That red line is the median Arctic ice extent from 1979-2000. The rate at which ice has shrunk since then has taken scientists by surprise—as the BBC notes, climatologists were forced to reassess the date at which we'd see the first ice-free Arctic summer.
They'd initially thought it'd be around 2100, if we were too stupid to change our trajectory—now, the goal post has been scooted up to 2030-2040. As in, we'll very likely an iceless Arctic in two or three decades.
The BBC has the details on the most recent projections:
Scientists at the US National Snow and Ice Data Center said data showed that the sea ice extent was tracking below the previous record low, set in 2007. Latest figures show that on 13 August ice extent was 483,000 sq km (186,000 sq miles) below the previous record low for the same date five years ago. The ice is expected to continue melting until mid- to late September.
"A new daily record... would be likely by the end of August," the centre's lead scientist, Ted Scambos, told Reuters. "Chances are it will cross the previous record while we are still in ice retreat."
And everyone loves breaking new records, right?