D&C 5

In a revelation given to the Prophet Joseph Smith at the request of Martin Harris, the Lord said to the Prophet -

"...you shall be ordained and go forth and deliver my words unto the children of men." (Doctrine and Covenants Section 5:6)

I believe that the Lord, sensing a concern of the Prophet that many would not believe his words unless he provided some proof, said -

"...if they will not believe my words, they would not believe you, my servant Joseph, if it were possible that you should show them all these things which I have committed unto you." (Doctrine and Covenants Section 5:7)

We know this was the case during the Savior's ministry in the meridian of time. Of the world in our day, the Lord said -

"...this unbelieving and stiffnecked generation—mine anger is kindled against them." Doctrine and Covenants Section 5:8)

And the Lord follows with this prophecy -

"For a desolating scourge shall go forth among the inhabitants of the earth, and shall continue to be poured out from time to time, if they repent not, until the earth is empty, and the inhabitants thereof are consumed away and utterly destroyed by the brightness of my coming." (Doctrine and Covenants Section 5:19)

For -

"...even as I also told the people of the destruction of Jerusalem; and my word shall be verified at this time as it hath hitherto been verified." (Doctrine and Covenants Section 5:20)

There are many ancient and modern prophecies of the destruction in the last days conditional if the people repent not - or in other words, believe the words of His prophets. This scourge or destruction will not happen all at once, but -

"...shall continue to be poured out from time to time..." (Doctrine and Covenants Section 5:19)

- suggesting to me that this will be periodic demonstration of warnings to assist many to repent. As the world becomes more numb to these catastrophic events, the more they will be past repentence and ripened for utter destruction.