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Published: 30 July 2012

Warming from rising CO2 could happen faster than expected


Scientists have shed new light on one of the most important questions in climate science: the time lag between changes in temperature and changes in atmospheric CO2 levels in the past.

Greenhouse warning: the time lag between rising greenhouse gas emissions and global warming might be shorter than predicted in the past.

Their findings suggest that feedbacks in the climate system – in which warming is linked to natural CO2 increase, driving further warming – may operate faster than previously thought.

In research just published in Climate of the Past the scientists used Antarctic and Greenland ice cores to examine temperature and CO2 changes during the largest natural climate change in recent climate history: Earth’s exit from the last ice age.

As Antarctic temperatures increased, ocean circulation altered, releasing CO2, most likely from the deep Southern Ocean, to the atmosphere. Previous studies had suggested it took up to 1000 years for this to happen. But that figure has been revised down by the new study, which draws on data from five separate ice cores.

‘The ice cores reveal a near-synchronous temperature and CO2 increase. If there was a lag at all, it was likely no more than 400 years,’ says Mr Joel Pedro from Hobart’s Antarctic Climate and Ecosystems CRC, who led the study.

Eric Steig, an American ice core expert based at the University of Washington, says almost all previous work had noted uncertainties on the time lag between temperature and CO2, in the order of many hundreds to even thousands of years

‘I cannot emphasise enough how important this result is,’ he said. ‘The authors collapse these values to something so short that it has major implications for our understanding of the carbon cycle and climate change.’

Beginning about 19,000 years ago, the extensive ice sheets covering Canada and Northern Europe began to melt. Over the next 8000 years, atmospheric CO2 levels increased by close to 50 per cent, helping to drive an eventual global average temperature increase of 5°C and a sea-level rise of over 100 metres.

‘The coupled rise in temperature and natural increase in CO2 that helped end the ice age took place gradually, over about 8000 years,’ explained Pedro. ‘What we have seen since the start of the industrial revolution is a similar CO2 increase occurring over only a few hundred years. This is way faster than anything in the ice core record and it’s clearly human-caused.

‘Just as the steady increase in CO2 helped to melt the ice caps and warm the Earth out of the ice age, the rapid increase now in CO2 is also driving up temperatures, only at a much faster rate,’ he said.

Pedro says the research raises the possibility that current human-induced warming may drive additional natural CO2 increases sooner than we thought, compounding the climate change problem – a possibility, he adds, that merits further research.

The research is a collaboration between the Antarctic Climate and Ecosystems CRC (ACE CRC), the Australian Antarctic Division, and the Niels Bohr Centre for Ice and Climate, Denmark.

Source: ACE CRC







Published: 25 November 2014

Things warm up as the East Australian Current heads south

Jaci Brown

Occasional erratic bursts southward of the East Australian Current (EAC) are thought to have moderated the weather of south-east Australia this autumn and winter and they continue to introduce tropical and sub-tropical marine species to Tasmanian waters.

Tasmania’s east coast: tropical and sub-tropical marine species normally found off NSW are finding their way further south, thanks to changes in the East Australian Current.
Tasmania’s east coast: tropical and sub-tropical marine species normally found off NSW are finding their way further south, thanks to changes in the East Australian Current.

Ocean monitoring by Australia’s Integrated Marine Observing System is providing scientists with significant new insights into the changing structure of the EAC. Over the past 50 years sporadic warm bursts have become more common as the EAC moves further south. With global warming, the warm burst we’ve seen this year may also become the norm.

Had our little friend Nemo the clownfish been riding the EAC this year he might have found himself holidaying in Tasmania rather than admiring the Sydney Opera House. He wouldn’t have been on the trip alone, though. Sea nettles (Chrysaora spp.) have headed from their usual home in Sydney to be found for the first time ever in Tasmania and the Gippsland Lakes.

<i>Chrysaora woodbridge</i>, or sea nettle, was found in surprising numbers in Tasmania this year.
Chrysaora woodbridge, or sea nettle, was found in surprising numbers in Tasmania this year.
Credit: copyright Lisa-ann Gershwin

Waters in the EAC travel southward along the east coast of Australia, with most of it splitting from the coast near Sydney and heading for New Zealand. A small part of the current, known as the EAC Extension, works its way southward past Victoria and Tasmania.

