Issues exist that currently prevent a shift over to a 100% renewable technologies. There is debate over the environmental impact of solar power, and the environmental impact of wind power. Some argue that the pollution produced and requirement of rare earth elements offsets many of the benefits compared to other alternative power sources such as hydroelectric, geothermal, and nuclear power. According to the 2013 "Post Carbon Pathways" report, which reviewed many international studies, the key roadblocks are: climate change denial, the fossil fuels lobby, political inaction, unsustainable energy consumption, outdated energy infrastructure, and financial constraints. However, according to a research paper published in 2014, renewable energy by itself, will not be able to stop climate change.