Lethal Heating: 05/17/21

17/05/2021

(NZ New Zealand Herald) Climate Change: How Future Oz Wild Fires Will Worsen NZ's Big Glacier Melt

New Zealand Herald - Jamie Morton

Manaaki Whenua-Landcare Research scientist Dr John Hunt collects snow at Fox Glacier soon after it was discoloured by dust from Australia's unprecedented bush fires. Photo / Phil Novis

Australia's catastrophic bush fires sent enough ash across the Tasman Sea to darken nearly all of the South Island's glaciers - compounding the already severe melting effect of climate warming.

Scientists say the "unprecedented" effects of the 2019-2020 bush fires - themselves driven by climate change - are a taste of what New Zealand will experience more of as the planet warms.

When the smoke reached our shores that summer, the most noticeable effect was the ghastly orange that temporarily tinted our skies.

But few may have pondered the dramatic impacts unfolding around our tourist-drawing glaciers.

Over the first few months of 2020, light-absorbing particles like black carbon and mineral settled on snow across almost the entire South Island, stretching more than 350km.

Now, a new study has found the snow-darkening effect of this dust was observed across an area of 2500 sq km of snow and ice - or 90 per cent of the glaciers.

Such particles drove melting by reducing within snow the amount of solar radiation reflected back - something called "albedo".

Because the albedo of pure snow was high, a large amount of the incoming radiation was reflected back before it could be absorbed and cause melting.

Coupled with the lowered albedo, the high solar radiation intensity over New Zealand during the southern summer, and other factors, the impact on the glaciers was going to be severe.

At the time, Monash University glacier researcher Professor Andrew Mackintosh estimated that the far-flung dust could have increased the season's melt rate by around a third.

In January 2020, Auckland's biggest drought in 25 years coincided with an orange haze created by Australia's devastating bush fires. Photo / Greg Bowker Visuals

In their study, just published in the journal Fundamental Research, scientists from China's Lanzhou University attempted to quantify precisely what it was.

Using satellite observations, they calculated the dust caused a mean enhanced snow melt rate of between 0.2cm and 0.41cm each day between January and March 2020 - with maximum daily melt rates of up to 0.66cm.

By the end of that period, they suggested the total enhanced melting could have been as high as 40cm - and generated as much as 750 million cubic metres of equivalent snow-water in the hydrologic cycle.

The researchers also reported how mean air temperatures increased by about 1.8C over the three months.

"In comparison, the air temperature over New Zealand has increased by 1.5C from pre-industrial times to the present," they said.

"This means that snow darkening caused by Australian wild fires resulted in a higher snow-melt acceleration than that caused by global warming over the past hundred years."

With climate change expected to drive larger and more frequent wild fire, the implications for the glaciers were grim.

"Wild fire-induced snow darkening may become more common not only in New Zealand," they said, "but also over the global cryosphere due to intensified future wild fires."

Manaaki Whenua Landcare researcher Dr Phil Novis, who is leading a million-dollar project investigating just that threat, said it was difficult to model snow and ice mass balance across all of New Zealand, even when using high-resolution data.

"In our opinion the authors did well with what they had available, and nicely illustrated that the impact of the bush fires was large, even if nailing down the actual magnitude of that impact is pretty difficult."

The decline of New Zealand glaciers like the Franz Josef will grow only more severe under climate change. Photo / Brian Anderson

But he pointed out that background albedo in the glaciers had changed over the last 20 years independently of the bush fires - which could affect some of the study author's calculations.

Novis also highlighted the researchers' suggestion that the impact of the fires on the hydrological cycle had been greater than that of climate warming since pre-industrial times.

"While this could possibly be true in a limited sense, the impact of climate warming has effects far beyond summer melting," he said.

"Because New Zealand glaciers occupy a high-precipitation environment, temperature changes have very large effects on snow accumulation and glacier area, and these will exceed the impact of the bushfires, even though the latter is very spectacular and obvious.

"So, while we welcome this work illustrating the substantial effect of the Australian bushfires on New Zealand glaciers, it's important to continue to recognise the enormous impact of climate warming and all its implications."

A recent study published in major journal Nature found that New Zealand's glaciers had been thinning at a rate of 1.5m a year between 2015 and 2019 - a nearly sevenfold increase compared to the period from 2000 to 2004.

And over the last four decades, other research has shown the Southern Alps have shed nearly a third of their ice volume - equivalent to the basic daily water use requirements of our current population for that whole period.

While Niwa's most recent aerial stocktake has found the glaciers fared better than expected over summer, the long-term prognosis for the icy wonders remains dire.

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(UK Reuters) BrItain To Treble Tree Planting By 2024 To Fight Climate Change

Reuters

Local youngsters Bella (L) and Daisy walk through a forest covered in bluebells near Marlborough in southern England, May 4, 2015. REUTERS/Toby Melville

Britain said it planned to treble tree planting rates over the next three years to help reach its target of net zero carbon emissions by 2050, as part of efforts to fight climate change.

The UK wants to push ahead with its environmental plans and encourage other nations to do the same ahead of its hosting of the United Nations Climate Change Conference in Glasgow, known as COP26, in November.

George Eustice, UK environment secretary, is set to announce on Tuesday that woodland creation rates will treble by May 2024, with around 7,000 hectares of woodlands planted per year.

