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Antarctic study points to ‘scary’ future with global warming

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Wellington: Global sea levels will rise substantially more than previously thought and almost irreversibly if greenhouse gas emissions continue, according to New Zealand-led research released on Thursday.

An international team led by Nicholas Golledge, of Victoria University’s Antarctic Research Centre, used state-of-the-art computer modelling to simulate the Antarctic ice-sheet’s response to a warming climate under a range of greenhouse gas emission scenarios.

They found that all but one of the scenarios, that of significantly reduced emissions beyond 2020, would lead to the loss of large parts of the Antarctic ice-sheet, which in turn would result in a substantial rise in the global sea-level, Xinhua reported.

“The long reaction time of the Antarctic ice-sheet, which can take thousands of years to fully manifest its response to changes in environmental conditions, coupled with the fact that CO2 (carbon dioxide) lingers in the atmosphere for a very long time means that the warming we generate now will affect the ice-sheet in ways that will be incredibly hard to undo,” Golledge said in a statement.

In its 2013 Assessment Report, the Intergovernmental Panel on Climate Change (IPCC) predicted that the Antarctic ice-sheet would contribute only 5 centimetres to global sea-level rise by the end of this century even for its warmest emissions scenario.

But Victoria University professor Tim Naish, who was a lead author of the IPCC report, cautioned that at the time the report was written there was insufficient scientific knowledge on how the Antarctic ice-sheet might respond to future warming, meaning the IPCC sea-level projections could have been too modest.

“Our new models include processes that take place when ice-sheets come into contact with the ocean. Around 93 percent of the heat from anthropogenic global warming has gone into the ocean, and these warming ocean waters are now coming into contact with the floating margins of the Antarctic ice sheet, known as ice-shelves,” said Golledge.

“If we lose these ice-shelves, the Antarctic contribution to sea-level rise by 2,100 will be nearer 40 centimetres.”

To avoid the loss of the Antarctic ice-shelves, and an associated commitment to many metres of sea-level rise, the study showed atmospheric warming needed to be kept below 2 degrees centigrade above present levels.

“Missing the 2 degrees centigrade target will result in an Antarctic contribution to sea-level rise that could be up to 10 metres above present day,” said Golledge.

“The stakes are obviously very high, 10 percent of the world’s population lives within 10 metres of present sea level.”

To restrict global warming to 2 degrees centigrade and prevent the more dangerous consequences of climate change, the United Nations climate change meeting in Paris later this year had to agree to reduce global CO2 emissions to zero before the end of the century, Naish said in the statement.

“To be on track this will require a global commitment to 30 percent reduction, below year 1990 levels, by the year 2030.”

The last time CO2 concentrations in the atmosphere were similar to present levels was about 3 million years ago, when sea levels were 20 metres higher than now, said Golledge.

 

(IANS)

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Climate Change’s Fight Harder Than Thought: Study

This new research suggests that accomplishing that goal requires countries to pull 25 percent more carbon out of the atmosphere than they've already committed to cleaning up.

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Oceans
People walk on the beach of Biarritz, southwestern France, along the Atlantic Ocean, Dec. 18, 2015. New research shows the oceans are storing much more heat than previously thought. VOA

A new report recently published in the journal Nature suggests the Earth’s oceans are absorbing more of the planet’s excess heat than previously thought.

Scientists have known for some time that oceans store excess heat energy, and this helps keep the planet in its balmy, just-right temperature for supporting the explosion of life on Earth.

Knowing how hot the ocean is getting, and how fast that temperature is rising, helps scientists understand more about human-impacted climate change. It helps them know how much excess energy is being produced, and it helps them predict how much heat the ocean is capable of absorbing and how much warming will be felt on the Earth’s surface.

Oceans, boats
Lobster boats are moored in the harbor in Stonington, Maine. VOA

Up until the report was issued this week, the Intergovernmental Panel on Climate Change (IPCC) thought it had a pretty good handle on how much excess energy the oceans were absorbing. Using those numbers, the panel set targets for the amount of carbon reduction necessary to slow, and ultimately reverse, potentially devastating planetary warming.

But these new numbers suggest those targets may have to be revised upward by 25 percent. Research by the study’s lead author, Princeton professor Laure Resplandy, indicates our oceans are absorbing about 60 percent more heat energy than previously estimated.

According to Resplandy, the world’s oceans have taken up more than 13 zettajoules of energy every year between 1991 and 2016. A joule is the standard unit of energy; a zettajoule is one joule, followed by 21 zeroes.

Oceans, arctic
FILE – A young polar bear walks on ice over deep waters of the Arctic Ocean. VOA

“Imagine if the ocean was only 30 feet deep,” Resplandy said. “Our data show that it would have warmed by 6.5 degrees Celsius every decade since 1991. In comparison, the estimate of the last IPCC assessment report would correspond to a warming of only 4 degrees Celsius every decade.”

How they got the new numbers

It’s not that the old numbers were wrong; it’s that the new numbers relied on new techniques and new ways to measure ocean warming. The old techniques used spot measurements of ocean temperature. But Resplandy and her team measured the amount of oxygen and carbon in the air, a number they call “Atmospheric Oxygen Potential (APO).” As oceans warm, they release oxygen and carbon into the atmosphere, which increases APO.

Another factor that raises APO is the burning of fossil fuels. Resplandy and her team compared the expected rise in APO due to the burning of fossil fuels, and compared it to the actual APO they were seeing. By looking at the difference, the team was able to predict how much carbon and oxygen were being released by the oceans and, therefore, how warm the world’s oceans were getting.

climate, global warming, celsisu, oceansac
A fisherman stands on his boat as he fishes at the Tisma lagoon wetland park, also designated as Ramsar Site 1141 in the Convention on Wetlands, in Tisma, Nicaragua. VOA

Why the new numbers matter

A host of countries, including the U.S. and China, signed the Paris Climate Accord in 2015, which aims to keep average global temperatures from rising more than 2 degrees Celsius above pre-industrial levels. Many climate scientists predict that if temperatures go above that mark, humans will be faced with devastating long-term global affects. Keeping those temperatures down requires cutting the amount of greenhouse gases pumped into the atmosphere.

Also Read: New Carbon Capture Technology Now Able To Fight Climate Change: Experts

The U.S. has since pulled out of that climate agreement, but most of the rest of the world remains focused on limiting the rise of the world’s average temperatures.

This new research suggests that accomplishing that goal requires countries to pull 25 percent more carbon out of the atmosphere than they’ve already committed to cleaning up. (VOA)