Climate change is causing tuna to migrate, which could spell catastrophe for the small islands that depend on them


Katherine Seto, University of Wollongong; Johann Bell, University of Wollongong; Quentin Hanich, University of Wollongong, and Simon Nicol, University of CanberraSmall Pacific Island states depend on their commercial fisheries for food supplies and economic health. But our new research shows climate change will dramatically alter tuna stocks in the tropical Pacific, with potentially severe consequences for the people who depend on them.

As climate change warms the waters of the Pacific, some tuna will be forced to migrate to the open ocean of the high seas, away from the jurisdiction of any country. The changes will affect three key tuna species: skipjack, yellowfin, and bigeye.

Pacific Island nations such as the Cook Islands and territories such as Tokelau charge foreign fishing operators to access their waters, and heavily depend on this revenue. Our research estimates the movement of tuna stocks will cause a fall in annual government revenue to some of these small island states of up to 17%.

This loss will hurt these developing economies, which need fisheries revenue to maintain essential services such as hospitals, roads and schools. The experience of Pacific Island states also bodes poorly for global climate justice more broadly.

Island states at risk

Catches from the Western and Central Pacific represent over half of all tuna produced globally. Much of this catch is taken from the waters of ten small developing island states, which are disproportionately dependent on tuna stocks for food security and economic development.

These states comprise:

  • Cook Islands
  • Federated States of Micronesia
  • Kiribati
  • Marshall Islands
  • Nauru
  • Palau
  • Papua New Guinea
  • Solomon Islands
  • Tokelau
  • Tuvalu

Their governments charge tuna fishing access fees to distant nations of between US$7.1 million (A$9.7 million) and $134 million (A$182 million), providing an average of 37% of total government revenue (ranging from 4-84%).



Tuna stocks are critical for these states’ current and future economic development, and have been sustainably managed by a cooperative agreement for decades. However, our analysis reveals this revenue, and other important benefits fisheries provide, are at risk.




Read more:
Warming oceans are changing Australia’s fishing industry


Climate change and migration

Tuna species are highly migratory – they move over large distances according to ocean conditions. The skipjack, yellowfin and bigeye tuna species are found largely within Pacific Island waters.

Concentrations of these stocks normally shift from year to year between areas further to the west in El Niño years, and those further east in La Niña years. However, under climate change, these stocks are projected to shift eastward – out of sovereign waters and into the high seas.

Under climate change, the tropical waters of the Pacific Ocean will warm further. This warming will result in a large eastward shift in the location of the edge of the Western Pacific Warm Pool (a mass of water in the western Pacific Ocean with consistently high water temperatures) and subsequently the prime fishing grounds for some tropical tuna.

This shift into areas beyond national jurisdiction would result in weaker regulation and monitoring, with parallel implications for the long-term sustainability of stocks.

Pacific Tuna: Feeling the Heat.

What our research found

Combining climate science, ecological models and economic data from the region, our research published today in Nature Sustainability shows that under strong projections of climate change, small island economies are poised to lose up to US$140 million annually by 2050, and up to 17% of annual government revenue in the case of some states.

The Intergovernmental Panel on Climate Change (IPCC) provides scenarios of various greenhouse gas concentrations, called “representative concentration pathways” (RCP). We used a higher RCP of 8.5 and a more moderate RCP of 4.5 to understand tuna movement in different emissions scenarios.




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In the RCP 8.5 scenario, by 2050, our model predicted the total biomass of the three species of tuna in the combined jurisdictions of the ten Pacific Island states would decrease by an average of 13%, and up to 20%.

But if emissions were kept to the lower RCP 4.5 scenario, the effects are expected to be far less pronounced, with an average decrease in biomass of just 1%.

While both climate scenarios result in average losses of both tuna catches and revenue, lower emissions scenarios lead to drastically smaller losses, highlighting the importance of climate action.

