Doubling clean power generation within 15 years could add $1.3 trillion to global GDP and improve wellbeing, says International Renewable Energy Agency, UN-backed think tank. A new report, released on Saturday, shows the benefits of ditching coal, oil and gas for domestic resources that counter climate change and spur national employment and health. Welfare, or happiness, may be tricky to quantify but cleaner energy sources reduce the frequency and misery of extreme weather. GDP growth creates jobs and boosts tax collection. Spent on education, health and environmental quality, global welfare will increase 2.7%, rather than 0.6% ordinarily.