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The IPCC says the longer it takes to switch to renewable energy sources, the more expensive and more difficult the target will become.
It warns that if current trends continue, the planet will be 3.7-4.8C warmer by 2100.
The report is the third and final chapter of a huge overview by the UN's IPCC – its first since 2007.
US Secretary of State John Kerry said the report was a reminder of the danger of climate change but also pointed to the commercial rewards from tackling the issue.
The report strongly advised disinvestment in non-renewable energy sources and specifically urged developing countries to cut their ties with coal and other non-renewables and to look towards renewable energy sources.
It conceded, however, that doing so would require massive investment.
The report called for “large-scale global changes in the energy supply sector”, which would come from “tripling or quadrupling” the share of renewable and nuclear sources.
Traditional sources of energy could remain if emissions were captured, according to the report.
The report offered options such as phasing out fossil fuel subsidies, investing in cleaner sources and rolling out technology to capture and store carbon emissions from power plants that burned coal, oil and gas.
