Mercury from the northern hemisphere is ending up in Australia



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Mercury pollution, often released from gold mining and coal power stations, is a global problem.
Shutterstock

Jenny Fisher, University of Wollongong; Dean Howard, Macquarie University; Grant C Edwards, Macquarie University, and Peter Nelson, Macquarie University

Mercury pollution has a long legacy in the environment. Once released into the air, it can cycle between the atmosphere and ecosystems for years or even decades before ending up deep in the oceans or land.

The amount of mercury in the ocean today is about six times higher than it was before humans began to release it by mining. Even if we stopped all human mercury emissions now, ocean mercury would only decline by about half by 2100.

To address the global and long-lasting mercury problem, a new United Nations treaty called the Minamata Convention on Mercury came into effect last month. The treaty commits participating countries to limit the release of mercury and monitor the impacts on the environment. Australia signed the Convention in 2013 and is now considering ratification.


Read more: Why won’t Australia ratify an international deal to cut mercury pollution?


Until now, we have only been able to guess how much mercury might be in the air over tropical Australia. Our new research, published in the journal Atmospheric Chemistry and Physics, shows that there is less mercury in the Australian tropics than in the northern hemisphere – but that polluted northern hemisphere air occasionally comes to us.

A global problem

While most of mercury’s health risks come from its accumulation in ocean food webs, its main entry point into the environment is through the atmosphere. Mercury in air comes from both natural sources and human activities, including mining and burning coal. One of the biggest mercury sources is small-scale gold mining – a trade that employs millions of people in developing countries but poses serious risks to human health and the environment.

Small-scale gold mining is an economic mainstay for millions of people, but it releases mercury directly into the air and water sources.

Once released to the air, mercury can travel thousands of kilometres to end up in ecosystems far away from the original source.

Measuring mercury in the tropics

While the United Nations was gathering signatures for the Minamata Convention, we were busy measuring mercury at the Australian Tropical Atmospheric Research Station near Darwin. Our two years of measurements are the first in tropical Australia. They are also the only tropical mercury measurements anywhere in the Maritime Continent region covering southeast Asia, Indonesia, and northern Australia.

We found that mercury concentrations in the air above northern Australia are 30-40% lower than in the northern hemisphere. This makes sense; most of the world’s population lives north of the Equator, so most human-driven emissions are there too.

More surprising is the seasonal pattern in the data. There is more mercury in the air during the dry season than the wet season.

The Australian monsoon appears to be partly responsible for the seasonal change. The amount of mercury jumps up sharply at the start of the dry season when the winds shift from blowing over the ocean to blowing over the land.

In the dry season the air passes over the Australian continent before arriving at the site, while in the wet season the air usually comes from over the ocean to the west of Darwin.
Howard et al., 2017 (modified)

But wind direction can’t explain the whole story. Mercury is likely being removed from the air by the intense rains that characterise the wet season. In other words, the lower mercury in the air during the wet season may mean more mercury is being deposited to the ocean and the land at this time of year. Unfortunately, there simply isn’t enough information from Australian ecosystems to know how this impacts local plants and wildlife.

Fires also play a role. Mercury previously absorbed by grasses and trees can be released back to the atmosphere when the vegetation burns. In our data, we see occasional large mercury spikes associated with dry season fires. As we move into a bushfire season predicted to be unusually severe, we may see even more of these spikes.

Air from the north

Although mercury levels were usually low in the wet season, on a few days each year the mercury jumped up dramatically.

To figure out where these spikes were coming from, we used two different models. These models combine our understanding of atmospheric physics with real observations of wind and other meteorological parameters.

Both models point to the same source: air transported from the north.

Australia is usually shielded from northern hemispheric air by a “chemical equator” that stops air from mixing. This barrier isn’t static – it moves north and south throughout the year as the position of the sun changes.

A few times a year, the chemical equator moves so far south that the top end of Australia actually falls within the atmospheric northern hemisphere. When this happens, polluted northern hemisphere air can flow directly to tropical Australia.

We observed 13 days when our measurement site near Darwin sampled more northern hemisphere air than southern hemisphere air. On each of these days, the amount of mercury in the air was much higher than on the days before or after.

Tracing the air backwards in time showed that the high-mercury air travelled over the Indonesian archipelago before arriving in Australia. We don’t yet know whether that mercury came from pollution, fires, or a mix of the two.

The highest mercury is observed when the air comes from the northern hemisphere.
Howard et al., 2017 (modified)

A global solution

To effectively reduce mercury exposure in sensitive ecosystems and seafood-dependent populations around the world, aggressive global action is necessary.