These projected losses compound the existing climate vulnerability of many Pacific Island people, who will endure some of the earliest and harshest climate realities, while being responsible for only a tiny fraction of global emissions.

Large tuna fish on the back of a fishing boat
Fishing access fees make up a large proportion of government revenue for these Pacific Island nations.
Shutterstock

What can be done?

Capping greenhouse gas emissions, and reducing them to levels aligning with the Paris Agreement, would reduce multiple climate impacts for these states, including shifting tuna stocks.

In many parts of the world, the consequences of climate change compound upon one another to create complex injustices. Our study identifies new direct and indirect implications of climate change for some of the world’s most vulnerable populations.




Read more:
The 2016 Great Barrier Reef heatwave caused widespread changes to fish populations


The Conversation


Katherine Seto, Research Fellow, University of Wollongong; Johann Bell, Visiting Professorial Fellow, University of Wollongong; Quentin Hanich, Associate Professor, University of Wollongong, and Simon Nicol, Adjunct professor, University of Canberra

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

Australian farmers are adapting well to climate change, but there’s work ahead


PETER LORIMER/AAP

Neal Hughes, Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES)Australian farmers have proven their resilience, rebounding from drought and withstanding a global pandemic to produce record-breaking output in 2020-21.

But while the pain of drought is fading from view for some, the challenge of a changing climate continues to loom large.

Farmers have endured a poor run of conditions over the last 20 years, including a reduction in average rainfall (particularly in southern Australia during the winter cropping season) and general increases in temperature.

While these trends relate to climate change, uncertainty remains over how they will develop, particularly over how much rain or drought farmers will face.

Research published today by the Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES) examines the effects of past and potential future changes in climate, and sets out how productivity gains to date have been helping farmers adapt to the drier and hotter conditions.

Conditions have been tough

The research examines the effect on farms of climate conditions over the past 20 years, compared to the preceding 50 years.

Holding other factors constant (including commodity prices and technology) ABARES estimates the post-2000 shift in conditions reduced farm profits by an average of 23%, or around A$29,000 per farm per year.




Read more:
Climate change since 2000 has cut farm profits 22%


As with past research, these effects have been strongest among cropping farmers in south-eastern and southern-western Australia, with impacts of over 50% observed in some of the most severely affected areas.


Effect of 2001 to 2020 climate conditions on average farm profit

Simulated broadacre farm profit with current (2015–16 to 2018–19) farms and commodity prices and recent (2000–01 to 2019–20) climate conditions. Interpolated farm-level percentage changes relative to 1949–50 to 1999–2000 climate.
ABARES farmpredict model (Hughes, Lu et al. 2021)

Farmers have been adapting

While these changes in conditions have been dramatic, farmers’ adaptation has been equally impressive.

After controlling for climate, farm productivity (the output from a given amount of land and other inputs) has climbed around 28% since 1989, with a much larger 68% gain in the cropping sector.

These gains have offset the adverse climate conditions and along with increases in commodity prices have allowed farmers to maintain and even increase average production and profit levels over the last decade.

While productivity growth in agriculture is nothing new, the recent gains have been especially focused on adapting to drier and hotter conditions.

Within the cropping sector, for example, a range of new technologies and practices have emerged to better utilise soil moisture to cope with lower rainfall.

As a result, Australian farmers have produced remarkable harvests making use of limited rain, particularly in Western Australia.

Adaptation has also involved movement of traditional Australian cropping zones, increasing cropping in higher rainfall coastal areas, and reducing cropping in marginal in-land areas.

Climate change could make conditions tougher

While climate models generally project a hotter and drier future, a wide range of outcomes are possible, particularly for rainfall.

Climate projections suggest that nationally farmers could experience reductions in average winter season rainfall of 3% to 30% by 2050 (compared to 1950-2000).

The study simulates the effect of future climate change scenarios with current farm technology and no further productivity gains.

As such, these scenarios are not a prediction, but an indication of which regions and sectors might be under the greatest pressure to adapt.

