The endeavor to use 100% renewable energy for electricity, heating/cooling and transport is motivated by global warming, pollution and other environmental issues, as well as economic and energy security concerns. Shifting the total global primary energy supply to renewable sources requires a transition of the energy system. In 2013 the Intergovernmental Panel on Climate Change said that there are few fundamental technological limits to integrating a portfolio of renewable energy technologies to meet most of total global energy demand. Renewable energy use has grown much faster than even advocates anticipated.