The Industrial Revolution kick-started global warming much earlier than we realised


Helen McGregor, University of Wollongong; Joelle Gergis, University of Melbourne; Nerilie Abram, Australian National University, and Steven Phipps, University of Tasmania

In the early days of the Industrial Revolution, no one would have thought that their burning of fossil fuels would have an almost immediate effect on the climate. But our new study, published today in Nature, reveals that warming in some regions actually began as early as the 1830s.

That is much earlier than previously thought, so our discovery redefines our understanding of when human activity began to influence our climate.

Determining when global warming began, and how quickly the planet has warmed since then, is essential for understanding how much we have altered the climate in different parts of the world. Our study helps to answer the question of whether our climate is already operating outside thresholds that are considered safe for human society and functional ecosystems.

Our findings show that warming did not develop at the same time across the planet. The tropical oceans and the Arctic were the first regions to begin warming, in the 1830s. Europe, North America and Asia followed roughly two decades later.

Surprisingly, the results show that the southern hemisphere began warming much later, with Australasia and South America starting to warm from the early 20th century. This continental-scale time lag is still evident today: while some parts of Antarctica have begun to warm, a clear warming signal over the entire continent is still not detectable.

The warming in most regions reversed what would otherwise have been a cooling trend related to high volcanic activity during the preceding centuries.

Global warming got underway much earlier in the north.

By pinpointing the date when human-induced climate change started, we can then begin to work out when the warming trend broke through the boundaries of the climate’s natural fluctuations, because it takes some decades for the global warming signal to “emerge” above the natural climate variability.

According to our evidence, in all regions except for Antarctica, we are now well and truly operating in a greenhouse-influenced world. We know this because the only climate models that can reproduce the results seen in our records of past climate are those models that factor in the effect of the carbon dioxide released into the atmosphere by humans.

These remarkable findings were pieced together from the most unusual of sources – not thermometers or satellites, but rather from natural climate archives. These include coral skeletons, ice cores, tree rings, cave deposits and ocean and lake sediment layers, all of which record the climate as they grow or accumulate.

These archives provide long records that extend back 500 years – well before the Industrial Revolution – and provide a critical baseline for the planet’s past climate, one that is impossible to obtain otherwise.

Corals can help reveal the climate of centuries past, long before weather records began.
Eric Matson/AIMS, Author provided

But why is there no clear warming fingerprint yet seen across Antarctica? The answer most likely lies in the vast Southern Ocean, which isolates the frozen continent from the warming happening elsewhere.

The westerly winds that circulate through the Southern Ocean around Antarctica keep warm air masses from lower latitudes at bay. Ozone depletion and rising greenhouse gas concentrations during the 20th century have also caused this wind barrier to get stronger.

The Southern Ocean currents that flow around Antarctica also tend to move warmer surface waters away from the continent, to be replaced with cold deeper water that hasn’t yet been affected by surface greenhouse warming. This process could potentially delay Antarctica’s warming by centuries.

Ocean insulation

The delay in warming observed in the rest of the southern hemisphere is something we do not yet fully understand. It could simply be because fewer records are available from the southern hemisphere, meaning that we still don’t have a full picture of what is happening.

Alternatively, like Antarctica, the southern hemisphere’s oceans could be holding back warming – partly through winds and currents, but perhaps also because of “thermal inertia”, whereby the ocean can absorb far more heat energy than the atmosphere or the land before its temperature markedly increases. Bear in mind that the southern half of the globe has much more ocean than the north.

Essentially, then, the coolness of the southern hemisphere’s vast oceans could be “insulating” Australasia and South America from the impact of global warming. The question is, for how long?

If our evidence of delayed warming in the southern hemisphere holds true, it could mean we are in in for more climate surprises as global warming begins to overcome the thermal inertia of our surrounding oceans. Could the recent record warming of Australian waters, and the subsequent damage to the Great Barrier Reef, be an early sign that this is already occurring?

Recent research suggest that the mass bleaching event of the reef was made 175 times more likely by climate change. Following the recent severity of such extremes, a better understanding of how anthropogenic greenhouse warming is already impacting the southern hemisphere is critical.

What to do about it

Leading scientists from around the world met in Geneva last week to discuss the goal of limiting average global warming to 1.5℃ – the more ambitious of the two targets enshrined in the Paris climate agreement.