For example, under most scenarios cropping farmers in Western Australia will face more pressure than those in eastern Australia.

Livestock farms will also face more pressure under high emissions scenarios as they are especially impacted by higher temperatures.

Generally, inland low-rainfall farming areas are expected to face greater challenges than regions closer to the coast.


Simulated change in farm profits relative to historical (1950 to 2000) climate

Change in simulated average farm profit for broadacre farms, assuming current commodity prices (2015–16 to 2018–19), and current farm technology (no adaptation), relative to historical climate conditions (1949–50 to 1999–2000). Bars show minimum, maximum and average across the GCMs for each scenario.
Source: ABARES farmpredict model (Hughes, Lu et al. 2021)

There is more work ahead

Recent experience shows that productivity growth can help offset the impact of a changing climate.

However, there remains uncertainty over how far technology can push farm efficiency beyond current levels.

Further, even if technology can offset climate impacts, other exporting nations could still become more competitive relative to Australia, if they are less affected by climate change or can adapt faster.

Here, investment in research and development remains crucial, including efforts to improve the productivity and reduce the carbon footprint of existing crop and livestock systems, along with research into more transformational responses to help diversify farm incomes.

Farmland can be repurposed.
Mick Tsikas

This could include for example, carbon and biodiversity farming, plantation forestry and the use of land to produce renewable energy.

Carbon and biodiversity farming schemes are the subject of ongoing research and policy trials, and already we have seen farmers generate significant revenue from carbon farming.

Uncertainty over the future climate, especially rainfall, remains a key constraint on adaptation. Efforts to refine and better communicate climate information through initiatives such as Climate Services for Agriculture could help farmers and governments make more informed decisions.

While the future is still highly uncertain, the challenge of adapting to climate change is here and now.

Significant resources have been committed in this area, including the Australian government’s Future Drought Fund.

We need to make the most of these investments to prepare for whatever the future holds.The Conversation

Neal Hughes, Senior Economist, Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES)

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

More livestock, more carbon dioxide, less ice: the world’s climate change progress since 2019 is (mostly) bad news


Thomas Newsome, University of Sydney; Christopher Wolf, Oregon State University, and William Ripple, Oregon State UniversityBack in 2019, more than 11,000 scientists declared a global climate emergency. They established a comprehensive set of vital signs that impact or reflect the planet’s health, such as forest loss, fossil fuel subsidies, glacier thickness, ocean acidity and surface temperature.

In a new paper published today, we show how these vital signs have changed since the original publication, including through the COVID-19 pandemic. In general, while we’ve seen lots of positive talk and commitments from some governments, our vital signs are mostly not trending in the right direction.

So, let’s look at how things have progressed since 2019, from the growing number of livestock to the meagre influence of the pandemic.

Is it all bad news?

No, thankfully. Fossil fuel divestment and fossil fuel subsidies have improved in record-setting ways, potentially signalling an economic shift to a renewable energy future.

The graph on the left shows an increase in fossil fuel divestment by 1,117 organisations based on data from 350.org, and the graph on the right shows a decrease in subsidies for fossil fuels based on the International Energy Agency subsidies database. The red lines show changes since our original publication in 2019.

However, most of the other vital signs reflect the consequences of the so far unrelenting “business as usual” approach to climate change policy worldwide.

Especially troubling is the unprecedented surge in climate-related disasters since 2019. This includes devastating flash floods in the South Kalimantan province of Indonesia, record heatwaves in the southwestern United States, extraordinary storms in India and, of course, the 2019-2020 megafires in Australia.

In addition, three main greenhouse gases — carbon dioxide, methane and nitrous oxide — set records for atmospheric concentrations in 2020 and again in 2021. In April this year, carbon dioxide concentration reached 416 parts per million, the highest monthly global average concentration ever recorded.

Time series of three climate-related responses. The red lines show changes since our original publication in 2019.

