Lethal Heating: 06/05/21

05/06/2021

(AU The Conversation) ‘Flash Droughts’ Can Dry Out Soil In Weeks. New Research Shows What They Look Like In Australia

The Conversation - Tess Parker | Ailie Gallant

Dan Peled / AAP

Authors

Tess Parker is a Research Fellow, Monash University
Ailie Gallant is Senior Lecturer, School of Earth, Atmosphere and Environment, Monash University

At the tail end of winter in 2015, the ground in the Wimmera in northwestern Victoria had been a little dry but conditions weren’t too bad for farmers. The crop season was going well.

The start of September looked promising. It was cool, and there were decent rains. One Wimmera lentil grower said, “As long as it doesn’t get too hot, we should actually be OK.”

A few weeks later, summer weather had arrived early. At the start of October, the soils were baked dry. Lentils and other pulse crops were devastated.

This kind of event, where drier-than-normal conditions transform into severe or extreme drought in the space of weeks, is called a “flash drought”.

While flash droughts are still not well understood, our research studies how they occur in Australia - which may help move us toward being able to warn of flash drought in advance.

The different kinds of drought

Scientists typically talk about drought as a lack or deficit of available moisture to meet various needs, such as in agriculture or for water resources. We often classify different types of drought depending on where there is a lack of water, or what its effects are:

meteorological drought is a deficit of rain or other precipitation
agricultural drought is a deficit of moisture in the soil and evaporating or transpiring into the air
hydrological drought is a deficit of water in runoff and surface storage such as dams
socioeconomic drought is a lack of water that affects the supply and demand of economic goods and services.

Different types of drought can occur at the same time, or a drought may evolve from one type to another. Droughts can last from months to decades, and can cover areas from a local region to most of the continent.

The different types of drought, showing how long they last and the size of the area they affect. Ailie Gallant, Author provided

Recently, a new characterisation of drought has been added to the drought spectrum: “flash” drought.

What causes flash droughts?

Flash droughts are droughts that begin suddenly and then rapidly become more intense. Droughts only occur when there is insufficient rainfall, but flash droughts intensify rapidly over timescales of weeks to months because of other factors such as high temperatures, low humidity, strong winds and clear skies.

These conditions make the air “thirsty”, which meteorologists call “increased evaporative demand”. This means more water evaporates from the surface and transpires from plants, and moisture in the soil is rapidly depleted.

Under these conditions, evaporation and transpiration increase for as long as moisture is available at the surface. When this moisture is depleted and there is no rain to replenish it, the lack of water limits evaporation and transpiration – and vegetation becomes stressed as drought emerges.

When there is a lack of rain accompanied by high temperature, low humidity, strong wind and clear skies, conditions are right for flash drought. Tess Parker, Author provided

Why haven’t we heard about flash drought before?

Flash droughts have always existed, and were first described in 2002. However, some particularly devastating flash droughts over the past decade have led to a surge of interest among researchers.

One such drought happened in the US Midwest. In May 2012, 30% of the continental United States was experiencing abnormally dry conditions. By August, that had extended to more than 60%. Although other rapidly developing droughts had been seen before, the widespread impacts of this event caught the attention of the US public and government.

Flash droughts are also increasingly a focus of attention in China and Australia. One of the few studies of flash drought in Australia examined an event when conditions in the country’s east suddenly changed from wet in December 2017, to dry in January 2018.

Anecdotal reports from farmers in the northern Murray–Darling Basin indicated removal of livestock from properties, and sheep numbers at record lows. By June 2018, there were reports of trees dying and a desert-like landscape, with little grass cover.

What happened in the Wimmera?

Our recent study of flash drought in Australia used several different measurements to capture a range of conditions related to drought.

precipitation describes the supply of moisture from the atmosphere to the surface
evaporative demand is the atmospheric demand for moisture from the surface
evaporative stress is the supply of moisture from the surface relative to the demand from the atmosphere
soil moisture is the wetness or dryness of the land surface.

The index we used to determine the atmospheric demand shows that the speed of development and the intensity of flash drought are driven by high temperatures, low humidity, strong winds and clear skies. All of these increase the demand for moisture from the surface.

After a drier than normal winter, southeast Australia experienced a cool and wet start to September 2015, with some rain in the first week of the month. Humidity and surface air pressure were roughly average, and surface sunshine below average, suggesting normal evaporative demand.

A warm spell began in mid-September, and intensified into a severe heatwave by early October, with temperatures over 35℃ persisting for several days in some areas. Throughout this period the overlying air became very dry. A persistent high-pressure system brought clear skies and increased sunshine.

By the end of October, the Wimmera was in severe or extreme drought conditions, devastating pulse and grain crops. Analysts estimated wheat production fell by 23%, with a loss of A$500 million in potential yields.

