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Scientists Confirm Burning Fossil Fuels Significantly Worsens Australian Drought

Climate

American scientists have just confirmed that parts of Australia are being slowly parched because of greenhouse gas emissions, which means that the long-term decline in rainfall over south and south-west Australia is a consequence of fossil fuel burning and depletion of the ozone layer by human activity.

Southern Australia has been experiencing declining rainfall since the 1970s. Here's a 2007 photo of Lake Hume clearly showing the impacts of drought. Photo credit: Creative Commons/ Suburbanbloke

Such a finding is significant for two reasons. One remains contentious: it is one thing to make generalized predictions about the consequences overall of greenhouse gas levels, but it is quite another to pin a measured regional climatic shift directly on human causes, rather than some possible as-yet-unidentified natural cycle of climatic change.

The other is contentiously political. Australia’s prime minister, Tony Abbott, has in the past dismissed climate science as “crap,” and more recently has cut back on Australian research spending.

Australia has already experienced a pattern of heat waves and drought—punctuated by catastrophic flooding—and even now, in the Australian winter, New South Wales is being hit by bush fires.

Tom Delworth, a research scientists at the U.S. National Oceanic and Atmospheric Administration, reports in Nature Geoscience that he and a colleague conducted a series of long-term climate simulations to study changes in rainfall across the globe.

Water depth marker in the dried out bed of Lake Albert, South Australia

Photo credit: Bidgee via Wikimedia Commons

Pattern of change

One striking pattern of change emerged in Australia, where winter and autumn rainfall patterns are increasingly a cause of distress for farmers and growers in two states.

The simulation showed that the decline in rainfall was primarily a response to man-made increases in greenhouse gases, as well as to a thinning of the stratospheric ozone layer in response to emissions of destructive gases by human sources.

The computer simulations tested a series of possible causes for this decline, such as volcanic eruptions and changes in solar radiation. But the only cause that made sense of the observed data was the greenhouse explanation.

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South Australia has never been conspicuously lush and wet, but decline in precipitation set in around 1970, and this decline has increased in the last four decades. The simulations predict that the decline will go on, and that average rainfall will drop by 40 percent over south-west Australia later this century.

Dr Delworth described his model as “a major step forward in our effort to improve the prediction of regional climate change.”

In May, scientists proposed that greenhouse gas emissions were responsible for a change in Southern Ocean wind patterns, which in turn resets the thermostat for the world’s largest island.

Australian scientists report in Geophysical Research Letters that they, too, have been using climate models to examine Antarctic wind patterns and their possible consequence for the rest on the planet.

The agreement between observed and model simulated rainfall changes supports the idea that human activity contributed to the drying of southwestern Australia and that the drying will increase in the 21st century. Changes in fall-winter rainfall from observations (top panel) as compared to model simulation of the past century (middle panel), and a model projection of the middle of the 21st century. (Click for a high resolution image. Credit: NOAA's Geophysical Fluid Dynamics Laboratory)

Temperature rise

“When we included projected Antarctic wind shifts in a detailed global ocean model, we found water up to 4°C warmer than current temperatures rose up to meet the base of the Antarctic ice shelves,” said Paul Spence, a researcher at Australian Research Council's Centre of Excellence for Climate System Science. This temperature rise is twice previous estimates.

“This relatively warm water provides a huge reservoir of melt potential right near the grounding lines of ice shelves around Antarctica,” Dr Spence said. “It could lead to a massive increase in the rate of ice sheet melt, with direct consequences for global sea level rise.”

Since the West Antarctic ice sheet holds enough water to raise sea levels by 3.3 meters, the consequences would indeed be considerable.

“When we first saw the results it was quite a shock,” Dr Spence said. “It was one of the few cases where I hoped the science was wrong."

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"This hasn't happened in 150 years or more," said Daniel Swain, a climate scientist at UCLA's Institute of the Environment and Sustainability to The Guardian. "There have even been a couple [of] wildfires – which is definitely not something you typically hear about in the middle of winter."

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On Thursday, the U.S. Drought Monitor said nearly 60 percent of the state was abnormally dry, up from 46 percent just last week, according to The Mercury News in San Jose.

The dry winter has included areas that have seen devastating fires recently, including Sonoma, Napa, Lake and Mendocino counties. If the dry conditions continue, those areas will once again have dangerously high fire conditions, according to The Mercury News.

"Given what we've seen so far this year and the forecast for the next few weeks, I do think it's pretty likely we'll end up in some degree of drought by this summer," said Swain, as The Mercury News reported.

Another alarming sign of an impending drought is the decreased snowpack in the Sierra Nevada Mountain range. The National Weather Service posted to Twitter a side-by-side comparison of snowpack from February 2019 and from this year, illustrating the puny snowpack this year. The snow accumulated in the Sierra Nevadas provides water to roughly 30 percent of the state, according to NBC Los Angeles.

Right now, the snowpack is at 53 percent of its normal volume after two warm and dry months to start the year. It is a remarkable decline, considering that the snowpack started 2020 at 90 percent of its historical average, as The Guardian reported.

"Those numbers are going to continue to go down," said Swain. "I would guess that the 1 March number is going to be less than 50 percent."

The National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center forecast that the drier-than-average conditions may last through April.

NOAA said Northern California will continue deeper into drought through the end of April, citing that the "persistent high pressure over the North Pacific Ocean is expected to continue, diverting storm systems to the north and south and away from California and parts of the Southwest," as The Weather Channel reported.

As the climate crisis escalates and the world continues to heat up, California should expect to see water drawn out of its ecosystem, making the state warmer and drier. Increased heat will lead to further loss of snow, both as less falls and as more of it melts quickly, according to The Guardian.

"We aren't going to necessarily see less rain, it's just that that rain goes less far. That's a future where the flood risk extends, with bigger wetter storms in a warming world," said Swain, as The Guardian reported.

The Guardian noted that while California's reservoirs are currently near capacity, the more immediate impact of the warm, dry winter will be how it raises the fire danger as trees and grasslands dry out.

"The plants and the forests don't benefit from the water storage reservoirs," said Swain, as The Mercury News reported. "If conditions remain very dry heading into summer, the landscape and vegetation is definitely going to feel it this year. From a wildfire perspective, the dry years do tend to be the bad fire years, especially in Northern California."

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