At the time of writing, it shows that the world must achieve zero emissions within six years, 219 days, one hour, six minutes and two seconds. By the time you read this, it will have ticked down further.
An online version of the clock shows the current countdown.
The clock on the side of a glass-fronted building in lower Manhattan was installed last September by climate activists and artists as part of the Climate Clock project to mark a week of climate action during the annual United Nations General Assembly.
“There’s good news. That number isn’t zero,” Gan Golan, an artist and activist who co-created the display, said when it was installed. We can meet this challenge, but we don’t have any time to lose."
In April this year, the Climate Clock began showcasing a more positive element, with a second number displaying the percentage of global energy produced from renewable sources.
“Our new LIFELINE shows the percentage of global energy generated from renwable resources,” the group said. “The current number if 12.2 per cent... but it’s not going up fast enough.”
The figure currently stands at 12.3 per cent.
The Climate Clock project also unveiled smaller travelling clocks that show both the time left to act and the percentage of renwable energy.
The United Nations Intergovernmental Panel on Climate Change has urged countries to work together to reduce emissions in order to curb global warming to 1.5C.
If the global temperature rises above that level, scientists warn the planet will see even greater devastating effects, from sea-level rise to loss of coral reefs, heat waves, wildfires, droughts and typhoons.
Current emission rates suggest the world will hit 1.5C in just over seven years.
The clock installation took over the Metronome, which has featured on the side of a glass-fronted building overlooking Union Square in Manhattan for the last 20 years. It has 15 spinning LED digits which count time down to a hundreth of a second.