Flash drought in Australia

Flash droughts in Australia occur in all seasons. In the Wimmera, flash droughts are most frequent in summer and autumn. They can end as rapidly as they start, but in some cases may last many months.

In several instances, flash droughts in the Wimmera have started in summer or autumn, and the region has remained in drought through the following winter, and sometimes into spring. In this way, flash drought can be the catalyst for the common droughts lasting 6-12 months typical of southeast Australia.

But there is some potential good news. We have long known that seasonal-scale droughts in Australia are strongly related to the El Niño-Southern Oscillation (ENSO), which gives us some ability to predict them.

ENSO strongly affects rainfall, which means it can also be linked to flash droughts in winter and spring.

Further, sub-seasonal forecasting, which predicts the climatic conditions weeks to a month in advance, has improved considerably in recent years. Given flash droughts occur on these timescales, we can be optimistic that prediction of flash droughts may be possible

Links

(USA New Yorker) Automakers Start To Figure Out The Climate Future

The New Yorker - Bill McKibben

Bankers, not so much.

Last month, Ford released an electric version of its F-150, the most popular motor vehicle of all time. Photograph courtesy Ford

Author

Bill McKibben is a founder of the grassroots climate campaign 350.org and a contributing writer to The New Yorker. He writes The Climate Crisis, The New Yorker’s newsletter on the environment.

If you want to meet an expert who understands where the world is heading, may I introduce a bushy-bearded Australian coal miner who features anonymously in a video that was shared by the Sydney Morning Herald last week.

He is sitting behind the wheel of a borrowed Tesla when a man in the back seat urges him to “just plant it. Hard as you can.”

The man punches the accelerator, is immediately pushed back in his seat, and breaks into a grinning cackle. “Fucking got some go, eh?” the man says. “It’s just instant. Like, fuck,” the driver replies, beaming. (Watch it; you’ll feel happier afterward).

Many of the changes needed to get us on the right climate path are going to meet with resistance, but it’s beginning to look as if getting people to accept electric vehicles may not be one of them. Elon Musk has done pioneering work, but the Tesla has mainly been a niche product—the niche being early adopters of cool things who live along the coasts. (Life in Muskworld is getting a little silly: last month, he started touting a model with ten rocket thrusters that will go from zero to sixty in 1.1 seconds, which sounds like a very bad idea.)

Things got very real, though, with last month’s announcement of an electric version of the Ford F-150 pickup, America’s best-selling vehicle every year since the Reagan Administration, and the most popular motor vehicle of all time. Within seven days, the company had reported seventy thousand preorders—and the stock had jumped eight per cent.

Having spent most of my life in rural America, where the F-150 is ubiquitous, I can tell you why this is going to succeed. It’s not the acceleration; it’s the plugs. The electric version will basically be a battery on wheels. The “power frunk” (where the engine used to be) has several outlets, useful for all the power tools you might need if you’re not near another electrical source—if you’re building a home, say—and replacing the noisy, smelly, dangerous gas generators that no one likes.

You say that most pickup drivers are not, in fact, home builders? It’s true—most Americans have no need of a pickup at all. But watch any truck commercial and see who it stars. Once blue-collar America endorses the electric approach, suburbia will follow. We need far more than electric cars, of course: buses and bikes, not to mention paths for those bikes, are crucial. But since, right now, public transit accounts for about one per cent of passenger miles travelled, the new pickup paradigm seems critical.

And, in any event, the car companies seem all in. Last week, Ford announced that it was putting down thirty billion dollars in new spending on E.V.s; General Motors has already said that it will be nothing but electric by 2035. By contrast, the banking sector seems determined to have it both ways, trying to make money off both fossil fuels and a renewable future.

Late last month, President Biden issued an executive order on climate financial risk that begins by noting that “the failure of financial institutions to appropriately and adequately account for and measure these physical and transition risks threatens the competitiveness of U.S. companies and markets, the life savings and pensions of U.S. workers and families, and the ability of U.S. financial institutions to serve communities.”

That failure was visible on many fronts in recent days. Deutsche Bank put forward a detailed plan to cut its carbon emissions by, say, reducing “fuel consumption for its company car fleet in Germany (roughly 5,400 cars) by 30 percent by 2025.”

That sounds fine, but, as the campaigners at the German environmental and human-rights organization Urgewald have pointed out, such proposals “are also an embarrassing testament to the fact that the bank’s understanding of sustainability is stuck in the 90s.

The measures are easy to integrate and don’t harm anyone. However, they won’t have a significant impact either”—not, say, like the bank’s plan to coördinate the initial public offering for the oil-and-gas group Wintershall, which plans to boost its fossil-fuel output by thirty per cent by 2023.

Closer to home, the world’s biggest fossil-fuel financier, JPMorgan Chase, has announced plans to cut not the amount of carbon that its loans liberate from the ground but, rather, the “carbon intensity” of its portfolio.

