Why today's global warming is "unprecedented"
Recent global warming is an "unprecedented" worldwide phenomenon that differs from the more regional and staggered climatic variations that occurred during the past 2,000 years, a new study concludes.
Why it matters: The paper in the peer-reviewed journal Nature underscores the scope of human-driven warming and how it contrasts with variations in the pre-industrial era.
Where it stands: The study, using information from tree rings, ice cores and more, reconstructs past periods to show that major fluctuations occurred in different places at different times.
- The paper finds "no evidence for preindustrial globally coherent cold and warm epochs" over the past 2,000 years.
- For instance, the "little ice age" was coldest in the eastern and central Pacific Ocean in the 15th century, in northwestern Europe and southeastern North America in the 17th century, and in most other places in the 19th century.
The big picture: The results support a "regional framing" for understanding the climate variability in the 2 millennia before the industrial revolution — and demonstrates that it's a very stark contrast to what's happening now.
"When we go back in the past these are regional phenomena. We found 98% of the globe has this coherent warming during this contemporary period after the Industrial Revolution,"— said co-author Nathan Steiger of Columbia University at a press briefing this week.
The bottom line: The findings provide "strong evidence that anthropogenic global warming is not only unparalleled in terms of absolute temperatures, but also unprecedented in spatial consistency within the context of the past 2,000 years," the paper states.
What they're saying: University College London scientist Mark Maslin, who was not part of the study, told Reuters the results should "finally stop climate change deniers claiming that the recent observed coherent global warming is part of a natural ... cycle."