This article is more than 11 years old

This article is more than 11 years old

New Yorkers leaving Penn station and the tenor Andrea Bocelli's concert at Madison Square Garden stadium were confronted with an unusual advert yesterday – a huge sign showing greenhouse gas levels in the atmosphere.

Updated in real time, using projections from monthly measurements of CO 2 and other greenhouse gases by Massachusetts Institute of Technology, the Carbon Counter is designed to get everyone to reduce their emissions.

Kevin Parker, the global head of Deutsche Bank's asset management division, which put up the 21-metre sign, said: "Carbon in the atmosphere has reached an 800,000-year high. We can't see greenhouse gases, so it is easy to forget that they are accumulating rapidly."

Yesterday the counter, which uses 40,960 low-energy LEDs and carbon-offsets its electricity usage, gave a figure of 3.64tn tonnes.

At current rates, the counter's figures are expected to rise by 2bn tonnes a month. The concentration of carbon dioxide in the atmosphere stands at about 387 parts per million (ppm), up by more than a third on pre-industrial revolution levels of about 280ppm.

Ronald Prinn, professor of atmospheric science at MIT, explained the data behind the sign: "The number on the counter is based on global measurements. It shows the total estimated tonnage of greenhouse gases expressed as their equivalent amounts of carbon dioxide, with seasonal and other natural cyclical variations removed to more clearly reveal the underlying long-term trends driven by human and other activity."

The carbon counter will be updated online at www.know-the-number.com.