There is no carbon budget for 1.5°C, which means that to achieve this outcome, from now on every tonne of emissions must be matched by a tonne of drawdown of atmospheric carbon.
From high altitude reflecting aerosols, temporary cooling is estimated at 0.7°C, so global warming is likely to accelerate in the next few decades if the cooling influence of human-generated aerosols declines. When this is taken into account, the implied warming for the current level of greenhouse gases is more than 2°C.

http://www.climatecodered.org/2018/05/what-goes-up-must-come-down-its-time.html?m=1