Temperature Graphs: Why Baselines Matter

May 24, 2019

Climate geeks will find this elementary – but not everybody is a climate geek.

Deke Arndt on Twitter:

The pretty graphic upthread is the annual global temperature anomaly (or departure) from the 20th century average. Each red dot is an individual year. Dots above the black line were warmer than the 20th century average; dots below were cooler than the 20th century average.
Pink bars are decadal average anomalies, very simply the average of the ten red dots in a decade. The most recent decade is in a different shade because it’s the current one, and partly it only has 9 member years. It’s getting warmer, but that’s not why we’re here right now. 3/n
We’re here to look at base periods, and how they [DON’T] affect things. Here’s the very same data, but with pretty red circles plotted as less pretty blue and red bars. Same logic applies. You can click this here very graph in CAG:

The trend since 1880? 1.26 degrees Fahrenheit per century (0.70 deg Celsius). 5/n
Sometimes, this data is plotted versus the 1981-2010 average (often called “normal” – a problematic but historically entrenched term). The red circles are lower; because they’re being compared to the warmer 1981-2010 period. But the trend is identical: 1.26 deg F / century. 6/n

The trend since 1880? 1.26 degrees Fahrenheit per century (0.70 deg Celsius). 5/n
Sometimes, this data is plotted versus the 1981-2010 average (often called “normal” – a problematic but historically entrenched term). The red circles are lower; because they’re being compared to the warmer 1981-2010 period. But the trend is identical: 1.26 deg F / century. 6/n

Sometimes, people want to compare to “preindustrial” times. We often use 1880-1900 as an imperfect but representative proxy. The circles in this case are higher, because the comparison period is cooler, but the trend through the years is the same: 1.26 deg F / century. 7/n

Changing the “base period” moves the dots up and down in unison (probably better to say the y-axis moves, but let’s not complicate things). Each frame tells us something relevant to a specific period of reference. The rate of change is not altered. 8/n Similarly, in life, perspective helps us see details relevant to our point of view, but perspective does not change the truth. Your perspective is unique and beautiful. So is the truth. They work together to make your life rich and worthwhile..

25 Responses to “Temperature Graphs: Why Baselines Matter”

  1. Terry Donte Says:

    Since we are talking about grafts why not throw in the satellite data grafts? Try the
    STAR data set. https://www.star.nesdis.noaa.gov/smcd/emb/mscat/

    It is going the other way.

    • Peter A. Dimitriou Says:

      Apples and Oranges when you are talking about the Troposhere (or lower) as compared to the stratosphere. Nice try though. #getsomescienceeducation.

    • jimbills Says:

      Ya know, earlier today I was going to make a snarky comment here along the lines of “I wonder what sort of mental gymnastics a denier would have to do to look at that chart and think it doesn’t mean anything”. But then I thought, “Ah, you know they’ll be able to manage it. It’s what they do.”

      In response to your comment:

      A) https://skepticalscience.com/Stratospheric-Cooling-and-Tropospheric-Warming.html

      B) Most humans and animal and plant life do not live in the stratosphere. Neither do the ocean, glaciers, forests, and farmland exist there. In other words, one chart has more relevance to our situation that the other. Guess which.

      • dumboldguy Says:

        Looking at the spatial trends graphs at the bottom of Terry’s link raises the possibility that he is also color-blind (in addition to being a denier, a bad speller, and a Moran).

        • jimbills Says:

          He’s trying a pun – ‘graft’ instead of ‘graph’. So he’s also saying he thinks it’s a fiction. A nice hedged bet there – a well executed mental backflip.

          Anything he doesn’t want to believe is fiction, and the things he does want to believe aren’t fiction – because life works that way.

          The chart referred to is in the bottom left corner of your link, Terry. Ch2/TMT. I know, it’s a fiction, right?

          • dumboldguy Says:

            A pun and a well executed mental backflip, you say? You are being far too kind.
            It is a stretch as a pun, and ceased to be funny the second time he used it.

          • jimbills Says:

            I am complimenting his remarkable capability to warp reality to fit his worldview. Some people are just really, really good at mental gymnastics – deniers are some of the best at it. Anything little thing at all is blown up to obscure the obvious staring them in the face.

            Terry employed a chart he didn’t understand fully, but he liked it because to him it showed he didn’t have to believe the chart in Peter’s post. But just in case – he also called both charts ‘grafts’. Just in case – because he could still fall back to the position that it’s all just made up.

            Katelyn Ohashi can do real gymnastics:

            Terry can do mental gymnastics.

          • redskylite Says:

            I agree with the DOG – maybe you are being too kind to ” Terry Donte” on his use of the word graft. I just got a feeling of Déjà vu because Terry has changed his blogging name at least once or twice and we have discussed this before on crocks, he has never answered and I suspect he doesn’t read responses to his postings. I have just been reading old posts, but couldn’t find his old identities, but was amazed at reading some of my old forgotten contributions – I think I have declined or just got fatigued.

