‘Failure is not an option’: after a lost decade on climate action, the 2020s offer one last chance


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Will Steffen, Australian National UniversityIn May 2011, almost precisely a decade ago, the government-appointed Climate Commission released its inaugural report. Titled The Critical Decade, the report’s final section warned that to keep global temperature rises to 2℃ this century, “the decade between now and 2020 is critical”.

As the report noted, if greenhouse gas emissions peaked around 2011, the world’s emissions-reduction trajectory would have been easily manageable: net-zero by around 2060, and a maximum emissions reduction rate of 3.7% each year. Delaying the emissions peak by only a decade would require a trebling of this task – a maximum 9% reduction each year.

But, of course, the decade to 2020 did not mark the beginning of the world’s emissions-reduction journey. Global emissions accelerated before dropping marginally under COVID-19 restrictions, then quickly rebounding.

Our new report, released today, shows the immense cost of this inaction. It is now virtually certain Earth will pass the critical 1.5℃ temperature rise this century – most likely in the 2030s. Now, without delay, humanity must focus on holding warming to well below 2℃. For Australia, that means tripling its emissions reduction goal this decade to 75%.

Young girl holds sign at climate protest
The 2020s offer a last chance to keep warming within 2℃ this century, and leave a habitable planet for future generations.
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Aim high, go fast

The Climate Council report is titled Aim High: Go Fast: Why Emissions Need To Plummet This Decade. It acknowledges the multiple lines of evidence showing it will be virtually impossible to keep average global temperature rise to 1.5℃ or below this century, without a period of significant overshoot and “drawdown”. (This refers to a hypothetical period in which warming exceeds 1.5℃ then cools back down due to the removal of carbon dioxide (CO₂) from the atmosphere.)

The increasing rate of climate change, insights from past climates, and a vanishing carbon budget all suggest the 1.5℃ threshold will in fact be crossed very soon, in the 2030s.

There is no safe level of global warming. Already, at a global average temperature rise of 1.1℃, we’re experiencing more powerful storms, destructive marine and land heatwaves, and a new age of megafires.




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As the Intergovernmental Panel on Climate Change has warned, the consequences of breaching 1.5℃ warming will be stark. Heatwaves, droughts, bushfires and intense rain events will become even more severe. Sea levels will rise, species will become extinct and crop yields will fall. Coral reefs, including the Great Barrier Reef, will decline by up to 90%.

And perhaps most frighteningly, overshooting 1.5℃ runs a greater risk of crossing “tipping points”, such as the collapse of ice sheets and the release of natural carbon stores in forests and permafrost. Crossing those thresholds may set off irreversible changes to the global climate system, and destroy critical ecosystems on which life on Earth depends.

An ice sheet in Greenland
Climate tipping points, such as melting ice sheets, may set off irreversible changes in natural systems.
John McConnico/AP

Every fraction of a degree matters

The outlook may be dire, but every fraction of a degree of avoided warming matters. Its value will be measured in terms of human lives, species and ecosystems saved. We can, and must, limit warming to well below 2℃. The goal is very challenging, but still achievable.

The strategies, technologies and pathways needed to tackle the climate challenge are now emerging as fast as the risks are escalating. And in the lead-up to the COP26 climate conference in Glasgow later this year, there’s widespread momentum for international cooperation and action.




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Many of Australia’s strategic allies and major trading partners – including the United States, Europe, the United Kingdom and China – are starting to move on climate change. But Australia is standing still. This is despite our nation being one of the most vulnerable to climate change – and despite us having some of the world’s best renewable energy resources.

We must urgently grab these opportunities. We propose Australia radically scale up its emissions-reduction targets – to a 75% cut by 2030 from 2005 levels (up from the current 26-28% target). Australia should also aim to reach net-zero emissions by 2035. Doing so by 2050 – a goal Prime Minister Scott Morrison says is his preference – is too late.

A coal plant
Polluting industries such as coal will have to give way to cleaner industries.
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A huge but achievable task

Such dramatic action is clearly daunting. There are political, technical and other challenges ahead because action has been delayed. But a 75% emissions-reduction target is a fair and achievable contribution to the global effort.

Australia’s unrivalled potential for renewable energy means it can transform the electricity sector and beyond. Electric vehicles can lead to carbon-free transport and renewably generated electricity and green hydrogen can decarbonise industry.

The emerging new economy is bringing jobs to regional Australia and building cleaner cities by reducing fossil fuel pollution. There is staggering potential for a massive new industry built on the export to Asia of clean energy and products made from clean hydrogen.




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State, territory and local governments are leading the way in this transformation. The federal government must now join the effort.

The transition will no doubt be disruptive at times, and involve hard decisions. Industries such as coal will disappear and others will emerge. This will bring economic and social change which must be managed sensitively and carefully.

But the long-term benefits of achieving a stable climate far outweigh the short-term disruptions. As our report concludes:

The pathway we choose now will either put us on track for a much brighter future for our children, or lock in escalating risks of dangerous climate change. The decision is ours to make. Failure is not an option.


Climate Council researcher Dr Simon Bradshaw contributed to this article.The Conversation

Will Steffen, Emeritus Professor, Fenner School of Environment & Society, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Sydney’s disastrous flood wasn’t unprecedented: we’re about to enter a 50-year period of frequent, major floods


Tom Hubble, University of SydneyLast month’s flood in the Hawkesbury-Nepean River region of western Sydney peaked at a staggering 12.9 metres, with water engulfing road signs and reaching the tops of many houses.

There hasn’t been a major flood on the Hawkesbury-Nepean for more than 30 years, with the last comparable one occurring in 1990. Long-term Sydneysiders, however, will remember that 12 major floods occurred during the 40 years before 1990. Five of these were larger than last month’s flood.

