Monday May 21, 2018
Home Uncategorized Antarctic stu...

Antarctic study points to ‘scary’ future with global warming

0
//
52
Republish
Reprint

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)

Click here for reuse options!
Copyright 2015 NewsGram

Next Story

Arctic permafrost may unleash carbon within decades: NASA

Plants remove carbon dioxide from the air during photosynthesis, so increased plant growth means less carbon in the atmosphere

0
//
37
NASA, Pixabay
  • Permafrost in Northern Arctic can potentially become a permanent source of Carbon
  • It was previously thought to be safe from the effects of Global Warming
  • Rising temperature in the Arctic can cause severe carbon emissions

Permafrost in the coldest northern Arctic — formerly thought to be at least temporarily shielded from global warming by its extreme environment — could thaw enough to become a permanent source of carbon to the atmosphere in a few decades, warns a NASA-led study. This will happen in this century, with the peak transition occurring in 40 to 60 years, said the study.

Permafrost in Northern Arctic can become a permanent source of carbon in this century itself, according to NASA. Wikimedia Commons
Permafrost in Northern Arctic can become a permanent source of carbon in this century itself, according to NASA. Wikimedia Commons

Permafrost is soil that has remained frozen for years or centuries under topsoil. It contains carbon-rich organic material, such as leaves, that froze without decaying, NASA said in a statement on Tuesday.

As rising Arctic air temperatures cause permafrost to thaw, the organic material decomposes and releases its carbon to the atmosphere in the form of the greenhouse gases carbon dioxide and methane.

The researchers calculated that as thawing continues, by the year 2300, total carbon emissions from the coldest northern Arctic will be 10 times as much as all human-produced fossil fuel emissions in 2016.

Warmer, more southerly permafrost regions will not become a carbon source until the end of the 22nd century, even though they are thawing now, said the study led by scientist Nicholas Parazoo of NASA’s Jet Propulsion Laboratory in Pasadena, California.

That is because other changing Arctic processes will counter the effect of thawing soil in these regions.

The finding that the colder region would transition sooner than the warmer one came as a surprise, according to Parazoo. The researchers used data on soil temperatures in Alaska and Siberia and a numerical model that calculates changes in carbon emissions as plants grow and permafrost thaws in response to climate change.

They assessed when the Arctic will transition to a carbon source instead of the carbon-neutral area it is today — with some processes removing about as much carbon from the atmosphere as other processes emit.

World is under threat due to Global Warming. Wikimedia Commons

They divided the Arctic into two regions of equal size, a colder northern region and a warmer, more southerly belt encircling the northern region. There is far more permafrost in the northern region than in the southern one.

Over the course of the model simulations, northern permafrost lost about five times more carbon per century than southern permafrost.

The southern region transitioned more slowly in the model simulations, Parazoo said, because plant growth increased much faster than expected in the south.

Also Read: Global warming portends ill for India’s flourishing Dairy sector: Experts

Plants remove carbon dioxide from the air during photosynthesis, so increased plant growth means less carbon in the atmosphere.

According to the model, as the southern Arctic grows warmer, increased photosynthesis will balance increased permafrost emissions until the late 2100s. IANS