When the topic of climate change arises the first thoughts that typically come to mind are vehicle fuel efficiency and carbon dioxide emissions. But there is a greenhouse gas that is significantly more abundant than carbon dioxide. In fact, scientists estimate this greenhouse gas to be approximately 3 times more abundant than carbon dioxide. Yet this greenhouse gas is generally not discussed by scientists and is not communicated to the public. Do you know what this greenhouse gas is?

Greenhouse gases allow direct sunlight (visible and ultraviolet) to reach the Earth’s surface unimpeded. When the sunlight (relative shortwave energy) heats the Earth’s surface then infrared (longer-wave) energy is re-radiated to the atmosphere. Greenhouse gases block the infrared energy from escaping the Earth’s atmosphere. This results in a build-up of heat in the lower atmosphere resulting in significant climate effects.

There are many non-environmentally friendly greenhouse gases inhabiting the Earth’s atmosphere that have the properties described above – they allow visible and ultraviolet light to pass through but block infrared. Some of these gases include carbon dioxide, ozone, nitrous oxide, methane and on and on...

The greenhouse gas that contributes most to the greenhouse effect is in fact water vapor. A rough approximation has water vapor contributing 60% to global warming whereas carbon dioxide contributes 20%. Much of the water vapor that exists in the Earth’s atmosphere is due to natural causes that the human population has no control over. Thus it is not part of our ecological footprint.

The effect of water vapor on the climate is poorly understood but it is speculated that it amplifies the greenhouse effect. As the atmosphere warms up more water vapor forms and has more of a greenhouse effect on the climate. On the other hand, water vapor may contribute to cloud formation that would block direct sunlight.  So the climate effect is fairly complex and current models do not accurately account for the effects of water vapor.

Some of the reasons why scientists “forget” to mention water vapor as a significant contributor to global warming are: (1) water vapor is mostly due to natural or secondary causes. Thus it is not considered part of our ecological footprint; (2) the climate effects of water vapor are poorly understood; (3) Unlike other greenhouse gases such as carbon dioxide, nitrous oxide and ozone, water vapor does not persist in the atmosphere for long periods of time (i.e. not for hundreds of years). Perhaps the most significant reason is that if us laymen believe that global warming and other climate effects are beyond our control then we will have a “why bother” attitude.

Before ending this post I would like to mention that several years ago President Bush stated his vision for America to be transformed into a hydrogen-based society, centered around the hydrogen fuel cell.  Now this was primarily to eliminate America’s dependence on fossil fuels, not to save the planet from the effects of climate change.

Now I would like to leave you with a question: Do you know what the output of a hydrogen fuel cell vehicle is? (And a second question: Do we know what we are getting ourselves into?)