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.
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℃.
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.
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 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 Paris climate agreement set a “safe” global warming limit of below 2℃, aiming below 1.5℃ by 2100. The world has already warmed about a degree since the Industrial Revolution, and on our current emissions trajectory we will likely breach these limits within decades.
However, we could still come back from the brink with a massive effort.
But let’s take a closer look at that warming limit. If we accept that 1.5-2℃ of warming marks the danger threshold, then this is true whether it applies tomorrow, in 2100, or some time thereafter. What we need is to stay below these limits for all time.
Put it this way: we wouldn’t be satisfied if the brakes on a new car only worked on the day of purchase, or for two weeks after that – we expect them to keep us safe throughout the car’s lifetime.
The trouble is, limiting warming to well below 2℃ forever is a much harder job.
Whatever warming we manage to prevent this century, the world will continue to respond to climate change after 2100.
Looking beyond 2100 is often considered irrelevant, given that electoral timescales only operate over several years, and individual development projects over several decades.
However, it is highly relevant to major infrastructure developments, such as overall city planning. Throughout Europe and Asia, the foundations of most city infrastructure date back centuries, or even millennia. Not incidentally, so do most of the supporting agricultural and fisheries traditions and transport routes.
Even the more recent developments in the Americas, Africa and Australia have fundamental roots that date back hundreds of years. Clearly, we need to think beyond the current century when we think about climate change and its impact on civilisation.
The climate system is made up of many different components. Some of these respond rapidly to changes, others over much longer timescales.
The components that respond rapidly to the impacts of greenhouse gas emissions include changes in cloud, snow and sea-ice cover, in dust content of the atmosphere, land-surface changes, and so on. Some work almost instantaneously, others over decades. Together these are known as the “transient” response.
Slow-responding components in the climate system include ocean warming, continental ice-sheets and exchanges of carbon between lifeforms, oceans, the sea floor, soils and the atmosphere. These work over many centuries and are known as the “equilibrium” response.
Large amounts of energy are needed to warm up such a large volume of water as the global ocean. The ocean has taken up more than 90% of all the extra heat caused by greenhouse gases emitted since the Industrial Revolution, especially into the upper few hundred metres.
However, the ocean is so vast that it will continue to warm from the top down over many centuries to millennia, until its energy uptake has adjusted to Earth’s new energy balance. This will continue even if no further emissions are made.
Ice sheets on Antarctica and Greenland respond to climate change like an accelerating heavy freight train: slow to start, and virtually unstoppable once they get going. Climate change has been building up since the onset of the Industrial Revolution, but only in recent decades have we started to see marked mass-loss increases from the ice sheets.
The ice-sheet freight train has at last come up to speed and now it will keep on rolling and rolling, regardless of what immediate actions we take regarding our emissions.
Carbon dioxide levels have reached 400 parts per million (ppm). To find out what this means for the coming centuries, we have to look between 3 million and 3.5 million years into the past.
Temperature reconstructions suggest the world was 2-3℃ warmer than before the Industrial Revolution, which is similar to the expected equilibrium response for the future.
Geological data from the last 65 million years indicate that the climate warms 3-5℃ for every doubling of CO₂ levels.
Before the Industrial Revolution, CO₂ levels were around 280 ppm. Under all but the most optimistic emission scenarios of the Intergovernmental Panel on Climate Change (IPCC), the first doubling (to 560 ppm) is approached or crossed between the years 2040 and 2070.
While we don’t know exactly how high sea level was 3.5 million years ago, we are confident that it stood at least 10 metres higher than today. Most studies suggest sea-level rise around 1m higher than today by 2100, followed by a relentlessly continued rise by some 2m per century. Even a rise of a metre or more by 2100 is murderously high for global infrastructure, especially in developing countries.
Today, some 600 million people live at elevations within 10m of sea level. The same area generates 10% of the world’s total GDP. It is estimated that a sea-level rise of 2m will displace almost 2.5% of the global population.
Even the more immediate impacts of sea-level rise are enormous. In 136 of the world’s largest port cities, the population exposed to flooding is estimated to increase by more than three times by 2070, due to combined actions of sea-level rise, land subsidence, population growth and urbanisation. The same study estimates a tenfold increase in asset exposure.
The eventual equilibrium (long-term) level of warming is up to twice the transient (short-term) level of warming. In other words, the Paris Agreement’s response of 1.5-2℃ by 2100 will grow over subsequent centuries toward an equilibrium warming of 2.3-4℃, even without any further emissions.
