It started with the rain machine. In our own hubris, we tried to "fix" the weather. But luck was on humanity's side, and we succeeded. The Earth cooled, and it rained. So, we tried again.
The rain machine was repurposed in the way only mankind could repurpose it -- it became a weapon. Hurricanes struck enemy countries and tornadoes ripped apart cities.
The protests began -- people demanding a return to the old ways of warheads and bullets.
The people would cry out, "you can't stop a force of nature. We cannot play God like this for long."
The rain machine brought the rain and soon all countries had some version of the device. The storm was swift and fierce, burying continents in water -- for 40 days and 40 nights.
The Earth was clean and new.