Climate change could lift sea level by 22 meters

WELLINGTON - The Earth's sea levels could rise up to 22 meters in the distant future even if this generation manages to limit global warming to 2 degrees Celsius, an international team of scientists said Tuesday.

"If the present levels of carbon dioxide in the atmosphere are not abated, and humans were to disappear from the planet and return in 2,000 years, they would find a world where the oceans have risen 20 meters," said Professor Tim Naish, of Wellington's Victoria University.

The research showed that if climate change was kept to the 2- degree limit recommended by the Intergovernmental Panel on Climate Change, sea levels could rise by 12 to 22 meters over the next few centuries.

Researchers from New Zealand and the United States studied sediment cores in Virginia in the United States, the Enewetak Atoll in the Pacific, and New Zealand's lower North Island region of Whanganui.

They investigated the late Pliocene epoch, or 2.7 million to 3.2 million years ago, the last time the carbon dioxide level in the atmosphere was at its current level, and atmospheric temperatures were 2 degrees higher than the present.

"We know that global sea levels at this time were higher than present, but estimates have varied from 5 to over 40 meters higher, " Naish said in a statement.

The team analyzed the position of the sea level 3 million years ago and concluded that it was extremely likely that sea levels peaked 10 to 30 meters above present levels, with a best estimate of 22 meters.

"Whanganui holds one of the world's best geological archives of global sea-level during the warm climate of the Pliocene and is a key data set in this new study," said Naish, who also led an international team to Antarctica to drill beneath the floor of the Ross Sea in 2006 and discovered that the Antarctic ice sheets retreated significantly during the Pliocene epoch.

"What we're seeing is that the evidence of Antarctic ice sheet collapse is consistent with evidence for sea-level rise in this new study," said Naish.

Study leader Professor Ken Miller, of Rutgers University in the US state of New Jersey, said that sea-level rise would take time.

"You don't need to sell your beach real estate yet, because melting of these large ice sheets will take from centuries to a few thousand years," Miller said in the statement.

The current trajectory for the 21st Century global rise of sea levels was 0.8 to 1 meter due to warming of the oceans, partial melting of mountain glaciers and partial melting of Greenland and Antarctica.

Naish said the study called into question the sensitivity of the Earth's large ice sheets to temperature change and showed that the natural state of the Earth under carbon dioxide already attained in the atmosphere was one with sea levels around 20 meters above present.

The research was published Tuesday in the journal Geology.