We are currently at an overall historical low temperature here on Earth. Sure, temperatures have ticked up slightly over the last two hundred years, but overall it’s near an all time low.
During earlier eras, the planet was far greener overall as the amount of carbon dioxide (plant food) in the atmosphere was far higher. Temperatures were much warmer, so water evaporated off the oceans in higher quantities and there was far more rainfall. We know this because of the massive amounts of oil and coal (dead dino plants) that were preserved from that era.
If we want to be truly efficient in capturing solar power, allowing more carbon dioxide in our atmosphere could be a solution as the Earth would become much warmer and greener. That would also use up the carbon dioxide we produce at a far faster rate.
Potential downsides could be that the temperatures increase beyond the range hot blooded mammals can handle, though there should still be plenty of north and south zones for us. It also would significantly change the types of plants growing, though this would be offset by a far higher amount of plants growing.