As land dwellers, we have a blind spot when it comes to appreciating the vital importance of the ocean to our lives and livelihoods. Yet, the ocean may represent our greatest opportunity in responding to the many threats climate change presents to all of humanity.

Few people know or appreciate the fact that the ocean, our ally, is the largest active carbon reservoir on Earth. The deep ocean, for example, holds more than 50 times as much carbon as the atmosphere, and mangrove forests sequester carbon more than ten times faster than mature terrestrial forests. Since the dawn of the Industrial Age, it has absorbed almost all the heat, and around a third of the carbon that humans have generated. The ocean is also the largest single living space on Earth and integral to governing flows of water and nutrients that are critical to the health of all life on the planet.

As immense and seemingly immutable as it is, the ocean as our ally is remarkably sensitive to the widespread changes that humans are inflicting on our planet. As carbon dioxide levels in the atmosphere have soared, so too have the ocean’s as it equilibrates with our rising fossil fuel emissions. Whole ocean ecosystems, many of which provide critical economic benefits to us on land, are changing in drastic, unpredictable ways or are in danger of disappearing entirely as a result of this and many other pressures. In just the last 15 years, an estimated 14% of coral reefs have disappeared as a result of warming water, overfishing, and unchecked development.

Thankfully, the ocean can also come to our rescue as an ally. In fact, at this critical moment of rising global temperatures and increasingly extreme weather, the ocean could be our greatest ally. But this can only be true if we act with care and urgency and we let science be our guide. Because, for as much as we don’t know about the ocean, we have learned quite a bit over the 150 years since the Challenger Expedition ushered in the era of modern oceanography. We have critical data and insight because, for decades, scientists have been deploying instruments into the ocean to measure critical vital signs of marine health. But we need more.

This global ocean observation enterprise includes moored and seafloor sensors like those deployed in the Ocean Observatories Initiative (OOI), autonomous mobile platforms like the Argo Program, and ship-based observations, including those supported by the global GO-SHIP expeditions. Like the ocean, which knows no boundaries, these are truly far-reaching collaborations. OOI maintains more than 700 instruments to keep watch on physical, chemical, and biological properties of critical parts of the ocean and makes the data publicly available to anyone with an internet connection. Argo has brought dozens of nations together to innovate on new instruments and to collect and share ocean data from more than 3,000 autonomous profiling floats spread throughout the global ocean. The GO-SHIP vessels cross the ocean several times a year, releasing sensors and collecting samples to measure carbon, oxygen, nutrients, and more essential ocean variables from wavetops to seafloor. These projects represent the gold standard of data that underpins our knowledge about the state of the ocean. When scientists make statements about how the deep ocean is warming, this is where the evidence comes from.

Data like this helps build a more prepared, resilient society. Rising seas, perhaps the most existential threat posed to humanity by a changing climate, are caused not just by melting ice sheets and glaciers, but also by thermal expansion as ocean water warms. We cannot accurately predict how the oceans will rise, and which coastlines will be most affected, unless we measure temperatures deep below the surface. A difference of a few inches in rise can make a great difference in where we focus resources first. For people like the Marshal Islanders, it could even mean the difference between having a country and not.

The changing ocean, as our ally, also has the potential to reach well beyond the coasts and hit everyone in a place they care – their wallet. The global blue economy, that portion of economic activity derived from jobs and trade connected to the ocean as well as the value of services provided by a healthy ocean and marine ecosystems – is valued around $1.5 trillion per year. This fast-growing sector (it is poised to double by 2030) employs more than 30 million people is a vital source of protein for three billion worldwide. In many cases, simply by doing what it does naturally, the ocean adds value to our lives, as evidenced by the global seaside tourism industry and innumerable artistic activities and cultural practices that draw inspiration from the ocean.

Of course, rapidly cutting emissions must be at the heart of our response to climate change. But the science is now clear that the world cannot meet its mutually agreed-upon targets in the Paris Agreement without also removing legacy carbon added to the atmosphere over the past century of industrial activity. So, the task is twofold: first phase out fossil fuels as quickly as possible; and second, find new solutions that help blunt the climate crisis. In both, the ocean has a critical role to play. The High Level Panel for a Sustainable Ocean Economy found that ocean-based solutions that are ready to implement today could close the emissions gap – the difference between how much excess carbon we are producing and how little we should be to stay on track – by as much as 35%. Options already within reach include developing off-shore energy, making ships carbon neutral, and growing carbon-capturing natural capital like mangroves, kelp and seagrass.

In addition, we may be able to harness the ocean’s vast capacity to take up carbon by leveraging those physical, chemical and biological processes that make it absorb carbon dioxide from the atmosphere and transport it to the deep ocean where the carbon that once contributed to global warming is locked safely away from the atmosphere for long periods of time. But before we do so, before the chase for profit initiates large-scale, industrial carbon dioxide removal we need to have the observational infrastructure in place to ensure that we can keep track of the ocean’s vital signs and avert any possible adverse effects of our action, however well-meaning they might be.

But we currently have nowhere near enough eyes in the ocean, a message our two institutions carried to COP28 this year in organising the Ocean Pavilion in Dubai and by publishing the Dubai Ocean Declaration endorsed by over 100 ocean science, advocacy, and philanthropic organisations from around the world. The science programs that enable reliable and accessible data from the harsh environment of the open ocean and deep sea have been hit hard by rising inflation and decreased funding. As a result, we have significantly less data from the ocean than we do from the land and atmosphere precisely at a time when we should have more.

Main photograph of a pink anemonefish looking out from the tentacles of its home by Simon Thorrold/© Woods Hole Oceanographic Institution.