Water vapor released by nuclear power plants worsens climate change

Nuclear power plants release water vapor, a powerful greenhouse gas, but it rapidly condenses into precipitation due to the limited ability of air to store it. These emissions therefore do not contribute to the increase in the greenhouse effect.

The white plumes emerging from cooling towers have undeniably become the symbol of nuclear power in the collective imagination. Yet these plumes are nothing but water vapor.

Too short a stay to make an impact

As water vapor is a powerful greenhouse gas, it is legitimate to ask how these releases effect our environment. However, the capacity of air to contain water vapor is limited. In the lower atmosphere, the water vapor concentration is close to the saturation level and any additional water vapor ends up recondensing. Anecdotally, a molecule of water stays in the atmosphere for only two weeks, on average. This stay is far too short for the water vapor produced by nuclear power plants to have any impact on global warming.

Water vapor and global warming

But then, why do we often hear about the impact of water vapor on global warming?

The key to understanding this is the feedback mechanism. Any increase in temperature at the Earth's surface increases the permissible concentration of water vapor in the air, an increase in concentration which, in turn, contributes to the rise in temperature. It is important to note that the situation is very different in the upper atmosphere: as the air is not saturated with water vapor, additional vapor does not condense. This is one of the mechanisms of aviation's contribution to climate change.