Abstract
Insolation changes caused by the axial precession induce millennial
trends in last millennium temperature, varying with season and latitude.
A characteristic seasonal trend pattern can be detected in both
insolation and modeled surface temperature response. In the
extratropical Northern Hemisphere, the maximum insolation trend occurs
around April/May, while the minimum trend occurs between July and
September. The temperature trend lags behind insolation trend by around a
month. Hence orbital forcing potentially affects long‐term trends in
proxy data, which are often sensitive to a distinct seasonal window. We
find that tree‐ring reconstructions based on early growing season
dominated records show different millennial trends from those for late
summer dominated proxies. The differential response is similar to that
seen in pseudo proxy reconstructions when considering proxy seasonality.
This suggests that orbital forcing has influenced long‐term trends in
climate proxies. It is therefore vital to use seasonally homogeneous
data for reconstructing multicentennial variability.
Original language | English |
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Article number | e2020GL088776 |
Number of pages | 13 |
Journal | Geophysical Research Letters |
Volume | 48 |
Issue number | 4 |
DOIs | |
Publication status | Published - 22 Feb 2021 |
Keywords
- Climate variability
- Insolation
- Last millennium
- Long-term trends
- Orbital forcing
- Proxy reconstructions