Last year, global temperatures crossed the 1℃ threshold, and 2016 is on track to be 1.2-1.3℃ above our climate baseline.

But here’s the kicker. That baseline is relative to 1850–1900, when most of our thermometer-based temperature records began. What our study shows is that for many parts of the world that estimate isn’t good enough, because global warming was already under way, so the real baseline would be lower.

The small increases in greenhouse gases during the 19th century had a small effect on Earth’s temperatures, but with the longer perspective we get from our natural climate records we see that big changes occurred. These fractions of a degree of extra warming might seem insignificant at first, but as we nudge ever closer to the 1.5℃ guardrail (and potentially beyond), the past tells us that small changes matter.


Helen McGregor will be online to answer your questions from 2pm AEST today. Post a query in the comments below.

The Conversation

Helen McGregor, ARC Future Fellow, University of Wollongong; Joelle Gergis, ARC DECRA Climate Research Fellow, School of Earth Sciences, University of Melbourne; Nerilie Abram, QEII Research Fellow, Australian National University, and Steven Phipps, Paleo Ice Sheet Modeller, University of Tasmania

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

An open letter to the Prime Minister on the climate crisis, from 154 scientists


Andrew Glikson, Australian National University

Dear The Hon. Malcolm Turnbull MP, Prime Minister of Australia,

The following is an open letter signed by 154 Australian atmospheric, marine, environmental, biological and medical scientists, including several leading climatologists, for your and your government’s attention.

There is no Planet B

In July 2016, global temperatures soared to the hottest in the 136 years of the instrumental record, 0.1℃ warmer than previous warm Julys in 2015, 2011 and 2009. It followed a succession of rising temperatures, moving from 0.42℃ above average in 2000, to 0.87℃ above average by 2015.

Developments in the atmosphere-ocean system reported by major climate research organisations (including NASA, the US National Oceanic and Atmospheric Administration, the US National Snow & Ice Data Center, the UK Met Office Hadley Centre, the Tyndall Centre, the Potsdam Institute; the science academics of dozens of nations; and in Australia the CSIRO and Bureau of Meteorology) include:

We are concerned that global warming, amplified by feedbacks from polar ice melt, methane release from permafrost, and extensive fires, may become irreversible, including the possible collapse of the Atlantic Meridional Overturning Circulation, a crucial component of the global climate system that transfers heat from the tropics to the North Atlantic.

According to James Hansen, NASA’s former chief climate scientist, “burning all fossil fuels would create a different planet than the one that humanity knows“. Joachim Schellnhuber, Germany’s chief climate scientist, has summed up the situation by saying: “We’re simply talking about the very life support system of this planet.”

We note your broad agreement with this point, in light of your 2010 statement that:

…we are as humans conducting a massive science experiment with this planet. It’s the only planet we have got… We know that the consequences of unchecked global warming would be catastrophic… We as a human species have a deep and abiding obligation to this planet and to the generations that will come after us.

While the Paris Agreement remains unbinding and global warming has received minimal attention in the recent elections, governments worldwide are presiding over a large-scale demise of the planetary ecosystems, which threatens to leave large parts of Earth uninhabitable.

We call on the Australian government to tackle the root causes of an unfolding climate tragedy and do what is required to protect future generations and nature, including meaningful reductions of Australia’s peak carbon emissions and coal exports, while there is still time.

There is no Planet B.