The cross-boundary influences on mercury that we have observed in northern Australia highlight the need for the type of multinational collaboration that the Minamata Convention will foster.

The ConversationOur new data establish a baseline for monitoring the effectiveness of new actions taken under the Minamata Convention. With the first Conference of the Parties having taken place last week, hopefully it will only be a matter of time before we begin to see the benefit.

Jenny Fisher, Senior Lecturer in Atmospheric Chemistry, University of Wollongong; Dean Howard, , Macquarie University; Grant C Edwards, Senior lecturer, Macquarie University, and Peter Nelson, Pro Vice Chancellor (Research Performance and Innovation), Macquarie University

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

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The new Great Barrier Reef pollution plan is better, but still not good enough


Jon Brodie, James Cook University; Alana Grech, James Cook University, and Laurence McCook, James Cook University

The draft water quality improvement plan, released by the federal and Queensland governments this week, aims to reduce the pollution flowing from water catchments to the Great Barrier Reef over the next five years.

It is part of the overarching Reef 2050 Long-Term Sustainability Plan to protect and manage the reef until mid-century.

Water quality is one of the biggest threats to the reef’s health, but the new guidelines still fall short of what’s required, given the available scientific evidence.


Read more: Cloudy issue: we need to fix the Barrier Reef’s murky waters.


The draft plan, which is open for comment until October, presents several important and commendable advances in the management of water quality on the Great Barrier Reef. It addresses all land-based sources of water pollution (agricultural, urban, public lands and industrial) and includes social, cultural and economic values for the first time.

The principal sources of pollution are nitrogen loss from fertiliser use on sugar cane lands, fine sediment loss from erosion on grazing lands, and pesticide losses from cropping lands. These are all major risk factors for the Great Barrier Reef.

The draft plan also presents updated water quality targets that call for reductions in run-off nutrients and fine sediments by 2025. Each of the 35 catchments that feeds onto the reef has its own individual set of targets, thus helping to prioritise pollution-reduction measures across a region almost as large as Sweden.

The reef’s still suffering

The Great Barrier Reef suffered coral bleaching and death over vast areas in 2016, and again this year. The 2017 Scientific Consensus Statement, released with the draft water quality plan (and on which one of us, Jon Brodie, was an author), reports:

Key Great Barrier Reef ecosystems continue to be in poor condition. This is largely due to the collective impact of land run-off associated with past and ongoing catchment development, coastal development activities, extreme weather events and climate change impacts such as the 2016 and 2017 coral bleaching events.

Stronger action on the local and regional causes of coral death are seen to be essential for recovery at locations where poor water quality is a major cause of reef decline. These areas include mid-shelf reefs in the Wet Tropics region damaged by crown of thorns starfish, and inner-shelf reefs where turbid waters stop light reaching coral and seagrass. Human-driven threats, especially land-based pollution, must be effectively managed to reduce the impacts on the Great Barrier Reef.

But although the draft plan provides improved targets and a framework for reducing land-based pollution, it still doesn’t reflect the severity of the situation. The 2017 Scientific Consensus Statement reports that “current initiatives will not meet the water quality targets” by 2025.

This is because the draft plan does not provide any major new funding, legislation or other initiatives to drive down land-based pollution any further. As the statement explains:

To accelerate the change in on-ground management, improvements to governance, program design, delivery and evaluation systems are urgently needed. This will require greater incorporation of social and economic factors, better targeting and prioritisation, exploration of alternative management options and increased support and resources.


Read more: The Great Barrier Reef’s safety net is becoming more complex but less effective


The draft plan calls on farmers to go “beyond minimum standards” for practices such as fertiliser use in sugar cane, and minimum pasture cover in cattle grazing lands. But even the minimum standards are unlikely to be widely adopted unless governments implement existing legislation to enforce the current standards.

The draft plan is also silent on the impact of land clearing on water quality, and the conversion of grazing land to intensively farmed crops such as sugar cane, as proposed in the White Paper on Developing Northern Australia.

The federal and Queensland governments have committed A$2 billion over ten years to protect the Great Barrier Reef. Under the draft plan, about half of this (A$100 million a year) will be spent on water quality management. This is not an increase in resourcing, but rather the same level of funding that has been provided for the past seven years.

More than loose change

There is a very strong business case for major increases in funding to protect the Great Barrier Reef. Even with conservative assumptions, the economics firm Jacobs has estimated that protecting the industries that depend on the reef will require A$830 million in annual funding – more than four times the current level.


