By Pep Canadell, CSIRO
Through burning fossil fuels, humans are rapidly driving up levels of carbon dioxide in the atmosphere, which in turn is raising global temperatures.
But not all the CO2 released from burning coal, oil and gas stays in the air. Currently, about 25% of the carbon emissions produced by human activity are absorbed by plants, and another similar amount ends up in the ocean.
To know how much more fossils fuels we can burn while avoiding dangerous levels of climate change, we need to know how these “carbon sinks” might change in the future. A new study led by Dr. Sun and colleagues published today in PNAS shows the land could take up slightly more carbon than we thought.
But it doesn’t change in any significant way how quickly we must decrease carbon emissions to avoid dangerous climate change.
Models overestimate CO2
The new study estimates that over the past 110 years some climate models over-predicted the amount of CO2 that remains in the atmosphere, by about 16%.
Models are not designed to tell us what the atmosphere is doing: that’s what observations are for, and they tell us that CO2 concentrations in the atmosphere are currently over 396 parts per million, or about 118 parts per million over pre-industrial times. These atmospheric observations are in fact the most accurate measurements of the carbon cycle.
But models, which are used to understand the causes of change and explore the future, often don’t match perfectly the observations. In this new study, the authors may have come up with a reason that explains why some models overestimate CO2 in the atmosphere.
Looking to the leaves
Plants absorb carbon dioxide from the air, combine it with water and light, and make carbohydrates — the process known as photosynthesis.
It is well established that as CO2 in the atmosphere increases, the rate of photosynthesis increases. This is known as the CO2 fertilisation effect.
But the new study shows that models may not have quite right the way they simulate photosynthesis. The reasons comes down to how CO2 moves around inside a plant’s leaf.
Models use the CO2 concentration inside a plant’s leaf cells, in the so called sub-stomatal cavity, to drive the sensitivity of photosynthesis to increasing amounts of CO2. But this isn’t quite correct.
The new study shows that CO2 concentrations are actually lower inside a plant’s chloroplasts — the tiny chambers of a plant cell where photosynthesis actually happens. This is because the CO2 has to go through an extra series of membranes to get into the chloroplasts.
This means that photosynthesis takes place at lower CO2 than models assume. But counterintuitively, because photosynthesis is more responsive to increasing levels of CO2 at lower concentrations, plants are removing more CO2 in response to increasing emissions than models show.
Photosynthesis increases as CO2 concentrations increase but only up until a point. At some point more CO2 has no effect on photosynthesis, which stays the same. It becomes saturated.
But if concentrations inside a leaf are lower, this saturation point is delayed, and growth in photosynthesis is higher, which means more CO2 is absorbed by the plant.
The new study shows that when accounting for the issue of CO2 diffusivity in the leaf, the 16% difference between modelled CO2 in the atmosphere and the real observations disappear.
It is a great, neat piece of science, which connects the intricacies of leaf level structure to the functioning of the Earth system. We will need to reexamen they way we model photosynthesis in climate models and whether a better way exists in light of the new findings.
Does this change how much CO2 the land absorbs?
This study suggests that some climate models models under-simulate how much carbon is stored by plants, and in consequence over-simulate how much carbon goes into the atmosphere. The land sink might be a little bigger — although we don’t know yet how much bigger.
If the land sink does a better job, it means that for a given climate stabilisation, we would have to do a little bit less carbon mitigation.
But photosynthesis is a long, long way before a true carbon sink is created, one that actually stores carbon for a long time.
About 50% of all CO2 taken in by photosynthesis goes back to the atmosphere soon after through plant respiration.
Of what remains, more than 90% also returns back to the atmosphere through microbial decomposition in the soils and disturbances such as fire over the following months to years — what stays, is the land sink.
Good news, but not time for complacency
The study is a rare and welcome piece of possible good news, but it needs to be placed in context.
The land sink has very large uncertainties, they have been well quantified, and the reasons are multiple.
Some models suggest that the land will continue to absorb more carbon all throughout this century, some predict it will absorb more carbon up to a point, and some predict that the land will start releasing carbon — becoming a source, not a sink.