Yours sincerely,

Dr Christine Adams-Hosking, Conservation planner, University of Queensland

Associate Professor Stephen Adelstein, Medical scientist, University of Sydney

Professor Ross Alford, Tropical ecologist, James Cook University

Dr Wallace Ambrose, Archaeological anthropologist, ANU

Dr Martin Anda, Environmental engineer, Murdoch University

Dr Marion Anderston, Geochemist, Monash University

Professor Michael Archer, Paleontologist, UNSW Australia

Dr Leanne Armand, Marine Researcher, Macquarie University

Professor Patricia Armati, Medical scientist, University of Sydney

Professor Owen Atkin, Plant respiration researcher, ANU

Professor Elaine Baker, Marine scientist, University of Sydney

Associate Professor Cathy Banwell, Medical scientist, ANU

Dr Andrew Barnes, Aquatic animal health researcher, University of Queensland

Dr Fiona Beck, Renewable energy researcher, ANU

Dr Tom Beer, Climatic and environmental change researcher, CSIRO

Professor Andrew Blakers, Photovoltaics/energy storage researcher, ANU

Professor Phillip Board, Medical scientist, ANU

Professor Justin Borevitz, Plant geneticist, ANU

Dr Caryl Bosman, Environmental planning researcher, Griffith University

Professor David Bowman, Forestry researcher, University of Tasmania

Dr Timothy Broadribb, Plant Scientist, University of Tasmania

Dr Helen Brown, Environmental health researcher, Curtin University

Dr Tim Brown, Medicine and environment researcher, ANU

Professor Ralf Buckley, Conservation/ecotourism researcher, Griffith University

Dr Florian Busch, Plant scientist, ANU

Dr Jason Byrne, Urban design researcher, Curtin University

Professor Maria Byrne, Marine and developmental biologist, University of Sydney

Dr Martina Calais, Renewable energy researcher, Murdoch University

Associate Professor Craig Carter, Engineering and IT researcher, Murdoch University

Dr Phill Cassey, Ecologist, Adelaide University

Professor Carla Catterall, Ecologist, Griffith University

Dr Juleen Cavanaugh, Biomedical scientist, ANU

Professor Fred Chow, Plant biologist, ANU

Associate Professor David Cohen, Geochemist, UNSW Australia

Professor Steven Cooper, Evolutionary biologist, SA Museum

Professor Rod Connolly, Marine scientist, Griffith University

Professor Jann Conroy, Plant scientist, Western Sydney University

Dr Lucy Coupland, Medical scientist, ANU

Dr Joseph Coventry, Solar energy researcher, ANU

Dr Chris Creagh, Physicist, Murdoch University

Professor Patricia Dale, Environment/planning researcher, Griffith University

Dr Armanda Davies, Planning geographer, Curtin University

Dr Ian Davies, Forestry fire management researcher, ANU

Dr Kirsten Davies, Ethno-ecology and environmental law researcher, Macquarie University

Dr Robert Davis, Vertebrate biologist, Edith Cowan University

Professor Keith Dear, Global health researcher, ANU

Dr Fjalar de Haan, Sustainability researcher, University of Melbourne

Professor Hans Peter Dietz, Medical scientist, Penrith Hospital

Professor Bob Douglas, Medical scientist, ANU

Associate Professor Mark Douglas, Medical scientist, University of Sydney

Dr Jen Drysdale, Climate and energy researcher, University of Melbourne

Professor Angela Dulhunty, Medical scientist, ANU

Professor Robyn Eckersley, Climate change governance researcher, University of Melbourne

Dr Elin Charles Edwards, Environmental geographer, University of Queensland

Professor David Eldridge, Evolutionary biologist, UNSW Australia

Professor David Elsworth, Environmental ecologist, Western Sydney University

Associate Professor Jason Evans, Climate change researcher, UNSW Australia

Dr Isabelle Ferru, Medical scientist, ANU

Professor Tim Flannery, Climate Council

Professor Barry Fox, Ecologist, UNSW Australia

Dr Evan Franklin, Solar energy researcher, ANU

Dr Diego Garcia-Bellido, Paleontologist, University of Adelaide

Dr Stephen Garnett, Conservation and sustainability researcher, Charles Darwin University

Dr John Gillen, Soil scientist, ANU

Dr Andrew Glikson, Paleoclimatologist, ANU

Dr Susan Gould, Climate change researcher, Griffith UNiversity

Professor Colin Groves, Anthropologist, ANU

Dr Huade Guan, Hydro-meteorologist, Flinders University

Professor Neil Gunningham, Global governance researcher, ANU

Dr Asish Hagar, Medical scientist, UNSW Australia

Dr Nina Hall, Sustainable water researcher, University of Queensland

Dr Willow Hallgren, Atmospheric scientist, Griffith University

Dr Elizabeth Hanna, Environmental health researcher, ANU

Associate Professor David Harley, Epidemiologist, ANU

Professor Robert S. Hill, Paleobotanist, University of Adelaide

Professor Ove Hoegh-Guldberg, Marine climatologist and Great Barrier Reef researcher, University of Queensland

Professor Geoff Hope, Archaeologist and natural history researcher, ANU

Associate Professor Michael Howes, Environmental scientist, Griffith University

Professor Lesley Hughes, Climate change and species researcher, Macquarie University

