That's the fourth angel, though. What about the first three? If the heat wave is the fourth bangel, what happened to the sores (first bowl), everything in the sea dying (second bowl), or the rivers and springs turning to blood (third bowl)?
I will jump in because it seems that everyone is trying to interpret God's prophecies with world events, Jerusalem Post, National Geography, or Astronomy Magazine.
We must allow Scripture to compare Scripture in order to find God's interpretation for his prophecies. Since the OP is asking about the fourth vial so I will explain that here for today. If you want to know more about the other bowls, ask me.
Revelation 16:8-9 KJV
[8] And the
fourth angel poured out
his vial upon the sun; and
power was given unto him to
scorch men with fire.
[9] And
men were scorched with great heat, and
blasphemed the name of God, which hath power over these plagues: and
they repented not to give him glory.
First I want to say that this has NOTHING to do with the physical sun, Earth's ozone layer, nuclear bomb, etc. Second, the vial judgment is not for the "world" but rather for God's unfaithful congregation, because the church is the New Testament Congregation of Israel, the body of Christ.
Jesus Christ is the "sun" which is the light of the world, and the church as the body of Christ is spoken of as the light of the world.
John 9:5 KJV
[5] As long as I am in the world,
I am the light of the world.
Jesus Christ is the light of the world.
Matthew 5:14 KJV
[14]
Ye are the light of the world. A
city that is set on an hill cannot be hid.
And we, as His Church, are the light of the world, because we represent Christ on Earth. The Sun is the visible light of the world, signifying also the kingdom of Christ on Earth. Therefore when the messenger pours out his vial on the Sun, it is God's judgment upon His unfaithful church!
Now, the messenger pouring out his vial upon the sun is an
illustration of judgment upon the church so that the people
therein are judged. The same illustration in Matthew 24 of the sun becoming blood and the moon not giving her light, it's signifying the fall of the church, as God judges her for
her degradations. It is because she is being judged that
these people within her blasphemed the name of God who had power over these plagues on her (spiritually Babylon) so that they would
NOT repent and giving God's glory. Why? Because of being deceived by false prophets and christs have usurped authority from God wherein they trust in themselves, they rule themselves as their own god, to do whatever is right in their own eyes. This is why God has loosened Satan to damn those who are snared in self-justification wherein they simply would not receive the love of the truth of God's word.
2 Thessalonians 2:9-12 KJV
[9] Even him, whose
coming is after the working of Satan with all power and signs and lying wonders,
[10] And
with all deceivableness of unrighteousness in them that perish;
because they received not the love of the truth, that they might be saved.
[11] And
for this cause God shall send them strong delusion, that
they should believe a lie:
[12] That they all might be damned who believed not the truth, but had pleasure in unrighteousness.
This is the judgment of the professed Christians who will believe the lies coming out of the mouths of false prophets and Christ. This is the same principle, which is God's loosing of Satan that His judgment of these plagues upon Babylon is poured out on the unfaithful church that she will never rise again. Revelation 16 speaks of them being
scorched with heat from the Sun to
signify this is God's judgment and they are overcome of the evil one that "He" has sent. Those faithful who "SEE" these abominations and come out of the church in time are those who endured great tribulation and trial to receive eternal life. Just as is pictured in James chapter 1.
James 1:11-12 KJV
[11] For the sun is no sooner risen with
a burning heat,
but it withereth the grass, and the flower thereof falleth, and the grace of the fashion of it perisheth: so also shall the rich man fade away in his ways.
[12] Blessed is the man that
endureth temptation: for when he is
tried, he shall receive the crown of life, which the Lord hath promised to them that love him.
See? Heat = Temptation or trail. The withered grass from the heat of the sun is those who are under God's judgment. God is testing people of his congregation all over the world. Those who refused to receive the love of the truth will not repent of their sin.
Revelation 3:10 KJV
[10]
Because thou hast kept the word of my patience, I also will
keep thee from the hour of temptation, which
shall come upon all the world, to
try them that dwell upon the earth.
But blessed are those that
endure trial/temptation because these are those truly in Christ who the heat cannot harm.
Isaiah 49:10 KJV
[10] They shall not hunger nor thirst;
neither shall the heat nor sun smite them: for he that hath mercy on them shall lead them, even by the springs of water shall he guide them.
Not literally smote by the physical sun. Rather with the Spirit of God, they will endure the trail/temptation. This is why God says, "come out of her my people, that ye be not partakers of her sins, and that ye receive not of her plagues", Revelation 18:4. The same plagues God says He has power over when
He scorched these men with great heat. In other words, God will scorch men with TEMPTATIONS (heat) as a judgment that they will NOT repent of their sin! That is the point that God is talking about here. There are a consistent theme and scenario that runs through this whole episode all throughout scripture.
Hope it helps.