Let me first tell you a story of a young student. Fast rewind to the beginning of the 1980s and this young, eager student took a practical exam chemistry. The exam consisted of some questions about lab practices and one practical test that had to be performed in the lab. That test was important because it counted for half of the points.
The easiest test that the students learned in that year was determining the amount of iron in a (self-prepared) iron salt solution. The procedure was pretty simple, it was by far the shortest test and the final calculation was also straight forward. Every student would get a different assignment, so all the students were dreaming of getting that specific question as their assignment.
At the beginning of the exam, the students had to draw a small piece of paper (with the name of the test that they had to perform) out of a box. When this young student drew his piece of paper out of the box, he read … determining the amount of iron in an iron salt solution.
Yabba dabba doooooo!
Imagine the joy he felt, realizing that this exam would be a walk in the park… He looked forward getting a good grade.
The questions were not that difficult and he could begin the assigned test of determining the amount of iron in a solution. The young student gathered all materials necessary and started the procedure. When performing the final titration, he however got an unexpected reaction. He was stuck and had no result.
No worries. Remember, this was the easiest and the shortest procedure. There would be plenty of time to do it again. So, he cleaned up and started all over again.
During the final titration, the worse thing that could happen happened: again this unexpected reaction.
Now it was time to panic … there was not enough time left to try it a third time.
Submitting the exam at this point would mean no result, so no points for this part of the test. That means that he would have to answer all the rest correctly to (just) pass the exam.
In full panic mode, he then came up with a cunning plan…
Unless the professor switched the substances, he knew exactly what iron salt he was dealing with. He also knew how much iron salt he used to make the solution. Therefor he could calculate exactly how much iron there was in that solution. The plan was to do the analysis backwards from the expected end result and see where that got him.
So he took his calculator and worked himself backwards towards the missing value. It worked like a charm. He then put the analysis in the right order and then proudly handed in his exam. He did well on the other questions and was confident of his master piece of backward engineering.
However, the smile disappeared soon from his face when it slowly started to sink in that he forget a crucial part in the calculation and therefor ended up with a difference of a factor of two at a certain part in the analysis. This meant that, from that point in the analysis, he started to calculate with numbers that were a factor of two too large and then calculate back to the desired end result in following steps.
Imagine the horror the student felt realizing that he worked with the wrong numbers, but, ahem, miraculously ended up with the expected result… Now there was no way that the professor wouldn’t notice that he fudged those numbers.
In the end, our young student passed the exam, but just barely. The other questions saved his neck.
For those who are wondering, that young student is of course me (at the tender age of 19).
I was reminded of this incident by reading the story that Daniel Fagre told the media about the model that spitted out that the “glaciers will be gone” by 2030 and his revision of the end date to 2020.
Let’s recapitulate. Two researchers used a model in order to figure out when the glaciers from Glacier National Park would be gone. They fed their model with temperature increase information forecast by the IPCC. The outcome of that model was that glaciers in Glacier National Park would be gone by 2030.
Time went by and actual observations on site revealed that the local temperature increase didn’t follow that of the IPCC, but that this increase was twice as great than they had put in their model. This new information compelled the investigator(s) in 2009 to set an earlier end date: according to the actual observed data, the glaciers would now be gone by 2020! This grim message was broadcast via the media as proof that impacts were worse than predicted. The estimate also got onto the National Park Service website and also onto the diorama signs in the visitor center (this is what inspired me to start this series).
Then 2020 came closer and it didn’t look good for the 2020 estimate. Justifications were stated why the 2020 estimate was wrong and the signs of the diorama were replaced. The 2020 end date was already removed from their website years earlier and replaced by the 2030 estimate from the 2003 model (leading to Wikipedia contributors assuming that the 2030 estimate was made after the 2020 estimate when it is in fact the reverse, see previous post).
The 2030 estimate is still used today as the potential end date when the glaciers would be gone, despite being based on the temperature increase that is a factor 2 smaller than what was actually observed and it is outperforming the 2020 estimate that was based on the correct (local) temperature increase data.
So, if I would perform a stunt like that at for example an exam, say putting numbers in an equation that are a factor 2 off and nevertheless get the right answer, then I surely would get an A+ and a pat on the back from the professor, right?
But, then … but … hey, wait a minute … 😉