Dr Paul Humphries, Environmental scientist, Charles Sturt University

Professor Phillip Jenning, Energy researcher, Murdoch University

Professor Darryl Jones, Behavioural ecologist, Griffith University

Dr Hugh Jones, Medical scientist, University of Western Australia

Dr Jochen Kaempf, Physical oceanographer, Flinders University

Professor Jeffrey Keelan, Medical scientist, University of Western Australia

Professor Peter Kershaw, Biogeographer and botanist, Monash University

Dr Carsten Kulheim, Plant physiologist, ANU

Professor Rakkesh Kumar, Medical scientist, UNSW Australia

Dr Lori Lach, Rainforest conservationist, James Cook University

Professor Barry Lacopetta, Medical scientist, University of Western Australia

Professor Trevor Lamb, Medical scientist, ANU

Professor Tony Larkum, Plant biologist, University of Technology Sydney

Dr Annie Lau, Geography and environmental management researcher, University of Quensland

Professor Bill Laurance, Tropical environment and sustainability researcher, James Cook University

Associate Professor Fred Leusch, Soil, water and energy researcher, Griffith University

Professor Andrew Lowe, Plant conservationist, University of Adelaide

Dr Fabio Luciano, Medical scientist, UNSW Australia

Professor Justin Marshall, Marine biologist, University of Queensland

Dr Melanie Massaro, Ecologist and ornithologist, Charles Sturt University

Associate Professor John F. McCarthy, Resource environment researcher, ANU

Dr Allison McInnes, Plant biologist, UTS

AssociateProfessor Andrew McKenzie, Landscape planning researcher, University of Canberra

Dr Kathryn McMahon, Environmental researcher, Edith Cowan University

Professor Andrew Millington, Land change scientist, Flinders University

Professor Angela Moles, Evolutionary ecologist, UNSW Australia

Professor Renee Morris, Medical scientist, UNSW Australia

Professor Barbara Norman, Urban planning researcher, University of Canberra

Professor Nikos Ntoumanis, Behavioural medicine researcher, Curtin University

Dr Bradley Opdyke, Climate historian, ANU

Professor Richard G. Pearson, Marine and tropical biologist, James Cook University

Dr Barrie Pittock, Climate scientist, CSIRO

Dr Jason Potas, Medical scientist, ANU

Professor Susan Prescott, Medical scientist, University of Western Australia

Dr Lynda Prior, Climate researcher, University of Tasmania

Dr Thomas Prowse, Biologist, University of Adelaide

Professor Marie Ranson, Molecular biologist, University of Wollongong

Professor Steve Redman, Medical scientist, ANU

Associate Professor Tracy Rogers, Evolutionary ecologist, UNSW Australia

Professor Chris Ryan, Eco-innovation researcher, University of Melbourne

Dr Oz Sahnin, Climate change researcher, Griffith University

Associate Professor Peter Sainsbury, Climate and health researcher, University of Sydney

Professor David Sinclair, Medical scientist, UNSW Australia

Dr Tom Sobey, Medical scientist, UNSW Australia

Professor Will Steffen, Climate change researcher, ANU

Professor Peter Steinberg, Marine scientist, UNSW Australia

Associate Professor Christian Stricker, Medical scientist, ANU

Professor Ian Suthers, Marine biologist, UNSW Australia

Associate Professor Sue Taylor, Medical scientist, University of Western Australia

Dr Sebastian Thomas, Sustainability researcher, University of Melbourne

Dr Andrew Thomson, Solar researcher, ANU

Associate Professor Thomas Thorsten, Marine biologist, UNSW Australia

Associate Professor Ian Tibbetts, Marine Scientist, University of Queensland

Professor David Tissue, Plant ecophysiologist, Western Sydney University

Professor Matthias Tomczak, Oceanographer, Flinders University

Mr Shane Toohey, Medical scientist, University of Western Australia

Dr Gail Trapp, Medical scientist, UNSW Australia

Professor Patrick Troy, Human ecologist, ANU

Professor Tom Trull, Antarctic, oceans and atmosphere researcher, CSIRO

Professor David Tscharke, Medical scientist, ANU

Professor Chris Turney, Antarctic climatologist, UNSW Australia

Dr Tania Urmee, Renewable energy technologist, Murdoch University

Professor René Vaillancourt, Plant geneticist, University of Tasmania

Professor John Veevers, Earth scientist, Macquarie University

Professor Charlie Veron, Marine scientist, Australian Institute of Marine Science

