You might not think water vapor in the air can impact the climate, but it can. This lesson will explore how water vapor and climate are related and will also explain how climate change is impacting the amount of water vapor in the air.
There’s a reason why Earth is called the blue planet. About 71% of the Earth’s surface is covered by water. There are 3,094 cubic miles of water in the atmosphere. Each day, 280 cubic miles worth of water evaporates and transpires into the atmosphere. And about 7,000,000 cubic miles of water can be found as ice in glaciers and ice caps around the world.
But how does water, mainly water vapor, impact climate variability on the blue planet? Before we get into that, we need to understand the words climate, temperature and climate variability.Temperature refers to conditions at a specific time and place. For example, today, in Fairbanks, Alaska, it’s currently 40 degrees F and sunny. Whereas climate refers to the pattern of weather over a long period of time.
For example, for this date, Fairbanks has an average temperature of 27 degrees F. Climate variability refers to the yearly variation in climate compared to the long-term average. For example, some winters are colder than normal, some have more precipitation, whereas others are warmer and drier.This lesson will focus on climate, and more specifically, how water vapor affects the climate.
The Greenhouse Effect
Water cycles through the Earth in the water cycle: evaporating and transpiring into the atmosphere and then returning to the ground through precipitation, ending up in plants, in the oceans, in freshwater ponds, and then evaporating; well you get the general idea. So, if you had to guess, do you think more water vapor in the atmosphere would make the temperature rise or decline? Well, let’s take a look!It’s a hot, sunny day, and the ground and water are warmed from the heat of the sun.
At night, when the sun sets, it starts to cool off. Now, without water vapor and other greenhouse gases, the heat from the ground and the lake would radiate back into space, and the Earth would get really cold at night.But greenhouse gases, like water vapor, capture that heat energy and then radiate it back. So, you can see how greenhouse gases get their name. They act like a greenhouse, trapping the heat. So, the more water vapor that’s in the atmosphere, the more heat energy gets radiated back to the Earth. So, to answer our question from before, more water vapor makes the Earth warmer.
You’ve probably already heard about climate change, or the change in climate patterns, and you’ve probably heard of global warming, or an increase in the world’s average temperature. But you may not be familiar with water’s role in climate change and global warming. Water is affected by global warming, and in turn leads to increased warming of the Earth. In fact, water vapor is responsible for about 60% of the warming, but why?As the overall temperature on Earth increases, more liquid water evaporates.
When the temperature increases, water molecules get more energy and are more likely to evaporate. With more evaporation, there is more water vapor in the atmosphere, which causes more heat to be radiated back to Earth.When more water evaporates into the atmosphere, several things can happen. First, warmer air can hold a greater amount of water vapor. In fact, for every 1.
8 degree F (1 degree C) rise in temperature, the air can hold about 7% more water vapor before it becomes saturated, or full of water vapor.A greater amount of water vapor in the atmosphere not only leads to more heat being trapped and radiated back to Earth through the greenhouse effect, but also more precipitation. So, there are areas in the world that are experiencing more rain and snow than they had in previous years.Yet another impact from increased water vapor is the intensity of storms. For example, cyclones are also impacted by water vapor in the atmosphere.
In order for a cyclone to intensify, it needs certain conditions, including warm ocean water, specific wind conditions and a lot of water vapor in the atmosphere. So, with an increase in water vapor in the atmosphere, scientists are finding cyclones are intensifying.The increased evaporation can cause droughts in other parts of the world, so while some areas are getting an increase in precipitation, other areas are getting less precipitation, or when it does rain or snow, they get an ‘all or nothing effect’, meaning they go long periods of time without anything and then a bunch at once, which can lead to flooding.
You can think of climate and water vapor as a continuing cycle. Each is impacted by the other. Let’s review why.
As the yearly temperature average varies from year to year, you can assume the amount of water vapor in the air will also vary, too. An increase in temperature results in more water vapor in the atmosphere for two reasons. First, higher temperatures result in more water evaporating. Second, there is more water vapor found in the warmer air versus colder air.
More water vapor in the atmosphere, in turn, raises the temperature of the Earth. This is because water vapor is one of the greenhouse gases, so it radiates heat energy back to the Earth and prevents it from radiating out into space. An increase in temperature causes more water to evaporate, which can cause droughts in some areas, whereas the increase of water in the atmosphere can result in increased precipitation and more intense storms in other areas.So, you can see water vapor is directly related to the temperature and climate variability. Depending on the yearly average temperature, you can expect different amounts of average water vapor in the air.
This can vary from year to year, causing droughts in some areas or increased storms in other years; however, as the world’s average temperature increases, you can expect more water vapor to be in the atmosphere each year.
After you’ve completed this lesson, you should be able to:
- Define temperature, climate and climate variability
- Recall why an increase in temperature results in more atmospheric water vapor
- Describe the impact of having more water vapor in the atmosphere
- Summarize the relationship between water vapor, temperature and climate variability