Last two weeks were quite hectic. Several projects kept me busy and not much time to read, let alone writing blog posts. Now I got some more time, I try to finish some posts that I started two weeks ago. In this last post I wrote about the online news reporting of the VRT news. One of them was Worldwide heat records can’t be a coincidence anymore (Dutch). In it they regurgitated the warmest-year-according-to-NASA stuff, but went much further and reporting that it is highly unlikely that this is a coincidence (tranlated from Dutch):
2014 was the warmest year since the beginning of the measurements in 1880. The climate on earth is an erratic phenomenon with peaks and valleys, so that could be a coincidence. That the long series of temperature records of the last decade is a coincidence, however, is highly unlikely.
Press Agency AP asked three statisticians (John Grego of the University of South Carolina, Kai Zhu of Stanford University en David Peterson, a retired statistician of Duke University), to calculate what are the odds that these temperatures are the result of pure chance. They came with following numbers:
- The odds that:
- the 3 warmest years since the beginning of the measurements are 2014, 2010 and 2005: 1 in 3,341
- 9 out of 10 warmest year fall in this century: 1 in 650 million
- 13 out of 15 hottest years fall in last 15 years: 1 in 41 trillion (41×1012)
- 15 years since 2000 all fall within the top 20 of warmest years ever: 1 in 1,5 quadrillion (1.5×1015)
- the last 358 months were all warmer than average in the 20th century: 1 in 1 googol (1×10100)
Looks impressive, but there is of course something really wrong with it: this is of course not how the climate system works! The temperatures we experience per year might be chaotic, but not random. The assumption of those statisticians is indeed that what we experience is acting randomly, like some kind of cosmic lottery. This is obviously not the case. The temperature of the Earth is influenced by many variables, not taken into account by those statisticians.
In the end, the AP reporter who originally brought the story had to eat crow in Clarification: Hottest Year story:
In a story Jan. 16, The Associated Press reported that the odds that nine of the 10 hottest years have occurred since 2000 are about 650 million to one. These calculations, as the story noted, treated as equal the possibility of any given year in the records being one of the hottest. The story should have included the fact that substantial warming in the years just prior to this century could make it more likely that the years since were warmer, because high temperatures tend to persist.
But strangely he thinks that he was basically right, only “forgot to mention that temperatures tend to persists”. In a way those things are true. He indeed mentioned that these odds were for random events. Those who weren’t asleep could figure it out that something was wrong (according to the reactions, a lot weren’t) and it is also true that temperatures tend to persists.
But none of those two is the actual reason he was criticized for! He was criticized for saying things like this:
But record and near record heat keep happening. Climate scientists say it’s not random but from heat-trapping gas spewed by the burning of coal, oil and gas. You know, global warming. And one of their many pieces of evidence is how statistically unlikely it is for the world to have warmed so much.
In fact he wanted to prove that the odds of having 9 out of 10 warmest year in this century are so astronomically small, therefor likely humans caused the higher temperatures (“you know, global warming”). Yet our climate system is not a random system and therefor their results are just useless when it comes to making conclusions about the climate system. This means that those numbers were just plain wrong for what those journalists used them, because their calculation didn’t represent any reality.
That is the real error and neither AP or the VRT reporter didn’t even acknowledged this.