Trees planted in the US and EU generally result in darkening the Earth's albedo, meaning that the Earth absorbs more solar energy than it otherwise would, resulting in increased warming.

Trees planted in the tropical climates, especially in those areas where trees were removed, generally have the opposite effect because they encourage cloud formation, lightening the earth's albedo and reflecting more solar energy away from the planet.

My understanding as a layperson is that trees do pull CO2 from the air, but they trap it in the tree itself, rather than putting it back in the ground. When the tree dies, or is cut down, or burns in a wildfire, "most of the carbon trapped in their trunks, branches, and leaves simply returns to the atmosphere".

I'm all for planting more trees; but it took hundreds of millions of years for all the carbon of dead organic matter to accumulate as it has, and we're returning it to the atmosphere (and ocean) in the space of a few hundred years. It's infinitely easier to not pull that carbon out of the ground in the first place, rather than trying to put it back.

If you read the article, they discuss it there.