We all know that weather can change quickly, sometimes 

in only a few minutes. Climate also varies, but over longer 

periods of time. You may have heard someone say, “Expert 

weather forecasters can’t accurately predict what the weather 

will be next week; how can anyone possibly know what the 

climate will be years from now?”

The answer is that forecasting climate is not the same 

as forecasting weather. Local weather predictions 

are based on natural processes that are more 

random and by their nature are difficult to precisely 

predict. Earth’s climate systems, though, obey 

the basic physical laws that operate throughout 

the Universe. For example, when a planet’s 

atmosphere traps heat, the planet’s surface tends 

to become warmer. This means that the behavior 

of the climate system can be understood and 

predicted by careful scientific studies. Environmental 

observations are the foundation for these studies. 

Instruments carried on satellites, ships, buoys, weather 

stations, and other platforms can gather information about 

many pieces of the present climate system. Information about 

past climates can be found in natural records such as tree 

rings, ice cores, and layers of sediment, as well as in historical 

documents and local knowledge. 

This information can be combined with theories about 

climate to construct computer models that make 

predictions about what the climate will be when the 

ocean and atmosphere have certain characteristics. 

Comparing these predictions with knowledge 

about actual climate when these characteristics 

exist allows scientists to improve the computer 

models and make additional observations and 

experiments to make better predictions about 

future climate conditions. 

A lot of research has been done about Earth’s 

climate system, and climate prediction models 

continue to improve. Today’s climate models are able 

to reproduce the average global temperature changes that 

occurred in the 20th century when they include all of the known 

natural and human-caused factors that affect climate. This gives 

us additional confidence that predictions about future climate 

conditions provide accurate information that will help societies 

decide how to prepare for the impacts of climate change.

How It Works

Weather Vane: Winds are named according to the direction 

from which the wind is blowing, so a “north wind” is blowing 

from the north. The head of the Weather Vane will point to the 

direction from which the wind is blowing. 

17

Activity 5: How Do We Know?

What You Will Do: Make additional weather sensors; set up a home weather station

What You Will Need*

Wind Vane Materials

Adult partner

1 – Broomstick or long wooden dowel, about 1 

inch diameter

1 – Aluminum baking dish, about 6 x 9 inches

1 – Wood stick, about 3/4 inch square and 12 

inches long

1 – Nail, about 1 inch long

1 – Metal washer with a hole slightly larger than 

the nail

Duct tape

Small saw or serrated knife

Scissors strong enough to cut the aluminum 

baking dish

Ruler or tape measure

Silicone or other glue that will stick to aluminum

Leather gloves

(Optional) Hand drill, and small drill bit slightly 

larger than the nail

Barometer Materials

1 – Ruler, about 30 cm (12 in)

1 – Clear drinking glass, glass jar, or other 

container with sides tall enough to support 

the ruler

1 – Clear plastic drinking straw or piece of clear 

plastic tubing, about 30 cm (12 in) long

Clear tape

Modeling clay or chewing gum

(Optional) Food coloring, your choice of color

Rain Gauge Materials

• Straight-sided glass or plastic container, with a 

diameter of about two inches or less (such 

as an olive jar)

• Coat hanger or wire bent to make a holding rack 

(see Figure 4)

• Measuring spoons: One teaspoon and 1/4 

teaspoon

• Hammer and nails to secure the rack

• Felt tip marker

* Scientists use many different instruments to make 

measurements that help predict weather and climate; but 

only a few instruments are needed to set up a Home Weather 

Station that can help you make your own weather predictions. 

You need to be able to measure temperature, wind speed, wind 

direction, and atmospheric pressure. You already know how to 

make an instrument for measuring temperature from Activity 4. 

Table 1 lists some clues that will help you estimate wind speed. 

To complete your Home Weather Station, you need a wind 

vane to measure wind direction, and a barometer to measure 

atmospheric pressure.

Image courtesy NOAA.

Big Idea

Our understanding of the climate 

system is improved through 

observations, theoretical studies, 

and modeling.

 (Climate Science Principle 5)

Discover Climate: Activities from NOAA

oceanservice.noaa.gov
18 oceanservice.noaa.gov

Beaufort Scale

Table 1

In 1805, Sir Francis Beaufort invented a scale from 0 – 12 for estimating wind speed based on features that can easily be observed. 