The reasons are multiple and include limited information on how the thawing of permafrost will effect large carbon reservoirs, how the lack of nutrients could limit the further expansion of the land sink, and how fire regimes might change under a warmer world.
These uncertainties put together are many times bigger than the possible effect of the leaf CO2 diffusion. The bottom line is that humans continue to be in full control of what’s happening to the climate system over the coming centuries, and what we do with greenhouse emissions will largely determine its trajectory.
Pep Canadell receives funding from the Australian Climate Change Science Program.
By Eamonn Bermingham
Where would we be without the ocean? Swimming, surfing, snorkelling would be tough, not to mention all the yummy food we’d miss. But it has also played a more important role in all of our lives; fulfilling the noblest of causes.
For many years the ocean has been on the front line in the fight to slow down climate change, absorbing around a quarter of the carbon dioxide we produce. The problem is that the scars of this attack are beginning to show.
Ocean acidification is often referred to as the “other CO₂ problem”, and is a chemical response to the dissolving of carbon dioxide into seawater.
The equation is simple: as CO₂ in the atmosphere goes up (and there was a record-breaking increase in 2013), the pH of the ocean falls, with negative impacts on marine biodiversity, ecosystems and society.
But how bad is it?
For the past two years we’ve been working as part of an international team brought together by the United Nations to investigate the impacts of ocean acidification, and our findings have been released today.
The rate of acidification since pre-industrial times and its projected continuation are unparalleled in the last 300 million years, and are likely to have a severe impact on marine species and ecosystems, with flow-on effects to various industries, communities and food security.
We’ve estimated that the loss of tropical coral reef alone – such as the Great Barrier Reef – could end up costing a trillion US dollars a year.
What does the future hold?
Ten years ago, only a handful of researchers were investigating the biological impacts of ocean acidification. Around a thousand published studies later, our understanding of ocean acidification and its consequences has increased tremendously.
Experimental studies show the variability of organisms’ responses to simulated future conditions: some are impacted negatively, some positively, and others are apparently unaffected.
If we are to truly understand the future impacts of ocean acidification, more research is needed to reduce the uncertainties, reduce emissions, and reduce the problem.
Read the full report: “An updated synthesis of the impacts of ocean acidification on marine biodiversity”
The report was compiled by the UN’s Convention on Biological Diversity, an international team of 30 scientists.
As heads of state gather in New York for tomorrow’s United Nations climate summit, a new report on the state of the world’s carbon budget tells them that greenhouse emissions hit a new record last year, and are still growing.
It shows that global emissions from burning fossil fuels and cement production reached a new record of 36 billion tonnes of CO2 in 2013, and are predicted to grow by a further 2.5% in 2014, bringing the total CO2 emissions from all sources to more than 40 billion tonnes. This is about 65% more fossil-fuel emission than in 1990, when international negotiations to reduce emissions to address climate change began.
Meanwhile, deforestation now accounts for just 8% of total emissions, a fraction that has been declining for several decades.
The growth of global emissions since 2009 has been slower than in the prior period of 2000-08. However, projections based on forecast growth in global gross domestic product (GDP) and continuance of improving trends in carbon intensity (emissions per unit of GDP) suggest a continuation of rapid emissions growth over the coming five years.
Global emissions continue to track the most carbon-intensive range among more than a thousand scenarios developed by the Intergovernmental Panel on Climate Change (IPCC). If continued, this situation would lead to global average temperatures between 3.2C and 5.4C above pre-industrial levels by 2100.
There have been other striking changes in emissions profiles since climate negotiations began. In 1990, about two-thirds of CO2 emissions came from developed countries including the United States, Japan, Russia and the European Union (EU) nations. Today, only one-third of world emissions are from these countries; the rest come from the emerging economies and less-developed countries that account for 80% of the global population, suggesting a large potential further emissions growth.
Continuation of current trends over the next five years alone will lead to a new world order on greenhouse gas emissions, with China emitting as much as the United States, Europe and India together.
Country emission profiles
There are several ways to explore countries’ respective contributions to climate change. These include current emissions, per capita emissions, and cumulative emissions since the industrial revolution.