A typical signature in this region are the large eddies, around 200 kilometres across and hundreds of metres deep. Some of the warm water is trapped here along with marine life.

The EAC starts at the Great Barrier Reef and travels south to Sydney before turning eastward to New Zealand. Some of the water can still push southward via a series of strong eddies.
The EAC starts at the Great Barrier Reef and travels south to Sydney before turning eastward to New Zealand. Some of the water can still push southward via a series of strong eddies.
Credit: Eric Oliver

This year a larger proportion of the EAC was sent southward instead of breaking away to the east. Winter ocean temperatures off Bass Strait were around 19°C, an increase of 4°C. This impacted local fishing, beach conditions and the weather.

In the video (above) the animation on the left shows the actual sea surface temperature and speed of the ocean currents. The animation on the right shows the difference in the temperature from average conditions.

Through autumn and winter, you can see two interesting changes occur. A strong warm current heads down the coast from Sydney to the coast of Victoria. At the same time, warm water peels off from the EAC and swirls around in large eddies as it meanders toward Tasmania.

An unusual catch down south

One advantage of warm eddies is the refuge they provide for tuna. They congregate in the centre of the eddy where the waters are warm and dine at the nutrient-rich edges.

Local fishers in north-east Tasmania report a remarkable year that allowed them to fish longer than usual, providing game fishers with more opportunities to catch tuna.

Last summer’s (2013–2014) warmth provided an abundance of skipjack and striped marlin, while winter brought a run of bluefin tuna.

Redmap is a website where locals can report sightings of marine species that are unusual for a given area.

Last summer a manta ray, a tropical cartilaginous fish (in a group including rays and skates), was sighted off the north-eastern coast of Tasmania. Previously the southern-most sighting of a manta ray was just south of Sydney.

<i>Manta birostris</i> spotted off north-east Tasmania on Australia Day 2014.
Manta birostris spotted off north-east Tasmania on Australia Day 2014.
Credit: Redmap/Leo Miller

It’s not just new species visiting Tassie either. Local jellyfish such as the Lion’s Mane (Cyanea) – more commonly known as ‘snotty’ – are usually quite elusive, but turned up in unprecedented numbers last summer in Tasmania.

But there’s a catch

This movement south of the EAC may have an impact on other systems, including our health. We rely on fish such as those from the Tasman Sea as a source of omega-3 fatty acids for our brain health. But the concentration of omega-3 fatty acids in the fish is likely to decrease with global warming.

Algae are the original source of fatty acids. As our waters warm, we will see more of the algae from the tropics take up residence in the south-east.

But the algae from the tropics are much smaller, which means more steps in the food chain from the algae to the fish we eat. The more steps in the food chain, the more the omega-3 fatty acids in the fish are replaced by fatty acids that are less favourable to brain health.

The warmer coastal waters also contributed to the balmy autumn and winter in south-eastern Australia this year. Afternoon sea breezes cool coastal temperatures by drawing cool oceanic air onto the coast.

Sydney’s heat wave in May this year had 19 consecutive days of 22°C or more – this is partly due to the sea breezes failing to bring in the usual cooling air.

What’s causing the EAC to move south?

Over the past 50 years the EAC Extension has stretched about 350 km further south. This extension doesn’t happen smoothly but in erratic bursts.

The southward extent of the EAC is controlled by the collective behaviour of the winds between Australia and South America. Over that same 50-year period these winds changed their pattern due to a strengthening of a climate system known as the Southern Annular Mode.

The changes to this mode have been attributed to a combination of ozone depletion and increasing atmospheric CO2.

One of the most robust and consistent responses of the climate system to increasing CO2 is a further strengthening of the Southern Annular Mode.

So the result will likely be a further enhancement of the EAC extension southward and even warmer waters in the Tasman Sea.

Dr Jaci Brown is a senior research scientist with the Centre for Australian Weather and Climate Research (CAWCR), a partnership between CSIRO and the Bureau of Meteorology. Her research focuses on the El Nino Southern Oscillation (ENSO) and climate change. This article was originally published on The Conversation. Read the original article.






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