So what’s going on? The long-term rainfall pattern in the region and corresponding river flow is cyclic in nature. This means 40 to 50 years of dry weather with infrequent small floods are followed by 40 to 50 years of wet weather with frequent major floods.

As river and floodplain residents take stock of the recent damage to their homes and plan necessary repairs, it’s vital they recognise more floods are on the way. Large, frequent floods can be expected to occur again within 10 or 20 years if — as expected — the historical pattern of rainfall and flooding repeats itself.

Living in a bathtub

Many of the 18,000 people who were evacuated live in and around a region known as the “Sackville Bathtub”. As the name suggests, this flat, low-lying section of the floodplain region was spectacularly affected.

The flooded Hawkesbury-Nepean River last month. Brown floodwater is evident between Penrith (right) and the Pacific Ocean (top left). The Sackville Bathtub is located left of centre.
Digital Earth Australia Map, Geoscience Australia, Tom Hubble

The Sackville Bathtub is located between Richmond and Sackville. It’s part of the Cumberland Plain area of Western Sydney and formed very slowly over 100 million years due to plate tectonic processes. The bathtub’s mudstone rock layers are folded into a broad, shallow, basin-shaped depression, which is surrounded by steep terrain.

Downstream of Sackville, the Hawkesbury-Nepean River flows through sandstone gorges and narrows in width. This creates a pinch-point that partially blocks the river channel.

Just as a bath plug sitting half-way over a plughole slows an emptying bath, the Sackville pinch-point causes the bathtub to fill during floods.

How the bathtub effect in the Hawkesbury-Nepean Valley causes floodwaters to back up and lead to deep and dangerous flooding.

Will raising the dam wall work?

The NSW state government is planning to raise the wall of the Warragamba Dam to help mitigate catastrophic floods in the region. But this may not be an effective solution.

Typically, somewhere between 40% and 60% of the floodwater that fills up the Sackville Bathtub comes from unimpeded, non-Warragamba sources. So, when the Hawkesbury-Nepean River floods, the bathtub is already quite full and causing significant problems before Warragamba begins to spill. The Warragamba water then raises the flood level, but often by only a couple of metres.

Raising Warragamba Dam’s wall as a mitigation measure will only control about half the floodwater, and won’t prevent major floods delivered by the Nepean and Grose rivers, which also feed into the region. This represents a small potential benefit for a very large cost.

The timing of observed flood peaks during the August 1986 Hawkesbury-Nepean flood, in relation to the time when Warragamba Dam began to spill. The arrival of Warragamba water in the Sackville Bathtub increased the flood depth only by about a metre above the floodwaters delivered earlier during the flood from the Grose and Nepean rivers.
Tom Hubble – Redrawn from data presented in Appendix One of the Hawkesbury-Nepean Flood Study; Infrastructure NSW 2019.

A long flooding period is on our doorstep

The idea of drought-dominated and flood-dominated periods for the Hawkesbury-Nepean River system was proposed in the mid-1970s by the University of Sydney’s Robin Warner. Since the late 1990’s, it hasn’t been the focus of much research.




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He showed a century-long cycle of alternating periods of dry weather and small floods followed by wet weather and big floods is normal for Sydney. This means the March flood may not have come as a surprise to older residents of the Sackville Bathtub, who have a lived experience of the whole 40-50 year flooding cycle.

As a rough average, one major flood occurred every four years during the last wet-weather period between 1950 and 1990. The largest of this period occurred in November 1961. It filled the Sackville Bathtub to a depth of 15 metres and — like the June 1964 (14.6 metres) and March 1978 (14.5 metres) events — caused more widespread flooding than this year’s flood.

A photo of a flood that occured in Maitland in September 1950.
Sam Hood/NSW State Library/Flickr, CC BY

We’re currently 30 years into a dry period, which may be about to end. Conditions might stay dry for another 10 or 20 years.

These cycles are likely caused by natural, long-term “climate drivers” — long-term climatic fluctuations such as El Niño and La Niña, the Pacific Decadal Oscillation and the Indian Ocean Dipole, which are driven by oceanic current circulations. These global phenomena bring both benevolent weather and destructive weather to Australia.

Eastern Australia experiences decades-long periods of wetter weather when these climate drivers sync up with each other. When they’re out of sync, we get dry weather periods.




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These long-term cycles are natural and have been operating for thousands of years, but climate change is amplifying and accelerating them. Dry periods are getting drier, wet periods are getting wetter.

The good news and bad news

The bad news is that 12-plus metre floods at Hawkesbury River (Windsor Bridge) are not all that unusual. There have been 24, 12-plus metre floods at Windsor Bridge since 1799.

The good news is meteorological forecasters are excellent at predicting when the storms that generate moderate, large and catastrophic floods are coming. We can expect several days’ to a week’s notice of the next big flood.

We can also prepare our individual and communal responses for more large and frequent floods on the Hawkesbury-Nepean. Residents of the area need to think about how they might live near the river as individuals. Decide what is precious and what you will fit into a car and trailer. Practice evacuating.

As a community, we must ensure the transport infrastructure and evacuation protocols minimise disruption to river and floodplain residents while maximising their safety. It’s particularly important we set up inclusive infrastructure to ensure disadvantaged people, who are disproportionately affected by disasters, also have a fighting chance to evacuate and survive.




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Upgrading the escape routes that enable people to evacuate efficiently is absolutely vital. As is rethinking whether we should continue urban expansion in the Sackville Bathtub.

So remember, the next major flood is going to occur sooner than we would like. If you live in this region, you must start preparing. Or as a wise elder once said, “Live on a floodplain, own a boat!”


This story is part of a series The Conversation is running on the nexus between disaster, disadvantage and resilience. Read the rest of the stories here.The Conversation

Tom Hubble, Associate Professor, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.