Claims by Brookfield Asset Management vice chair Mark Carney, the former Bank of England governor and current UN climate adviser, that the firm had reached "net zero" emissions in its portfolio were sharply rebuked by experts, prompting Brookfield to reverse its position. The situation has intensified concerns over companies' use of creative accounting to greenwash their portfolios.

Among the methods Denver is considering to reduce its carbon footprint are new regulations on buildings beyond a requirement to add green roofs to new structures. For example, the city could require new buildings to be "net zero" energy, with incremental improvements required for existing structures.

Portland Community College in Oregon needs a new roof to replace a high-tech design installed in 2011 that has failed, leaving a classroom building with extensive rotting that will cost $3 million to repair. The roof, which used structural insulated panels, was intended to help the structure become a "net zero" building. Consultants say the panels work if installed properly; however, they are highly susceptible to rot if there are any problems with the installation.

Royal Dutch Shell has become part of an initiative that aims to bring global carbon emissions to "net zero" by the end of the century. The initiative, called the Trillion Tonne Communique, was signed by Shell and 70 other companies. "We recognize that over the long term, net global emissions must trend towards zero. Both of our New Lens Scenarios show that this objective can be realized by the end of this century, but not without action by governments to stimulate changes in the energy system and considerable deployment of carbon capture and storage," a Shell spokesman said.

Outagamie County, Wis., is set to open a new "net zero" general aviation terminal this fall. The building will be able to generate most of the energy it requires using geothermal heating and rooftop solar panels. County Executive Tom Nelson says that the project will make a positive impression on visitors to the area, as well as keep costs low. "It shows we're a cutting edge, progressive community," he says.