The HACIDYS project
The understanding of how and why the regional climate has changed in the most recent past is an important question in itself, but also important in the quest to separated the natural climate changes from the man made climate changes.
Our approach draws upon many disciplines to include data from lake sediments, tree rings, ice cores and mathematical modeling of the atmosphere. One of the key elements is the use of stable water isotopes to reconstruct the temperature and atmospheric circulation of the past. The relative abundance of the 18O isotope in precipitation (written as delta-18O) is strongly dependent on the local temperature. The delta-18O can be measured in both lake sediments, tree rings and ice cores. In this way a climate history can be established for the location of the lake, tree or ice sheet.
In addition to this an atmospheric circulation model, not unlike the models used to produce weather forecasts, is used to test the hypothesis made from analyzing the data from the lake sediments, tree rings and ice cores. The model used here is capable of calculating the isotopic composition of precipitation, making a direct comparison to the other data possible.
The first step in our project is to identify events of climate change for the past 1000 years and find out what could have caused the change. We will for example focus the period around 1000 to 1200 AD. There is evidence that this period was particularly warm in the Northern Atlantic area, and we will investigate the reasons for this. Furthermore the warmest part of the Holocene from 6000 to 8000 BP is also a target for this project.