This would permit it to keep making loans to companies that want to continue producing the same amount of oil and also allow it to vastly increase the amount of natural gas that they pump; gas is somewhat less carbon-intensive than oil, so this increase would slide right through this loophole.

At a House Committee on Financial Services hearing last week, Representative Alexandria Ocasio-Cortez did her best to cut through this blatant greenwashing, and Jamie Dimon, the Chase C.E.O., seemed to say that the bank was working to cut absolute emissions in its portfolio as well—but for the moment the plans are secret.

If you’re wondering how much this matters: a new report shows that the carbon produced by the loans from British bankers alone would make them, if they were a country, the ninth-biggest emitter on earth.

It’s good news of a sort that so much is suddenly up in the air: the fallout from the various court rulings and shareholder votes of late May is less a blueprint for the future than a simple acknowledgment that something must change. Sticks are being stuck in hornets’ nests, and there’s some shrieking from the industry and its friends. (Check out the fifteen G.O.P. state treasurers threatening to withdraw state funds from banks that don’t lend to the oil industry.)

But, at least for the moment, the delighted laughter of a miner behind the wheel of an E.V. drowns out the noise.

Links

(The Guardian) Climate Crisis Is Suffocating The World’s Lakes, Study Finds

The Guardian - Damian Carrington

Falling oxygen levels harming already struggling wildlife and drinking water supplies, say scientists

Lake Ammersee near Munich, Bavaria, Germany. Oxygen levels in lakes have fallen three to nine times faster in the past 40 years. Photograph: Lukas Barth-Tuttas/EPA

The climate crisis is causing a widespread fall in oxygen levels in lakes across the world, suffocating wildlife and threatening drinking water supplies.

Falling levels of oxygen in oceans had already been identified, but new research shows that the decline in lakes has been between three and nine times faster in the past 40 years. Scientists found oxygen levels had fallen by 19% in deep waters and 5% at the surface.

Rising temperatures driven by global heating is the main cause, because warmer water cannot hold as much oxygen. Furthermore, rising summer heat leaves the top layer of lakes hotter and less dense than the waters below, meaning mixing is reduced and oxygen supply to the depths falls.

Oxygen levels have increased at the surface of some lakes. But this is most likely due to higher temperatures driving algal blooms, which can also produce dangerous toxins.

Cutting emissions to tackle the climate crisis is vital, the scientists said, as well as cutting the use of farm fertiliser and urban sewage pollution that also damages lakes.

“All complex life depends on oxygen and so, when oxygen levels drop, you really decrease the habitat for many different species.” said Prof Kevin Rose, of the Rensselaer Polytechnic Institute (RPI) in the US, who was part of the research team.

“This study proves that the problem is even more severe in fresh waters [than in oceans], threatening our drinking water supplies and the delicate balance that enables complex freshwater ecosystems to thrive,” said Curt Breneman, RPI’s dean of science.

Freshwater habitats are rich in fish, insects, birds and animals, and are important for food and recreation for humans. But they have already suffered great damage, with average wildlife populations having fallen by 84% since 1970. In addition to global heating and pollution, the causes include overuse of water for farming.

The study, published in the journal Nature, analysed 45,000 dissolved oxygen and temperature profiles collected from nearly 400 lakes worldwide. Most records started in about 1980, though one went back to 1941.

Most of the lakes were in temperate zones, particularly in Europe and the US, but there were a few records from higher latitudes, nearer the poles, and for tropical lakes in Africa. In both cases, oxygen was falling as in the other lakes.

In lakes where oxygen levels have fallen to almost zero, phosphorus can be drawn out of sediments, providing an essential nutrient for bacteria. These can proliferate and produce the powerful greenhouse gas methane, driving further heating.

Oxygen levels in surface waters were increasing in about a fifth of the lakes studied, almost all of which were prone to pollution. This is an indicator of widespread increases in algal blooms, said Rose. “Without taxonomic data, we can’t say that definitively, but nothing else we’re aware of can explain this pattern.”

Global temperatures are still rising, pushing lake oxygen levels ever lower, so just keeping the status quo requires action to clean up freshwater bodies.

Rose said a positive example was Oneida Lake in New York state, where a clean-up led to better water clarity, which in turn allowed more photosynthesis from oxygen-producing algae.

60% of fish species could be unable to survive in current areas by 2100 – study. Read more

“The new study provides a much-needed global overview of what happens in the limited freshwater stores of the planet – their health is a prime concern,” said Prof Hans-Otto Poertner, of the Alfred-Wegener-Institute in Bremerhaven, Germany, who was not part of the team.

Lakes are isolated and small compared with oceans, in which global currents can still provide oxygen to deeper waters, he said.

“Climate change, together with [agricultural pollution], threatens vulnerable freshwater systems, adding to the urgency to strongly cut emissions,” Poertner said.

Links