Read more: What’s the economic value of the Great Barrier Reef? It’s priceless.


The draft water quality plan acknowledges the need for a “step change” in reef management, and to “accelerate our collective efforts to improve the land use practices of everyone living and working in the catchments adjacent to the Reef”.

This need is echoed in many other reports, both government and scientific. For example, the 2017 Scientific Consensus Statement makes several wide-ranging recommendations.

One of them is to make better use of existing legislation and policies, including both voluntary and regulatory approaches, to improve water quality standards.

This recommendation applies to both Commonwealth and Queensland laws. These include the federal Great Barrier Reef Marine Park Act 1975, which restricts or bans any activities that “may pollute water in a manner harmful to animals and plants in the Marine Park”, and the Environment Protection and Biodiversity Conservation Act 1999, which prohibits any action, inside or outside the marine park, that affects the Great Barrier Reef’s World Heritage values.

Another recommendation is to rethink existing land-use plans. For instance, even the best practice in sugar cane farming is inconsistent with the nitrogen fertiliser run-off limits needed to meet water quality guidelines. One option is to shift to less intensive land uses such as grazing in the Wet Tropics region – a priority area for nitrate fertiliser management because of its link to crown of thorns starfish outbreaks. This option is being explored in a NESP project.

The ConversationThese changes would require significantly increased funding to support catchment and coastal management and to meet the draft plan’s targets. Government commitment to this level of management is essential to support the resilience of the Great Barrier Reef to climate change.

Jon Brodie, Professorial Fellow, ARC Centre of Excellence for Coral Reef Studies, James Cook University; Alana Grech, Assistant Director, ARC Centre of Excellence for Coral Reef Studies, James Cook University, and Laurence McCook, Adjunct Principal Research Fellow, Partner Investigator, ARC Centre of Excellence for Coral Reef Studies, James Cook University

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

Noise from offshore oil and gas surveys can affect whales up to 3km away



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Migrating humpback whales avoid loud, nearby sounds.
BRAHSS, Author provided

Rebecca Dunlop, The University of Queensland and Michael Noad, The University of Queensland

Air guns used for marine oil and gas exploration are loud enough to affect humpback whales up to 3km away, potentially affecting their migration patterns, according to our new research.

Whales’ communication depends on loud sounds, which can travel very efficiently over distances of tens of kilometres in the underwater environment. But our study, published today in the Journal of Experimental Biology, shows that they are affected by other loud ocean noises produced by humans.

As part of the BRAHSS (Behavioural Response of Humpback whales to Seismic Surveys) project, we and our colleagues measured humpback whales’ behavioural responses to air guns like those used in seismic surveys carried out by the offshore mining industry.


Read more: It’s time to speak up about noise pollution in the oceans


Air guns are devices towed behind seismic survey ships that rapidly release compressed air into the ocean, producing a loud bang. The sound travels through the water and into the sea bed, bouncing off various layers of rock, oil or gas. The faint echoes are picked up by sensors towed by the same vessel.

During surveys, the air guns are fired every 10-15 seconds to develop a detailed geological picture of the ocean floor in the area. Although they are not intended to harm whales, there has been concern for many years about the potential impacts of these loud, frequent sounds.

Sound research

Although it sounds like a simple experiment to expose whales to air guns and see what they do, it is logistically difficult. For one thing, the whales may respond to the presence of the ship towing the air guns, rather than the air guns themselves. Another problem is that humpback whales tend to show a lot of natural behavioural variability, making it difficult to tease out the effect of the air gun and ship.

There is also the question of whether any response by the whales is influenced more by the loudness of the air gun, or how close the air blast is to the whale (although obviously the two are linked). Previous studies have assumed that the response is driven primarily by loudness, but we also looked at the effect of proximity.

We used a small air gun and a cluster of guns, towed behind a vessel through the migratory path of more than 120 groups of humpback whales off Queensland’s sunshine coast. By having two different sources, one louder than the other, we were able to fire air blasts of different perceived loudness from the same distance.

We found that whales slowed their migratory speed and deviated around the vessel and the air guns. This response was influenced by a combination of received level and proximity; both were necessary. The whales were affected up to 3km away, at sound levels over 140 decibels, and deviated from their path by about 500 metres. Within this “zone”, whales were more likely to avoid the air guns.

Each tested group moved as one, but our analysis did not include the effects on different group types, such as a female with calf versus a group of adults, for instance.

