Explain what caused concentrations of CO2 to decline during cold glacial periods in the Pleistocene?

1.What caused concentrations of CO2 to decline during cold glacial periods in the Pleistocene?

2.Scientists say that changes in Earth’s snow and ice cover are both a cause and consequence of changes in climate.Explain what they mean.

3.What molecules absorb infrared light, but water vapor is not believed to contribute to global warming. Why not?

4.In what ways does deforestation contribute to the increase in greenhouse gases in the atmosphere?