It’s been Australia’s hottest ever October, and that’s no coincidence

David Karoly, University of Melbourne and Mitchell Black, University of Melbourne

This has been Australia’s hottest October on record. Barring an (extremely unlikely) cold snap, it will also be the hottest October for Victoria, and for Melbourne. And the record-breaking temperatures are at least six times more likely thanks to human-induced global warming.

But hold up, you say, October isn’t over yet! That’s true, but going by the current forecast from the Bureau of Meteorology we can see that new record high October average maximum temperatures are virtually certain.

In fact, the maximum temperature on Saturday would need to be below freezing across Victoria for the record not to be set, and there is no physically plausible scenario that could lead to that happening. Maybe if an asteroid landed in Victoria on Saturday (Halloween) and threw up enough dust to block out the sun? But that is very, very unlikely!

What’s driving the heat?

A record hot spell affected southeast Australia in the first week of October and a second exceptional hot spell followed two weeks later.

The very hot spell that hit Australia in early October. Note parts of south east Australia experienced temperatures 8-10C above average.
Australian Bureau of Meteorology

New record highs have been set for monthly and seasonal average temperatures across Australia at 12 times the rate of new record lows. Global warming is the cause.

To understand the role of human-caused global warming in the new records we compare simulations of the Earth’s climate from nine different models from around the world.

We only select climate models that do a good job of simulating the natural year-to-year variability of Australian temperatures. We then compare simulations for the current climate (with human influence) and for the climate without human influence.
This approach has been used already to show the important role of global warming in record high Australian temperatures in 2013.

Using this method we can figure out the chances of breaking a record even before it happens. The previous hottest October in Australia was in 2014 with a temperature of 32.9°C. Our analysis shows an increase by at least a factor of six in the chances of setting the new October record maximum temperature for Australia due to global warming.

What about El Niño?

But we also have to factor in El Niño. As noted by the Bureau of Meteorology, such hot and dry spells are typical for the strong El Niño that is currently occurring in the Pacific Ocean.

To do this we use a huge set of data from a citizen science project called Weather@home ANZ. Weather@home allows you to donate your computer’s processing power to simulate Australia’s climate with and without human-caused climate change, and including El Niño.

This modelling approach, undertaken in partnership with the University of Oxford, has been used to assess the role of climate change in extreme weather and climate events in Australia in 2013 and 2014 and for typical El Niño conditions, such as this October.

We have more than 4,000 independent simulations of Australian weather and climate in October under El Niño conditions in the present world, and more than 8,000 simulations for El Niño conditions in a pre-industrial world with no human influences on climate.

These simulations allow us to assess the chances of breaking the existing records for October mean maximum temperature for the whole of Australia, for Victoria and for Melbourne under the current El Niño conditions.

For example, the figure below shows the simulated frequency of different October mean maximum temperatures for Melbourne with and without global warming.

The chances of higher October mean maximum temperature in Melbourne during an El Niño year are much greater due to global warming. The current record is shown by the vertical line.

The current record high mean maximum temperature of 23.7°C was set in October 1940. The chances of breaking the current record are much greater for the current climate, including the influence of global warming, than they would have been with no global warming.

In fact, human-caused climate change has very likely increased the chances of setting the new record for Melbourne by at least six times, even under El Niño conditions.

For the whole state of Victoria, global warming has increased the chances of breaking the existing record by at least six times, while for Australia under El Niño conditions, global warming has increased the chances by at least ten times. This is more than the increase found using the other climate models mentioned above, because now we have also taken into account the influence of El Niño.

Climate change due to human activity has dramatically increased the chances of setting new record temperatures in Melbourne, Victoria and Australia in October this year.

Of course, we have to wait another couple of days to see if our predictions hold true. But we are pretty confident they will.

The Conversation

David Karoly, Professor of Atmospheric Science, University of Melbourne and Mitchell Black, PhD Candidate, University of Melbourne

This article was originally published on The Conversation. Read the original article.


Australia’s plantation boom has gone bust, so let’s make them carbon farms

Jason Alexandra, Charles Darwin University

In the rolling hills of Victoria’s Strzelecki Ranges, among paddocks of pasture and potatoes, stands a simple steel monument to the world’s tallest tree. The tree itself, which stood a mighty 115 m tall, was chopped down in the 1880s so that a registered surveyor could measure it.

Almost a century and a half later, Australia’s attitude to its forests is seemingly no less perverse.

