Recently, led by the Jet Propulsion Laboratory of California Institute of technology, a joint research team from the United States, the United Kingdom, China, Belgium and Germany, has launched an international collaborative research on sea-level observation and the influencing factors of sea-level changes, and clarified the causes of sea-level rise in the world and various sea basins since 1900. The paper was published in nature on August 20 》Go ahead. Global warming leads to sea-level rise, which brings great risks to low-lying, coastal areas and small island countries. Sea level rise and related disasters are one of the important challenges for sustainable development of human society and economy in the future. < / P > < p > there is a lot of evidence to show that the global sea level has been rising continuously since the beginning of the 20th century. But “what caused the sea level rise since 1900?” This issue has long been controversial. The lack of understanding of the past sea level change also brings great uncertainty to the future sea level change prediction, which is one of the key scientific topics of ocean and global change. < / P > < p > “we have been discussing this issue since 2016. However, there has been no progress until 2019. The biggest obstacle is that there are many factors affecting sea-level change, including thermal expansion, retreat of mountain glaciers, melting of Greenland and Antarctic ice sheets, and many contributing factors did not have global observation or reconstruction data for research in the last century. ” “Until 2019, a series of reconstructed data on the contribution factors of sea level change since the 20th century will be published, and these advances are the premise for the research to be carried out and published,” said Cheng Lijing, associate researcher of the Institute of Atmospheric Physics, Chinese Academy of Sciences. < p > < p > based on a series of latest scientific progress, 11 authors including 9 young scientists will jointly study the reconstruction of sea level change and its main contribution factors in 2019. Finally, this study gives the most accurate estimates of the reconstruction of sea level rise since 1900 and its three main contribution factors. For example, due to the systematic bias between the observational data and the lattice method, previous studies underestimated global warming and the specific volume sea-level rise caused by it. The latest research data (including IAP data of IAP) provide more accurate estimation of specific volume sea-level change. For another example, after taking into account the deviations caused by vertical land movements (such as land subsidence), the new tide gauge based sea-level rise in the 20th century is slightly lower than that previously estimated (listed in the ipcc-ar5 report). < p > < p > < p > for the first time in the world, this study has clarified that the observed total sea-level rise after 1900 is equal to the sum of the three contribution factors, namely, the mass loss of mountain glacier and ice sheet, the change of ocean water volume caused by the change of land water storage, and the change of temperature and salinity including thermal expansion (Fig. 1). Among them, land water storage includes three main factors: sea land water transfer caused by natural variability, groundwater loss caused by human utilization, and impact of dam impoundment (Fig. 1b). < / P > < p > “our study shows that the contribution of mountain glaciers and ice sheet mass loss is twice as much as that of ocean warming and thermal expansion from 1900 to 2018, and is the leading factor of sea level rise in the past century.” T. “However, the main contribution factors of sea-level rise are not the same in different basins. For example, the contribution of sea water quality increase in the Northwest Pacific is equivalent to that of temperature and salinity change, and the contribution of sea water quality increase in the eastern Pacific is greater (Figure 1),” frederikse said < p > < p > the study also found that the sea level did not rise linearly since 1900, and there were significant interdecadal scale fluctuations in the rising speed (Fig. 1c). In the 1940s, the rapid rise of global sea level was mainly caused by the mass loss of mountain glaciers and Greenland ice sheet, which led to the import of fresh water into the ocean. In the 1970s, the rate of sea-level rise slowed down, which was mainly due to the increase of land water reserves and the decrease of ocean water due to the large number of dams built on land. The accelerated rise of sea level since the 1990s is mainly due to the accelerated warming of the ocean and the accelerated melting of the Greenland ice sheet. Since 2000, the contribution of Antarctic ice sheet loss has been increasing (Fig. 1D). < / P > < p > Figure 1. Observed sea level rise and its contribution factors. Where a and B are the observed total sea level rise (dark blue) and its contribution factors, and the sea level change is the anomaly value relative to 2002-2018. C and D are the 30-year sliding line% confidence interval of sea level observation and its contribution factors. A and B give the contribution of sea water quality and specific volume sea level; B and d give the contribution factors of sea water quality change, including the mass loss of Greenland ice sheet and Antarctic ice sheet, the change of land water storage, the melting of mountain glacier, etc. < / P > < p > the study marks that the scientific community has been able to understand the mechanism of sea-level change in the past 100 years. The study is a key breakthrough in the study of sea-level change through the joint efforts of international scientific research teams in the fields of ocean, land, atmosphere and cryosphere. < / P > < p > the study was organized by Thomas frederikse and Felix landerer, JPL. Among them, the ocean temperature and salinity data and specific volume sea-level change are in the charge of Cheng Lijing and Laure Zanna of New York University; Lambert Caron and Surendra Adhikari of JPL are responsible for glacier equilibrium adjustment and solid earth process; David Parkes of Leuven University in Belgium is responsible for mountain glacier data; Vincent W. of California University of technology is responsible for land water storage. Humphrey, Peter Hogarth, National Oceanographic center, UK, is responsible for the data of tide gauge station; sonke dangendorf, University of siken, Germany, provides sea level change reconstruction based on tide gauge station; and Yun Hao Wu from Taiwan, China is responsible for dam impoundment data. < p > < p > the research was funded by the national key R & D program global change and response special project “observation data processing method and product development of key parameters of marine environmental change” (2017yfa0603200), and used the marine temperature and salinity grid data independently constructed by China.