Unseasonably Warm Weather A Clear Sign Of Climate Change, Say Scientists

The Guardian - Michael Slezak

El Niño driving current spike in warm weather and May almost certain to be warmer than average from 1961 to 1990

The sun rises over Port Philip Bay in Melbourne. Blair Trewin from the Bureau of Meteorology said the unseasonal weather was happening against a background of global warming. Photograph: Tracey Nearmy/AAP

Unseasonably warm weather across Australia, which is set to continue through the coming month, might be putting a spring in people's step but is a clear sign of dangerous climate change, according climate scientists and meteorologists. Australia and the rest of the world have been reeling from a string of temperature records being smashed. February caused alarm when it was the most unusually warm month on record by a huge margin. But that record was broken immediately by March.
In Australia March 2016 was the warmest March on record. And this week the Bureau Of Meteorology released its seasonal outlook, showing above average temperatures are set to continue across the country at least throughout May.
According to David Karoly, a climate scientist from the University of Melbourne, climate change increased the chance of March breaking the temperature record in Australia by at least seven times.
xx"The previous record had about a one in 43-year chance due to natural climate variations alone but now occurs about one year in six in the present climate, that is already affected by human-caused climate change," he told Guardian Australia.
"It's evidence that climate change is already happening – and increasing the risks of hot extremes."
Blair Trewin from the Bureau of Meteorology said: "April won't be a record but it will be well above normal."
Throughout May temperatures across most of the country have an 80% chance of being warmer than the average from 1961 to 1990. By June and July most coastal regions will continue to have unusually warm weather, however temperatures will return to normal around central and southern Australia.
The current spike in warm weather is happening partly because of the monster El Niño that spread a pulse of warm water across the Pacific Ocean in 2015. That El Niño is dissipating, spreading the warmer water around Australia, raising temperatures.
But all that was happening on top of the background of global warming, Trewin said. He said that these days, in an El Niño year, the world tended to experience extreme temperatures and merely "above average" temperatures in other years. Only when a La Niña cooled the globe were there normal or slightly cool temperatures.

Links

• Great Barrier Reef: Greens call for new tax on mining to pay for damage
• Great Barrier Reef bleaching made 175 times likelier by human-caused climate change, say scientists
• CSIRO job cuts fewer than feared but climate scientists say reduction a 'con'
• Climate change: website reveals which homes will be swamped by rising sea levels
• Climate change makes past five-year period the warmest on record: WMO
• Climate change report: 'The worst is yet to come' – as it happened
• Climate forecast for Australia: hot days, higher fire risk, more severe droughts
• Climate change: Weather of Olympian extremes
• Know any climate change sceptics? Turn off their air conditioning

Emerging Threat From Climate Change: Ocean Oxygen Levels Are Starting To Drop

Fairfax - Peter Hannam

Just when you thought you had most of the threats from climate change covered.
We are looking on now as warming oceans stress the world's coral reefs, prompting them to turn white, including our Great Barrier Reef.

The world's oceans are warming up along with the rest of the planet. Photo: Leigh Henneingham

We also know that our oceans have become about 30 per cent more acidic since pre-industrial times as they absorb the billions of tonnes a year of carbon dioxide released from our burning of fossil fuels and forests, making it harder for shellfish and crabs to form shells.
But now, some of the first evidence is emerging of what scientists have been expecting for decades: oxygen levels in some oceans are beginning to fall and widespread evidence of the trend should be evident from 2030 onwards.
Warming seas absorb less oxygen at the surface. Another effect of a changing climate is that oceans turn over less, so that oxygen at the surface has less chance of moving deeper.

