Cities could get more than 4°C hotter by 2100. To keep cool in Australia, we urgently need a national planning policy



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Mark Maund, University of Newcastle; Kim Maund, University of Newcastle; Marcus Jefferies, University of Newcastle, and SueAnne Ware, University of Newcastle

In cities around the world, temperatures could rise by more than 4℃ by 2100 under a high-emissions climate change scenario, suggests research published this week in Nature Climate Change.

It comes as the Bureau of Meteorology’s annual climate statement, released today, shows 2020 was Australia’s fourth-warmest year on record, despite being an “La Niña” year, which usually leads to cooler temperatures.

Cities occupy just 3% of Earth’s surface. As this portion of land is so small, they’ve typically been left out of most climate models, which generally make projections on global scales.

Yet more than half the world’s population live in urban environments (set to jump to 70% by 2050). This is why the researchers call for “multi-model projections” of local climates for cities.

In the study, the researchers say their predictions on climate will give “urban planners and decision-makers in any city […] access to city-specific projections for any planning horizon they need”.

It’s important these planning horizons include the cooling and shading provided by green infrastructure — the network of green spaces such as street trees and green walls — in urban areas.




Read more:
Here’s how green infrastructure can easily be added to the urban planning toolkit


For Australia, this means getting a national green infrastructure policy that provides for green spaces within our cities, open spaces and buildings to help with increasing density and rising global temperatures.

What the research found

Heat events, such as heatwaves, pose a significant health risk and can hit people harder in cities.

Cities are hotter than in surrounding regional areas due to “the urban heat island” effect, a result of heat created by all the densely packed people, vehicles and industries, and the heat retained among buildings and other infrastructure.

Sydney highway
Cars, asphalt on roads, buildings and people, all densely packed together, are why cities are hotter than regional areas.
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Despite having the highest population density, the researchers point out that urban areas aren’t often represented in the Coupled Model Intercomparison Project. This project is important because it informs the global authority on climate change (the International Panel on Climate Change).

So the research authors built a statistical model emulating a complex climate model with urban regions. And they estimate that, by the end of the century, average warming across global cities will increase by 1.9℃ under an intermediate emissions scenario, and 4.4℃ with high emissions.

Urban warming would most affect mid-to-northern parts of the United States, southern Canada, Europe, the Middle East, northern Central Asia and northwestern China.




Read more:
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They also predict that the heat index would increase faster than air temperature alone over almost all cities. “Heat index” refers to how hot the human body actually feels, a combination of relative humidity and air temperature. This would mean urban residents would experience higher heat stress.

What does this mean for Australia?

While the research found most urban warming would occur in the northern hemisphere, Australian cities are also projected to continue to warm. But we need only look to the recent record-breaking years to realise climate change will result in more extremely hot days here.

2019 was Australia’s hottest (and driest) year on record. And today’s annual climate statement from the Bureau of Meteorology shows the highest temperature ever recorded in the Sydney Basin, at a whopping 48.9℃, occurred in 2020, on January 4. It also found the average national temperature for 2020 was 1.15℃ higher than normal.

These are nationwide findings, but how Australia manages climate in urban areas is particularly important as around 80% of population growth occurs in capital cities.

In fact, 2020 research found we’re increasingly facing more frequent and prolonged heatwaves that intensify urban heat islands in places such as Sydney, by raising inland temperatures by as much as 10℃ more than in coastal zones.

Keeping cities cool

The best way to ensure our cities are kept cool is through greening urban spaces. Green spaces can be developed by planting trees in streets, yards and parks for shade, recreation and relief from the heat. This will create cooler urban “microclimates” for social interaction and natural retreats from city life.




Read more:
The world endured 2 extra heatwave days per decade since 1950 – but the worst is yet to come


Greater Sydney, for example, has a welcome new policy to ensure five million more trees are planted by 2030. This is an important long-term goal as 2016 research from Canada found tree cover in daytime reduced air temperature by up to 4℃ in Montreal city.

The design of buildings and their immediate surroundings are also important to help manage increasing heat in our cities.

Our open spaces are places of exercise, retreat, relaxation and, in a new COVID world, socially distant interactions. The pandemic has allowed us to rediscover the importance of our community and local connections in these spaces.

Multi-storey buildings also provide opportunity for vertical greening. The Victorian government, for example, is seeking to increase the amount of green infrastructure in our urban areas to help us cope with predicted warmer conditions.

