4) Why do scientists investigate greenhouse gases?

When Earth's surface gets hotter, more evaporation occurs, which releases water vapor into the atmosphere. “Water vapor is a greenhouse gas. ... “That extra infrared heat evaporates more water vapor, which traps more heat, then, in turn, evaporates even more water vapor, and so on. It becomes a feedback loop.

explanation:

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.