Nah, you can't just say less forest == higher temperatures. Earth temperatures have been much higher in the distant past with plenty of forests covering her land masses.
Alexis is right that deforestation is one variable in a rapidly unbalanced equation that makes up our atmosphere mix.
A cool book to read on the widespread environmental impact of deforestation is
"Collapse: How Societies Choose to Fail or Succeed" by Jared Diamond. In the first hundred pages or so he does a deep dive of how humans were wiped off the face of Easter Island as a result of overtaxing the land. An interesting analysis of a more contained micro-ecosystem.
I also caught that Seattle Weekly article. The good news is that recently they passed Washington State legislation designed to provide incentives for urban forestry to repopulate some of the canopy. They've eliminated most of the loopholes.