Professor Phil Waite, Medical scientist, UNSW Australia

Dr Elaine Walker, Physics and energy researcher, Murdoch University

Dr Hayden Washington, Environmental researcher, UNSW Australia

Professor David Watson, Water and society ecologist, Charles Sturt University

Dr Scarla J. Weeks, Biophysical oceanographer, University of Queensland

Professor Adrian Werner, Hydrologist, Flinders University

Mr Peter Weiske, Medical and environmental scientist, ANU

Dr Jonathan Whale, Energy researcher, Murdoch University

Associate Professor George Wilson, Wildlife management researcher, ANU

Dr Phillip Zylstra, Forests and fire researcher, University of Wollongong

The Conversation

Andrew Glikson, Earth and paleo-climate scientist, Australian National University

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

154 Australian scientists demand climate policy that matches the science


James Whitmore, The Conversation

154 Australian experts have signed on open letter to Prime Minister Malcolm Turnbull demanding urgent action on climate change that matches the dire warnings coming from climate scientists.

The letter, organised by Australian National University climatologist Andrew Glikson, calls on the federal government to make “meaningful reductions of Australia’s peak carbon emissions and coal exports, while there is still time”.

Signatories include leading climate and environmental scientists such as the Climate Council’s Tim Flannery, Will Steffen, and Lesley Hughes, as well as reef scientists Ove Hoegh-Guldberg and Charlie Veron.

They point out that July 2016 was the hottest month ever recorded, and followed a nine-month streak of record-breaking months. Average carbon dioxide concentrations in the atmosphere reached 400 parts per million (ppm) in 2015, and are rising at a rate of nearly 3 ppm each year.

The world is already witnessing the effects of climate change, the letter argues, including an increase in extreme weather events, melting of the polar ice sheets, and ocean acidification.

Australia, along with 179 other nations, has signed the climate treaty brokered in Paris last year, aiming to limit average global warming to “well below 2℃ above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5℃”.

However Glikson warned that “the Paris Agreement, being non-binding, is in danger of not being fulfilled by many of the signatories”. The deal will not enter into force until it is ratified by 55 nations accounting for at least 55% of the world’s greenhouse emissions.

Glikson called for action to “transition from carbon-emitting technologies to alternative clean energy as fast as possible, and focus technology on draw-down (sequestration) of greenhouse gases from the atmosphere”.

Australia’s current greenhouse gas target, which it took to December’s Paris climate summit, calls for emissions to be reduced by 26-28% below 2005 levels by 2030. It has been widely criticised by experts as not ambitious enough.

Andrew Blakers, professor of engineering at the Australian National University, said Australia could reduce emissions by two-thirds by 2030 “at negligible cost”.

He said the falling cost of renewable energy, particularly solar and wind, the replacement of gas with electricity for heating, and the advent of electric vehicles would eliminate most emissions. Solar and wind installation, currently at 1 gigawatt each year, would need to be increased to 2.5 gigawatts each year to reach 100% renewable energy by 2030.

Remaining emissions, from shipping, aviation, and industry, could be eliminated after 2030 at slightly higher costs.

Lesley Hughes, a member of the Climate Council and professor at Macquarie University, said there were a number of factors causing the gap between science and policy, including vested interests, perception of economic downsides of climate action, ideological biases, and inertia in the system from current investment in fossil fuels. But she said the “most important issue” was the difficulty in convincing people to act to reduce risk decades in the future.

The Climate Change Authority, which advises the government on climate policy, in 2014 recommended Australia adopt a target of 40-60% below 2000 levels by 2030.

In a report released yesterday, The Climate Institute highlighted that aiming for 1.5℃ instead of 2℃ would avoid longer heatwaves and droughts, and give the Great Barrier Reef a better chance of survival.

The institute recommended that Australia adopt an emissions reduction target of 65% below 2005 levels by 2030 and phase out coal power by 2035.

The Conversation

James Whitmore, Editor, Environment & Energy, The Conversation

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

Stopping land clearing and replanting trees could help keep Australia cool in a warmer future


Clive McAlpine, The University of Queensland; Jozef Syktus, The University of Queensland, and Leonie Seabrook, The University of Queensland

Land clearing is on the rise in Queensland and New South Wales, with land clearing laws being fiercely debated.

