Climate change is an issue that pervades the environmental circles nowadays. But is there really climate change? Are there evidences that support this worldwide phenomenon that brings many nations together to collectively take actions to address its effects? This article describes what has been learned so far about the disturbing impacts of climate change. It focuses on sea level rise as one of the indicators of climate change.
Evidences of Sea Level Rise
Historically, high levels of sea water have already been deduced from past fossil records (Figure 1). A group of researchers led by Dr. Jonathan Overpeck of the University of Arizona (Overpeck et al., 2006) explained that corals on tectonically stable coasts from the last interglaciation period (LIG) provided strong evidence that sea level was 4 to greater than 6 m above present levels. It was estimated that the sustained high level of water lasted from 129,000 ± 1000 years ago to at least 118,000 years ago. This means that the earth’s waters had already risen in the past and that it is possible that this will happen again and will last a long time.
Fig. 1. A fossil coral that served as one of the bases for the reconstruction of sea level changes during the Last Interglaciation period (Photo by H. A. Curran)
Causes of Sea Level Rise
The causes of the increase in sea level are not very well understood. But in recent years, particularly with the aid of computer-based gadgets and modern telecommunications equipment, explanations are arrived at. The most sensible and convincing explanations to increase in sea level are those advanced by the group of Dr. Gerald Meehl of the University Corporation for Atmospheric Research (UCAR) and Dr. Vivien Gornitz of the National Aeronautics and Space Administration (NASA).
Dr. Meehl and his group of scientists explain that sea level increase is due to the thermal expansion of the oceans. Simply stated, heating water will cause it to expand because of the tendency of the water molecules to dissociate and turn into gaseous state. They used computer models and atmospheric observations through satellites to validate their claim.
On the other hand, Dr. Gornitz et al. (1982) and R. Barnett (1984) attribute the increase in sea level rise to the melting of Greenland ice sheets and mountain glaciers in the polar, cold regions of the earth. Further, they observed that the global mean sea level has been rising in the past 100 years. The rise in mean sea level is estimated at 1.05 millimeters per year by the Intergovernmental Panel of Climate Change (1990).
Increase in Sea Level
Recently, Michaelova (2010) observed that mean sea level rise increased. Accordingly, over the period of 1961–2003, the ocean level increased at a mean rate of 1.8±0.5 millimeters per year, while over the period of 1993–2003, the average rate of the ocean level rise reached 3.1±0.7 millimeters per year. Although these annual increases in sea level are very small, in the long run, from centuries to millennia, sea level rise will be high enough to inundate the low lying areas of the world. These low lying areas specifically the coastal regions are heavily populated regions thus lead to land-related issues and concerns.
While there are still unconvinced sectors of society about climate change, more modern or advanced equipment might shed light and reduce prediction uncertainty in the future. In the meantime, it pays to adopt the precautionary rule to avoid disastrous consequences of climate change to human affairs.
Barnett, T. (1984): The estimation of global sea level change: a problem of uniqueness. J. Geophys. Res., 89, C5, pp. 7980–7988.
Gornitz, V.; L. Lebedeff; and J. Hansen (1982): Global sea level trend in the past century. Science. No. 215. pp. 1611–1614.
Michaelova, M. 2010. Problems with assessment of sea level rise impact on low-lying coastal regions including river delta. Environmental Research, Engineering and Management. No. 3(53).p. 3-4.
Overpeck, J.; B. Otto-Bliesner; G. Miller; D. Muhs; R. Alley and J. Kiehl. 2006. Paleoclimatic evidence for future ice-sheet instability and rapid sea-level rise. Science. Vol. 311. pp. 1747-1750.
©Patrick Regoniel Facts About Sea Level Rise