Last year was also the second hottest year in recorded history, with the five hottest years on record all occurring since 2015.

Ruminant livestock — cattle, buffalo, sheep, and goats — now number more than 4 billion, and their total mass is more than that of all humans and wild mammals combined. This is a problem because these animals are responsible for impacting biodiversity, releasing huge amounts of methane emissions, and land continues to be cleared to make room for them.

There are now more than 4 billion livestock on Earth.
Flickr

In better news, recent per capita meat production declined by about 5.7% (2.9 kilograms per person) between 2018 and 2020. But this is likely because of an outbreak of African swine fever in China that reduced the pork supply, and possibly also as one of the impacts of the pandemic.

Tragically, Brazilian Amazon annual forest loss rates increased in both 2019 and 2020. It reached a 12-year high of 1.11 million hectares deforested in 2020.

Ocean acidification is also near an all-time record. Together with heat stress from warming waters, acidification threatens the coral reefs that more than half a billion people depend on for food, tourism dollars and storm surge protection.

Map of land-ocean temperature index anomaly in June, relative to the 1951-1980 baseline.
Oregon State/NASA

What about the pandemic?

With its myriad economic interruptions, the COVID-19 pandemic had the side effect of providing some climate relief, but only of the ephemeral variety.

For example, fossil-fuel consumption has gone down since 2019 as did airline travel levels.

But all of these are expected to significantly rise as the economy reopens. While global gross domestic product dropped by 3.6% in 2020, it is projected to rebound to an all-time high.

So, a major lesson of the pandemic is that even when fossil-fuel consumption and transportation sharply decrease, it’s still insufficient to tackle climate change.

There is growing evidence we’re getting close to or have already gone beyond tipping points associated with important parts of the Earth system, including warm-water coral reefs, the Amazon rainforest and the West Antarctic and Greenland ice sheets.

Warming waters are threatening West Antarctic and Greenland ice sheets.
Flickr

OK, so what do we do about it?

In our 2019 paper, we urged six critical and interrelated steps governments — and the rest of humanity — can take to lessen the worst effects of climate change:

  1. prioritise energy efficiency, and replace fossil fuels with low-carbon renewable energy
  2. reduce emissions of short-lived pollutants such as methane and soot
  3. curb land clearing to protect and restore the Earth’s ecosystems
  4. reduce our meat consumption
  5. move away from unsustainable ideas of ever-increasing economic and resource consumption
  6. stabilise and, ideally, gradually reduce human populations while improving human well-being especially by educating girls and women globally.

These solutions still apply. But in our updated 2021 paper, we go further, highlighting the potential for a three-pronged approach for near-term policy:

  1. a globally implemented carbon price
  2. a phase-out and eventual ban of fossil fuels
  3. strategic environmental reserves to safeguard and restore natural carbon sinks and biodiversity.

A global price for carbon needs to be high enough to induce decarbonisation across industry.

And our suggestion to create strategic environmental reserves, such as forests and wetlands, reflects the need to stop treating the climate emergency as a stand-alone issue.

By stopping the unsustainable exploitation of natural habitats through, for example, creeping urbanisation, and land degradation for mining, agriculture and forestry, we can reduce animal-borne disease risks, protect carbon stocks and conserve biodiversity — all at the same time.

A kangaroo in burnt bushland
There has been a worrying number of disasters since 2019, including Australia’s megafires.
Shutterstock

Is this actually possible?

Yes, and many opportunities still exist to shift pandemic-related financial support measures into climate friendly activities. Currently, only 17% of such funds had been allocated that way worldwide, as of early March 2021. This percentage could be lifted with serious coordinated, global commitment.

Greening the economy could also address the longer term need for major transformative change to reduce emissions and, more broadly, the over-exploitation of the planet.

Our planetary vital signs make it clear we need urgent action to address climate change. With new commitments getting made by governments all over the world, we hope to see the curves in our graphs changing in the right directions soon.




