17.3: What Can We Do?

Impact of sea level rise

At present, the Earth is on a trajectory for a 1-meter sea level rise by 2100. The economic and environmental damages that a 1-meter sea level rise will inflict on humans and ecosystems should not be underestimated. A 1-meter sea level rise will affect our coastlines worldwide, their assets, homes, industries, and airports; populations will have to move inland and entire ecosystems will disappear. Sea level rise will affect our water resources (for example, by salt infiltration), security, and safety; it will force massive immigration of millions of people who cannot afford to move to higher ground. Flooding by rising sea level is there to stay once it occurs. Seawater does not recede after a few days of warm weather, as in the case of a rain storm. Humanity has to think of it as a permanent storm.

Changes in polar ice produce the most dramatic changes in sea level in areas farthest from the ice sheets because of the nature of the readjustment of the crust and gravity field associated with mass removal. Sea level will actually decrease near the sources of melting land ice as the crust rebounds; conversely, the ground will subside far from the ice sheets, hence increasing the rate of sea level rise compared with the global average. The effects of melting in Antarctica and Greenland add up to raise sea levels by about 20% to 30% more at low latitudes than on average around the globe. While the ice sheets may seem remote, they are therefore most relevant to us at low latitudes. Sea level rise will also vary regionally depending on local tectonics, geology, erosion, slopes, tides, and oceanic conditions.

Paleo record of sea level rise

As discussed earlier, there is a possibility for sea level to rise by multiple meters in a warmer future. Sea level rose by 4 meters per century about 13,000 years ago during the demise of northern ice sheets and portions of Antarctica. If the climate warms up by 4°C–5°C by the end of the century, the ice shelves in Antarctica will not survive. The world therefore faces the risk of unabated multiple-meter sea level rise if we do not change the course of our greenhouse gas emissions.

Figure 17.3.1 In the Eemian period, during the last interglacial, temperature at the surface of the Earth was only 0.5°C–1°C warmer than present, but sea level was 6 to 9 meters higher. If the Earth climate reaches a similar state, it is likely that sea level will rise multiple meters again. Reproduced from Dutton et al. 2015.

A most important finding from the paleoclimate records in recent years is that during the Eemian period, in the last interglacial, when the temperature of the Earth surface was only slightly warmer than present, sea level was 6 to 9 meters higher (Figure 17.3.1). At that time, a large share of Greenland probably melted away, West Antarctica was left as an archipelago, and parts of East Antarctica probably collapsed. If the world commits to a climate system similar to that in the Eemian, it is likely that sea level will rise to a similar level again. Paleo records do not indicate how fast we will reach that state. But they do show that the end state will be 6 to 9 meters of sea level rise, which would yield a massive redefinition of the world’s coastlines and a complete transformation of our polar regions and global climate.

What can we do about this?

There is no benefit to humanity from rapid multiple-meter sea level rise from the collapse of Greenland and Antarctica. The poorest people on the planet will be affected first, but the world’s population will be affected as well. Coastal ecosystems and the entire global climate system will change as ice sheet melt threatens to slow down, and eventually stop, the ocean’s thermohaline circulation. In 2015, 180 countries signed an agreement to limit climate warming to 1.5°C above the preindustrial temperature. This agreement was a giant step that needs to be confirmed by prompt actions. The world may fail to keep the temperature from rising more than 1.5°C. A recent IPCC report indicates that a world with an increase of 2°C above the preindustrial temperature would be significantly worse than a world with an increase of 1.5°C. Yet limiting warming to 1.5°C may not be sufficient to stabilize ice sheets. We need to make our energy production free of greenhouse gas emissions rapidly. Curbing our carbon emissions is a first step, to be followed by carbon sequestration to reduce the concentration of carbon in the atmosphere to more sustainable levels. Prompt actions on carbon emissions may take 30–40 years to take effect on the climate. They may take even longer to affect the ice sheets, and by that time we will have cumulated a significant amount of sea level change, but we may be able to prevent multiple meters of sea level rise.

Becoming a world with carbon-free energy production and better, equitable, sustainable management of our natural resources comes with large benefits, at all levels of society, especially to the poorest populations of the world. Cleaner air, cleaner water, sustainable use of our natural resources, reduction of conflicts bound to petroleum resources, energy available where the sun shines, new jobs, and new technologies will not only protect the glaciers and ice sheets and their magical beauty, but protect us from massive changes in the climate, permanent damage to ecosystems, loss of biodiversity, and the very existence of life as we know it.