But none of the coverage I saw included the fact that parts of the Greenland Ice Sheet had entered the same sort of cycle as much as a decade ago. In fact, just one glacier – the Jakobshavn Isbrae – on its own contributed 3 percent of worldwide sea-level rise over the past 10 years.
Back in March, when I was working as a freelance journalist, I interviewed the two scientists whose research is central to yesterday’s announcement, and found them both concerned about what their data were showing.
There is uncertainty about just how quickly these cycles can move. Exposure to ocean currents and warming waters dramatically accelerates calving and melting of glaciers, in part because the water pushes the ice around, whether it is floating or grounded on the sea floor.
As a result of these effects, Jakobshavn, for example, has tripled its speed toward the ocean in 20 years. You might have seen this glacier calve in the 2012 film Chasing Ice: It was the glacier that calved a mile of ice in a single event, a scene spectacular in its power and scary in its import for those of us who live near the ocean.
Eventually, perhaps in about 100 years, Jakobshavn will retreat so far that it will be landlocked and no longer a significant contributor to sea-level rise. But the topography beneath the West Antarctic Ice Sheet glaciers is very different, getting farther and farther below sea level as one moves toward the center of Antarctica, meaning that as the glaciers retreat their exposure to the melting and calving effects of the ocean will only grow. They will only melt faster and faster, until they are entirely gone.
These are only some of the effects of global warming that are already in the pipeline, resulting from emissions we have already released into the atmosphere. Monday’s announcement is a crucial reminder that we must both adapt to the changes that are already inevitable, and step up our efforts to forestall the even more calamitous and rapid changes scientists warn are in store if we fail to reduce our emissions of greenhouse gases.
The world has the tools now to begin reducing carbon emissions, conserving energy, and transitioning to renewable sources of power. We must act to prevent other irreversible cycles from beginning to transform Earth beyond our ability to adapt – or even contemplate.