The Climate Clock Now Ticks With a Tinge of Optimism The display in New York’s Union Square, which reports the window to address global warming, now also measures the rising use of renewable energy. Video April 19, 2021Updated 12:33 p.m. ET A hint of optimism has been added to the Climate Clock, the set of decreasing numbers on the facade of a building in New York’s Union Square that was conceived by two artists and activists, to communicate the urgency of curbing carbon emissions. Seven months ago, the artists Andrew Boyd and Gan Golan, assisted by others, redid “Metronome,” a public art project commissioned by the developers of One Union Square South and unveiled in 1999: Its clock, instead of measuring the time of day, would measure the time remaining, by some counts, to reduce emissions and prevent some effects of global warming from becoming irreversible. (About seven years, the clock’s creators said.)