recent Atlantic hurricanes, in Puerto Rico and across the Caribbean, and well underway in more arid regions of the planet, is more likely to play out over a timescale measured in centuries than in decades, and will not be contained by continental or hemispheric boundaries.

On a recent trip with students to Charleston, South Carolina, we paused at a storm drain to observe seawater pulsating into a parking lot in syncopation with the nearby lapping of the tide. We were surrounded by building sites. One of the many challenges presented by the rapid transition to a new planetary epoch is that our economic systems are firmly rooted in a set of unspoken environmental assumptions that are no longer operational. The persistence of this fallacy may constitute a greater threat than the rising sea itself.

But the rising sea is a threat on two primary fronts: as a slow-moving occupier of densely settled land and as an acute hazard during extreme weather. The succession of powerful hurricanes forming in the Atlantic basin in 2017 compressed more weather-related destruction and economic loss into a few weeks than ever before experienced in the Americas. The quantity of rain deposited on Houston during Hurricane Harvey was consistent with at least a 500-year storm – a flooding event so rare as to be expected to occur only once between the discovery of the New World and today. Yet Houston has experienced a ‘500-year’ flood in each of the last three years.

For the last 10,000 years, the probability of a 500-year storm occurring in three successive years would have been 1 in 125,000,000. In the current age of climate instability, the probability of such an occurrence is unknown but appears to be rising. The assumption that a weather event rare in the past will remain rare in the future is reasonable only in a stable climate. Among the many untruths we tell ourselves about climate change, the assertion that yesterday’s flood zone will protect us against tomorrow’s flood may be the least defensible.

Oceans are less often the primary dumping ground for industrial waste than they used to be, but virtually all of our most persistent pollution finds its way to the sea. Two gyres of industrial refuse the size of Texas float beneath the surface of the North Pacific – two ceaseless, swirling hurricanes of plastic to which every reader of these words has probably contributed. The post-consumer lifetime of the billions of plastic bottles now spinning in the Pacific is estimated to be 450 years, a period of slow biodegradation that will leave the oceans far more degraded than they are now.

Yet even such an infusion of industrial waste is unlikely to alter the ocean’s chemistry as substantially as the fuel consumed in its production and use. The carbon dioxide released from the burning of fossil fuels is both heating the atmosphere and cycling into the oceans. Were the oceans not increasing their uptake of atmospheric carbon dioxide, we would be much farther along the global warming trajectory than we are. Converted by seawater into carbonic acid, our carbon pollution since the Industrial Revolution has increased the acid content of the oceans by 30 per cent, bleaching corals worldwide and eroding the base of the oceanic food web. The fact that we now eat species not long ago referred to as ‘trash fish’ is only the most visible symptom of a dying ocean. Some studies project the loss of all wild seafood within three decades.

The most pressing environmental threats – violent weather, pollution, resource scarcity – are not new, but rather a heightened version of long-established threats, which come at the same time as an exponential increase in our numbers. The intertwining of population overshoot and ecosystem collapse has informed more than a generation of wildlife management practices, but the texts never depict our own species as subject to such natural laws. Every ecological indicator available to us today suggests they should.

A recently convened group of experts from the physical, natural and social sciences did not include climate change among the top three existential threats to our species, ranking it below genetically engineered pathogens, a unforeseen threat such as an alien invasion, and artificial intelligence. What seems to unite these perceived threats, and to elevate them beyond the far more likely but familiar scenarios of a global pandemic or climate-induced famine, is their exotic nature, and the common tendency to assign excessive risk to the unknown. Complacency has a recurring role in the annals of human miscalculation, and nothing breeds complacency like the familiar.

We might do better to see the parallels between our overshooting society and the many that have succumbed to ecological limits in the past. What then might we do? For a growing number of people, the most promising course of action would harness the very forces that have fuelled the climate problem in order to contain it – more and better technology. Having engineered the climate to make the Earth inhospitable, we simply need some reverse engineering to restore stability – giant mirrors in space, perhaps, or machines to suck carbon from the air. But our track record in directing the Earth’s many complex workings to our purposes – a record stretching over millennia – suggests that geo-engineering is hubris.

An alternative path still open to us may be less exotic than a geo-engineered world, but it is also less uncertain. It is still possible for us to re-engage in a way of life not so long ago lost – adhering to an ecological budget, acknowledging codependency with other species, and elevating the shared responsibilities of humanity. To understand climate change not as a new environmental problem, but as the long-running interplay of all environmental problems, is to return to an immutable truth: the only way out is through the door we came in by. It is, for now, still open.