            Amazed Peter has keep up challenging our beliefs and keeping us mentally agile – on so many vital topics. Thanks Peter for keeping it real and warding off dementia and nasty age related mind problems.

            Lets hope that some really good news breaks soon and we can toast with a well earned celebratory beverage.

            At least we have a log of historic major events over the last decade on wordpress, with some great views, visuals, videos and gems.

            Yours in appreciation.

    • rhymeswithgoalie Says:

      Adding greenhouse gases makes the temperature of the troposphere go up while the temperature of the stratosphere goes down. This is because the infrared radiation from the planet is being trapped by GHGs and no longer warm the stratosphere. If the warming were just a matter of increased insolation, both the stratosphere and the troposphere would warm up.


    • LOL! Is this meant to be a joke?

      Stratospheric cooling is an expected sign of ‘greenhouse’ gas warming.

    • Do you know the difference between the troposphere and the stratosphere?

      Once you get that nailed down, we can proceed.

    • rsmurf Says:

      You really like showing your ignorance.

  2. Boyd Carter Says:

    Until “annual global temperature” is well defined and everyone agrees with the definition, none of the examples make any sense.

    • jimbills Says:

      Good scissors kick, Boyd! Until 100% of people agree on the thousands of data points gathered, collated, and analyzed by scientists for decades then we have absolutely no idea that the Earth is warming.


      I mean, the data sets collected from agencies all over the world are so far off from each other, we haven’t had direct temperature readings for every square mile of the planet for 100+ years, plus we really need to get everyone person to agree to the results before we can even begin to consider it accurate:

      • rhymeswithgoalie Says:

        Until 100% of people agree on the thousands of data points gathered, collated, and analyzed by scientists for decades then we have absolutely no idea that the Earth is warming.

        I dunno. Maybe all of the missing polar ice is disappearing through a cross-dimentional vortex established by Reptiloid Queen Elizabeth and her invasion fleet.

        I mean, can we really be sure it’s due to increased heat?

        • jimbills Says:

          No! We can’t! And until we figure that out and everyone agrees to it, then absolutely none of this global warming data collected by hundreds of scientists all over the world makes any sense!

        • dumboldguy Says:

          Maybe it’s due to decreased cold rather than increased heat? Terry?

          And what percentage out of all the scientists on the planet are gathering this data anyway? Hundreds, thousands even? That’s not many—-what do all the OTHER scientists think?

    • NASA, NOAA etc don’t’ report “annual global temperatures”; they report “annual global temperature *changes*”.

      Go to https://data.giss.nasa.gov/gistemp/graphs_v3/ and look at the temperature plots there. Examine the Y-axis range on the plots. What does the Y-axis range represent?

    • rsmurf Says:

      Keep trying!

  3. rhymeswithgoalie Says:

    Sometimes I get downright petulant when even climate scientists that should know better talk about surface temperature rather than cumulative heat. The ocean takes up the bulk of the heat and ENSO is just an irregular tide of heat moving back and forth between the ocean and the atmosphere.

    Yes, yes, yes I know that 99.99% of people don’t know the difference between T and heat, so they have to speak in those terms, but I still reserve the right to pout about the communication.

    Next pedantic rant in [ 45 ] minutes.

    • jimbills Says:

      Hi. I’m using sarcasm that’s not quite working, so okay, I hear you.

      I’ve been suspecting you’re right about Terry not checking back as well. That suggests he’s purely a troll – a guy whose purpose here is mainly to sow confusion. A true believing denier would most likely check back and enter into endless arguments to maintain their beliefs – at least occasionally. Has he ever done that?

  4. redskylite Says:

    This is a graph of a terrifying future awaiting, and the time to slow and plateau the upward trend is nearly out (if not already burnt away).

    With the school protesting escalating, something drastic must give soon.

    An Earth scientist, with aid of graphs and visuals reminds us, hope the oblivious wake up from their plastic reality and join the thrust to progress.

    Climate change: ‘We’ve created a civilisation hell bent on destroying itself – I’m terrified’, writes Earth scientist.

    “Oh, I think we’re heading towards 3°C at least,” he said.

    “Ah, yes, but heading towards,” I countered: “We won’t get to 3°C, will we?” (Because whatever you think of the 2°C threshold that separates “safe” from “dangerous” climate change, 3°C is well beyond what much of the world could bear.)

    “Not so,” he replied.

    That wasn’t his hedge, but his best assessment of where, after all the political, economic, and social wrangling we will end up.

    “But what about the many millions of people directly threatened,” I went on. “Those living in low-lying nations, the farmers affected by abrupt changes in weather, kids exposed to new diseases?”

    He gave a sigh, paused for a few seconds, and a sad, resigned smile crept over his face. He then simply said: “They will die.”


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