The largest emitters in 2013 were China, the United States, the 28 EU countries (considered as a single bloc), and India. Together, they account for 58% of global emissions and 80% of the emissions growth in 2013 (with the majority the growth coming from China, whereas the EU cut its emissions overall).
Here’s how the major emitters fared in 2013.
Emissions grew at 4.2%, the lowest level since the 2008 global financial crisis, because of weaker economic growth and improvements in the carbon intensity of the economy. Per capita emissions in China (7.2 tonnes of CO2 per person) overtook those in Europe (6.8 tonnes per person).
A large part of China’s high per capita emissions is due to industries that provide services and products to the developed world, not for China’s domestic use. China’s cumulative emissions are still only 11% of the total since pre-industrial times.
Emissions increased by 2.9% because of a rebound in coal consumption, reversing a declining trend in emissions since 2008. Emissions are projected to remain steady until 2019 in the absence of more stringent climate policies, with improvements in the energy and carbon intensity of the economy being offset by growth in GDP and population. The United States remains the biggest contributor of cumulative emissions with 26% of the total.
Emissions fell by 1.8% on the back of a weak economy, although reductions in some countries were offset by a return to coal led by Poland, Germany and Finland. However, the long-term decrease in EU emissions does not factor in the emissions linked to imported goods and services. When accounting for these “consumption” emissions, EU emissions have merely stabilised, rather than decreased.
Emissions grew by 5.1%, driven by robust economic growth and an increase in the carbon intensity of the economy. Per capita emissions were still well below the global average, at 1.9 tonnes of CO2 per person, although India’s total emissions are projected to overtake those in the EU by 2019 (albeit for a population nearly three times as large). Cumulative emissions account for only 3% of the total.
Emissions from fossil fuels declined in 2013, largely driven by a 5% decline of emissions in the electricity sector over the previous year (as shown by the Australian National Greenhouse Gas Accounts). Fossil fuel emissions per person remain high at 14.6 tonnes of CO2.
Is it too late to tame the climate?
Despite this apparently imminent event, economic models can still come up with scenarios in which global warming is kept within 2C by 2100, while both population and per capita wealth continue to grow. Are these models playing tricks on us?
Most models invoke two things that will be crucial to stabilising the climate at safer levels. The first is immediate global action to develop carbon markets, with prices rapidly growing to over US$100 per tonne of CO2.
The second is the deployment of “negative emissions” technologies during the second half of this century, which will be needed to mop up the overshoot of emissions between now and mid-century. This will involve removing CO2 from the atmosphere and storing it in safe places such as saline aquifers.
These technologies are largely unavailable at present. The most likely candidate is the production of bioenergy with carbon capture and storage, a combination of existing technologies with high costs and with environmental and socio-economic implications that are untested at the required scales.
There are no easy pathways to climate stabilization, and certainly no magic bullets. It is still open to us to choose whether we halt our CO2 emissions completely this century – as required for a safe, stable climate – or try instead to adapt to significantly greater impacts of climate change.
What we have no choice about is the fact that the longer emissions continue to grow at rates of 2% per year or more, the harder it will be to tame our climate.
Pep Canadell received support from the Australian Climate Change Science Program.
Michael Raupach has previously received funding from the Australian Climate Change Science Program, but does not do so now.
As World Water Week draws to a close, we want to tell you about a water management project we’re involved with in the developing world.
The Koshi River basin covers some of the poorest parts of China, India and Nepal. The river stretches more than 700km, from China in the north, down through Nepal and across the Himalayas, and finally feeds into the Ganges River. Millions of people live in the region – many of them in flood-prone areas – and rely on the river and the fertile floodplain for their livelihoods.
We’re helping to manage the river better and improve the circumstances of the people living there.
The area is subject to floods, droughts landslides and flows of debris. Erosion also leads to heavy sedimentation, and rivers have been known to change their course.
The effects of climate change aren’t helping, either. Glaciers in the upper reaches of the Basin are melting, bringing water and sediments down to the plains. The people of the Koshi River Basin are in an increasingly vulnerable situation. The impacts of climate change are disturbing water supply and agricultural production. Adding more pressure, the demand for energy and food production is rising.
