In 2016, several regions in the world smashed
their heat records for the third straight year in a row. Record warmth
occurred in Europe, Australia, and parts of the Pacific. California
also hit record high temperatures, including one of the worst droughts in history.
So what's happening with our weather? Are high temperatures the new
normal? Let's take a look at some statistical data from NASA
to see how summer weather in the northern hemisphere has changed since
1950. Summer temperatures vary a lot
even in a constant climate. But, if you take an average of summer
temperatures from year to year, and plot them on a chart, you'll
eventually see a pattern of numbers that resembles the shape of a bell.
This is a normal distribution of temperatures, or what's known as the bell curve.
In a constant climate, summer temperatures should fit this
bell curve shape. With average temperatures occurring most often
and extremely cold or extremely hot temperatures occurring less
frequently. So statistically speaking, if the average
temperature occurs here at zero, anything within one
standard deviation from zero is considered statistically the same -
or pretty much an average summer temperature.
But temperatures occurring two or three standard deviations away from zero
are considered statistically extreme. So the hottest and
coldest recorded temperatures would occur in these areas.
Now let's take a step back and look at what summer temperatures looked like 50 years ago.
We'll use this as our baseline for temperature comparison.
in the 1950s, 60s and 70s
summer mean temperatures were close to this type of bell-shaped distribution.
but in each subsequent decade, the
distribution of temperatures has shifted, with hotter temperatures becoming the new
norm. Notice that as the distribution curve shifted to the right
the probability of extreme heat greatly increased.
The decade of 2001-2011 showed record temperatures
nearly 5 standard deviations away from the normal temperatures of the
1950s, 60s and 70s. But also note that
the decade of 2001-2011 continued to show temperatures
of extreme cold. Some of the coldest temperatures were nearly 3 s
standard deviations away from zero. So even though the temperature pattern
showed an increased tendency for unprecedented heat, due to
variability in the weather, there were also brief burts of extreme cold.
Still the periods of extreme heat today already
far outweigh the periods of extreme cold. IN 2016
according to research from the National Center for Atmospheric Research
there were roughly 4 times as many days with record highs, as days
with record lows. So what's our takeaway from this?
Well, it's important to realize that normal temperature patterns are shifting.
If the temperature distribution curve continues to shift to the right
we'll probably see some pretty extreme effects. Warmer
summers will occur more often, and cooler summers will occur less often.
Rising temperatures will lead to more extreme weather patterns.
And the probability of extreme storms, heat waves, drought
and floods will increase. Of greater concerns are some projections
made by climate change models. According to studies by the National
Academy of Sciences, and the National Center for Atmospheric Research,
the ratio of daily record highs to daily records lows in the lower 48 states
could soar to 15 to 1 by mid-century,
and 50-1 by 2100.