Let me ‘splain.
If you want to know exactly where your dog is, you could put at GPS sensor in the middle of it’s body, perhaps near the pancreas. It would give you an average position for your dog, and would be most accurate most of the time.
If you put the GPS sensor on the tip of the dog’s tail, and used that to estimate where your dog is, you would be nearly wrong much of the time, even if over the long term this would be a good estimate for where your dog has been.
More importantly, if you wanted to measure the movement of your dog, the GPS sensor in the middle of the dog’s body would tell you pretty accurately if the dog is moving or still. But a GPS sensor on the tip of the dog’s tail would often indicate movement when the dog is, essentially still (but wagging its tail).
The question has been brought up: Is global warming stalled? People suggest this because atmospheric temperatures have not gone up as much as they might be expected to go up if we used a straight line matched to the last 30 or 40 years of data. Like this:
(That graph is from here.)
Thinking that this means that global warming has stalled, however, is like thinking that your dog is on the bottom step of your porch jumping up and down, when really, it is on the top step of your porch sleeping (and the dog’s tail is hanging down by the lower setp, wagging because it is having a happy-dream).
When the sun’s light reaches the earth, a certain amount of it bonces off shiny things and goes back into space. The light that does not bounce off is absorbed momentarily by atoms and converted to heat. That heat eventually goes out into out space as well, but it takes time. Greenhouse gasses in the atmosphere cause the departure of the heat to slow down. Increased greenhouse gasses have caused the entire system to heat up because the atmosphere does a poorer job conducting this heat to the upper reaches of the atmosphere and beyond.
But, only a tiny percentage of the sun’s energy that is converted to heat actually contributes to warming of the atmosphere and thus to things like how hot it is outside, or how much evaporation there is (which causes both drought and heavy rain, depending). About 93.4% of this energy actually goes into the ocean, 2.3% into the air, and the rest into other things.
For this reason, when you focus on just the heat in the atmosphere (or, for that matter, just the atmosphere and the surface of the sea), to measure or describe global warming, it is like tracking the tip of your dog’s tail to determine its location, instead of the body of the dog. It will work, and over time be a good approximation of global warming/dog location, but over shorter time scales, looking only at the atmosphere/tail will show more variation than is useful in answering the important questions.
Those important questions being “Is global warming continuing?” and “Where is my dog?”
Don’t let the tail wag the dog.
Dog Tail Photo Credit: buzzsnap via Compfight cc
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As someone who works professionally, communicating science to the public I find your analogy to be a great means to address this issue of the alleged “stalled warming”. Thank you for the good idea!
I really like this analogy, too. But there’s one thing I’d like to add: today we have only the tail to put our sensor on, say, we can measure the global mean surface temperature to a good approximation but trying to specify the global mean temperature of the oceans is nearly impossible. That’s why we stick to the first.
That is indeed a fantastic metaphor, and Mark nails the reason why we’re stuck using the dog’s tail anyway. It’s the part we can reach most easily, since a tail is easier to grab than a pancreas.
Of course, even in that graph showing that temperatures haven’t risen as much as expected, there is still a very strong trend. Looking at just the last two data points is a very poor way of assessing the data, and I think even most of the strident climate change denialists know this. They just hope nobody notices.
Very well done!
Sadly, out in the world of newspaper reporting, the stories are all about wagging (or not) tails. Here’s another one
http://www.spiegel.de/international/world/interview-hans-von-storch-on-problems-with-climate-change-models-a-906721.html
I like the bathtub analogy because it will work for this issue and works for the attribution issue. What do you all think of this analogy?
Basically, if you have a bathtub with cold water in it, say half full, and start adding hot water to it, it takes quite a bit of water to start making the cold water noticeably warmer, particularly at the far end of the tub.
The more you mix the water, the faster the difference is felt at the far end. However, if you mix more slowly, heat builds more quickly where the hot water enters and takes more time to equalize with continued mixing.
Meanwhile, the entire time the average and/or mean temperature of the water in the tub – and the tub and the bathroom, for that matter, are rising regardless of the distribution.
Regarding attribution, the level and heat of water in the tub is climate and the waves generated represent weather.
Imagine slowly filling the tub with water while sloshing the water back and forth with your hand. In the beginning the waves created are small. As more water enters the tub the waves get bigger and more splashing and sloshing occurs.
Since we are also adding heat, more energy is entering the tub, so the hand sloshing moves with more energy, i.e. faster and harder. The waves thus get even bigger. The eventual result is waves crashing over the edge of the tub and flooding the bathroom.
Basically, as the well-known climate scientist who passe away recently said, every weather event has a climate component. Some will be within bounds of normal variability, as determined by preceding long-term means or averages, but more and more will be outside the bounds of the previous normal. But even those within the bounds are likely to have been more energetic than without the additional energy in the system.
misspelling.(which causes both drought and heavy raid, depending). should be(which causes both drought and heavy RAIN, depending).
“About 93.4% of this energy actually goes into the ocean, 2.3% into the air, and the rest into other things.” good to know! I have been looking for solid data on this for a while.
Are you aware that the chart of 10-year averages would actually point down if it used 2002-2011 or 2003-2012 data? 2001-2010 is flat, but later data is not (see http://rankexploits.com/musings/2013/hide-the-decline-trenberths-trick/).
If you’re using a chart to show that there have been similar flat decades in the past, don’t you think it would have been more straightforward not to omit the recent data?
Well jeff, if you add carbon dioxide to the atmosphere and let the system re-equilibrate, most of the extra energy eventually ends up in the oceans because they can hold more heat than the atmosphere can. I dunno if it is 93.4% of the total, but that sounds plausible.
It takes a long time for the system to equilibrate, though. Even if the atmosphere temperature drop of the last few years is real and not measurement error, the oceans are still getting warmer because they are still “catching up.”
Dubious, I address your comment here:
http://scienceblogs.com/gregladen/2013/06/19/why-you-sound-so-stupid-when-you-say-global-warming-has-stopped/#comment-131940