Given that we have already reached 1℃ of warming, if the aim is to avoid dangerous warming beyond 2℃ over the long term, we have to avoid any further warming from now on.
We can’t do this by simply stopping all emissions. This is because there is still some warming to catch up from the slower transient processes. To stop any further warming, we will have to reduce atmospheric CO₂ levels to about 350 ppm. Doing so requires both stopping the almost 3ppm rise per year from new emissions, and implementing carbon capture to pull CO₂ out of the atmosphere.
Global warming would be limited to 1-1.5℃ by 2100, and 2℃ over the long term, and in addition ocean acidification would be kept under control. These are essential for containing the impacts of climate change on global ecosystems.
This is the real urgency of climate change. Fully understanding the challenge can help us get to work.
Australia’s ecosystems are already showing the signs of climate change, from the recent death of mangrove forests in northern Australia, to the decline in birds in eastern Australia, to the inability of mountain ash forests to recover from frequent fires. The frequency and size of these changes will only continue to increase in the next few years.
This poses a major challenge for our national parks and reserves. For the past 200 years the emphasis in reserves has been on protection.
But protection is impossible when the environment is massively changing. Adaptation then becomes more important. If we are to help wildlife and ecosystems survive in the future, we’ll have to rethink our parks and reserves.
Climate change is predicted to have a substantial effect on our plants and animals, changing the distribution and population of species. Some areas will become unfavourable to their current inhabitants, allowing other, often weedy, species to expand. There will likely be widespread losses in some ecosystems as extreme climate events take their toll, either directly by killing plants and animals, or indirectly by changing fire regimes.
While we can model some of these changes, we don’t know exactly how ecosystems will respond to climate change.
Australia has an extensive natural reserve system, and models suggest that much of this system is expected to be altered radically in the next few decades, resulting in the formation of totally new ecosystems and/or shifts in ecosystems.
Yet with rapid climate change, it is likely that ecosystems will fail to keep up. Seeds are the only way for plants to move, and seeds can only travel so far. The distribution of plants might only shift by a few metres a year, whereas the velocity of climate change is expected to be much faster.
As a result, our ecosystems are likely to become dominated by a low diversity of native and exotic invasive species. These weedy species can spread long distances and take advantage of vacant spaces. Yet the exact nature of changes is unknown, particularly where evolutionary changes and physiological adaptation will assist some species but fail others.
Conservation managers are concerned because with increasing weediness will come a loss of biodiversity as well as declines in the overall health of ecosystems. Plant cover will decrease, triggering erosion in catchments that provide our water reservoirs. Rare animal species will be lost because a loss of plant cover makes them more susceptible to predators. A cascade of changes is likely.
While climate change threats are acknowledged in reports, we continue to focus on conserving the state of our natural environments, devoting scarce resources to keeping out weedy species, viewing vegetation communities as static, and using offsets to protect these static communities.
One way of preparing for the future is to start the process of deliberately moving species (and their genes) around the landscape in a careful and contained manner, accepting that rapid climate change will prevent this process from occurring quickly enough without some intervention.
Overseas plots covering several hectares have already been established that aim to achieve this at a large scale. For instance, in western North America there is a plot network that covers 48 sites and focuses on 15 tree species planted across a three-year period that covers temperature variation of 3-4°C.
In Australia, a small section of our reserve system, preferably areas that have already been damaged and/or disturbed, could be set aside for such an approach. As long as these plots are set up at a sufficiently large scale, they can act as nursery stock for the future. As fire frequency increases and exceeds some plants’ survival capabilities, the surviving genes and species in these plots would then serve as sources for future generations. This approach is particularly important for species that set seed rarely.
Our best guesses about what will flourish in an area in the future will be wrong in some cases, right in others, but ongoing evolution by natural selection in the plots will help to sort out what really can survive at a particular location and contribute to biodiversity. With a network of plots established across a range of natural communities, our protected areas will become more adaptable for a future where many species and communities (along with the benefits they provide) could otherwise be lost entirely.
As in the case of North America, it would be good to see plots set up along environmental gradients. These might include from wet to dry heading inland, and from cold to warm heading north-south or with changing altitude.
One place to start might be the Australian Alps. We could set aside an area at higher altitude and plant low-altitude grasses and herbs. These may help current plants compete against woody shrubs that are expected to move towards our mountain summits.
Lower down, we might plant more fire-tolerant species in mountain ash forests. Near the coast, we might plant species from further inland that are better at handling drier conditions.
The overall plot network should be seen as part of our national research infrastructure for biodiversity management. In this way, we can build a valuable resource for the future that can serve the general community and complement our current ecosystem monitoring efforts.