How fast should we start working on greenhouse gas emission reduction?

Climate change, though inevitable, can still be mitigated. If we are to enable the scenario with a maximum 2 °C increase, we need to construct emission targets corresponding to reaching that goal in a timely fashion. But how timely?

Already two years ago the New Climate Institute and the Netherlands Environment Assessment Agency compared the results of different organizations in determining the target years for greenhouse gas (GHG) and carbon dioxide (CO₂) net zero emissions.

• The Intergovernmental Panel on Climate Change (IPCC) reported in their Fifth Assessment Report (AR5) from 2014 that, if we want to have a 66% chance of meeting the 2 °C target, global GHG emissions should be net zero around 2100 and CO₂, the main contributor of GHG emissions, should be net zero around 2085. That is to say, if we start measures in 2010 to reach that target.
• The United Nations Environmental Program (UNEP) analyzed in 2014 what would happen if we started reducing emissions in 2020 rather than 2010, which is a more likely starting time for many countries. This led to global GHG emissions having to be net zero around 2075, and CO₂ around 2065.
• The Climate Action Tracker used the IPCC data but instead analyzed how we could have an 85% chance of meeting the 2 °C target. For this, GHG emissions would have to be net zero around 2070, and CO₂ around 2055. 

It seems that with our current research vision of 80% GHG emission reduction and beyond for 2050, we would not be able to achieve this target on time, and our emphasis should be on ‘and beyond’ even more. 

Figure based on Net phase out of global GHG emissions, NCI, 2015.