Not chopping it down might have been a more fitting tribute.
Author provided

Not far north of where the tree once stood is the Latrobe Valley, dominated by some of Australia’s most carbon-intensive coalmines and power stations. Covering much of the surrounding hills are timber plantations, which store tonnes of carbon. Plantations can be used to soak up emissions – except the current rules don’t officially recognise this.

Intensive plantations don’t count as carbon sinks under Australia’s carbon farming rules. The boom that led to the creation of almost a million hectares of new plantation timber died with the global financial crisis – but with a bit of smart thinking these could be put to use as carbon farms, rather than being allowed to die off and returned to pasture.

Boom and bust

The see-sawing fortunes of Australian forestry have largely been driven by government policy. The 1990s saw major policy reforms, which spawned protests (including log trucks blockading the national parliament) and ultimately resulted in a widespread expansion of timber plantations.

The area of eucalyptus plantations grew from almost nothing in 1998 to about 1 million hectares by 2008, spurred by a massive influx of finance encouraged by the Managed Investments Act (1998), which turned plantations into tax-effective investments.

But then came the global financial crisis, which saw Managed Investment Scheme (MIS) companies like Timbercorp and Great Southern Plantations go bust. Shareholders and investors lost out, but the plantations themselves were in the ground.

Since then, plantation ownership has been consolidated into the hands of a few dominant players such as NewForests, which acquired more than 700,000 ha, and Global Forest Partners (more than 150,000 ha).

An expensive experiment

Some MIS plantations were poorly sited, in terms of climate and soils, used inappropriate species, or suffered pest or disease problems. Some have been written off, bulldozed and returned to pasture. Many more are likely to be.

Current estimates suggest that a third of the eucalyptus plantations are uneconomic with harvesting unlikely, another third will probably be harvested but are unlikely to be replanted. The rest will form Australia’s future hardwood estate. In this sense it has been a massive and expensive experiment.

This story shows the power of financial incentives, but reflects the problem of using tax inducements to fund an industry. For investors, tax deductions became the primary goal, rather than the quality of the investment.

The plantations’ boom and bust, with its focus on using fast money for fast-growing eucalypts, mostly for pulpwood, has obscured other important opportunities.

First, it shifted the focus away from the opportunities of integrating forestry into farming systems.

Second, the reputation of Australian forestry and forestry investments has almost certainly suffered.

Third, it may have blinded us to the potential of using Australia’s rich diversity of tree species for other purposes. Australia’s genetic gifts to the world include trees that grow prolifically in poor soils, can withstand fire and drought, store carbon, and produce hard, strong, richly coloured timbers.

A treasure trove for carbon farmers.
T. Grove/CSIRO/Wikimedia Commons, CC BY

Already planted across millions of hectares throughout the world, Australia’s eucalypts, acacias and casuarinas offer a genetic treasure trove for carbon farming.

With much to learn about Australia’s diverse and productive flora – including how to farm it for carbon – it seems perverse that investment in Australian forestry research and education is now declining.

Carbon crops

Carbon markets and emerging technologies could fundamentally alter the way we conceive of trees as crops.

With a million hectares of eucalyptus plantation approaching maturity, there is almost certainly an active search for commercial markets for the standing timber – as wood fibre, for bioenergy fuel, or for non-wood products.

Nonetheless, large areas are likely to be reconverted to pasture, resulting in less carbon being stored in these landscapes. But there’s another, even simpler option for what to do with these plantations.

Perhaps it is time to reconsider whether to credit the carbon captured by these trees, given that their plantings were sponsored by our taxes. Changes to the carbon farming rules might make these and other multi-use plantations more viable.

The Australian Forest Industry estimates that Australia’s Kyoto-compliant forestry plantations (those established on cleared land since 1990) offset about 4.5% of Australia’s total emissions, but these are not credited under Australia’s Carbon Farming Initiative.

There are no approved CFI methodologies for plantations that sequester carbon and produce commercial timbers, but if there were, multipurpose plantations could form a key plank of Australia’s Direct Action carbon abatement policy.

In addition to carbon, there is potential for plantings that deliver economic development and ecological benefits in terms of restoring landscapes. But new models of plantations are needed, supported with different policy setting that drive their development.

Any large-scale bio-energy or carbon plantings in the future need to heed the lessons from Australia’s plantation boom and bust. In emerging carbon-constrained economies, how we define resources in rural landscapes, including carbon credits, will literally shape our future.

The Conversation

Jason Alexandra, Honorary Fellow, Charles Darwin University

This article was originally published on The Conversation. Read the original article.