In the world, energy sources such as oil and coal are the most used and they are also the biggest contributors to carbon emissions. However, we should focus on cutting back on oil since wealthy countries use it more than coal and they also are the biggest contributors to emissions. For example, the US which produces the most and consumes the most oil also is near the top of Co2 emissions. If it cuts back on its use of oil then its emissions will decrease by a large amount.