Submission + - Nature: global temeratures are a falling trend (nature.com) 3
sosume writes: An article in Nature shows that the temperature in the roman times were actually higher than current temperatures. A team lead by dr Esper of the University of Mainz has researched tree rings and concluded that over the past 2,000 years, the forcing is up to four times as large as the 1.6Wm2 net anthropogenic forcing since 1750 using evidence based on maximum latewood density data from northern Scandinavia, indicating that this cooling trend was stronger (0.31C per 1,000years, ±0.03C) than previously reported, and demonstrate that this signature is missing in published tree-ring proxy records. This is a big setback for global warming scientists.
Is it a setback? (Score:2)
"The forcing is substantial over the past 2,000 years, up to four times as large as the 1.6Wm2 net anthropogenic forcing since 1750"
If that means what it appears to mean, then 2000 years of solar forcing = approx. 4 times 260 years of anthropogenic forcing, which means that the overall anthropogenic forcing is about twice as fast as the solar forcing.
Now why choose 1750 as a baseline when anthropogenic forcing didn't really get started till the 19th century and has accelerated since? Perhaps
Re: (Score:2)
N-scan shows a succession of warm and cold episodes including peak warmth during Roman and Medieval times alternating with severe cool conditions centred in the fourth and fourteenth centuries (Fig. 2). AD 21–50 (+1.05C, with respect to the 1951–1980 mean) was the warmest reconstructed 30-year period, ~2C warmer than the coldest AD 1451–1480 period (1.19C) and still ~0.5C warmer than maximum twentieth-century warmth recorded AD1921–1950 (+0.52C).
Doesn't seem to agree with your parsing of the sentence.
trying to understand methods & analysis (Score:2)
Here's my understanding of their reasoning.
Motivation:
- Insolation changes and CO2 ecosystem feedbacks have been identified as the main causes of climate variability for the past million years.
- However, global climate models are either too short or don't integrate low-frequency insolation changes, which might mean they're mis-estimating temperatures and temperature changes.
- and while tree ring records are important and widespread, a suitable long-term record th