In the complex dance of Earth's climate, water vapor takes centre stage as both a vital component and a significant consequence.
As Earth's most abundant greenhouse gas, water vapour plays a crucial role in regulating our planet's temperature and sustaining life as we know it.
"Water vapour is responsible for approximately half of Earth's greenhouse effect, a phenomenon where gases in the atmosphere capture the Sun's heat," explains Dr Rosemary Owigar, a climatologist. "Without these greenhouse gases, Earth's surface temperature would be significantly colder, about 59 degrees Fahrenheit or 33 degrees Celsius."
The water cycle, an essential natural process, sees water take on various forms as it cycles between the atmosphere, land, and oceans. "Water vapour is a key player in Earth's water cycle, transitioning between liquid water, solid ice, and gaseous form," remarks Jeremiah Lumbasi, a hydrogeologist.
Since the late 1800s, average global surface temperatures have risen by approximately 2 degrees. Evidence from satellites, weather balloons, and ground measurements indicates that atmospheric water vapour is on the rise in tandem with the warming climate. Intergovernmental Panel on Climate Change highlights a concerning trend: total atmospheric water vapor is increasing by one to two per cent per decade.
For every degree Celsius that Earth's temperature increases, the concentration of water vapour can surge by around seven per cent. However, Owigar clarifies this misconception. "Water vapour is not the cause of global warming; rather, it is an outcome of it. As temperatures rise due to greenhouse gas emissions, water vapour amplifies the warming effect initiated
"Rising temperatures lead to increased evaporation from both water bodies and land surfaces. The ability of warmer air to hold more moisture results in heightened concentrations of water vapor in the atmosphere," elaborates Owigar "The increased water vapor then traps heat radiated from Earth, preventing its escape into space. This in turn raises atmospheric temperatures further, creating a loop of warming."
The greenhouse gases present in Earth's dry atmosphere, including carbon dioxide, methane, nitrous oxide, ozone, and chlorofluorocarbons, comprise only a minute portion of the atmosphere, around 0.05 per cent.
