1. Introduction

As society develops, the environment has become more and more important to people. As climate change takes place, more studies have been done to study the potential impact of climate change on the ecosystem. Due to the lack of case studies, fossil records from the past have been brought to labs to acquire climatic information from the past, aiming to better understand current climate change through studying past major climate changes.

Fossils have long been used as a valuable material to help people nowadays learn about the Earth in the past few billion years, as well as the evolution and changes of creatures on the planet. This research investigates how fossil records provide insight into current weather patterns and climate projections, aiming to advance the understanding of climate change in the future through multidisciplinary sciences, including paleontology, geology, and biogeochemistry, and provide a more comprehensive framework for comprehending and forecasting Earth’s climate system. Research articles will be used and referenced to provide different aspects to the study of fossils, as well as the identification of research limitations and future research aims. Beyond organisms, by providing vital insights into previous climatic conditions and the evolution of life, fossil records act as a crucial window into Earth's prehistoric climate systems. Studying fossil remains and geological structures can reconstruct climate and weather patterns from different periods. In addition to improving our knowledge of past climate variability, this retrospective research helps forecast future patterns in climate. The long-term perspective on natural climate variation provided by the fossil record aids in differentiating between natural variability and the effects of human activity.

2. Relationship between the fossil record and ancient climate

2.1. Prehistoric climate information from fossils

Widely known, the climate of Earth has been changing vigorously since the planet’s birth. As concern for the global climate is growing increasingly nowadays, the climate back when there was no human activity has been studied more, aiming to investigate the difference between natural climate change and modern human-caused climate change. Since then, ways to investigate fossils with this aim have been developed.

Fossils can only offer proxy evidence because they cannot provide direct proof of previous environments [1]. Through the investigation of the different isotope records of various fossils, including plant and animal fossils, the past photosynthesis and nitrogen-fixation systems, which in turn can be related to climate, can be known. The most common and well-tried research strategy would be studying carbon isotopes. Compared to the primary fixation stage of the C4 plant, which uses PEP carboxylase, the initial fixation of carbon dioxide by C3 plants, which uses the photosynthetic enzyme complex Rubisco, discriminates more successfully against the 13C isotope. The ratio of ẟ13C indicates the 13C: 12C ratio concerning a standard; for C3 plants, this is around -26 parts per thousand, while for C4 plants, it is approximately -12 parts per thousand. Because this ratio is transferred to grazers and stored in their bone collagen, it can be utilized to analyze the diets of herbivores as well as disclose the photosynthetic approach involved in the creation of fossil plant material [2]. This can be a very powerful method, even for small amounts of fossils. A study conducted in the Negev desert of Israel on snail shells has shown the potential value fossil data have in reconstructing paleoclimates. Carbon isotope ratios found in snail shells dating back three to four thousand years demonstrate that the northern boundary of C4 vegetation was 20 to 30 kilometers south of the current boundary, suggesting a less arid condition back then [2].

Another informative thing to study is the nitrogen isotope ratio. In legumes, the nitrogen fixed by symbiotic bacteria has a 15N: 14N ratio that is roughly equal to that of the surrounding air, but most non-symbiotic plants have ratios that are greater by five or more parts per thousand. The nitrogen isotope ratio can, therefore, be used as a sign of how much nitrogen-fixing organisms contributed to its construction [2].

2.2. Prehistoric climate change patterns indicated by fossils

With fossils’ ability to provide climate information from the past, it is also found to provide profound information about past prehistoric climate change patterns. The climate of the Earth may be related to the circumstances required to retain fossils. Through the study of phosphorus and the phosphorylation of fossils found, researchers can analyze and predict past climate differences and, hence, prehistoric climate change.

