Following from 1 & 2, we need to plant 1 trillion trees to offset global CO2 emissions from fossil fuels.
This doesn’t mean that we stop the other initiatives, it just means that with a simple (not easy) solution such as planting mini forests, we can offset our CO2 emissions and reap additional benefits.
The EU forest strategy for 2030 plans to plant an additional 3 billion trees. The report is very detailed and addresses concerns such as space needed to plant the trees, etc. as well as the tree planting benefits such as lowering temperature in cities by 2-8°C, diminishing air conditioning by 30% and saving 20-50% energy used for heating. 
The picture below is from Afforestt, a company following the Miyawaki Technique for planting dense mini forests. More than 3,000 forests have been created globally so far. One of the main benefits of this technique is that after 3 years the forests become self-sustainable and require no maintenance. 
Turns out that there is already a Trillion Tree Campaign. Worth checking out.