Can state-dependent effects of natural forcing resolve mismatches of simulated and reconstructed climate variability?

Online seminar by Prof. Kira Rehfeld from Tübingen University, Tübingen, Germany

16 February 2022
KST 16:00 – 17:00

Join us online: Meeting ID: 861 3923 1406 Passcode: 770854

Temperature variability at the last Glacial Maximum was higher than during the Holocene. Can we extrapolate from this to a state-dependency of Earth surface temperature variability? Another explanation could be that the climate system changes its sensitivity to natural forcing with global warming. There is some evidence for this: For example, strong volcanic eruptions were shown to induce smaller post-eruption cooling in warmer climate states. They also were hypothesized to have led to substantial cooling in the Glacial state. Hence, a logical question is whether the response of the climate system to natural forcing is state-dependent, and changing systematically from Glacials to Interglacials. 
Here, we quantify the response to volcanic and solar forcing in Last Glacial and Pre-Industrial conditions in an ensemble of climate model simulations.
We evaluate forcing-induced changes in climate variability on annual-to-multicentennial scales. 
The global temperature response reveals no state dependency. This implies that findings on the ability of models to simulate past variability should translate to future climates. Smaller local differences result mainly from state-dependent sea ice extent and dynamics. 
While biases at timescales beyond the multidecadal is still underestimated, variability in forced simulations matches paleoclimate reconstructions significantly better than in control scenarios. We find that considering natural forcing is therefore important for model-data comparison and future projections.