Raising the stakes even higher, the Koshi Basin also has areas of significant biodiversity, including a UNESCO World Heritage Site.
With funding from the Department of Foreign Affairs and Trade – Australian Aid, we’re working with partners including the International Centre for Integrated Mountain Development, the International Water Management Institute and eWater to develop an integrated modelling framework for the entire basin. We’re helping to develop water balance models that capture the relationship between climate (both rainfall and temperature) and stream-flow (and flood risk) in the Koshi River Basin.
We’re also working on characterising the seasonality and variability of stream flow, and, if possible, the expected trends in stream-flow. We’ll also develop techniques for understanding the likelihood of particular stream-flow estimates.
We aim to use the research and knowledge gained from these projects to allow a regionally coordinated approach to developing and managing the Koshi Basin’s water resources. The people of the area, and the environment, should both benefit.
We rely a lot on climate models. They not only help us understand our present climate, but also allow us to understand possible future conditions and how different regions of our planet are likely to be impacted by climate change.
Having access to this information is vital for the community, government and industries to make informed decisions – sectors like tourism, farming and transportation to name a few.
As useful as these tools are, the reality is that the Earth’s climate system is incredibly complicated. It is affected by an infinite number of variations in the atmosphere, land surface, oceans, ice, and biosphere. How these factors interact with one another, and our socio-economic decisions, further complicates the issue.
In the absence of a twin Earth to use as an experimental control, simulations are the only method we have to understand the future.
Using observed data, advanced algorithms and software systems, scientists have been developing and refining these valuable climate models for years. However in recent times, there has been conjecture about a key aspect of the reliability of these models; whether they are accurately predicting temperature trends?
A new study, published today in Nature Climate Change, shows that yes in fact, they are.
According to the study’s lead author Dr James Risbey, the key to evaluating decadal climate variations is recognising the difference between climate forecasts and climate projections.
He explains that climate forecasts track the detailed evolution of a range of factors, including natural variations like El Niño and La Niña (which put simply is, warm water sloshing around the ocean). This is important because in El Niño and La Niña dominated periods, temperature trends will naturally speed up and slow down.
“Climate projections, on the other hand, capture natural variations, but have no information on their sequence and timing. Since these can impact the climate on a short timescale as much as human activities, their omission from projections creates a mismatch with observed trends. In other words, comparing the two wouldn’t pass the old ‘apples with apples’ test,” he said.
For this latest study, James and his colleagues looked at a range of different climate models that were in phase with natural variability. In doing so, they were able to make meaningful comparisons between model projections and observed trends.
Their analysis showed that in these instances climate models have been very accurate in predicting trends in our climate over the past half century. In other words, climate change models are a lot more than hot air.
Fine out more about our research into climate in our recent report State of the Climate: 2014.
Media Contact: Simon Torok +61 409 844 302 or firstname.lastname@example.org
Over the past few months, a lot of attention has been paid to the potentially strong El Niño event brewing in the Pacific Ocean. But there is also the potential for an emerging climate phenomenon in the Indian Ocean that could worsen the impacts of an El Niño, bringing drought to Australia and its neighbours.
The Indian Ocean Dipole is a phenomenon that has already been shown to have a significant impact on rainfall in countries bordering the Indian Ocean.
The main effects are drought in Australia, while east Africa suffers floods. And our new work published in the international journal Nature today shows that the frequency of these extreme events is set to increase as the world warms this century.
The Indian Ocean Dipole is a year-to-year see-saw pattern in surface temperature and rainfall across the tropical Indian Ocean. During a positive Indian Ocean Dipole phase, sea surface temperatures off Sumatra and Java in Indonesia are colder than normal. Meanwhile, off east Africa, surface waters are unusually warm.
Like an El Niño, a positive Indian Ocean Dipole brings heavy rainfall to eastern parts of Africa and drought to countries around the Indonesian Archipelago, including Australia. A negative Indian Ocean Dipole phase tends to do the opposite.
