(Climate Central)

13 of the 15 hottest years have happened since 2000 -- What are the odds of that happening without global warming?

Spoiler: Very, very, very, very, very slim


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Joanna Rothkopf
January 23, 2015 8:30PM (UTC)

Evidence often cited by climate scientists and also normal people attempting to demonstrate just how much we've destroyed the Earth shows that we've experienced 13 of the hottest 15 years on record since 2000. Climate deniers will respond, reminding you that they aren't scientists, but they have it on pretty good authority that the climate is always changing -- we just don't have anything to do with it.

So, the people at Climate Central made an animation in which they examine just how likely it is for us to have experienced so many record-breaking years in such a short period of time if human-influenced global warming isn't to blame. The odds? 1-in-27 million.

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Here's how they got to that number:

Our statistical approach was to consider all the possible combinations you can get by reordering the 135-year climate record, and then calculate how many of those combinations have 13 of the hottest 15 within a 15-year period...

To capture [short-term climatic variability], we randomly reordered the period of record using 2-year blocks. By randomly choosing a start year for the block assignments, there are two sets of year pairings. The top 15 are found in the last 20 years of the series. Looking at those 10 pairs, the two possibilities are set1 = {2, 2, 2, 1, 2, 2, 2, 0, 2, 0} and set2 = {1, 2, 2, 1, 2, 2, 2, 1, 1, 1}. There are 472 ways to choose an appropriate subset from set1 and only 10 ways to choose them from set2. With equal chances of which set is chosen, the average is 241 ways to choose 8 two-year blocks that contain at least 13 of the hottest 15 years.  There are 6,522,361,560 ways to choose 8 blocks from 67 (you can fit 67 2-year blocks into a 135-year period of record). So a conservative estimate of this probability is 1 in 27,063,741 or about 1-in-27 million.


Joanna Rothkopf

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Climate Change Global Warming Not A Scientist Odds Statistics Video

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