What's the Difference Between Weather and Climate?

When concepts are as intertwined as weather and climate, it can be easy to mix them up. Learn the difference, and why it matters so much in discussions about the environment, in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:02):
Welcome to brain Stuff from How Stuff Works, Pay brain
Stuff Lauren Vogelbaum. Here. You might remember when in Republican
Senator James Inhoff of Oklahoma set out to refute the
quote hysteria over global warming by tossing a snowball around
inside the US capital. The obvious implication was, how could

(00:22):
the climate be changing that radically from humans burning fossil
fuels and pumping greenhouse gases into the atmosphere, since we
still have snowfall and chilly temperatures on a winter day.
But even if you're not a U. S. Senator from
an oil producing state, you might be wondering how it
is that scientists can predict climate trends over many years
but can't predict what the weather will be three weeks

(00:42):
from today. The reason is that weather and climate are
two very different things. Basically, whether it is what happens
today or tomorrow or this week, it's the day to
day variations. Climate, meanwhile, happens over many years. It's the
combined long term average of weather events. Scientists look at
climate in terms of fixed thirty year periods. Right now,

(01:04):
for example, scientists are comparing the daily temperature to the
period that started in nineteen eighty one and ended in one.
They'll shift forward ten years and start comparing temperatures to
the period between nine and twenty and so on. Scientists
rely on thirty year periods because it's an amount of
time that's long enough to produce meaningful comparisons, but just

(01:26):
short enough that any changes that occur will be subtle
without being imperceptible. Twenty years might not show enough change,
and fifty years might be too drastic. To make sense
of those, thirty year periods help us put the weather
on a particular day in the right context. Comparing the
temperature on December to the same day a hundred years
ago wouldn't provide that much useful information because the climate

(01:48):
was too different then, but comparing it to the average
of the temperature readings for every December five between nine
and twenty ten, when the climate conditions were pretty much constant,
makes it possible to say whether a given to number
five is an unusually cold or warm day. We spoke
with Jonathan Martin, a professor of atmospheric and oceanic studies
at the University of Wisconsin Madison. He explained or trying

(02:11):
to compare apples to apples when it comes to prediction.
Whether in climate are also very different. Weather forecasting, Martin explains,
is based upon observation of conditions that are already occurring
in real time in the atmosphere. Because those conditions only
exist for a short time, whether it can be reliably
forecast only over relatively short periods of ten to fourteen

(02:32):
days at most, though Martin said that's theoretical, My confidence
ends at day eight. Envisioning climate, in contrast, is much
more low resolution. Scientists are trying to project what the
trend will be over a long period, not what the
weather will be like on a specific day fifty or
a hundred years from now. That involves gathering and crunching
huge amounts of data in powerful computers and doing modeling.

(02:56):
We also spoke with Jeffrey S. Duke's director of the
Climate Change Research Center at Purdue University. He said, in
one sense, climate does not affect weather. It's a description
of the weather over a long period. You could turn
that around and say that climate provides you with information
about how likely you are to get a given type
of weather at a given time of year. But historically
the climate has been determined by the weather over long periods.

(03:19):
He continued In another sense, though, climate for a given
location is determined by a bunch of factors, such as
the latitude and position on the planet, which affects how
it is influenced by the circulation of the atmosphere and oceans,
and the daytime heating of continents. Climate is also influenced
by the composition of the atmosphere, the transport of water
from soil to air by plants, and other factors. On

(03:41):
a given day, the sum of all these influences determines
the weather, but as some of these larger scale factors
change over time, they will drag the weather and the
climate along with them. In recent years, some of the
sharp distinction between weather and climate has blurred slightly as
scientists have used increasingly phisticated models and accumulated knowledge in

(04:02):
an effort to figure out the extent to which some
specific weather events, say a hurricane, a heat wave, or
a monster snowstorm, is actually a function of climate change
driven by humans releasing greenhouse emissions into the atmosphere. By
running thousands of computer simulations, they can conduct what if experiments,
seeing how the atmosphere would behave if you removed one
factor or another. Although such analysis is still a work

(04:25):
in progress, Martin thinks that eventually it will be possible
to determine the extent to which specific weather events are
influenced by climate change. Some of that research is already
bearing results. The National Oceanic and Atmospheric Administration presented a
paper in December in which they concluded that three extreme
weather events in that year's record global heat, extreme heat

(04:46):
over Asia, and unusually warm waters in the Bearing Sea
would not have been possible without human caused climate change.
Today's episode was written by Patrick J. Keiger and produced
by Tyler Clang. For more on this and lots of
other stormy topics, visit our home planet, how stuff Works
dot com. M