Marine life will be hit hard if oxygen levels sink. Photo: NOAA

Matthew Long, lead author of a study published in the American Geophysical Union's journal, Global Biogeochemical Cycles, said deoxygenation poses a major threat to marine life and is one of the most serious side-effects from a warming atmosphere.
"Oxygen is a necessary ingredient for marine life, for all sorts of marine organisms," Dr Long, a scientist with the US's National Centre for Atmospheric Research and based in Colorado.
"The extent we care about marine ecosystems for their intrinsic value, we should care," Dr Long told Fairfax Media. "We're also reliant on these systems for food - fisheries will be vulnerable."
According to the models, the process is likely to be underway in the southern Indian Ocean and parts of the eastern tropical Pacific and Atlantic.
The study found that eastern Australia, eastern Africa and south-east Asia may be relatively spared, with impacts likely to be delayed until the next century.
The effects of lower oxygen levels will compound other harmful trends for wildlife such as oceans becoming more acidic.
"We're driving pretty massive changes in the environment - and we're not just changing one variable," Dr Long said. "We're changing a suite of variables to which marine organisms are sensitive, and basically putting significant demands on their adaptive capacities."

CSIRO cuts
Dr Long said it was important for governments to invest in long-term, consistent research to help predict and manage the impacts. This role was particularly vital given observation records for much of the world's oceans are limited.
He also questioned the decision by Australia's CSIRO to cut climate monitoring and modelling programs.
The agency has trimmed the number of scientists to go from two key research programs from almost 100 to about 45, a move that has drawn wide criticism from researchers at home and abroad.
"I don't understand it, and it does seem short-sighted in my view," Dr Long said.
In the longer term, the world had to curb carbon impacts and limit global warming.
"If the carbon dioxide-driven warming continues, the trend in ocean deoxygenation is basically an inexorable component associated with that warming," he said.

Work 'in jeopardy'
Richard Matear, a senior research scientist at CSIRO, said a 2001 paper that he and a team of researchers had worked on had detected some changes to oxygen levels south of Tasmania. The new paper, though, suggests, natural fluctuations may be the key there.
"We're just slowly getting a handle on how much natural variability there is in the system," Dr Matear said.
The Southern Ocean to Australia's south has relatively high oxygen levels compared with other oceans, and a strengthening of the circumpolar winds with climate change may foster more mixing of oxygen-rich waters, he said.
Still, changing circulation would alter which seas become more oxygenated - and at what depths. Those shifts could impact more mobile species such as tuna and squid, whose larger ranges require more oxygen to match their higher metabolism.
The current cuts to CSIRO climate science will remove about 13 researchers from Dr Matear's program. His unit has yet to determine which projects will be scaled back or dropped, to cope with reduced funding.
Some of his colleagues have just left on a research voyage to conduct "repeat lines" of an area studied in the Pacific, to detect changes.
"We have no funding going forward to do that cruise again in the next five to 10 years," Dr Matear said, hindering the ability to track changes to oxygen and other elements.
Of the other key areas being monitored, cruises to the region south of Tasmania may continue with funds cobbled together from other sources. The region south of Perth is another area where monitoring may be disrupted, he said.
"In the current situation, there's really no funding to support them," Dr Matear said of the cruises.
"We're an important player in the southern hemisphere and the Southern Ocean, and that work is in jeopardy," he said.
The evidence suggests that the combination of rising CO2 and falling oxygen levels "will be worse than each one acting independently", Dr Matear said.
CSIRO is a principal sponsor of a conference in Hobart next week on "The oceans in a high CO2 world".

Links

• CSIRO creates climate centre after cuts
• Just 7% of Great Barrier Reef unaffected from bleaching
• The Great Barrier Reef: 93% hit by coral bleaching, surveys reveal
• Confusion over future of CSIRO Melbourne lab as climate science moves to Hobart
• Labor would introduce carbon market, pledge deeper carbon cuts if elected
• CSIRO's new climate centre won't resolve future of research in Australia
• Election 2016: Greens would tax coal, ban new mines in bid to save Great Barrier Reef
• Sir David Attenborough makes heartfelt plea for the Reef
• Can we reverse coral bleaching?