"We will make sure that the right trees are planted in the right places and that more green jobs are created in the forestry sector," Eustice is due to say, according to a government statement published on Sunday.

The statement gave no other details of the plan and did not say how many trees would be planted or where, and did not say how much the planting scheme would cost or how it would be funded. It also did not give a comparison figure for how many hectares of woodland had been planted previously.

Britain's climate tsar and COP26 President Alok Sharma warned on Friday that world leaders must agree to end coal use at the November summit to prevent a climate catastrophe.

Ahead of COP26, the UK government said it was focused on four goals: securing global net zero, protecting communities and natural habitats from the impacts of climate change, mobilising finance, and nations working together to accelerate action.

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(AU Monash University) Victoria's Water Catchments May Not Recover From Drought: Study

Monash University

Study shows that rivers may not always eventually recover from drought.

Summary

Australian-first research by Monash University discredits the theory that rivers and underground water supplies eventually replenish following droughts or floods.
Following the Australian Millennium Drought, one-third of Victoria’s water catchments included in the study still had not recovered from drought by mid-2017, nearly eight years later.
For those water catchments not recovered, roughly 80 per cent showed no evidence of recovering anytime soon. This suggests less rain is going into streamflow and ground water than it used to.

Study

Dr Tim Peterson (Monash University, Department of Civil Engineering) led this study, in close collaboration with the University of Melbourne's Dr Margarita Saft, Dr Murray Peel and Dr Andrew John.
The study was predominantly funded by the Victorian Government’s Victorian Water and Climate Initiative with more recent support from the Australian Research Council.

One-third of the water catchments included in a Victorian study had not recovered from a severe drought nearly eight years later, Australian-first research from Monash University shows.

Globally, science holds the common view that rivers and underground water supplies eventually replenish following periods of severe drought or flood.

This study, led by Dr Tim Peterson from Monash University’s Department of Civil Engineering and published today in the prestigious international journal Science, is the first in the world to challenge this widely held view.

Researchers used statistical models of rainfall and streamflow at 161 water catchments across Victoria, each with over 30 years of data and no upstream dams or water extractions. The area surveyed is about the size of the United Kingdom or half that of the US state of California.

Dr Peterson and research colleagues from The University of Melbourne discovered that when the drought ends, some rivers continue to behave like they’re still in a drought for years afterwards and many have not yet recovered.

Specifically, the runoff, as a fraction of precipitation, had not recovered in 37 per cent of water catchments in Victoria after Australia’s Millennium Drought, and the number of recovering water catchments remained stagnant.

This means that 100mm of precipitation before the drought in 1990 created more river flow than the same 100mm in 2017, therefore delivering a 30 per cent reduced streamflow after the drought.

The number of water catchments with a low or very low runoff state increased rapidly from 1996 to the end of the meteorological drought in summer 2010. By 2011, only 15 per cent of water catchments had recovered.

The Millennium Drought, regarded as one of the worst droughts to hit Australia in its modern history, crippled the Murray-Darling Basin and placed extreme pressure on ecosystems, agricultural production and urban water supply in the south-eastern part of the country. It ended with a La Nina weather event in 2010.

A water catchment, or watershed, is any area of land that captures precipitation, which then flows into common outlets, such as a river, stream, bay or lake. Almost all of Victoria’s water supply comes from streamflow.

Dr Peterson said the regeneration of water catchments after severe drought had major implications for global long-term water resource planning and aquatic environments, especially when climate change is added on top of their findings.

“Our findings suggest hydrological droughts can persist indefinitely after meteorological droughts and that the mechanism for recovery remains an open question,” Dr Peterson said.

“This new discovery just appears to be the way catchments naturally behave. It’s not explained by factors like land use. They are just more complex than we thought.”

Percentage of the 161 study water catchments that displayed low runoff behaviour before, during and after the Millennium Drought from ~1997-2010. The shaded area from 2010 shows the percentage of water catchments that had not recovered from the drought.

Each water catchment analysed for this study had at least 15, seven and five years of streamflow observations before, during and after the Millennium Drought respectively, and had no major upstream reservoirs or river extractions.

Across all 161 water catchments, researchers found eight years into the drought, 51 per cent of the catchments switched into a low or very low runoff state. When the drought ended in 2010, primarily the eastern water catchments returned to a normal runoff state (see figure).

Importantly, by mid-2017, nearly eight years after the drought, more than one-third of water catchments still remained within a low runoff state, and have not recovered back to the pre-drought behaviour.

Dr Peterson said evidence also suggested vegetation responded to the drought by increasing the fraction of precipitation going to transpiration – the process of water movement through a plant and its evaporation from leaves.

“Practically, this implies that in response to the Millennium Drought, vegetation in selected water catchments responded by maintaining similar rates of transpiration,” he said.

Researchers say they’ve shown that water catchments are more complex than previously thought and that the findings are helping water agencies to better plan for the future.

Dr Peterson and his co-authors at The University of Melbourne have been working with, and communicating the findings to, the Victorian and national water agencies; most recently through the broader findings of the Victorian Water and Climate Initiative.

He says: “it’s exciting that the findings have already begun to be used in how water is managed. We are now developing mathematical tools to further help water management use these findings to ensure long-term water supply within a challenging and changing climate.”

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