In a study, dead bodies of deceased marine animals that are about 183 million years old were found. Fish with their gills and eye tissue intact, elaborate crab claws, and vampyropods that resemble squids with ink sacs are among the fossilized creatures [3]. Fossils from three Lower Jurassic Lagerstätten—the Strawberry Bank in the United Kingdom, Ya Ha Tinda in Canada, and Posidonia Shale in Germany—were analyzed. All three Lagerstätten were deposited during the Toarcian OAE (TOAE), according to biostratigraphy. A scanning electron microscope (SEM) was used to detect chemical element composition present in the minerals within the biological tissues of the fossil, further analyzed using energy dispersive X-ray spectroscopy (EDS). Surprisingly, each deposit was found to contain a variety of taxa preserved as phosphatized skeletons and tissues, as shown in Figure 1.

Figure 1. EDS elemental maps of specimens from Strawberry Bank, Posidonia Shale, and Ya Ha Tinda Lagerstätten fossils.

Accordingly, all of these Lagerstätten were deposited in settings that are conductive to phosphatization, despite the different regions and lithologies. Phosphatization occurs in environments conducive to phosphogenesis, or the precipitation of phosphorus as apatite minerals in sediment. Both the reduction of iron oxide particles and remineralization by microbial sulfate reduction are typical causes of phosphogenesis. Through cyclic “iron-pumping,” in which particulates absorb phosphate produced deeper in the sediment and inhibit its escape, these particles aid in limiting the efflux of phosphate from the pore to the bottom water. In marine habitats with (dys)oxic bottom water, phosphatization may be preferred due to the redox-sensitive nature of sulfate and iron oxide reduction processes. The overall process can be better visualized in Figure 2. below.

Figure 2. The proposed model showing the relationships between fossilization and environmental changes caused by OAE

It's possible that phosphate delivery from the weathering of continents and sea level change caused phosphatization, with anoxic basins serving as phosphorus traps driven by climate change [4].

3. The potential value of the fossil record for climate prediction

3.1. Links between long-term climate trends and fossil evidence

Fossils as geological records and paleontological evidence are not only helpful in understanding the planet’s past climate system but also provide the chance to predict and simulate future climate change patterns. Computer simulations of the atmosphere have proven to be pretty accurate, and they have been effectively integrated with other computer simulations of ocean and land surface process components. However, the computational capacity at hand limits the precision of these models, and many small-scale processes can only be approximated. The geologic record provides special hints about how the climate system functioned under radically different circumstances in the past and how it changed states and can also be used to validate ground-truth predictions of computer models. These hints can assist us in comprehending any future changes to the system[5].

In one study, fossil sediments collected at the upper 360 centimeters of core “ODP1084B”, located about 300 kilometers off the coast of Namibia, were collected and studied. Radiocarbon dating was employed and indicated the age of the fossil was at least 22,000 years old. Mg/Ca of another species, Globigerina bulloides, was also measured. Results indicated a sharp decrease in Mg/Ca, representing a decrease in sea surface temperature between 11,500 and 13,000 years ago. Based on the data collected from ODP1084B, it appears that the Younger Dryas climatic shift—which has historically been associated with modifications in the North Atlantic—also significantly alters the tropical South Atlantic. The vast influence that changes in ocean circulation may have on the planet’s climate system is highlighted by the Younger Dryas’ worldwide impact. The most plausible explanation for this impact appears to be that modifications to the “conveyor” circulation of the deep ocean affect tropical sea surface temperatures (SST), which in turn affects the circulation of the African monsoon [6]. The deep-ocean circulation is predicted to shift as a result of anthropogenic climate change in the future, so knowing the specific interactions that led to previous events like the Younger Dryas will help us predict potential changes in the future. Future lab work by me and my colleagues will involve pushing the palaeoceanographic record of ODP1084B back several millennia in time. Apart from the evidence of the Younger Dryas, there is also some evidence that suggests the South Atlantic was impacted by other major climate events. These climate occurrences, commonly referred to as “Heinrich Events,” were initially identified in the North Atlantic. Pebbles too big to have been carried by ocean currents are found in several layers of deep ocean sediments in the North Atlantic; an increase in the amount of ice drifting out to sea from the glaciers around the region is most likely the cause of their presence. When the ice melts, stones that were frozen in it fall to the ocean floor. It is crucial to research natural climate cycles like Heinrich Events because doing so will help us anticipate future changes in the climate system.

