Three Greenpeace activists on Tuesday climbed the 20 meter glass wall outside of the Microsoft building in Herzliya.

Activists climbed and then cleaned the huge glass wall of the Microsoft building, and opened a 100 square meter banner from its roof.

The stunt was part of Greenpeace's global campaign against Microsoft, which Greenpeace says uses coal to power its data centers.

The act of cleaning was symbolic of Greenpeace's demand that Microsoft use "cleaner" or more environmentally-friendly energy resources

The activists' banner showed a replica of a Microsoft error message which reads “still using coal” and "clean up your cloud from coal."

The messages are a reference to Microsoft's data centers, known as the "cloud," which are being powered by what Greenpeace dubs "dirty" or environment-damaging energy.

Microsoft says that, contrary to Greenpeace's assertions, it is making vast strides in its environmental efforts. The software giant recently announced that starting July 1, it will be carbon neutral across all direct operations, including data centers.

Reacting to the incident, Microsoft reaffirmed its commitment to carbon neutrality and environmental sustainability, saying, "We are continually working to make our data centers more efficient in energy consumption and cooling. Our latest modular data centers use about 50 percent less energy than those from three years ago."

To decrease its carbon footprint, Microsoft wrote on its blog, it is instituting an internal carbon fee, giving each of its units economic incentive to reduce their carbon output. Already, the company says, it is the third largest purchaser of green power in the US, buying more than 1.1 billion kilowatt-hours (kWh) of green power annually.

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