The ConversationOur results suggest that when regulating to reduce the impact of loud noise on whale behaviour, we need to take into account not just how loud the noise is, but how far away it is. More research is needed to find out how drastically the whales’ migration routes change as a result of ocean mining noise.

Rebecca Dunlop, Senior Lecturer in Physiology, The University of Queensland and Michael Noad, Associate Professor, The University of Queensland

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

Australia emits mercury at double the global average


Robyn Schofield, University of Melbourne

A report released this week by advocacy group Environmental Justice Australia presents a confronting analysis of toxic emissions from Australia’s coal-fired power plants.

The report, which investigated pollutants including fine particles, nitrogen oxides and sulfur dioxide, also highlights our deeply inadequate mercury emissions regulations. In New South Wales the mercury emissions limit is 666 times the US limits, and in Victoria there is no specific mercury limit at all.

This is particularly timely, given that yesterday the Minamata Convention, a United Nations treaty limiting the production and use of mercury, entered into force. Coal-fired power stations and some metal manufacturing are major sources of mercury in our atmosphere, and Australia’s per capita mercury emissions are roughly double the global average.


Read more: Why won’t Australia ratify an international deal to cut mercury pollution?


In fact, Australia is the world’s sixteenth-largest emitter of mercury, and while our government has signed the Minamata convention it has yet to ratify it. According to a 2016 draft impact statement from the Department of Environment and Energy:

Australia’s mercury pollution occurs despite existing regulatory controls, partly because State and Territory laws limit the concentration of mercury in emissions to air […] but there are few incentives to reduce the absolute level of current emissions and releases over time.

Mercury can also enter the atmosphere when biomass is burned (either naturally or by people), but electricity generation and non-ferrous (without iron) metal manufacturing are the major sources of mercury to air in Australia. Electricity generation accounted for 2.8 tonnes of the roughly 18 tonnes emitted in 2015-16.

Mercury in the food web

Mercury is a global pollutant: no matter where it’s emitted, it spreads easily around the world through the atmosphere. In its vaporised form, mercury is largely inert, although inhaling large quantities carries serious health risks. But the health problems really start when mercury enters the food web.

I’ve been involved in research that investigates how mercury moves from the air into the food web of the Southern Ocean. The key is Antartica’s sea ice. Sea salt contains bromine, which builds up on the ice over winter. In spring, when the sun returns, large amounts of bromine is released to the atmosphere and causes dramatically named “bromine explosion events”.

Essentially, very reactive bromine oxide is formed, which then reacts with the elemental mercury in the air. The mercury is then deposited onto the sea ice and ocean, where microbes interact with it, returning some to the atmosphere and methylating the rest.

Once mercury is methylated it can bioaccumulate, and moves up the food chain to apex predators such as tuna – and thence to humans.

As noted by the Australian government in its final impact statement for the Minamata Convention:

Mercury can cause a range of adverse health impacts which include; cognitive impairment (mild mental retardation), permanent damage to the central nervous system, kidney and heart disease, infertility, and respiratory, digestive and immune problems. It is strongly advised that pregnant women, infants, and children in particular avoid exposure.


Read more: Climate change set to increase air pollution deaths by hundreds of thousands


Australia must do better

A major 2009 study estimated that reducing global mercury emissions would carry an economic benefit of between US$1.8 billion and US$2.22 billion (in 2005 dollars). Since then, the US, the European Union and China have begun using the best available technology to reduce their mercury emissions, but Australia remains far behind.

But it doesn’t have to be. Methods like sulfur scrubbing, which remove fine particles and sulfur dioxide, also can capture mercury. Simply limiting sulfur pollutants of our power stations can dramatically reduce mercury levels.

Ratifying the Minamata Convention will mean the federal government must create a plan to reduce our mercury emissions, with significant health and economic benefits. And because mercury travels around the world, action from Australia wouldn’t just help our region: it would be for the global good.


The ConversationIn an earlier version of this article the standfirst referenced a 2006 study stating Australia is the fifth largest global emitter of mercury. Australia is now 16th globally.

Robyn Schofield, Senior Lecturer for Climate System Science and Director of Environmental Science Hub, University of Melbourne

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

Human noise pollution is disrupting parks and wild places



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A red fox listening for prey under the snow in Yellowstone National Park. Noise can affect foxes and other animals that rely on their hearing when they hunt.
Neal Herbert/NPS

Rachel Buxton, Colorado State University

As transportation networks expand and urban areas grow, noise from sources such as vehicle engines is spreading into remote places. Human-caused noise has consequences for wildlife, entire ecosystems and people. It reduces the ability to hear natural sounds, which can mean the difference between life and death for many animals, and degrade the calming effect that we feel when we spend time in wild places.

