There is a mind-blowing scene of natural destruction at the edge of the glaciers. A mile wide section of the glacier front is collapsing into the ocean.
The giant columns of ice are being thrown around. A frothing maelstrom is flinging ice cubes of several tons high into the air, after the previously submerged portion of this immense block of glacier ice just breeched the ocean. The resulting wave inundates all in its path as it sweeps across the glacier.
I'm watching from a clifftop. Even here, I can feel the earthquakes.
I am aware that this is bad news for the low-lying coastlines.
I have worked on ice sheets for more than three decades. Some gobsmacking changes have happened to me. The past few years have been frightening for the pace of change. I was taught in my textbooks that ice sheets respond over time.
The study shows for the first time that the ice sheet is out of balance with the climate in the north. It is irreversibly committed to retreat by at least 59,000 square kilometers, which is more than the entire state ofDenmark.
If the greenhouse gas emissions driving global warming stopped today, we find that the sea level will rise by at least 10.8 inches. Current models forecast less than that, and it is a highly conservative estimate. The irreversible commitment to sea level rise would triple if a heat wave were to hit the island. Climate conditions we have already seen are not a hypothetical future scenario.
Our study is based on observations and theories rather than models. Climate and ice sheet models are used to forecast sea level rise, but they fail to capture the processes that are causing the loss of ice in the region.
The ice sheet is large and has an inverted pudding bowl-like shape. The ice is constantly flowing from the interior, where it is over 3 kilometers thick, to the edges, where it is less dense.
Global sea level will be raised by 24 feet by the ice sheet.
There are at least two dozen or so ice age cycles lasting between 70,000 and 100,000 years that have lasted for about 2.6 million years. The amount of solar radiation reaching the Earth's surface is influenced by shifts in Earth's orbital position. The variations are reinforced by snow reflectivity and atmospheric greenhouse gases.
There is an interglacial period going on right now. The rest of the planet has benefited from a mild and stable climate for the past 6,000 years. The mass balance has gone into the red since 1990 as the atmosphere and ocean have warmed. Ice losses due to enhanced melt, rain, ice flow and calving are much larger than the net gain from snow.
How fast does Greenland lose its ice and what does it mean for sea level rise?
Over the past decade, the global sea level rise has been caused by the loss of ice in Greenland.
The net loss is divided between surface melt and dynamic processes that speed outlet glacier flow. The idea is simple: Ice sheets don't like warm weather and the heat is on.
It's hard to say what the future will look like.
According to the models used by the Intergovernmental Panel on Climate Change, a sea level rise of around 4 inches (10 centimeters) is predicted by the end of the century, with a worst-case scenario of 6 inches (15 centimeters)
That prediction is not in line with what field scientists are seeing.
Over 100 trillion metric tons of ice is expected to be lost by Greenland. The ice that must melt and the glaciers that must calve are already committed.
Many emerging processes that the models don't account for are increasing the ice sheet's vulnerability. It's for example:
Part of the problem is that the models used for forecasting only include processes that are quantifiable and important.
Reality is reduced to a set of equations that are solved on very fast computers. I know the value of models for experimentation and testing of ideas. They are not replacements for reality and observation. Current model forecasts underestimate the threat of global sea level rise. There is a realization that the models used for long-term sea level forecasting are not fit for purpose.
There are processes and feedbacks that we don't know about and that models can't anticipate. Direct observations and drilling into the ice are the only ways to understand them.
We base our study on proven glaciological theory, which is constrained by two decades of actual measurement from weather stations, satellites and ice geophysics.
The societal stakes are high and the risk is real. Most of the billion or so people who live in low-lying coastal zones of the planet are unaware of the consequences of coastal flooding.
I think we can get on track. I don't think we've reached a tipping point that floods the coastline. It is not too late to act on what you know about the ice sheet.
Fossil fuels and emissions need to be stopped now because time is short and the water is rising faster than expected.
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Alun Hubbard is the author of it.
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