I would like to plant some trees to further my personal efforts to halt global warming. This article says that it may only be a relevant thing to do in the tropics, while in the more temperate areas it can increase the process.

https://publicaffairs.llnl.gov/news/news_releases/2006/NR-06-12-02.html

Any recommendations?

Rex Weyler: This article is referring to the albedo effect, the reflective qualities of snow-covered land versus darker forests cover. This is, indeed, a counter-impact of forests. Nevertheless, planting trees anywhere, anytime, is a positive act. Trees absorb carbon. The best place to plant trees for this effect is in regions that once had trees that were removed. So replanting clear-cuts or urban areas is always a net benefit. It is true that as the climate warms and forest move both farther into north and south latitudes, the darker forest cover will absorb more heat than the snow-cover. But you don’t need to worry about this in regard to planting trees. Plant as many as you can.