CM8001

Water vapour is a greenhouse gas. Thus as more water is released into the environment, more heat energy get captured and radiated back to the Earth, making the Earth warmer.
Switching to a hydrogen economy may result in ozone depletion due to leakage of hydrogen gas.
Because of UV radiation, hydrogen gas may form free radicals that act as a catalyst for ozone depletion.

Fossil fuels were formed as the result of photosynthetic processes that took place hundreds of millions of years ago. Solar energy was a necessary ingredient in the formation, so the energy that is stored in chemical bonds in fossil fuels originally was invested from the Sun.

most of the electricity is generated using technologies that result in greenhouse gas emissions and are energy intensive. The capital cost of an electrolyzer unit is high as well as the balance of system, and energy got converting electricity to hydrogen is not very efficient.