The close connection that exists between the atmosphere and the ocean is not surprising considering that 70% of the planet is covered by water—about 360 million km2—and the few dozen km of air is extremely thin compared to the 12,750 km diameter of Earth. This means that about 90% of the atmospheric heating caused by rising concentrations of CO2 is transferred to the oceans.
In approximate terms, about one-third of the carbon dioxide we add to the atmosphere by burning fossil fuels stays there for centuries, about one-third is captured and sequestered in various land forms such as forests, soils and vegetation, although one recent United Nations study suggests the terrestrial sequestration may only be about 25%, possibly because forest and plant cover is being diminished by agriculture and fires, and because a higher global temperature is reducing the photosynthesis process by which plants process carbon dioxide into carbon, sugars and oxygen. Much of the remaining one-third of our CO2 emissions that is not absorbed by marine algae dissolves in the oceans to form carbonic acid.
As for the transfer of heat from the atmosphere to the oceans, this close connection is good news and bad news. The good news is that the atmosphere is sufficiently cooled by this transfer of heat that we are able to continue living in a place that, otherwise, we would have rendered uninhabitable decades ago. In this respect, the oceans act as a very efficient shock absorber, collecting about 2,100 times more heat than can be stored in an equal volume of air.
The bad news is that the shock absorber is disguising and delaying the symptoms of our anthropogenic climate crisis. Indeed, this crisis is unfolding exactly as the laws of physics dictate, but with unpredictable surprises that we are just discovering.
The surface of the oceans, described as the top 700 metres, has warmed by about 1°C since 1901 measurements. This means that the water is able to contain less dissolved gases such as the oxygen needed by marine animals. Warmer water is also less able to absorb the carbon dioxide helping to keep down the atmospheric concentrations. And warming water expands, already increasing sea levels by an estimated 21-24 cm since 1880, with another 38 cm expected by 2100 as global temperatures rise.
But there’s more bad news. A warmer atmosphere holds more humidity—it increases by about 7% for every Celsius degree, which yields about a 14% increase in precipitation since pre-industrial times. So our 1.5°C higher global temperature means a 10.5% increase in humidity and a 21% increase in precipitation. Unfortunately, this precipitation is not distributed equally, so some places get huge deluges causing flash floods, while others may experience rapid and excessive drying as moisture is sucked out of soils by “flash droughts”.
For even more bad news, most of our weather is generated from the oceans, and its higher temperature “supercharges” storms. Whereas the deep ocean temperature is about 4°C, the average surface temperature is about 17°C, which can vary from -2°C at the poles to 30°C in the tropics. It’s these high temperatures, either shifting northward from the tropics or being produced locally, that generate the super storms with high winds and heavy precipitation. They cause havoc for us. A warming atmosphere and ocean indicate that the frequency and severity of these storms is going to increase, something that is now happening almost everywhere on the planet.
This means that we are paying a price for our carbon dioxide emissions one way or another, if not directly in taxes that are intended to reduce emissions, then in property damage, higher insurance rates, floods, washed out roads, forest fires, heat domes, droughts, bomb cyclones, higher food prices, cancelled ferries, power outages, missed appointments, dislocation, health problems, financial stress for governments and individuals and, for some people, death. As climatologists remind us ,we are bringing to an end the Holocene Climatic Holiday of the last 12,000 years.
Beside the short-term consequences of our carbon dioxide emissions, we will eventually have to confront the long-term effects. Unless we undergo a radical psychological transformation that instigates a dramatic change in our behaviour, and we manage to perform some revolutionary acts of technological magic, we are on an unstoppable trajectory to higher temperatures. Some parts of our planet will become uninhabitable, unleashing hundreds of millions of refugees. And most of our coastal cities and settlements will eventually have to be abandoned to an inexorable rise in ocean levels.
We seem to think that, individually and collectively, we can carry on as we always have. But, if we do, the eventual consequences will be dire. Unfortunately, the “eventual” is creeping closer.
Ray Grigg-for Sierra Quadra
Top image credit: Marbled godwit is walking at Ocean Beach at low tide against the sun.- Photo by Brocken Inglory (Own Work) via wikimedia (CC BY-SA 3.0)