Sailors still use the Beaufort scale, but professional weather forecasters usually report wind speed in miles per hour or kilometers per hour. 

(source: http://www.srh.noaa.gov/jetstream/ocean/beaufort_max.htm#beaufort)

Beaufort Wind Wind Forecast Observations

Scale No. Speed Speed Term Sea Land

 (km/hr) (mi/hr)

0 0-1 0-1 Calm Sea surface smooth Smoke rises vertically

1 1-5 1-3 Light Sea surface rippled Smoke drift indicates wind direction,

 wind vanes do not move

2 6-11 4-7 Light Small wavelets, crests have glassy Wind felt on face, leaves rustle, 

 appearance but do not break wind vanes begin to move

3 12-19 8-12 Gentle Large wavelets, crests begin to break Leaves constantly moving, 

 light flags extended

4 20-28 13-18 Moderate Small waves, numerous whitecaps Leaves, and loose paper lifted, small tree 

 branches move

5 29-38 19-24 Fresh Moderate waves, many whitecaps Small trees in leaf begin to sway

6 39-49 25-31 Strong Larger waves, whitecaps common, some spray Larger branches moving, whistling in 

 wires, umbrella use difficult

7 50-61 32-38 Strong Sea heaps up, white foam streaks off breakers Whole trees moving, resistance felt 

 walking against wind

8 62-74 39-46 Gale Moderately high (18-25 ft) waves, foam blown in streaks Twigs breaking off trees, walking 

 difficult

9 75-88 47-54 Gale High waves (23-32 ft), dense streaks of foam Slight structural damage may occur, 

 slate blows off roofs

10 89-102 55-63 Whole Gale Very high waves (29-41 ft) with overhanging crests, Trees broken or uprooted, considerable 

 sea white with foam structural damage

11 103-117 64-72 Whole Gale Exceptionally high (37-52 ft) waves, foam covers sea Extensive damage

12 118-132 72-82 Hurricane Air filled with foam, waves over 45 ft, sea completely white Countryside devastated

Discover Your Changing World with NOAA
19

5. How Do We Know?

Barometer: The water level in the barometer tube 

will rise and fall as atmospheric pressure changes. 

When atmospheric pressure increases, air presses 

on the surface of the water in the container 

causing the height of the water in the tube to rise. 

When atmospheric pressure decreases, there is 

less pressure on the surface of the water in the 

container so the height of the water in the tube falls. 

Decreasing atmospheric pressure usually indicates 

that a low-pressure area is approaching, and this 

often brings clouds and rain. Increasing atmospheric 

pressure often indicates fair weather.

How to Do It

Make the Wind Vane

Be careful of the sharp edges on the pieces of cut aluminum! 

Use gloves to protect your hands until the edges are taped.

1. Use the saw or serrated knife to cut a notch about 

1/2-inch deep into each end of the wood stick. 

The notches should be parallel (Figure 1).

2. Rotate the stick so that the two slots are vertical. 

Use the ruler or tape measure to find the exact 

center of the wood stick. Mark this spot on the 

upper surface of the stick, and drive a nail through 

the marked spot. Be careful: if the nail is too big, 

the stick will probably split. To avoid this, drill 

a hole slightly larger than the nail through the 

marked spot. You may need your adult partner to 

help with the drilling.

3. Cut the head and tail pieces of the Weather Vane 

from the aluminum baking dish using Figure 2 as 

a guide. Be Careful—The Edges Are Sharp! Use 

duct tape to cover the sharp edges.

Nail

Washer

Broomstick

or Dowel

Head

Tail

Wood

Stick

Figure 1. Wind Vane Assembly

Head

Tail

Figure 2. Wind Vane Pattern

Climate Science Principle 5. Our understanding of the climate system is improved through observations, theoetical studies, and modeling.
oceanservice.noaa.gov 20

Sample Weather Journal Data Form

Date Time Temperature Barometric Pressure Wind Precipitation Other Events

 Instrument NWS Speed Direction Type Amount

4. Fit the head piece into one of the slots in the 

wood stick and fit the tail piece into the other slot. 

Glue the head and tail pieces into place and allow 

the glue to dry.