Read more:
11,000 scientists warn: climate change isn’t just about temperature


The Conversation


Thomas Newsome, Academic Fellow, University of Sydney; Christopher Wolf, Postdoctoral Scholar, Oregon State University, and William Ripple, Distinguished Professor and Director, Trophic Cascades Program, Oregon State University

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

‘One of the most damaging invasive species on Earth’: wild pigs release the same emissions as 1 million cars each year


Pixabay

Christopher J. O’Bryan, The University of Queensland; Eve McDonald-Madden, The University of Queensland; Jim Hone, University of Canberra; Matthew H. Holden, The University of Queensland, and Nicholas R Patton, University of CanterburyWhether you call them feral pigs, boar, swine, hogs, or even razorbacks, wild pigs are one of the most damaging invasive species on Earth, and they’re notorious for damaging agriculture and native wildlife.

A big reason they’re so harmful is because they uproot soil at vast scales, like tractors ploughing a field. Our new research, published today, is the first to calculate the global extent of this and its implications for carbon emissions.

Our findings were staggering. We discovered the cumulative area of soil uprooted by wild pigs is likely the same area as Taiwan. This releases 4.9 million tonnes of carbon dioxide each year — the same as one million cars. The majority of these emissions occur in Oceania.

A huge portion of Earth’s carbon is stored in soil, so releasing even a small fraction of this into the atmosphere can have a huge impact on climate change.

The problem with pigs

Wild pigs (Sus scrofa) are native throughout much of Europe and Asia, but today they live on every continent except Antarctica, making them one of the most widespread invasive mammals on the planet. An estimated three million wild pigs live in Australia alone.

A herd of wild pigs
Wild pigs are one of the most widespread invasive animals on Earth.
Shutterstock

It’s estimated that wild pigs destroy more than A$100 million (US$74 million) worth of crops and pasture each year in Australia, and more than US$270 million (A$366 million) in just 12 states in the USA.

Wild pigs have also been found to directly threaten 672 vertebrate and plant species across 54 different countries. This includes imperilled Australian ground frogs, tree frogs and multiple orchid species, as pigs destroy their habitats and prey on them.

Their geographic range is expected to expand in the coming decades, suggesting their threats to food security and biodiversity will likely worsen. But here, let’s focus on their contribution to global emissions.

Their carbon hoofprint

Previous research has highlighted the potential contribution of wild pigs to greenhouse gas emissions, but only at local scales.

One such study was conducted for three years in hardwood forests of Switzerland. The researchers found wild pigs caused soil carbon emissions to increase by around 23% per year.

Similarly, a study in the Jigong Mountains National Nature Reserve in China found soil emissions increased by more than 70% per year in places disturbed by wild pigs.

Wild pigs turn over 36,214 to 123,517 square kilometres of soil each year.
Shutterstock

To find out what the impact was on a global scale, we ran 10,000 simulations of wild pig population sizes in their non-native distribution, including in the Americas, Oceania, Africa and parts of Southeast Asia.

For each simulation, we determined the amount of soil they would disturb using another model from a different study. Lastly, we used local case studies to calculate the minimum and maximum amount of wild pig-driven carbon emissions.

And we estimate the soil wild pigs uproot worldwide each year is likely between 36,214 and 123,517 square kilometres — or between the sizes of Taiwan and England.

Most of this soil damage and associated emissions occur in Oceania due to the large distribution of wild pigs there, and the amount of carbon stored in the soil in this region.




Read more:
Feral pigs harm wildlife and biodiversity as well as crops


So how exactly does disturbing soil release emissions?

Wild pigs use their tough snouts to excavate soil in search of plant parts such as roots, fungi and invertebrates. This “ploughing” behaviour commonly disturbs soil at a depth of about five to 15 centimetres, which is roughly the same depth as crop tilling by farmers.