In Queensland in 2013–14, 278,000 hectares of native vegetation were cleared (1.2 times the size of the Australian Capital Territory). A further 296,000ha were cleared in 2014–15. These are the highest rates of deforestation in the developed world.

Land clearing on this scale is bad for a whole host of reasons. But our research shows that it is also likely to make parts of Australia warmer and drier, adding to the effects of climate change.

How do trees change the climate?

Land clearing releases greenhouse gases into the atmosphere, but the effect of land clearing on climate goes well beyond carbon emissions. It causes warming locally, regionally and even globally, and it changes rainfall by altering the circulation of heat and moisture.

Trees evaporate more water than any other vegetation type – up to 10 times more than crops and pastures. This is because trees have root systems that can access moisture deep within the soil. Crops and pastures have 70% of their roots in the top 30cm of the soil, while trees and other woody plants have 43% of their roots in the deeper part of the soil.

The increased evaporation and rough surface of trees creates moist, turbulent layers in the lower atmosphere. This reduces temperatures and contributes to cloud formation and increased rainfall. The increased rainfall then provides more moisture to soils and vegetation.

The clearing of deep-rooted native vegetation for shallow-rooted crops and pastures diminishes this process, resulting in a warmer and drier climate.

We can see this process at work along the “bunny fence” in southwest Western Australia, where there is a moister atmosphere and more clouds over native vegetation compared with nearby farming areas during summer.

Studies in Amazonia also indicate that as deforestation expands rainfall declines. A tipping point may be reached when deforestation reaches 30-50%, after which rainfall is substantially reduced. Complete deforestation results in the greatest decline in rainfall.

More trees, cooler moister climate

We wanted to know how land clearing could affect Australia’s climate in the future. We did this by modelling two scenarios for different amounts of land clearing, using models developed by CSIRO.

In the first scenario, crops and pasture expand in the semi-arid regions of eastern and southwest Australia. The second scenario limits crops and pastures to highly productive lands, and partially restores less productive lands to savanna woodlands.

We found that restoring trees to parts of Australia would reduce surface temperatures by up to 1.6℃, especially in western Queensland and NSW.

We also found that more trees reduced the overall climate-induced warming from 4.1℃ to 3.2℃ between 2050 and 2100.

Replanting trees could increase summer rainfall by 10% overall and by up to 15.2% in the southwest. We found soil moisture would increase by around 20% in replanted regions.

Our study doesn’t mean replanting all farmed land with trees, just areas that are less productive and less cost-effective to farm intensively. In our scenario, the areas that are restored in western Queensland and NSW would need a tree density of around 40%, which would allow a grassy understorey to be maintained. This would allow some production to continue such as cattle grazing at lower numbers or carbon farming.

Political and social challenges

Limiting land clearing represents a major challenge for Australia’s policymakers and farming communities.

The growing pressure to clear reflects a narrow economic focus on achieving short- to medium-term returns by expanding agriculture to meet the growing global demand for food and fibre.

However, temperatures are already increasing and rainfall is decreasing over large areas of eastern and southwest Australia. Tree clearing coupled with climate change will make growing crops and raising livestock even harder.

Balancing farming with managing climate change would give land owners on marginal land new options for income generation, while the most efficient agricultural land would remain in production. This would need a combination of regulation and long-term financial incentives.

The climate benefits of limiting land clearing must play a bigger part in land management as Australia’s climate becomes hotter and drier. Remnant vegetation needs to be conserved and extensive areas of regrowth must be allowed to regenerate. And where regeneration is not possible, we’ll have to plant large numbers of trees.

The Conversation

Clive McAlpine, Professor, The University of Queensland; Jozef Syktus, Principal Research Fellow, Global Change Institute, The University of Queensland, and Leonie Seabrook, Landscape Ecologist, The University of Queensland

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

Keeping global warming to 1.5C, not 2C, will make a crucial difference to Australia, report says


James Whitmore, The Conversation and Michael Hopkin, The Conversation

Australia could avoid punishingly long heatwaves and boost the Great Barrier Reef’s chances of survival by helping to limit global warming to 1.5℃ rather than 2℃, according to a report released by the Climate Institute today.

Australia, along with 179 other countries, has formally signed the Paris climate agreement. The deal, which has not yet come into force, commits nations to limit Earth’s warming to “well below 2℃” and to aim for 1.5℃ beyond pre-industrial temperatures.