Protected areas in the United States, such as national parks and wildlife refuges, provide places for respite and recreation, and are essential for natural resource conservation. To understand how noise may be affecting these places, we need to measure all sounds and determine what fraction come from human activities.

In a recent study, our team used millions of hours of acoustic recordings and sophisticated models to measure human-caused noise in protected areas. We found that noise pollution doubled sound energy in many U.S. protected areas, and that noise was encroaching into the furthest reaches of remote areas.

Pine siskin song as a car passes by, Rocky Mountain National Park.
Recorded by Jacob Job, research associate with Colorado State University and the National Park Service, Author provided268 KB (download)

Our approach can help protected area managers enhance recreation opportunities for visitors to enjoy natural sounds and protect sensitive species. These acoustic resources are important for our physical and emotional well-being, and are beautiful. Like outstanding scenery, pristine soundscapes where people can escape the clamor of everyday life deserve protection.

What is noise pollution?

“Noise” is an unwanted or inappropriate sound. We focused on human sources of noise in natural environments, such as sounds from aircraft, highways or industrial sources. According to the Environmental Protection Agency, noise pollution is noise that interferes with normal activities, such as sleeping and conversation, and disrupts or diminishes our quality of life.

Human-caused noise in protected areas interferes with visitors’ experience and alters ecological communities. For example, noise may scare away carnivores, resulting in inflated numbers of prey species such as deer. To understand noise sources in parks and inform management, the National Park Service has been monitoring sounds at hundreds of sites for the past two decades.

Estimating human-generated noise

Noise is hard to quantify at large-landscape scales because it can’t be measured by satellite or other visual observations. Instead researchers have to collect acoustic recordings over a wide area. NPS scientists on our team used acoustic measurements taken from 492 sites around the continental United States to build a sound model that quantified the acoustic environment.

National Park Service staff set up an acoustic recording station as a car passes on Going-to- the-Sun Road in Glacier National Park, Montana.
National Park Service

They used algorithms to determine the relationship between sound measurements and dozens of geospatial features that can affect measured average sound levels. Examples include climate data, such as precipitation and wind speed; natural features, such as topography and vegetation cover; and human features, such as air traffic and proximity to roads.

Using these relationships, we predicted how much human-caused noise is added to natural sound levels across the continental United States.

To get an idea of the potential spatial extent of noise pollution effects, we summarized the amount of protected land experiencing human-produced noise three or 10 decibels above natural. These increments represent a doubling and a 10-fold increase, respectively, in sound energy, and a 50 to 90 percent reduction in the distance at which natural sounds can be heard. Based on a literature review, we found that these thresholds are known to impact human experience in parks and have a range of repercussions for wildlife.

Few escapes from noise

The good news is that in many cases, protected areas are quieter than surrounding lands. However, we found that human-caused noise doubled environmental sound in 63 percent of U.S. protected areas, and produced a tenfold or greater increase in 21 percent of protected areas.

Map of projected ambient sound levels for a typical summer day across the contiguous United States, where lighter yellow indicates louder conditions and darker blue indicates quieter conditions.
Rachel Buxton, Author provided

Noise depends on how a protected area is managed, where a site is located and what kinds of activities take place nearby. For example, we found that protected areas managed by local government had the most noise pollution, mainly because they were in or near large urban centers. The main noise sources were roads, aircraft, land-use conversion and resource extraction activities such as oil and gas production, mining and logging.

We were encouraged to find that wilderness areas – places that are preserved in their natural state, without roads or other development – were the quietest protected areas, with near-natural sound levels. However, we also found that 12 percent of wilderness areas experienced noise that doubled sound energy. Wilderness areas are managed to minimize human influence, so most noise sources come from outside their borders.

Finally, we found that many endangered species, particularly plants and invertebrates, experience high levels of noise pollution in their critical habitat – geographic areas that are essential for their survival. Examples include the Palos Verdes Blue butterfly, which is found only in Los Angeles County, California, and the Franciscan manzanita, a shrub that once was thought extinct, and is found only in the San Francisco Bay area.

Of course plants can’t hear, but many species with which they interact are affected by noise. For example, noise changes the distribution of birds, which are important pollinators and seed dispersers. This means that noise can reduce the recruitment of seedlings.