Wild pigs uproot soil in search of food, such as invertebrates and plant roots.
University of Kentucky, Department of Forestry and Natural Resources, Forestry Extension.

Because wild pigs are highly social and often feed in large groups, they can completely destroy a small paddock in a short period. This makes them a formidable foe to the organic carbon stored in soil.

In general, soil organic carbon is the balance between organic matter input into the soil (such as fungi, animal waste, root growth and leaf litter) versus outputs (such as decomposition, respiration and erosion). This balance is an indicator of soil health.

When soils are disturbed, whether from ploughing a field or from an animal burrowing or uprooting, carbon is released into the atmosphere as a greenhouse gas.

This is because digging up soil exposes it to oxygen, and oxygen promotes the rapid growth of microbes. These newly invigorated microbes, in turn, break down the organic matter containing carbon.

Wild pigs have a rapid breeding rate, which makes controlling populations difficult.
Shutterstock

Tough and cunning

Wild pig control is incredibly difficult and costly due to their cunning behaviour, rapid breeding rate, and overall tough nature.

For example, wild pigs have been known to avoid traps if they had been previously caught, and they are skilled at changing their behaviour to avoid hunters.




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In Australia, management efforts include coordinated hunting events to slow the spread of wild pig populations. Other techniques include setting traps and installing fences to prevent wild pig expansion, or aerial control programs.

Some of these control methods can also cause substantial carbon emissions, such as using helicopters for aerial control and other vehicles for hunting. Still, the long-term benefits of wild pig reduction may far outweigh these costs.

Working towards reduced global emissions is no simple feat, and our study is another tool in the toolbox for assessing the threats of this widespread invasive species.




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The Conversation


Christopher J. O’Bryan, Postdoctoral Research Fellow, School of Earth and Environmental Sciences, The University of Queensland; Eve McDonald-Madden, Associate professor, The University of Queensland; Jim Hone, Emeritus professor, University of Canberra; Matthew H. Holden, Lecturer, School of Mathematics and Physics, The University of Queensland, and Nicholas R Patton, Ph.D. Candidate, University of Canterbury

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

The North American heatwave shows we need to know how climate change will change our weather


NASA

Christian Jakob, Monash University and Michael Reeder, Monash UniversityEight days ago, it rained over the western Pacific Ocean near Japan. There was nothing especially remarkable about this rain event, yet it made big waves twice.

First, it disturbed the atmosphere in just the right way to set off an undulation in the jet stream – a river of very strong winds in the upper atmosphere – that atmospheric scientists call a Rossby wave (or a planetary wave). Then the wave was guided eastwards by the jet stream towards North America.

Along the way the wave amplified, until it broke just like an ocean wave does when it approaches the shore. When the wave broke it created a region of high pressure that has remained stationary over the North American northwest for the past week.

This is where our innocuous rain event made waves again: the locked region of high pressure air set off one of the most extraordinary heatwaves we have ever seen, smashing temperature records in the Pacific Northwest of the United States and in Western Canada as far north as the Arctic. Lytton in British Columbia hit 49.6℃ this week before suffering a devastating wildfire.

What makes a heatwave?

While this heatwave has been extraordinary in many ways, its birth and evolution followed a well-known sequence of events that generate heatwaves.

Heatwaves occur when there is high air pressure at ground level. The high pressure is a result of air sinking through the atmosphere. As the air descends, the pressure increases, compressing the air and heating it up, just like in a bike pump.

Sinking air has a big warming effect: the temperature increases by 1 degree for every 100 metres the air is pushed downwards.

The North American heatwave has seen fires spread across the landscape.
NASA

High-pressure systems are an intrinsic part of an atmospheric Rossby wave, and they travel along with the wave. Heatwaves occur when the high-pressure systems stop moving and affect a particular region for a considerable time.

When this happens, the warming of the air by sinking alone can be further intensified by the ground heating the air – which is especially powerful if the ground was already dry. In the northwestern US and western Canada, heatwaves are compounded by the warming produced by air sinking after it crosses the Rocky Mountains.

