The New Ice Age was an ice age that was newer than the other ice ages. Is there really anything else to say?
A few years after Weegee and his allies took over the Earth in 2026, they got bored and started randomly making things that humans liked illegal. This included the May kit, the primary cause of global warming. As a result, its effects were almost completely undone by the time I.M. Meen was reincarnated as the Ice King in 2079, allowing him to easily freeze everything north of Maine.
By the mid-2080s, most of the Weegees had decided ruling Earth in its new state was more trouble than it was worth and returned to the United 'Gees Universe. Many northern countries, like Canada and the United States, nearly collapsed, while those with more hospitable climates, like Mexico, thrived. Over the following centuries, numerous warlords tried to take advantage of this chaos, including the invading Mongolians of 2087, Hankborg's Texan rebellion of 2095, and even a pair of Hitler clones who were killed by Superman in 2102. Making matters even worse, Tatanga destroyed much of the planet's non-frozen surface in 2302, only to be killed by Overkill and Slugfest. Things only began to return to normal when a time-travelling Dr. Robotnik enforced a ban on all forms of water, including ice in 2355. Obviously, this created its own problems, but I won't get into that here.