How does this link up with “Target 350”?
Very simply: Target-350 is a campaign to limit long-term carbon dioxide levels to 350 parts per million. To achieve this, we will need to limit cumulative carbon dioxide emissions to less than one trillion tonnes of carbon. But the case for limiting cumulative emissions to less than one trillion tonnes of carbon is even more immediate: to avoid temperatures more than 2°C above pre-industrial in the next century, we have to keep cumulative emissions below a trillion tonnes regardless of the long-term concentration of carbon dioxide we aim for thereafter.