Dear Tom,
Would the world’s weather be different if the water in the oceans were fresh rather than salty?
Simmy Thompson

Dear Simmy,
There would be no change. The climates around the world and the world’s weather would be exactly the same if the oceans consisted of fresh rather than salty water.
Water is an important component of Earth’s climate. Water in the atmosphere results from the vaporization of liquid or frozen water on the Earth’s surface and also from the exhalation of volcanoes and thermal features, but water vapor is always fresh water.
Only pure water exists in vapor form. All other substances that might be contained in the water, such as oceanic salt, are left behind when water evaporates. (Ocean spray, however, leaves behind tiny salt particles floating in the air when it evaporates.)