The 2015 Paris agreement saw 195 countries agree to limit global warming to below 2°C. At the current rate of emissions, to achieve the target of 2°C set in Paris, global emissions need to peak by 2020.
As long as emissions remain above what natural systems can re-absorb, the concentration of carbon and other greenhouse gases in the atmosphere will continue growing every year (even once emissions have started decreasing). If emissions do not peak by 2020, it will be almost impossible to avoid surpassing the 2°C target set in Paris – because the rate of decrease required after this point would need to be so steep as to be almost impossible.
This will also be a turning point for the sustainable development goals, which we are aiming to reach by 2030.