This was written with Ilissa Ocko:
Everyone's talking about the weirder -- and more dangerous -- weather. Here are 10 things you should know about weather, climate and El Niño during a record-breaking 2015
Spoiler alert: Those off-the-charts warm December days in the Northeast did NOT happen because of El Niño.
1. Global temperature records in 2015 smashed all records as the warmest year ever recorded in human history.
2. The US had its 2nd hottest year on record.
3. 14 of the 15 hottest years in a 135-year record have happened in the last 15 years.
4. Global temperature records were broken in 10 out of 12 months of 2015.
5. At least 4000 people in India and Pakistan died from heat waves in 2015; temperatures in Iran felt like 163 F in July.
6. 29 states had the hottest December -- by far -- ever in their recorded history.
And the weather is weirder than ever: In early 2015, and especially February, the eastern U.S. was way colder than normal.
By the end of 2015, the eastern U.S. recorded off-the-charts hottest temperatures.
7. CO2 concentrations have gone above 400 ppm for the first time ever -- this is the highest level in at least 800,000 years. We're changing the composition of the atmosphere, and Earth is warming as a result.
Confused about the difference between weather and climate? Think of it this way: Weather is your mood -- it can fluctuate rapidly. Climate is your personality.
8. We are now experiencing what might become the strongest-ever El Niño. El Niños, natural climate cycles, are still a bit of a scientific mystery; they happen irregularly, and scientists aren't entirely sure what triggers them. They tend to warm the planet.
9. We can't blame those warm Northeastern winter records on El Niño, because El Niño has no discernible effect on temperatures in this region. Scientists have looked at temperature data in the Northeast US during previous El Niño events, and have found at best only a weak temperature impact.
10. Scientists can now measure the impact of climate change on extreme weather events. Climate Central did an "attribution study" for warming in 2015 to answer the question: how big of a role did El Nino play in the 2015 global heat record?
Only 5% of warming -- 5% of the extra warming, the temperature increase -- in 2015 can be attributed to El Nino.
95% of the global warming in 2015 was from greenhouse gas emissions -- the methane, carbon dioxide and other pollution that is trapping the Earth's heat in our atmosphere, preventing it from escaping to space.
*Source: Climate Central has set up a World Weather Attribution service, to figure out how much climate change plays a role in a certain phenomenon, in real time, so it can inform the conversation in media and at the dinner table.