When it comes to studying climate change, researchers can only go back about 150 years before they run out of temperature and meteorological recordings to explore. For any time before that, they need to use a number of techniques to figure out what the climate was like in a given area for a given time period.
One such way of doing this is to study trees that were alive at the time, and see how their rings grew. Another is to study pollen embedded at the bottom of lakes, which can imply what plants were in an area and can help up understand what the climate was like.
Still another form is a climate model, which is based on simulating important climate drivers and how they interact. Recently, researchers applied such a model to the northern Mediterranean in the mid-Holocene period (between 9,000 and 5,000 years ago). The climate model found that the period was warmer than expected, especially because pollen-based studies had determined that the period was colder there than it has been since.
The difference between the climate model and the paleoecological evidence is due in part the pollen used for the measurements. The previous measurements were based on the existence of silver fir pollen, which would imply colder temperatures. However, other could be other factors at work there, which can be take into account by the climate model method.
At first, the model was rejected because it seemed too contradictory, but interdisciplinary research bore out that the model is right and the pollen is wrong, or at least incomplete.
“It is only discussions between researchers from differing disciplines which enabled the new hypothesis to be developed and examined in detail,” said study co-author Oliver Heiri of the University of Bern.
What all of this does say, though, is that researchers need to keep working to improve our methods for studying the history of the Earth’s climate. While it may seem more pressing to study the current changing climate of the planet, it’s hard to track change when you have nothing with which to compare it. Furthermore, looking at climate changes in the past can provide insight into how the world can adapt to current changes, and might even help scientists to find ways to reduce the effects of climate change.