What is the meaning of "v'Esa'arem"?
Rashi: I will make them stormy in Galus - and so I did!
Radak: I will be pained with them in Galus. This is like "b'Chol Tzarasam Lo Tzar" (Yeshayah 63:9); Dibrah Torah k'Leshon Bnei Adam 1 (Brachos 31b).
Radak citing Ibn Ezra: I will bring a storm against them and scatter them in Galus. Malbim - I will not hear them (13), rather, so I will do to them.
This is an anthropomorphism. In truth, pain and emotions do not apply to Hashem. (PF)
What is the significance of "veha'Aretz Nashamah Achareihem"?
Radak: This is the opposite of "veha'Negev veha'Shefelah Yoshev" (7).
Who made Eretz Chemdah desolate?
Rashi: They did, via their sin. They caused the fast and lamentation.
Malbim: I warned them while Yerushalayim was serene. Also now that it is desolate, they do not hear. They cause the desolation to persist - it will not cease until they listen!