25 August 2010

Were the 70s cold?

I was surprised to see that the 1970s weren't particularly cold.  My surprise is partly because where I lived (Chicago area) we were busy setting all-time records for cold, and that was true for much of the US and across to the UK. 

The other part of the surprise is that it's common to hear people (see them write) something on the lines of "Of course we're seeing a warming since the 70s; it was cold in the 70s!"  Surely someone along the way did their homework and checked out what the global temperatures were?

Fortunately, if we're looking at science, we don't have to assume that other people did their work, or did it correctly.  The alternate word for it is, skepticism.  Real skeptics don't make those assumptions, they do the work themselves.  The fact that it's work also explains why there are a lot of fake skeptics -- it's much easier to pick the answer you like and reject everything else.

So let's apply some real skepticism and ask what was really going on with temperatures in the 1970s.
I'm working from the NCDC global mean temperatures.  I'll take the average of each decade they give, and plot that:

That's rather disappointing.  The 1970s were the 4th warmest (of 12) decades in that record.  Actually a little worse, as you'll notice I don't have the decade starting in 2000 computed.  (I downloaded the file in 2009, it's gotten warmer since then). 4th warmest of 13 decades, behind only 1940s, 1980s, 1990s, and 2000s. But -- be a proper skeptic -- compute for yourself the average for January 2000 through December 2009.  I got +0.35 for the 1990s.

My disappointment is twofold.  First off is that the decade that I remember as being so very cold, wasn't.  In my area it was, and even for a good distance away.  But the entire US is only about 2% of the globe.  The global average could easily be quite different, and turns out that it was.  The 1970s were a relatively warm decade.

The second part of my disappointment is that those people calling themselves skeptics are clearly not skeptics.  They never computed decadal temperatures, and never looked to see whether the 1970s were particularly cold.  Not only were they not cold, but they were warmer than the two decades before them.  Real skeptics would not claim that they were cold in talking about climate change.


rab said...

It's hard to find Chicago data that covers continuously from well before the 70s, but here's a good one near by

Robert Grumbine said...

Thanks RAB.

I hadn't seen that site before. The official recording stations for Chicago were Midway (from 1920s through about 1981) and O'Hare (since then), so splicing the two together on an eyeball basis ...

Darn. Averaged over the year, even those ferociously cold winters I remember were not enough to bring down the annual averages in the mid-1970s.

Alastair said...


I am not sure that your argument would hold water with the general public. I suspect that when they think of cold years they are remembering the winters, and when they think of hot years they are thinking of summers.

I don't have time to do the sums myself at present, but if no one gets there first I may have a go in a few days time.

Anonymous said...

I've always had the impression that the 70s were pretty hot in the UK, mainly due to the 1976 Drought. Being told that you have to wait until they switch the water on to drink on a scorching day is a memory that's stayed with me.

Robert Grumbine said...

Interesting thoughts Alastair and yea-mon.

You're both right, of course; and I illustrated the behavior myself. People tend to remember events, not long-term averages. And people put more reliability on things as they remember them than on what research reference would show to have been the case.

What we remember is weather, but what we're (sometimes) trying to think about is climate.

Steve Bloom said...

Hmmph. Well, I grew up in the upper Midwest during the time span, and I can tell you from personal observation that snows in the early '60s were mcuh deeper than in the early '70s.

Well, OK, I was a lot shorter in the early '60s, but should that be enough to discount my persoanl experience? :)

Regarding cold and heat, I would submit that we see the same effect: People will recall their initial experience with an extreme as more notable than it in fact was. Of course in my case the snow really was neck-deep ~1961. :)

Anonymous said...

I'm sure how people build to the local climate also plays a role, in addition to any first experience of an extreme.

E.g. In Northern Ireland our average summer temps are around 20 degrees C - one consequence of this is that we don't have air conditioning. Winters can be a little bit cold, but not snowy. Our homes tend to be built with central heating. You can see that with this set-up we are going to remember unusual heat more than unusual cold - as we can just crank up the heating with the cold, and we also lack the memorable visuals of heavy snowfall.

Robert Grumbine said...

Steve, yea-mon:
Even though I expect Steve was writing at least partly tongue-in-cheek, I think the points are good. We remember things against our own experiences. That includes our own height at the time. (I remember a certain snow as being more than head-height on me. Well, between the snow itself, the fact there was already snow on the ground, and the fact that I was less than 1 m tall at the time ....)

How well-adapted our area is to certain types of weather is also a factor in what is considered memorable. Even if we didn't think much of an event, the many people around us can make something remembered.

Anonymous said...

There's a lot of random images and clips being shuffled in this video but the point behind it talks about why the 70's were colder than most other times.