When a positive Indian Ocean Dipole is coupled with an El Niño event, rainfall declines are more widespread across Australia, and more intense, particularly in the southeast.
Currently, as we move into Australia’s winter, the outlook is for a neutral Indian Ocean Dipole in October. But some models are projecting the development of a positive Indian Ocean Dipole. This should not come as a surprise. Over the past 50 years, around 70% of positive Indian Ocean Dipole events coincided with an El Niño event.
Predicting an Indian Ocean Dipole event is more difficult than forecasting an El Niño. Like an El Niño, autumn conditions create a barrier that prevents forecasters from being able to predict accurately what state an Indian Ocean Dipole will be — positive, negative or neutral at its peak. This is because its development relies on easterly winds off Sumatra and Java which occur after autumn, and usually last until November.
So, unlike an El Niño, which peaks in summer, Indian Ocean Dipole events form in winter and then peak in spring. This creates a narrower predictability window that gives little warning to industries, such as farming, that depend on rain through spring.
What’s more, because of the strong monsoon seasonality, these events do not have a prominent warm water volume that an El Niño has as a precursor to the event, so there is no time to see the event unfolding. This is also partly because the Indian Ocean is smaller than the Pacific and is bounded by Asia to the north, which prevents a slow, large accumulation of heat like that seen in the Pacific.
In 2012, while conditions in the Pacific Ocean suggested an emerging El Niño, a positive Indian Ocean Dipole abruptly developed in July. The El Niño that year dissipated before it was expected to peak in summer 2013. The preceding two consecutive strong La Niñas helped to alleviate the Indian Ocean Dipole’s drying impact on Australia. But it could still have played a role in the January 2013 bushfires in southeastern Australia by drying out soils.
What the future holds
Just like an El Niño, Indian Ocean Dipole events can vary in size. Our work in Nature today shows that extreme positive Indian Ocean Dipole events are characteristically distinct from moderate ones.
During an extreme event, the cold waters off Sumatra extend farther west along the equator as ocean currents and winds reverse their flow and head towards eastern Africa. This makes the western part of the Indian Ocean warm even more strongly than during moderate events.
Our research shows that global warming is likely to triple the number of these extreme events. This would increase the frequency of droughts over the southern parts of our continent. The research follows another recent study that showed extreme El Niño events were also likely to increase with global warming.
Even though the two climate phenomena are not directly connected, it makes sense that both would increase in frequency under global warming. This is because under a warmer climate, the Walker Circulation, which creates easterly winds in the tropical Pacific and westerly winds in the tropical Indian Ocean, is predicted to weaken.
This weakening will create a faster warming rate in the western Indian Ocean than in the east. As a result, westerly winds and ocean currents at the Equator weaken and so they can more easily reverse direction. This is exactly the environment needed in the Indian Ocean to create an extreme positive Indian Ocean Dipole and in the Pacific Ocean to enable the development of extreme El Niño events.
Deadly floods and droughts
Extreme positive Indian Ocean Dipole events are unusual and have only occurred three times in recent decades: in 1961, 1994 and 1997. Of these three, only the 1997 event coincided with a significant El Niño event. This El Niño turned out to be the strongest ever recorded in the 20th century.
Remarkably, Australia was spared the worst of this extreme combination, but other countries in our region and in Africa were not so lucky. There were devastating floods in Somalia, Ethiopia, Kenya, Sudan and Uganda that killed thousands and displaced hundreds of thousands.
Indonesia suffered a serious drought that led to famine, riots and fires that caused smoke haze to spread across Singapore, Malaysia and Thailand.
What’s in store this year?
At the beginning of June this year, the conditions in the Pacific Ocean are still on track to cross the threshold for an El Niño. The characteristics of this developing event suggest we could be in for a significant El Niño this summer. With models starting to suggest a possible development of a positive Indian Ocean Dipole, could we be moving into a situation like the 1997 event? We hope not.
The picture will become clearer over the coming months, but it is vital that we prepare for this potential event. More importantly still, we need to get ready for these extreme events to become more common as global warming continues in the coming decades.
