1 ) 

Increased CO₂ in the atmosphere → warmer temperatures → plants grow quicker removing CO₂ from the atmosphere by photosynthesis → levels of atmospheric CO₂ reduced.

2 ) 

Increased CO₂ in the atmosphere acts as a greenhouse gas → atmosphere warms up → methane released as permafrost melts → levels of greenhouse gases increase.

3 ) 

Increased greenhouse gases in the → atmosphere atmospheric temperatures rise → increasing evaporation from the surface → water vapour condenses forming clouds → clouds reduce the warming effect.

4 ) 

Increased water vapour in the atmosphere acts as a greenhouse gas → atmosphere warms up → more water is evaporated from the oceans → vapour increases in the atmosphere.