Understanding the past to predict the future
We can use thermometers and other instruments to measure and monitor climate parameters such as temperature, precipitation and atmospheric pressure. A few weather stations have recorded temperature and precipitation since the mid- to late-18th century, but it was not until the mid-19th century that weather stations were widespread around the globe. These measurements provide us with a record of global surface temperature change covering roughly the last 160 years, a long time in a human perspective, several generations, but for the Earth it is really not that long!
Looking further back in time and investigating parameters besides temperature help us to better understand the complex interaction between air temperature, atmospheric circulation, ocean currents, sea ice and glaciers. A better understanding of how the Earth’s climate system works is essential to be able to better predict the future.
So, how can we go about investigating climate fluctuations before the time of thermometers or even further back when there were not even people around? We can turn to nature, to so-called geological climate archives. For example, in the ocean or in a lake, little particles of dirt fall, year after year, through the water column to the bottom where they settle. These little grains are often made up of plants, tiny animals or fragments of crushed rock and contain information about the climate of that particular time. As particles accumulate, they archive information about past climates. To access this information we can drill to retrieve core samples from these sediment accumulations and then analyze the cores layer by layer.