The new research, compiled by the international agency Climate Analytics, suggests that limiting global warming to 1.5℃ rather than letting it reach 2℃ could make a significant difference to the severity of extreme weather events in Australia. Heatwaves in southern Australia would be an average of five days shorter, and the hottest days a degree cooler. In the north, hot spells would be 20-30 days shorter than the 60-day heatwaves potentially in store if warming hits 2℃.

Under 2℃ warming, the world’s coral reefs would have a “very limited chance” of survival, whereas limiting warming to 1.5℃ would allow “some chance for a fraction of the world’s coral reefs to survive”, the report says.

Sarah Perkins-Kirkpatrick, a climate researcher at UNSW Australia, said that while the 0.5℃ difference between the two targets might not sound like a lot, it would lead to “clearly noticeable” differences in regional climates, including Australia’s.

“This is particularly true for extreme events, where just a small change in average temperature corresponds to larger changes in events like temperature extremes, especially in their frequency and duration,” she said.

Protesters at December’s Paris climate summit make their feelings clear about the 1.5-degree goal.
Reuters/Jacky Naegelen

University of Melbourne researcher Andrew King, who studies climate extremes, said the report “paints a grim picture for the future”, given that Australia is already experiencing climate-driven events such as this year’s unprecedented bleaching on the Great Barrier Reef.

“There are many benefits if warming could be limited to 1.5℃, with less frequent and intense extreme weather. On the other hand, we are entering the unknown if we allow warming to surpass 2℃, as tipping points in the Earth’s climate system make accurate predictions difficult to make,” Dr King said.

The report predicts that half of the world’s identified tipping points – such as the collapse of polar ice sheets and the drying out of the Amazon rainforest – would be crossed under 2℃ warming, compared with 20% of them at 1.5℃.

Tall order

The problem is that keeping warming to 1.5℃ is now a very onerous, if not impossible, task. It would require the world to peak its emissions by the end of this decade, with a future “carbon budget” of just 250 billion tonnes of CO₂. To put that in context, global carbon emissions in 2014 were 36 billion tonnes.

Given the low probability of reducing emissions at the speed required, the report argues that untested “negative emissions” technologies (removing carbon dioxide from the atmosphere) will be needed after 2030.

However, Kate Dooley, a PhD candidate at the University of Melbourne, questioned the report’s suggested reliance on negative emissions.

“Assuming carbon can be removed from the atmosphere on a large scale later in the century is a bad strategy for climate mitigation. Relying on negative emissions to “undo” earlier emissions may lock us into higher levels of warming if the expected technologies do not materialise or pose unacceptable social and ecological risk,” she said.

Stronger targets

In a separate report, the Climate Institute recommends that Australia adopt greenhouse gas targets of 45% below 2005 levels by 2025, and 65% by 2030, if it is to do its fair share in achieving the Paris Agreement’s goals.

The institute also recommended that Australia phase out coal-fired electricity generation by 2025, increase renewable generation to 50% by 2030, and double energy productivity by 2030.

It argues for a carbon price, and urges politicians to factor the costs and benefits of climate change and climate action formally into all policy decisions.

Australia’s current climate target under the Paris Agreement is 26-28% below 2005 levels by 2030. Labor has proposed a 45% target, and the Greens zero or negative emissions within a generation.

Australia will review its climate policies in 2017, ahead of the first global stocktake of nations’ Paris Agreement targets in 2018.

Dooley said that ultimately “we have left climate action so late that some level of carbon removals will be required due to historical emissions already in the atmosphere. Assuming negative emissions will only be available at very low levels will force us to re-examine what is possible in terms of dramatic emission reductions.”

Dr King said the results “highlight the pressing need to take immediate and drastic action to reduce our greenhouse gas emissions”. In a recent Conversation article, he and his colleague Ben Henley explained that the world is already closing in fast on the 1.5℃ warming target.

“We know that we will go past 1.5℃ in the near future and we would need large-scale negative emissions schemes to bring the world back down to 1.5℃ warming. Such big schemes are prohibitively expensive and impractical with current technologies, so it would be better to act now rather than later,” he said.

Dr Perkins-Kirkpatrick added that “we need to work as a global community to reduce our emissions as quickly and efficiently as possible, so that regional changes and their impacts are minimised.”

The Conversation

James Whitmore, Editor, Environment & Energy, The Conversation and Michael Hopkin, Environment + Energy Editor, The Conversation

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