Despite current efforts, greenhouse gas emissions could grow 50% over the next 40 years, according to a report from the international Organisation for Economic Co-operation and Development. This could increase the global average temperature by up to 11° F by 2100 — far exceeding the internationally agreed limit of about 3.5°. The report says the cheapest policy solution would be to set a global carbon price that would link existing trading schemes. It also suggests putting an end to fossil fuel subsidies.