For a long time, people were hesitant to discuss adapting to climate change. Some called it defeatist, others worried it would be used as an excuse to delay action on emissions reduction. That was a long time ago. The science of climate adaptation – developing tools, systems and technologies that improve the ability of communities and businesses to survive and prosper as the climate changes around them – has come a long way.
What emerges from this substantial and growing body of work are four powerful yet simple conclusions:
First: adapting to climate change is about people.
As the world warms, people are exposed to greater levels of risk. The State of the Climate 2014 report, recently released by CSIRO and the Bureau of Meteorology, shows that climate change is here and is happening now . The risk of bushfires has increased. Communities are more exposed to extreme heat. Over the past several years, extreme flooding in Australia has caused incalculable suffering. Without serious action to reduce emissions, these trends will strengthen. Adaptation means protecting people from the impacts already occurring and that we’ll see in future by changing the way we plan, design, and operate the places we live: keeping cities cooler by retaining and enhancing urban tree canopies and greenspaces; building houses to current fire codes; continuing to improve our ability to predict fire weather and provide early warning so communities can prepare; planning housing development to avoid exposed floodplains and retrofitting existing buildings to ensure survivability. Adaptation saves lives.
Second: adapting to climate change is good business.
During the recent Queensland floods, mines were flooded, rail lines washed out, and power disrupted, resulting in hundreds of millions of dollars in lost production. Studies by Stern, Garnaut, and others estimate that climate change, unchecked, will cause economic losses in the billions. CSIRO estimates that by 2070, the value of buildings in Australia exposed to climate-related events will exceed five trillion dollars. But carefully planned and timed adaptation can reduce the damage and cost impact of climate change on businesses and our economy by up to half, and in some cases more. Many businesses in Australia are already starting to plan resilience into their operations, driving down risk levels. But many have not, and remain significantly exposed. Adaptation, properly done, saves money.
Third: Adaptation is a good deal, but the longer we wait to act, the lower the benefits.
Many of the practical adaptive actions we can do to protect our families, communities and businesses are low cost, and yield significant improvements in resilience. Some adaptation measures, like preserving coastal ecosystems (dunes and mangroves, for instance), protect homes, coastal infrastructure and industry from storm surges and sea-level rise, and cost almost nothing. Building or retrofitting homes to current fire codes costs relatively little, and substantially improves survival rates. Recent CSIRO research shows that protecting buildings from coastal flooding can yield up to $40 in net benefit for each dollar invested. Another study on protecting infrastructure from high winds shows that net benefits of adaptation are large, but drop by half if we wait 20 years to implement. Act early, reap the rewards.
Fourth: There are economic and ecological limits to adaptation.
Adaptation is good news, and compared to the challenge of cutting emissions, much can be achieved quickly and with little fuss. But it is important to recognise that there are limits to what adaptation can do.
There are economic limits. We will exhaust the lowest cost – highest benefit adaptation options first. Dunes and mangroves are great, if you have them, but they can only do so much. As the climatic changes persist and worsen, as is projected, other measures will be needed. Sea walls and tidal barriers can help protect coastal communities from sea-level rise and storms. But they can pose significant engineering challenges, and carry big price tags. In the next few decades, with business-as-usual emissions, the costs of adaptation could start not only to stress the ability of society to pay, but could begin to surpass the cost we would have had to pay to transform our energy systems in the first place.
There are ecological limits, too. While there are things we can do to help reduce the impacts on species and ecosystems, like planning reserves to provide corridors for migration, and transplanting vulnerable species into refuges in new suitable locations, the rates of ecosystem change implied by our current emissions trajectory will leave many creatures behind. Landmark work done by CSIRO predicts that at current emission rates, virtually every native ecosystem in Australia will have been replaced by something else by 2070.
Adaptation makes sense, on a number of levels. Understanding the practical and economic limits of adaptation will help us frame the case for emissions reduction, highlight the risks we face, and show the importance of starting our adaptation journey now.
The Intergovernmental Panel on Climate Change Working Group II released its Fifth Assessment Report on climate change impacts, adaptation and vulnerability today. In this video Dr Mark Howden discusses how CSIRO is developing strategies to help reduce the impacts of climate change on ecosystems and communities: