Sea level rise 'is accelerating'
There will be increased flooding of low-lying areas when there are stormsurges Dr John Church Global sea levels could rise by about 30cm during this century if current trends continue, a study warns.
Australian researchers found that sea levels rose by 19.5cm between 1870 and 2004, with accelerated rates in the final 50 years of that period. The research, published in the journal Geophysical Research Letters, used data from tide gauges around the world. The findings fit within predictions made by the Intergovernmental Panel on Climate Change (IPCC).
The IPCC's Third Assessment Report, published in 2001, projected that the global average sea level would rise by between 9 and 88cm between 1990 and 2100. In an attempt to reduce the scale of uncertainty in this projection, the Australian researchers have analyzed tidal records dating back to 1870. The data was obtained from locations throughout the globe, although the number of tidal gauges increased and their locations changed over the 130-year period. These records show that the sea level has risen, and suggest that the rate of rise is increasing. Over the entire period from 1870 the average rate of rise was 1.44mm per year.
Over the 20th Century it averaged 1.7mm per year; while the figure for the period since 1950 is 1.75mm per year. Although climate models predict that sea level rise should have accelerated, the scientists behind this study say they are the first to verify the trend using historical data.
Floods and surges
If the acceleration continues at the current rate, the scientists warn that
sea levels could rise during this century by between 28 and 34cm. Dr John Church, a scientist with the Commonwealth Scientific and Industrial Research Organization based in Tasmania and an author of the study, said that higher sea levels could have grave effects on some areas. "It means there will be increased flooding of low-lying areas when there are storm surges," he told the Associated Press. "It means increased coastal erosion on sandy beaches; we're going to see increased flooding on island nations."
There is now a consensus among climate scientists that rising atmospheric
concentrations of greenhouse gases such as carbon dioxide are the major
factor behind rising temperatures.
Increased temperatures can lead to higher sea-levels through several
mechanisms including the melting of glaciers and thermal expansion of sea
water. Through the 1997 Kyoto protocol, industrialized countries have
committed to cut their combined emissions to 5% below 1990 levels by
2008-2012. But the US and Australia have withdrawn from the treaty. Dr Church urged: ""We do have to reduce our emissions but we also have to recognize climate change is happening, and we have to adapt as well."
CO2 'highest for 650,000 years'
By Richard Black Environment Correspondent, BBC News website
Current levels of the greenhouse gases carbon dioxide and methane in the atmosphere are higher now than at any time in the past 650,000 years. That is the conclusion of new European studies looking at ice taken from 3km below the surface of Antarctica. The scientists say their research shows present day warming to be exceptional. Other research, also published in the journal Science, suggests that sea levels may be rising twice as fast now as in previous centuries.
The evidence on atmospheric concentrations comes from an Antarctic region called Dome Concordia (Dome C). Over a five year period commencing in 1999, scientists working with the European Project for Ice Coring in Antarctica (Epica) have drilled 3,270m into the Dome C ice, which equates to drilling nearly 900,000 years back in time. Gas bubbles trapped as the ice formed yield important evidence of the mixture of gases present in the atmosphere at that time, and of temperature. "One of the most important things is we can put current levels of carbon dioxide and methane into a long-term context," said project leader Thomas Stocker from the University of Bern,
"We find that CO2 is about 30% higher than at any time, and methane 130% higher than at any time; and the rates of increase are absolutely
exceptional: for CO2, 200 times faster than at any time in the last 650,000 years."
Last year, the Epica team released its first data. The latest two papers
analyse gas composition and temperature dating back 650,000 years. This extends the picture drawn by another Antarctic ice core taken near Lake Vostok which looked 440,000 years into the past. The extra data is crucial because around 420,000 years there appears to have been a significant shift in the Earth's long-term climate patterns. Before and after this date, the planet went through 100,000 year cycles of alternating cold glacial and warm interglacial periods. But around the 420,000 year mark, the precise pattern changed, with the contrast between warm and cold conditions becoming much more marked. The Dome C core gives data from six cycles of glaciation and warming; two from before this change, four from after. "We found a very tight relationship between CO2 and temperature even before 420,000 years," said Professor Stocker. "The fact that the relationship holds across the transition between climatic regimes is a very strong indication of the important role of CO2 in climate regulation." Epica scientists will now try to extend their analysis further back in time.
Another study reported in the same journal claims that for the last 150
years, sea levels have been rising twice as fast as in previous centuries.
Using data from tidal gauges and reviewing findings from many previous
studies, US researchers have constructed a new sea level record covering the last 100 million years. They calculate the present rate of rise at 2mm per year.
"The main thing that's changed since the 19th Century and the beginning of modern observation has been the widespread increase in fossil fuel use and more greenhouse gases," said Kenneth Miller from Rutgers University. The Intergovernmental Panel on Climate Change, the body which collates scientific evidence for policymakers, concludes that sea level rose by 1-2mm per year over the last century, and will rise by a total of anything up to 88cm during the course of this century.
CO2 Levels highest for 650,000 years