In recent years, humans have faced the spread of acid rain, the frequent occurrence of catastrophic climate and natural phenomena such as heavy rains, droughts, mudslides, avalanches, and earthquakes, the extinction of species, the intensification of the El Ni?o phenomenon, and the increasingly deteriorating natural environment. The environment threatens human survival and development. As early as 1972, scientists around the world had organized themselves and declared to the world to protect the earth's environment on which we depend; after entering the 1980s, especially in the late 1980s, catastrophic weather occurred frequently around the world, and various new human The spread of diseases, the acceleration of the extinction of animal and plant species, the continued destruction of tropical rainforests, and the protection of the earth's natural environment have become increasingly prominent. Nowadays, global environmental problems have attracted the attention of all mankind. In order to correctly predict future global environmental changes, it is necessary to accurately grasp the changing laws of the global environment.

In the process of studying global environmental changes, scientists from all over the world have reached a consensus on the following two issues: ① It is believed that the world’s natural environment is gradually changing, and the magnitude of changes over the past century has been than in the past; ② Through the study of earth history, it is believed that changes in the earth's natural environment have their own change laws and cycles, and human activities only enhance or reduce this change.

At present, in order to solve the problems of natural environment degradation faced by human beings, scientists from various countries, with the support of their governments, have established many international cooperation projects, such as the famous "International Geosphere-Biosphere Program" (referred to as "International Geosphere-Biosphere Program"). IGBP" is one of them. This plan treats the earth's natural environment as an overall system, decomposing it into the lithosphere, atmosphere, hydrosphere and biosphere. The earth's natural environment is the result of the interaction between the various layers. We humans hope to take a proactive position in the future environmental evolution process, consciously avoid and reduce some disasters caused by human activities in the continued development of mankind, and be able to predict some inevitable natural disasters and reduce the losses caused by these natural disasters. Reduce to lowest level. In order to accurately predict the changing trends and scope of the human living environment in the future, we must first accurately grasp the changing patterns, cycles and amplitudes of the earth's natural environment in the past. Only by taking the spatial distribution patterns of the modern natural environment as the basis can we be more accurate. To predict the changing trend of human living environment in the future. Therefore, the International Geosphere-Biosphere Program lists "Past Global Environmental Changes (PAGES)" as one of its core projects. At the same time, the National Science and Technology Commission and the National Natural Science Foundation of China have established a series of projects to support my country's global change research. Taking this opportunity, the Chinese government held the "National Academic Symposium on Climate Change and Environmental Issues" in Beijing in 1991, attended by Scientists at the meeting extensively discussed the issue of global environmental change and the stance that our government and Chinese scientists should take in global change research, as well as the missions and research tasks they face. The minutes of the meeting have become the basis for the National Science and Technology Commission and the National Natural Science Foundation of China in the next 10 to 20 years. Key research areas funded in the year. The purpose of the PAGES project is to quantitatively explain past environmental changes on the earth and reveal natural environmental variables, so that we can evaluate human impacts on the earth's biosphere, lithosphere, and atmosphere. Through the concerted coordination and efforts of domestic and foreign scientists, we seek to obtain and explain Effective data from predictive climate models, and synthesis and comparison of ice core and continental paleogeological records, are the consistent and basic methods to improve paleoenvironmental science research.

The research focus of the PAGES project focuses on the following five specialized questions:

1) How did the global climate and the earth's natural environment change in the past? What factors caused or controlled these changes? How to obtain this knowledge Let us understand future climate and environmental changes?

2) To what extent have human activities changed the climate and global environment? How can we dynamically solve the human-induced changes from natural influences to external drivers and internal systems? Origin and developmental changes?

3) What were the internal conditions of the Earth system before the emergence of humans?

4) What are the limits of natural greenhouse gas changes? What are the impacts on the global climate system? Natural feedback? What are the series of changes in greenhouse gases, surface climate and ecosystems that occurred in past environmental changes?

5) In the socio-historical time scale, what are the important driving factors that produce climate change? In a quasi-stable climate state on a ten-year or century-time scale, what causes catastrophic climate, environmental events, and rapid environmental transition periods?

Currently, domestic and foreign scientists have analyzed the past global climate over more than ten years. The study of environmental changes is considered to focus on the Quaternary geological period on a time scale. The Quaternary geological period is the last page of earth's history, during which a series of major events occurred: ① The earth has experienced global-scale climate changes; ② Large-scale glaciers have occurred in the polar and mountainous areas of the earth; ③ Global oceans Large oscillations and ups and downs have occurred; ④ The emergence of humans and the accompanying flourishing of plants, mammals and marine life. Due to changes in climate, other environmental conditions undergo corresponding large-scale changes, leading to changes in the global environmental system. The current human living environment was formed and developed during the Quaternary geological period. It is far from the natural environment of any previous geological era. Therefore, the largest time scale for our study of global environmental changes is the Quaternary geological period, that is, the last 3 million years. years since. Secondly, due to the cyclical changes in climate, according to the research results obtained, there were several periods of large-scale glaciation development in the Quaternary geological period, that is, glacial periods, and the corresponding warm periods between the two glacial periods are called interglacial periods. , studying the global environmental change patterns of the last interglacial and glacial periods (that is, since 150,000 years ago) is the second time scale. Third, during the Holocene period (since 10,000 years ago), human civilization has experienced the temper of the last ice age. Driven by global climate warming and the prosperity of animals and plants, it has produced unprecedented rapid development and progress. This is the research the third time scale. In the past 2,000 years, humans have continuously changed the natural environment in the process of production and life, from early deforestation, the rise of farming agriculture, and large-scale hunting of large herbivores, to the transformation of mountains and rivers after the industrial revolution, and the exploitation of natural resources. The role of human activities on the natural environment is becoming more and more significant. At this time, human activities have become one of the important factors causing changes in the natural environment. This is the fourth time scale for studying global environmental changes. Our study of past global environmental changes is to extract the spatiotemporal changes in environmental factors in the sediments of the Quaternary geological period, and use the method of "discussing the present to analyze the past" to restore the spatial distribution of the global environment at that time. Through the efforts of scientists, it has been confirmed that climate change is one of the leading factors controlling global environmental changes. Research on loess, ice core, deep sea sediments, lake sediments and karst accumulations (five types of Quaternary accumulations), which are five key areas that can reflect past global environmental changes, has achieved fruitful results. Research on the three aspects of ice core and deep-sea sediments has achieved an internationally recognized complete high-resolution paleoclimate change series, thus bringing the study of world paleoclimate and past global environmental changes to a new height.