Shifting Baselines and the New Normal: Visual Evidence of Climate Change

I recently read this post by Randall Munroe. Needless to say I was inspired, both by his message and technique. The media hypes up the ‘polar vortex’ and shows images of the United Sates freezing from Miami to Minnesota. Unfortunately, this is all too often seized upon as evidence that climate change (i.e. global warming) isn’t real. The fact is, the extreme temperatures we saw this January used to be normal. They seem extreme now because they just don’t happen that often any more.

What do I mean? Well, let’s look at Chicago’s historical weather data I downloaded from a NOAA weather station.

Brrrr? Well.. not really

Brrrr? Well.. not really

The number of days with a low temperature below 0˚F as fallen dramatically since the 1950’s and 1960’s (plot on the left). What’s more, the number of days with a HIGH temperature below 0˚F has fallen from around 35 frigid days per year to next to none. The polar vortex seems extreme now, in 2014, but would have been just another January day in 1950’s Chicago.

That’s cold, and people in sunny Florida, like me, might not be able to fathom such extreme lows. What I can fathom, however, is extreme heat. Unfortunately that is becoming more and more common in Miami.


The number of days with a low temperature above 70˚F is increasing rapidly. Used to be that low temperatures were above 70 for only 50% of the year. Now, they’re above 70˚ 66% of the year. Similarly, the number of days with a high above 90˚F is climbing steadily (aside from 1951, which may have had an anomalous heat wave). Bad news for snowbirds, they may have to start heading to Cuba or Jamaica to find the pleasant temperatures that popularized Miami as a vacation destination and winter retreat during the mid-20th century.

Because climate change is slow, our perception of normal shifts with it. Nowadays, the polar vortex is seen as a freak weather incidence, when that used to be the norm. Blistering hot days in Miami are now the status quo, when they used to be much rarer. Climate change requires a historical perspective, otherwise.. we’re in trouble.


3 thoughts on “Shifting Baselines and the New Normal: Visual Evidence of Climate Change

  1. Great post Nate. I was recently stuck in O’Hare because the fuel lines froze and planes couldn’t refuel. While 20 below (F) is a cold temp, it is by no means outlandishly cold and the inability to deal with even moderate cold in at a major airport in a northern city led to the needless delay/cancellation of thousands of flights.

    • Thanks buddy. I actually thought I scheduled this for tomorrow. Looks like I screwed up.

      I would like to throw out one caveat: Plotting a few years weather station data on a graph isn’t a rigorous assessment of climate change, and I certainly didn’t spend a lot of time on it. However, the point was more pedagogical (visual effects and whatnot). I’m not putting this comment here for you, but for other real climatologists who might get their knickers in a twist about this.

  2. Pingback: Chart of the Month: Declining extreme weather events in Miami | Climate Change Ecology

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s