Global Warming and Daylight Savings Time
Date: Winter 2010-11
We were discussing global warming in science, today, and I
thought of a great solution! Why not eliminate daylight savings time
so that we would get less sunlight and not warm the Earth as much? My
teacher said that we would still get as much sunlight. But if the sun
sets at 7 instead of 8, wouldn't we have less sunlight? Please let me
know if this is a good idea.
I like the way you try to solve a problem! Let's think this one
through. Pretend we are in a place on Earth where there is 12 hours of
daylight and 12 hours of night. Let's say that the sun rises at 7 AM
and sets at 7 PM with standard time. During daylight savings time,
you are correct in saying that the sun would set at 8 PM. However,
since Earth is still turning at the same rate and that determines when
the sun rises and sets, during daylight savings time the sun would
rise at 8 AM. So in standard time we have sun from 7 AM to 7 PM, or 12
hours. In daylight savings time, we have sun from 8 AM to 8 PM, also
12 hours. So there really is not any change in the amount of daylight
from standard time to daylight savings time. It is just a matter of
shifting when daylight happens. Hope this helps.
Your teacher is correct. "Daylight savings time" has no effect on
how long the sun shines. If the sun sets at 7, instead of 8, it
rises earlier on 7 day. Daylight savings time is a simple convince
to give people more daylight time after work.
"the practice of temporarily advancing clocks during the summertime
so that afternoons have more daylight and mornings have less"
Here is something I want you to try: get out a ruler that has both
the inches and centimeter markings on it. Measure something, say
the edge-length of your computer, first in inches, then in
centimeters. You will notice that the number in the centimeter
measurement is higher than the number you got for the inches
measurement. But that did not mean that while you were measuring
the length of the object with the centimeter units that the length
changed, became longer, did it?
Now try this, using the inches measuring unit, measure the object
again, but this time, do not put the starting edge at the zero-mark
of your ruler. Put the edge at the 1-inch mark and measure the
length from there. You should notice that it will appear that the
length of the object has increased by one inch. Again, this does
not mean that the length of the object changed just because you
started at 1-inch and not at zero, did it?
It is the same with daylight savings time. How we measure time does
not affect time or anything that comes with that time (like the
amount of sunlight), the object is still the same regardless of how
we measure it. The 24-hour clock is a human invention which only
controls when we, humans, are awake, working etc. It does not
control the physics of the Earth.
Greg (Roberto Gregorius)
I think it is wonderful that you are thinking about ways that we can
help global warming.
To think about your idea, we need to consider a few things:
Global warming is something that affects the entire planet, no
matter how long the sun shines in a certain place. There are a lot
of things involved, such as sunshine, chemicals, and the layers in
Think about what the Earth does 24 hours a day, all year long. It
turns on its axis while moving around the sun at the same time and
is always going at the same speed. At a given place on the Earth,
the sun hits it as Earth turns.
Now, imagine a ball turning on a pole always at the same speed. If
you shine a light bulb on the ball, it is a bit like the sun shining
on Earth. The ball turns in the light at the same speed. If you
draw a vertical line on the ball, that line always comes back into
the light in the same amount of time. You could time this. Now, let
us say that you could draw a line on Earth and stand at a place in
space and watch the Earth turn. If you timed the turn from the line
passing and then turning around to the line again, it would take 24 hours.
No matter what time the clock on the wall says, it would take the
same time for the line to turn back into the light. So, the total
amount of light hitting the Earth over the course of the 24 hours is
the same no matter what time it is. So, stopping Daylight Saving
Time would not help global warming.
Unfortunately, how we set clocks does not affect how much sunlight
we get, just when we get up and go to bed.
Under daylight savings time the sun goes down an hour "later". But
it also gets up (rises) an hour later. The time the sun is in the
sky is the same the day before and the day after we mess with the
clocks. Under regular time, the sun sets earlier but rises an hour
earlier in the morning, too.
Next time we switch, look in the local newspaper at the sunrise and
sunset times for before and after the switch. The clock times
change with the clocks, but the time the sun is up [sunset time -
sunrise time] will no change.
It is kind of fun to think about what would happen if the clocks
really did control the amount of daylight.
Arizona, which does NOT go on daylight savings time, would be cooler
than New Mexico next door. As soon as you crossed the boarder from
New Mexico the temperature would drop several degrees.
And, what if we pushed our clocks back 10 hours? Would we start
another ice age? (That might make a neat science fiction story!)
Hope this helps
R. W. "Bob" Avakian
Sorry but, yours is not a good idea because
It will not have any effect on how much sunlight reaches the earth during
The hours that we set here on Earth, whether it be Daylight Savings Time or
Standard time is just the human way of measuring what happens naturally.
So we set noon (Standard Time) to be when the Sun is directly overhead and
midnight to be when the Sun is directly overhead on the other side of the
world. The universe does not care if we move the clock up an hour or back an
hour, so changing our clocks will not have an impact on global warming.
Here is another question you might ask:
Why are there 12 hours in the day and not 10 or some other number (after all
it is irrelevant to what nature actually does)? The answer to this
interesting question can be found at this URL:
Nice try! But there are still the same number of hours of day and night no
matter what time you call it. The earth does not know what time it is; humans
define the rules for telling the time. So, if we call 8 oclock, 7 oclock all we
have done is change what we are calling it. It does not change the hours of
When we set the clocks back one hour the sun sets one hour earlier. But guess what…
it also rises one hour earlier, so, the length of the day remains the same (it just
starts earlier and ends earlier). Earth still receives the same amount of incoming
solar energy, it just starts and ends earlier.
One reason why we use daylight saving time (not savings) is to take advantage of the
sun lit part of the day and avoid working when it’s dark outside.
We are now (January) in standard time; daylight saving time resumes when we set our
clocks forward on the second Sunday of March. In March, when we set our clocks ahead,
we will have sunlight later into the evening (saving daylight) and therefore we may
not use as much energy for lighting because it will still be light outside!
If we save energy, and burn fewer fossil fuels, we might reduce the amount of carbon
dioxide in the atmosphere, and thus slow down global warming.
There have been numerous studies that have tried to figure out if we are saving energy
(or not) by implementing daylight saving time. It is not a simple answer, but it is
nice to have light later in the evening, on summer nights, to play outside later and
enjoy the beautiful summer weather.
Can you come up with ideas for global cooling? We sure could use some new ideas…
Leslie Kanat, Ph.D.
Professor of Geology
Department of Environmental Sciences
Your teacher is correct. The amount of light that the Sun shines depends
upon where you are on the Earth's surface at a given season of the year. For
example, if you are at the North pole in the SUMMER, the Sun never "sets".
It's light for the whole day, but at the South pole at the SAME TIME, the
Sun never "rises". It is dark the whole day. The number of hours of sunlight
varies between these two extremes at intermediate latitudes. The number we
assign on the clock doesn't change the rotation or the tilt of the Earth.
That number makes no difference. It helps to understand, if you remember
that we use a 12 hour clock AM and PM. But the military and other technical
applications use a 24 hour clock, starting at midnight (time is 00:00
hours/minutes) turning to noon at (time is 12:00 hours/minutes) returning to
midnight 24 hours later at (time = 23:60 = 00:00 hours/minutes).
The best way to understand daylight savings time is to think about
what happens at noon. Noon is the point in the day when the sun is at
the highest point in the sky. When daylight savings time is NOT in
effect, we call this time of day 12 o'clock (assuming you are in the
middle of your time zone). During the time of year when DST is in use,
we call noon 1 o'clock instead. Whether DST is in use does not change
how the earth moves, just what numbers we see on our clocks.
- Isaac Tamblyn
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Update: June 2012