A new scientific analysis finds that the Earth’s oceans are rising nearly three times as rapidly as they were throughout most of the 20th century, one of the strongest indications yet that a much feared trend of not just sea level rise, but its acceleration, is now underway.

“We have a much stronger acceleration in sea level rise than formerly thought,”

said Sönke Dangendorf, a researcher with the University of Siegen in Germany who led the study along with scientists at institutions in Spain, France, Norway and the Netherlands.

Their paper, just out in the Proceedings of the National Academy of Sciences, isn’t the first to find that the rate of rising seas is itself increasing — but it finds a bigger rate of increase than in past studies. The new paper concludes that before 1990, oceans were rising at about 1.1 millimeters per year, or just 0.43 inches per decade. From 1993 through 2012, though, it finds that they rose at 3.1 millimeters per year, or 1.22 inches per decade.

The cause, said Dangendorf, is that sea level rise throughout much of the 20th century was driven by the melting of land-based glaciers and the expansion of seawater as it warms, but sea level rise in the 21st century has now, on top of that, added in major contributions from the ice sheets of Greenland and Antarctica.

Dangendorf said.

Studying the changing rate of sea level rise is complicated by the fact that scientists only have a precise satellite record of its rate going back to the early 1990s. Before that, the records rely on tide gauges spread around the world in various locations.

But sea level rise varies widely in different places, due to the rising and sinking of land, large-scale gravitational effects on the waters of the globe and other local factors.

Read more: The Washington Post

AS MUCH as half the Great Barrier Reef may have died in the back-to-back bleachings over the past two years.

But the head of the authority in charge of the reef says the actual extent of damage is tricky to calculate because some parts are growing well.

The Great Barrier Reef Marine Park Authority believes about 30 per cent of coral, in the reef’s northern part, died last year in bleaching caused by warmer ocean waters, chairman Russell Reichelt told a Senate committee on Monday.

Surveys after this year’s bleaching are still being done but initial observations suggest 20 per cent of coral — mainly in the central area of the 344,000 sq km reef — is dead.

“Don’t think of these figures as the net amount of coral on the Barrier Reef because there are quite big movements upwards as well as downward,”

Dr Reichelt told the senators at an estimates hearing in Canberra.

The southern part of the reef had grown by about 40 per cent in recent years because it hadn’t been hit by cyclones or bleaching — but it was likely it would suffer from those in the future.

Dr Reichelt said the bigger picture question was the coral’s resilience in the face of bleachings, tropical storms and other threats such as the crown of thorns invasions.

“It depends on the frequency of these major impacts and the concern is the frequency could well be increasing and the recovery time will be insufficient,”

he said.

“If the recovery time is very short, there won’t be a lot of coral.”

Read more: News.com.au