How Rossby waves drive weather

This leaves two questions: what makes a high-pressure system, and why does it stop moving?

As we mentioned above, a high-pressure system is usually part of a specific type of wave in the atmosphere – a Rossby wave. These waves are very common, and they form when air is displaced north or south by mountains, other weather systems or large areas of rain.




Read more:
We’ve learned a lot about heatwaves, but we’re still just warming up


Rossby waves are the main drivers of weather outside the tropics, including the changeable weather in the southern half of Australia. Occasionally, the waves grow so large that they overturn on themselves and break. The breaking of the waves is intimately involved in making them stationary.

Importantly, just as for the recent event, the seeds for the Rossby waves that trigger heatwaves are located several thousands of kilometres to the west of their location. So for northwestern America, that’s the western Pacific. Australian heatwaves are typically triggered by events in the Atlantic to the west of Africa.

Another important feature of heatwaves is that they are often accompanied by high rainfall closer to the Equator. When southeast Australia experiences heatwaves, northern Australia often experiences rain. These rain events are not just side effects, but they actively enhance and prolong heatwaves.

What will climate change mean for heatwaves?

Understanding the mechanics of what causes heatwaves is very important if we want to know how they might change as the planet gets hotter.

We know increased carbon dioxide in the atmosphere is increasing Earth’s average surface temperature. However, while this average warming is the background for heatwaves, the extremely high temperatures are produced by the movements of the atmosphere we talked about earlier.

So to know how heatwaves will change as our planet warms, we need to know how the changing climate affects the weather events that produce them. This is a much more difficult question than knowing the change in global average temperature.

How will events that seed Rossby waves change? How will the jet streams change? Will more waves get big enough to break? Will high-pressure systems stay in one place for longer? Will the associated rainfall become more intense, and how might that affect the heatwaves themselves?




Read more:
Explainer: climate modelling


Our answers to these questions are so far somewhat rudimentary. This is largely because some of the key processes involved are too detailed to be explicitly included in current large-scale climate models.

Climate models agree that global warming will change the position and strength of the jet streams. However, the models disagree about what will happen to Rossby waves.

From climate change to weather change

There is one thing we do know for sure: we need to up our game in understanding how the weather is changing as our planet warms, because weather is what has the biggest impact on humans and natural systems.

To do this, we will need to build computer models of the world’s climate that explicitly include some of the fine detail of weather. (By fine detail, we mean anything about a kilometre in size.) This in turn will require investment in huge amounts of computing power for tools such as our national climate model, the Australian Community Climate and Earth System Simulator (ACCESS), and the computing and modelling infrastructure projects of the National Collaborative Research Infrastructure Strategy (NCRIS) that support it.

We will also need to break down the artificial boundaries between weather and climate which exist in our research, our education and our public conversation.The Conversation

Christian Jakob, Professor in Atmospheric Science, Monash University and Michael Reeder, Professor, School of Earth, Atmosphere and Environment, Monash University

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

Climate explained: how the IPCC reaches scientific consensus on climate change


Fabrice Coffrini/AFP via Getty Images

Rebecca Harris, University of Tasmania


CC BY-ND

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz


When we say there’s a scientific consensus that human-produced greenhouse gases are causing climate change, what does that mean? What is the Intergovernmental Panel on Climate Change and what do they do?

The Intergovernmental Panel on Climate Change (IPCC) provides the world’s most authoritative scientific assessments on climate change. It provides policymakers with regular assessments of the scientific basis of climate change, its impacts and risks, and options for cutting emissions and adapting to impacts we can no longer avoid.

The IPCC has already released five assessment reports and is currently completing its Sixth Assessment (AR6), with the release of the first part of the report, on the physical science of climate change, expected on August 9.