5. Attach the Weather Vane to the broomstick or 

dowel, by placing the washer on one end of 

the dowel and hammering the nail through the 

wooden stick into the dowel. Be sure the stick still 

moves freely around the nail. 

6. Mount your Weather Vane outside where there 

are no nearby obstructions to block the wind. 

Try to get the dowel as high as you can while still 

keeping it steady and secure. 

Make the Barometer

1. Tape the plastic straw or plastic tubing to the ruler 

so that one end is lined up with the “1 cm” (“1/2-

inch”) mark on the ruler.

2. Stand the ruler-tubing assembly upright in the 

glass (or other container), and tape the assembly 

to the top of the container.

3. Fill the container about 3/4-full of water. If you 

want colored water, first mix food coloring with 

the water in another container.

4. Use the modeling clay or chewing gum (you’ll 

have to chew it until it is soft enough) to plug the 

end of the straw or plastic tubing near the top of 

the ruler.

5. Carefully pour out some of the water so the 

container is about half full. Be sure the lower end 

of the straw or tubing stays beneath the water 

surface while you do this! When you are finished, 

the water in the straw or tube should be higher 

than the water in the container. Your barometer 

is now finished. Since barometers are sensitive 

to minor changes in weather conditions, keep 

your barometer indoors for greatest accuracy. 

(See Figure 3 for finished barometer.) The water 

level in the tube will rise and fall as atmospheric 

pressure changes. When atmospheric pressure 

increases, air presses on the surface of the water 

in the container causing the height of the water 

in the tube to rise. When atmospheric pressure 

decreases, there is less pressure on the surface 

of the water in the container, so he height of the 

water in the tube falls. Decreasing atmospheric 

pressure usually indicates that a low pressure 

area is approaching, and this often brings clouds 

and rain. Increasing atmospheric pressure often 

indicates fair weather.

Ruler

Straw or

Plastic Tubing

Clay or Gum

Tape

Glass

End of Tubing Container

lines up with

1 cm mark

Figure 3. Barometer

Discover Your Changing World with NOAA
21

5. How Do We Know?

Climate Science Principle 5. Our understanding of the climate system is improved through observations, theoetical studies, and modeling.

Keep a daily record of outside temperature, 

barometric pressure, wind speed, wind direction, 

and recent precipitation or other significant weather 

events. When you record barometric pressure, 

record the height of the water in the barometer 

tube (using the scale on the ruler), as well as 

barometric pressure reported by a local office of 

the National Weather Service. That way, you will 

know how readings from your Home Weather 

Station barometer compare to measurements 

from barometers used by professional weather 

forecasters. 

Make the Rain Gauge

1. Rain gauges measure the amount of rainfall in 

cubic inches. So your first task is to make a scale 

for your container that shows how many cubic 

inches of water are in the container. One cubic 

inch of water is about 3 1/4 teaspoons, so you can 

draw the scale on your container by measuring 

3 1/4 teaspoons of water to your container, then 

drawing a short line at the level of the water. If you 

look closely, the top of the water will seem to be 

slightly curved and thickened. Draw your line so 

that it matches the bottom of the curved surface 

(which is called a meniscus). This line corresponds 

to a rainfall of one inch. 

2. Add another 3 1/4 teaspoons of water to the 

container and draw another line. The second line 

corresponds to a rainfall of two inches. 

3. Repeat Step 2 until you have at least five marks 

on the container. This will be enough for most rain 

events; but you may want to add another line or 

two, just in case!

4. Find a location for your 

rain gauge where there is 

nothing overhead (such 

as trees or a building 

roof) that could direct 

water into or away from 

your gauge. The edge 

of a fence away from 

buildings is often a good 

spot. Another possibility 

is to attach your rain 

gauge to a broomstick 

driven into the ground 

in an open area. Be sure 

to record rainfall soon 

after a rain event to avoid 

false readings caused by 

evaporation. 

Empty your gauge after 

each reading, and you are 

ready for the next event!

This activity is adapted from 

“Build Your Own Weather 

Station” by the Educational 

Technology Programs Team 

at the Franklin Institute, 

Philadelphia, PA (http://

www.fi.edu/weather/todo/

todo.html).

coat hanger or

vinyl-covered wire

glass or plastic

container

Figure 4. Rain Gauge