F-4 fighter jets pass through ‘Star Wars Canyon’ in Death Valley National Park, a spot popular with military pilots.

Turning down the volume

Noise pollution is pervasive in many protected areas, but there are ways to reduce it. We have identified noisy areas that will quickly benefit from noise mitigation efforts, especially in habitats that support endangered species.

The ConversationStrategies to reduce noise include establishing quiet zones where visitors are encouraged to quietly enjoy protected area surroundings, and confining noise corridors by aligning airplane flight patterns over roads. Our work provides insights for restoring natural acoustic environments, so that visitors can still enjoy the sounds of birdsong and wind through the trees.

Rachel Buxton, Postdoctoral Research Fellow, Colorado State University

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

Climate change set to increase air pollution deaths by hundreds of thousands by 2100


Guang Zeng, National Institute of Water and Atmospheric Research and Jason West, University of North Carolina – Chapel Hill

Climate change is set to increase the amount of ground-level ozone and fine particle pollution we breathe, which leads to lung disease, heart conditions, and stroke. Less rain and more heat means this pollution will stay in the air for longer, creating more health problems.

Our research, published in Nature Climate Change, found that if climate change continues unabated, it will cause about 60,000 extra deaths globally each year by 2030, and 260,000 deaths annually by 2100, as a result of the impact of these changes on pollution.

This is the most comprehensive study to date on the effects of climate change on global air quality and health. Researchers from the United States, the United Kingdom, France, Japan and New Zealand between them used nine different global chemistry-climate models.

Most models showed an increase in likely deaths – the clearest signal yet of the harm climate change will do to air quality and human health, adding to the millions of people who die from air pollution every year.


Read more: Can we blame climate change for thunderstorm asthma?


Stagnant air

Climate change fundamentally alters the air currents that move pollution across continents and between the lower and higher layers of the atmosphere. This means that where air becomes more stagnant in a future climate, pollution stays near the ground in higher concentrations.

Ground-level ozone is created when chemical pollution (such as emissions from cars or manufacturing plants) reacts in the presence of sunlight. As climate change makes an area warmer and drier, it will produce more ozone.

Fine particles are a mixture of small solids and liquid droplets suspended in air. Examples include black carbon, organic carbon, soot, smoke and dust. These fine particles, which are known to cause lung diseases, are emitted from industry, transport and residential sources. Less rain means that fine particles stay in the air for longer.

While fine particles and ozone both occur naturally, human activity has increased them substantially.

The Intergovernmental Panel on Climate Change has used four different future climate scenarios, representing optimistic to pessimistic levels of emissions reduction.

In a previous study, we modelled air pollution-related deaths between 2000 and 2100 based on the most pessimistic of these scenarios. This assumes large population growth, modest improvements in emissions-reducing technology, and ineffectual climate change policy.

That earlier study found that while global deaths related to ozone increase in the future, those related to fine particles decrease markedly under this scenario.

Emissions will likely lead to deaths

In our new study, we isolated the effects of climate change on global air pollution, by using emissions from the year 2000 together with simulations of climate for 2030 and 2100.

The projected air pollutant changes due to climate change were then used in a health risk assessment model. That model takes into account population growth, how susceptible a population is to health issues and how that might change over time, and the mortality risk from respiratory and heart diseases and lung cancer.

In simulations with our nine chemistry-climate models, we found that climate change caused 14% of the projected increase in ozone-related mortality by 2100, and offset the projected decrease in deaths related to fine particles by 16%.

Our models show that premature deaths increase in all regions due to climate change, except in Africa, and are greatest in India and East Asia.

Using multiple models makes the results more robust than using a single model. There is some spread of results amongst the nine models used here, with a few models estimating that climate change may decrease air pollution-related deaths. This highlights that results from any study using a single model should be interpreted with caution.

Australia and New Zealand are both relatively unpolluted compared with countries in the Northern Hemisphere. Therefore, both ozone and fine particle pollution currently cause relatively few deaths in both countries. However, we found that under climate change the risk will likely increase.

The ConversationThis paper highlights that climate change will increase human mortality through changes in air pollution. These health impacts add to others that climate change will also cause, including from heat stress, severe storms and the spread of infectious diseases. By impacting air quality, climate change will likely offset the benefits of other measures to improve air quality.

Guang Zeng, Atmospheric Scientist, National Institute of Water and Atmospheric Research and Jason West, Associate Professor, Department of Environmental Sciences and Engineering , University of North Carolina – Chapel Hill

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