Each assessment cycle brings together scientists from around the world and many disciplines. The current cycle involves 721 scientists from 90 countries, in three working groups covering the physical science basis (WGI), impacts, adaptation and vulnerability (WGII) and mitigation of climate change (WGIII).

A group photo showing the diversity of people contributing to the Intergovernmental Panel on Climate Change
People contributing to IPCC reports come from 90 countries and different backgrounds. This image shows the Working Group II team.
Author provided

In each assessment round, the IPCC identifies where the scientific community agrees, where there are differences of opinion and where further research is needed.

IPCC reports are timed to inform international policy developments such as the UN Framework Convention on Climate Change (UNFCCC) (First Assessment, 1990), the Kyoto Protocol (Second Assessment, 1995) and the Paris Agreement (Fifth Assessment, 2013-2014). The first AR6 report (WGI) will be released in August this year, and its approval meeting is set to take place virtually, for the first time in the IPCC’s 30-year history.

This will be followed by WGII and WGIII reports in February and March 2022, and the Synthesis Report in September 2022 — in time for the first UNFCCC Global Stocktake when countries will review progress towards the goal of the Paris Agreement to keep warming below 2℃.

During the AR6 cycle, the IPCC also published three special reports:

Graph of curent warming across the globe.
The IPCC’s special report on global warming at 1.5 showed present-day warming across the globe.
IPCC, CC BY-ND

How the IPCC reaches consensus

IPCC authors come from academia, industry, government and non-governmental organisations. All authors go through a rigorous selection process — they must be leading experts in their fields, with a strong publishing record and international reputation.

Author teams usually meet in person four times throughout the writing cycle. This is essential to enable (sometimes heated) discussion and exchange across cultures to build a truly global perspective. During the AR6 assessment cycle, lead author meetings (LAMs) for Working Group 1 were not disrupted by COVID-19, but the final WGII and WGIII meetings were held remotely, bringing challenges of different time zones, patchy internet access and more difficult communication.




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Top climate scientist: I put myself through hell as an IPCC convening lead author, but it was worth it


The IPCC’s reports go through an extensive peer review process. Each chapter undergoes two rounds of scientific review and revision, first by expert reviewers and then by government representatives and experts.

This review process is among the most exhaustive for any scientific document — AR6 WGI alone generated 74,849 review comments from hundreds of reviewers, representing a range of disciplines and scientific perspectives. For comparison, a paper published in a peer-reviewed journal is reviewed by only two or three experts.

The role of governments

The term intergovernmental reflects the fact that IPCC reports are created on behalf of the 193 governments in the United Nations. The processes around the review and the agreement of the wording of the Summary for Policymakers (SPM) make it difficult for governments to dismiss a report they have helped shape and approved during political negotiations.

Importantly, the involvement of governments happens at the review stage, so they are not able to dictate what goes into the reports. But they participate in the line-by-line review and revision of the SPM at a plenary session where every piece of text must be agreed on, word for word.

Acceptance in this context means that governments agree the documents are a comprehensive and balanced scientific review of the subject matter, not whether they like the content.




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IPCC 1.5℃ report: here’s what the climate science says


The role of government delegates in the plenary is to ensure their respective governments are satisfied with the assessment, and that the assessment is policy relevant without being policy prescriptive. Government representatives can try to influence the SPM wording to support their negotiating positions, but the other government representatives and experts in the session ensure the language adheres to the evidence.

Climate deniers claim IPCC reports are politically motivated and one-sided. But given the many stages at which experts from across the political and scientific spectrum are involved, this is difficult to defend. Authors are required to record all scientifically or technically valid perspectives, even if they cannot be reconciled with a consensus view, to represent each aspect of the scientific debate.

The role of the IPCC is pivotal in bringing the international science community together to assess the science, weighing up whether it is good science and should be considered as part of the body of evidence.The Conversation

Rebecca Harris, Senior Lecturer in Climatology, Director, Climate Futures Program, University of Tasmania

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