Bandung-BRIN Public Relations. Global climate change takes place not only through the process of global warming. Climate change can also be triggered by a series of human activities that are directly related to the environment. A comprehension of climate history is needed to understand global warming, including climate phenomena from year to year. This requires data of climate parameters from the present back to the past.

Studies of past climate or paleoclimate studies can provide data and information on climate parameters from the present to the past that are not available in term of measurement data. The parameters of past climate are recorded in natural archives, such as marine sediments, lake sediments, tree rings, corals and so forth. Each natural archive complements each other, both in terms of resolution and the length of data available.

Various data of climate proxy contained in natural archives are used to reconstruct the variability and trends of climate and environmental change from time to time. The data of past climate parameter and model data can be used to mutually verify and validate the climate data, so that the prediction on climate change can be more accurate.

Research on Climate Change in Indonesia

Research on climate change is necessary, because Indonesia’s location which is passed by the equator line makes the climate in Indonesia influenced by several rainfall patterns, namely monsoon pattern, equatorial pattern, and local pattern. These rainfall patterns and temperature variability are strongly influenced by global and regional phenomena in seasonal, annual, inter-annual, and decades time scales.

Changes in the global and regional phenomena will greatly affect the climate in Indonesia, for example it can lead to a prolonged dry season or extreme rainy season, to rising sea levels. Indonesia is an interesting place for climate studies, as this country is rich in natural resources such as marine sediments, lake sediments, corals, trees, speleothems, and even ice cores.

Sri Yudawati, Head of Climate and Environmental Research of BRIN’s Geotechnology Research Center, explained that Scleractinia corals or known also as stony corals from the Porites genus are able to provide quite convincing past climate data. The combination of live and dead corals is able to provide continuous climate data from the present back to thousands of years, even hundreds of thousands of years ago with monthly resolution.

The coral’s geochemical content can be used to reconstruct sea surface temperature, precipitation and sea surface salinity. In addition, X-rays or Rontgen can identify Porites coral annual growth layers which record information on chronology or time sequences, as well as information on the speed of coral classification. By correlating the temperature and annual growth of coral, the effect of temperature on coral growth can be seen. The results of this kind of research have been used to support coral reef conservation.

“In broad outline, the objective of research on the past climate of Porites corals is to improve our understanding of climate variability in Indonesian region and to understand the phenomena of ENSO (El Nino Southern Oscillation) and IOD (Indian Ocean Dipole) climate in the past, to understand the effect of temperature on the annual growth of Porites coral and for evaluation and development of proxy data calibration methods and the methodology of seawater reconstruction from data on coral proxy,” he explained.

Some of her research reveals that based on reconstruction of the temperature and salinity from the geochemical content of live coral of Porites from the waters of Timor Island (Ombai Strait), over a long period of 90 years (1914–2004), the IOD significantly affects the temperature and salinity, while the ENSO affects the temperature significantly, but not on salinity. These results need to be taken into account when interpreting the past climate in Indonesia. Recordings of sub-fossil corals from the Sunda Strait region show an increase in the frequency of IOD/ENSO events from the Middle Ages to the present.

Amanda, a researcher in the field of carbonate sediments, from the ancient climate and environmental research group, explained that coral reefs need a suitable living environment to grow, such as warm sea water temperature, sufficient sunlight, nutrients, salinity, clear sea water, and so on.

Changes that occur in the living environment of coral reefs will be recorded in the reefs’ body, just as trees record changes in their surrounding and can be seen in tree rings. Therefore, the climate change as reflected in changes in sea water temperature, changes in salinity, and fluctuations in the sea level will be recorded on coral reefs.

“The data on historical climate and historical sea level changes generated from our group’s research can be used as the basis for recognizing the characteristics of climate change in Indonesia, and for studies on environmental vulnerability due to hydrometeorological hazards, as well as for projection of climate change in the future,” he said.

The benefits for the community to know trends of climate change are to analyze the vulnerability of an area to hydrometeorological disasters, such as droughts, floods, rising sea level and rising temperatures and for making projections of future climate change.

“We hope that people will be more aware of the environment by doing reforestation, reducing emissions and living in an environmentally friendly manner, all of this for the purpose of reducing the impact of global warming,” he concluded. (DS, ed. kg)