It has been suggested that a tropical trigger is responsible for Heinrich events. Two paleoceanographers proposed that solar energy redistribution caused by variations in Earth’s orbit strengthens the African monsoon system every several thousand years, and this strengthening of atmospheric circulation changes the upwelling along the equator and the export of heat to the high latitudes, ultimately causing Heinrich events. We would anticipate evidence of similar shifts outside of the North Atlantic if it is true that changes in the tropical climate cause Heinrich Events [7]. Support for McIntyre and Molfino's theory would increase if additional proof of these episodes in the Southern Hemisphere's Benguela upwelling system could be found. The climate event known as the Younger Dryas serves as a warning that shifts in the climate in a small area, like the North Atlantic, can have an impact on the entire planet by altering the deep-ocean circulation.

The lesson of the Heinrich events may be that slight variations in the tropical environment can affect atmospheric circulation worldwide [5].

3.2. Challenges

Though technologies to study fossil records have been prevalent and well-used nowadays, there are still certain uncertainties and challenges when predicting future climate change using fossils.

One major challenge is spatial separation. In most cases, the discovered fossil records are region-specific and concentrated in one area. This only allows the capture of regional past climate information, and the prediction from the fossils discovered may not be the best representative for a global-scale climate change prediction. At the same time, using fossil records also implies that only the species that survived in the past and discovered at present are used and analyzed, which can also cause species bias, influencing the accuracy of the predictions.

Another drawback is that, as fossils only provide indirect evidence for past information, the information acquired is only a proxy for past climate conditions. The actual relationship between the proxies and actual climate variables can be complex instead of an ideal linear relationship.

At the same time, paleography and continental drift can greatly affect the predictions. The positions of continents and ocean basins have changed dramatically over time. Those changes influence climate patterns, and there is a chance that the historical configurations do not accurately match up with conditions in the present or the future.

4. Conclusion

Fossil records serve as crucial evidence of ancient life, offering invaluable insights into past environmental conditions and patterns of climate change. Scientists use elements like carbon, nitrogen, and phosphorus that are present in ancient records to determine the climate conditions of particular regions and geographical locations. Scientists hope to reconstruct historical climatic fluctuations, such as changes in air temperatures, humidity levels, and sea levels, by examining these components.

Long-term climatic patterns are revealed by comparative analyses of paleontological evidence from various epochs, previous Earth climate conditions, and contemporary climate trends. Understanding the processes of climate change and projecting possible ecosystem responses to current and upcoming environmental changes depend heavily on these comparisons.

Fossils’ elemental makeup offers a glimpse into the environmental circumstances that prevailed during the organism's lifespan. Through the analysis of these proxies in a range of fossil specimens and geological strata, scientists can determine the ways in which climatic variables such as temperature and precipitation have changed over thousands of years. Additionally, by examining fossilized plants and animals in conjunction with geological data, scientists are able to map out historical ecosystems and their ability to adapt to changing climates. Paleontology, geochemistry, and climatology are used in this multidisciplinary method to create a thorough account of Earth’s climatic history. These revelations not only broaden our comprehension of historical climate dynamics but also offer crucial background information for evaluating current climate change and its possible effects on human civilization and world biodiversity. In conclusion, fossil records are priceless archives that help us piece together the history of Earth’s climate, guiding the development of mitigation and adaptation plans for present and future environmental threats.

However, certain limitations do exist when fossil records are used as the source of research, including inaccuracies in prediction due to different environmental variables and continental drift, which result in ambiguity in the prediction results. Notwithstanding these difficulties, fossil records are nonetheless a useful resource for comprehending long-term climate trends and for making future climate projections. Further research will be needed, focusing on the prediction of future climate change trends using information acquired from fossil records for a better and more mature adaptation to future rapid climate changes for humans.