How much Arctic sea ice have you melted today?
For every metric tonne of carbon dioxide emitted, three square metres of sea ice is lost, climate scientists calculated. Amy Middleton reports.
Human carbon emissions are directly correlated with the Arctic’s shrinking sea ice – and this time, it’s personal.
Dirk Notz at the Max Planck Institute for Meteorology in Germany and Julienne Stroeve at the US National Snow and Ice Data Centre tracked Arctic sea ice extent and anthropogenic carbon emissions over three decades. Writing in Science, they calculated for every metric tonne of carbon dioxide emitted, three square metres of sea ice were lost.
In other words, if you take a one-way flight from Sydney to London, that's five square metres gone.
While Antarctic sea ice has never been healthier, it’s a different story around the north pole. Arctic sea ice extends in winter and shrinks in summer, but the area it covers has been contracting.
This has far-reaching consequences, including habitat loss, accelerated warming of the region and possible flow-on effects on global weather patterns.
So just how long until an Arctic summer has no sea ice at all? It depends on which climate scientist you ask. While some models suggest sea ice will remain year-round in the Arctic into the next century, others predict the Arctic could be void of summer sea ice in a matter of decades.
To draw a more accurate picture, Notz and Stroeve compared sea ice levels with human-induced carbon emissions over time and found an almost linear relationship over a 30-year period.
The data suggests that the Arctic loses around three square metres for every metric tonne of carbon dioxide emitted by humans – an equation staggering enough to get people’s attention, the researchers say.
“This number is sufficiently intuitive to allow one to grasp the contribution of personal [carbon dioxide] emissions to the loss of Arctic sea ice,” they write.
“For example, based on the observed sensitivity, the average personal [carbon dioxide] emissions of several metric tonnes per year can be directly linked to the loss of tens of [square metres] of Arctic sea ice every single year.”
If a one-way flight between Australia and the UK emits 2.5 tonnes of carbon dioxide, then the cost of air travel for Arctic sea ice becomes all too evident.
By their equation, the researchers estimate that another 1,000 gigatonnes of carbon dioxide could strip the Arctic of summer sea ice completely.
And with current emissions of 35 gigatonnes per year, that limit will be reached before mid-century, they warn – and that’s a conservative estimate.
On the up-side, the work also suggests that any efforts made to mitigate carbon dioxide emissions into the future will have a positive effect on levels of Arctic sea ice: “For future total emissions compatible with reaching a 1.5°C global warming target […] Arctic summer sea ice has a chance of long-term survival at least in some parts of the Arctic Ocean.”