For many years the evidence that linked increased carbon dioxide levels to the greenhouse effect and global warming was not enough to convince everyone. In recent years more and more evidence has been collected and many scientists believe that this is the case. The evidence used by scientists is 'peer reviewed' by other scientists, which is the method used by the science community to ensure that research findings are valid. Peer review ensures that the science community are confident in the accuracy of data and any conclusions made.
The National Oceanic and Atmospheric Administration (NOAA) in the USA have recorded the top ten hottest years since records begin in 1880. They are shown in the table below and put in order of the warmest.