Some pictures to explain climate change

It occurs to me that it’s not at all obvious why people worry about temperature changes of a few degrees. I thought it would be nice to have a few pictures showing why.

I went over to the University of Nebraska’s web site and downloaded the daily temperatures for Lincoln, NE for every day from 1920 to 1998. Here’s a plot of how the daily highs looked for just the summer months, June through August:

The blue area marks days over 95°F. I chose that temperature because (according to Purdue’s site) this is a day hot enough to significantly “stress” a corn crop, i.e. knock down its yield by several percent per day. (Less hot days can do damage too if there isn’t enough moisture, but 95 is trouble no matter what)

Now, the thing is: When people talk about the average temperature rising, what it means is that the center of this plot – the average daily temperature – moves however many degrees to the right. And every time you do that, more bars move into the “over 95” category. In fact, here’s a plot of how many days per summer would be over 95 as the temperature goes up:

Right now, there are about 18 days per summer over 95. If the average temperature went up five degrees Fahrenheit, you’d suddenly have 38 – out of 92 days in June, July and August.

There’s a bit more to it, too — when people talk about a “3°C global temperature rise,” what it really means is that some places (e.g. the Antarctic Ocean) get cooler, and some get a lot hotter. For example, Scenario A2, the worst-case scenario in the GISS-E paper that I’ve been talking about, talks about a 2.7°C global average temperature rise by 2100, but a 3.5 or 4°C (6 or 7°F) temperature rise for Nebraska.

It could be worse; the same model predicts 15 to 20 degrees F rise for India.

By the way, the second plot here is almost linear (for temperature changes up to ten degrees or so): the conversion is roughly that for every 1°C (local, not global) temperature change, you get an extra 7.4 days per summer above 95.

Anyway, this is the short science journalism post for the evening. Sorry if it isn’t horribly polished.

Published in: on May 10, 2006 at 22:19  Comments (7)  


  1. Maybe not polished, but the graphs speak volumes. Pictures are worth so much with this kind of data.

  2. Maybe not polished, but the graphs speak volumes. Pictures are worth so much with this kind of data.

  3. Thanks you, again.

  4. er…. Thank you. Wow, I can bollocks a three word sentence. 😉

  5. Doesn’t have to be polished, as long as you’re writing about it. Not enough other people are.
    I’m not joining your climate change community, because I don’t have the technical background to contribute much. But I’ll be reading.

  6. Eh…. I don’t know how much tech background is needed. But please keep reading and commenting!

  7. Congratulations and Mazel Tov!

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