Great Barrier Reef Bleaching Would Be Almost Impossible Without Climate Change

The Conversation - Andrew King | David Karoly | Mitchell Black | Ove Hoegh-Guldberg | Sarah Perkins-Kirkpatrick

Coral Bleaching at Lizard Island on the Great Barrier Reef. © XL Catlin Seaview Survey

The worst bleaching event on record has affected corals across the Great Barrier Reef in the last few months. As of the end of March, a whopping 93% of the reef has experienced bleaching. This event has led scientists and high-profile figures such as Sir David Attenborough to call for urgent action to protect the reef from annihilation.
There is indisputable evidence that climate change is harming the reef. Yet, so far, no one has assessed how much climate change might be contributing to bleaching events such as the one we have just witnessed.
Unusually warm sea surface temperatures are strongly associated with bleaching. Because climate models can simulate these warm sea surface temperatures, we can investigate how climate change is altering extreme warm conditions across the region.

Daily sea surface temperature anomalies in March 2016 show unusual warmth around much of Australia. Author provided using OSSTIA data from UK Met Office Hadley Centre.

We examined the Coral Sea region (shown above) to look at how climate change is altering sea surface temperatures in an area that is experiencing recurring coral bleaching. This area has recorded a big increase in temperatures over the past century, with March 2016 being the warmest on record.

March sea surface temperatures were the highest on record this year in the Coral Sea, beating the previous 2015 record. Source: Bureau of Meteorology. 

Examining the human influence
To find out how climate change is changing the likelihood of coral bleaching, we can look at how warming has affected the likelihood of extremely hot March sea temperature records. To do so, we use climate model simulations with and without human influences included.
If we see more very hot March months in simulations with a human influence, then we can say that climate change is having an effect, and we can attribute that change to the human impact on the climate.
This method is similar to analyses we have done for land regions, such as our investigations of recent Australian weather extremes.
We found that climate change has dramatically increased the likelihood of very hot March months like that of 2016 in the Coral Sea. We estimate that there is at least a 175 times increase in likelihood of hot March months because of the human influence on the climate.
The decaying El Niño event may also have affected the likelihood of bleaching events. However, we found no substantial influence for the Coral Sea region as a whole. Sea surface temperatures in the Coral Sea can be warmer than normal for different reasons, including changes in ocean currents (often related to La Niña events) and increased sunshine duration (generally associated with El Niño conditions).
Overall, this means that the influence of El Niño on the Coral Sea as a whole is weak. There have been severe bleaching events in past El Niño, neutral and La Niña years.
We estimate that climate change has increased temperatures in the hottest March months by just over 1℃. As the effects of climate change worsen we would expect this warming effect to increase, as has been pointed out elsewhere.
March 2016 was clearly extreme in the observed weather record, but using climate models we estimate that by 2034 temperature anomalies like March 2016 will be normal. Thereafter events like March 2016 will be cooler than average.
Overall, we're observing rapid warming in the Coral Sea region that can only be understood if we include human influences. The human effect on the region through climate change is clear and it is strengthening. Surface temperatures like those in March 2016 would be extremely unlikely to occur in a world without humans.
As the seas warm because of our effect on the climate, bleaching events in the Great Barrier Reef and other areas within the Coral Sea are likely to become more frequent and more devastating.
Action on climate change may reduce the likelihood of future bleaching events, although not for a few decades as we have already built in warming through our recent greenhouse gas emissions.

A note on peer review
We have analysed this coral bleaching event in near-real time, which means the results we present here have not been through peer review.
Recently, we have started undertaking these event attribution analyses immediately after the extreme event has occurred or even before it has finished. As we are using a method that has been previously peer-reviewed, we can have confidence in our results.
It is important, however, that these studies go through a peer-review process and these results will be submitted soon. In the meantime we have published a short methods document which provides more detail.
Our results are also consistent with previous studies (see also here and here).

Links

• The oceans are becoming too hot for coral, and sooner than we expected
• Coral bleaching comes to the Great Barrier Reef as record-breaking global temperatures continue
• Great Barrier Reef disaster is the latest harbinger of a global mass extinction
• David Attenborough says the Great Barrier Reef is in 'grave danger' – it's time to step up