Connecticut
NATURE
Common Core Standards CCSS.ELA-Literacy.RI.3.1-3.10/4.1-4.10/5.1-5.10
Can People Change The Weather?
Written by Michelle Eckman, Connecticut Audubon Society
Could you or I stop the snow from falling at any given point? Could we, at any moment, make a sunny
day turn rainy or a hot day turn cold? At any given point or moment, the answer, of course, is “No way!”
Sometimes we may even answer this question with an “I wish!” But, people can and do change the weather
over a longer period of time. This may sound unbelievable to you, but you shall soon understand how we
change the weather by what we do with our land.
American Heritage dictionary defines weather as the “the state of the atmosphere with respect to wind, temperature,
cloudiness, moisture, pressure, etc.” Another term related to weather is the water cycle. The U.S. Geologic Service explains that the water cycle is the movement of water from the oceans to the atmosphere and to the earth and return to the
atmosphere through various stages or processes such as precipitation, condensation, evaporation, and transpiration.
The weather patterns of any particular area are affected by its climate. Remember -- climate is the long-term condition of the
atmosphere in a given area; we consider climate over thousands of years. Our climates are changing all over the world, and so are
our short-term weather patterns. The burning of fossil fuels for energy is the major contributor to the speed of climate change, but
people engage in other activities that change the weather, too.
Let’s think about the water cycle for a moment. Condensation is the transformation of water vapor (gas) that has evaporated from
earth’s surface into liquid water in the atmosphere. Water vapor turns to liquid as it condenses into clouds and eventually those
clouds may precipitate in the form of rain, sleet, or snow.
Transpiration is the evaporation of water from plant leaves. Approximately 10% of the water in the atmosphere at any given time
is from transpiration; this is quite an important contribution and the key to one way people can change the weather. Imagine the
tropical rainforest. That habitat is filled with plants of varying heights, most with large and very broad leaves. Now think about an
arid desert, filled with cacti and other spiny plants with small and narrow leaves. Both leaf types have strategies for dealing with the
water cycle in two different climates. Which habitat rains more? Obviously the rainforest receives more rain. Which type of leaf do
you think transpires more water – a large, broad leaf or a small and narrow one? Again, this answer is obvious – the large leaves
will lose more water because there is more surface where the water can be lost.
Think about what would happen if people planted tropical plants in the desert. You would think that those plants would not survive
– they would not receive enough water. And you would be correct. However, millions of people have been moving to the deserts of
New Mexico, Arizona and California over the past several decades where they have built large cities. Millions of those people have
planted tropical plants in their yards and throughout their cities and water them to keep them alive. And over these past several
decades, do you know what has happened as a result? It rains more in these cities than it did over 100 years ago. Why is this happening? Transpiration! Tropical plants with their large, broad leaves are transpiring more water into the atmosphere than the native
plants that typically grow in those deserts. The result is more condensation and therefore more precipitation. A total change in the
water cycle with huge effects on the plants, animals and people that live in these areas!
What do you think happens when people cut down large areas of plants? When an area loses plants, there is less transpiration.
When there is less transpiration, there is less condensation and ultimately, less precipitation. Scientists have a term for this process: desertification. In fact, there are thousands of miles of tropical rainforests in South America and
Africa that have become deserts because people have cut down the trees so they could graze cattle on the
fertile soil. Over time, the lack of tropical plants contributing water to the atmosphere through transpiration
affects all of the plants and animals that depend on the weather patterns of the tropical rainforests. And
ultimately, this affects all organisms on the planet because the tropical rainforests contribute most of the
oxygen in the atmosphere on earth.
As you can see, over time, people, including you, can change the weather. The fact that you now
understand how people can change the weather, you can do things to help by preserving trees and
conserving water use.
Student
Did You Know?
Activity
Planting native plants is one of the best ways to help
maintain the weather that all of the plants and animals
that depend upon it. Native plants are those that have
lived in a given region for hundreds of years and are
adapted to the local climate, weather, soil, etc.
You can easily find out what types of plants are native to
Connecticut by visiting the state’s Department of Energy
and Environmental Protection’s website about Native
Plants:
www.ct.gov/deep/cwp/view.asp?A=2690&Q=322452
Prove it:
You can easily get proof that plants transpire water. All you need is:
a plant, 2 plastic bags, 2 rubber bands, and a little time.
1. In the morning, tie a plastic bag tightly on a branch, sealing in
at least a few leaves. Use the rubber band to hold the bag onto the
branch. Try to seal the bag with the rubber band as tightly as possible.
2. Repeat this process on a branch without leaves as a control experiment.
3. Go on about your day. You will need to leave the bags on the branches for at least 2
hours. It is okay if you leave the bags overnight.
4. Remove the bags from the branches and count the water droplets inside the bags – any
water droplets outside the bag would not be from transpiration from the plant, but from condensation from the air.
5. Which bag has more water droplets?