Gotta love a savior with a sagacious sense of humor!
Imagine a person who thinks they know someone, approaches them demanding favors from them, yet they don't know them at all. Now imagine someone demanding signs from the Lord after he returns according to prophecy (with plenty of signs already), obviously such a person does not know Christ. We can presume that the sign of Jonah would be what they get according to scripture:
...“Whenever it is evening you say, 'It will be fair weather, for the sky is red'. And in the morning you say, 'There will be a storm today, for the sky is gloomily red.' Respecters of persons! You know how to observe the appearance of the sky; do you not know how to distinguish the signs of this time? A wicked and adulterous generation seeks a sign, and a sign is not given to it, but the sign of Jonah The Prophet." Matthew 16:2-4
How would the sign of Jonah apply today?
Consider the times we are in and the apparent signs all around us indicating the truth of him who was sent to save us. It's true we needn't anymore signs than we already have, it would be presumptuous to think we deserve more than this. Jonah the Prophet was disobedient to God and needed to be put in his place, thus in an ironic turn of events "the sign of Jonah" in this case has caused the Lord to respond in quite a sagacious way yet again...