Studying Earth's past climates is important for scientists because it helps them understand how the climate system works and how it might change in the future. By comparing the past and present climate, scientists can identify the natural and human factors that influence climate variability and change. They can also test and improve their climate models by checking how well they can reproduce the past climate.
Scientists can gain a lot of information from investigating the Earth's past, such as the temperature, precipitation, atmospheric composition, ocean circulation, ice sheet extent, sea level, vegetation, and biodiversity of different time periods. They can also learn about the causes and consequences of past climate events, such as ice ages, warm periods, droughts, floods, and extinctions. These information can help them assess the risks and impacts of future climate change on humans and ecosystems.
The data obtained by paleoclimatologists are not based on direct observations, but they are derived from natural sources that record climate signals, such as tree rings, ice cores, corals, stalagmites, and ocean and lake sediments. These sources are called proxies, because they provide indirect evidence of past climate conditions. Paleoclimatologists use various methods and techniques to analyze these proxies and reconstruct the past climate. They also compare and calibrate their proxy data with instrumental records, such as thermometers and satellites, to ensure their accuracy and reliability. Therefore, their discoveries and models can be trusted, as long as they are based on sound scientific principles and supported by multiple lines of evidence.