Melbourne has many trees and green spaces that help negate the effects of the urban heat island.
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Australia needs a national planning policy

Urban planning and greening urban spaces is largely a local government responsibility, usually overseen by state and territory governments.

And there is national recognition of the importance of green cities through the federal government’s Smart Cities Plan. It states:

Green, sustainable cities […] improve the quality of air and water, reduce the heat island effect, protect biological diversity and threatened species, and enhance general amenity.

But what’s needed, urgently, is a national planning framework of green city principles so no regions get left behind. Climate change is a national issue, and all urban residents from all socioeconomic backgrounds should benefit from green cities.




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This national planning policy would describe how our cities across the nation should develop appropriately spaced trees and other vegetation, to better manage and prepare for increasing density and greater activity as climate change brings hotter weather.

And importantly, more research is needed to better inform climate models. We need more information into the ways our climates will change within different land areas — whether rural, suburban or in cities — so we can develop better national plans for how we will live and work in the future.




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In a heatwave, the leafy suburbs are even more advantaged


The Conversation


Mark Maund, Research Affiliate, School of Architecture and Built Environment, University of Newcastle; Kim Maund, Discipline Head – Construction Management, School of Architecture and Built Environment, University of Newcastle; Marcus Jefferies, Senior Lecturer School of Architecture and Built Environment, University of Newcastle, and SueAnne Ware, Professor and Head of School of Architecture and Built Environment, University of Newcastle

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

The world may lose half its sandy beaches by 2100. It’s not too late to save most of them



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John Church, UNSW

For many coastal regions, sea-level rise is a looming crisis threatening our coastal society, livelihoods and coastal ecosystems. A new study, published in Nature Climate Change, has reported the world will lose almost half of its valuable sandy beaches by 2100 as the ocean moves landward with rising sea levels.

Sandy beaches comprise about a third of the world’s coastline. And Australia, with nearly 12,000 kilometres at risk, could be hit hard.




Read more:
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This is the first truly global study to attempt to quantify beach erosion. The results for the highest greenhouse gas emission scenario are alarming, but reducing emissions leads to lower rates of coastal erosion.

Our best hope for the future of the world’s coastlines and for Australia’s iconic beaches is to keep global warming as low as possible by urgently reducing greenhouse gas emissions.

Losing sand in coastal erosion

Two of the largest problems resulting from rising sea levels are coastal erosion and an already-observed increase in the frequency of coastal flooding events.

Erosion during storms can have dramatic consequences, particularly for coastal infrastructure. We saw this in 2016, when wild storms removed sand from beaches and damaged houses in Sydney.

After storms like this, beaches often gradually recover, because sand from deeper waters washes back to the shore over months to years, and in some cases, decades. These dramatic storms and the long-term sand supply make it difficult to identify any beach movement in the recent past from sea-level rise.

What we do know is that the rate of sea-level rise has accelerated. It has increased by half since 1993, and is continuing to accelerate from ongoing greenhouse gas emissions.

If we continue to emit high levels of greenhouse gases, this acceleration will continue through the 21st century and beyond. As a result, the supply of sand may not keep pace with rapidly rising sea levels.

Projections for the worst-case scenario

In the most recent Intergovernmental Panel on Climate Change (IPCC) report, released last year, the highest greenhouse gas emissions scenario resulted in global warming of more than 4°C (relative to pre-industrial temperatures) and a likely range of sea-level rise between 0.6 and 1.1 metres by 2100.

For this scenario, this new study projects a global average landward movement of the coastline in the range of 40 to 250 metres if there were no physical limits to shoreline movement, such as those imposed by sea walls or other coastal infrastructure.




Read more:
What does the science really say about sea-level rise?


Sea-level rise is responsible for the vast majority of this beach loss, with faster loss during the latter decades of the 21st century when the rate of rise is larger. And sea levels will continue to rise for centuries, so beach erosion would continue well after 2100.

For southern Australia, the landward movement of the shoreline is projected to be more than 100 metres. This would damage many of Australia’s iconic tourist beaches such as Bondi, Manly and the Gold Coast. The movement in northern Australia is projected to be even larger, but more uncertain because of ongoing historical shoreline trends.

What happens if we mitigate our emissions

The above results are from a worst-case scenario. If greenhouse gas emissions were reduced such that the 2100 global temperature rose by about 2.5°C, instead of more than 4°C, then we’d reduce beach erosion by about a third of what’s projected in this worst-case scenario.

Current global policies would result in about 3°C of global warming.
That’s between the 4°C and the 2.5°C scenarios considered in this beach erosion study, implying our current policies will lead to significant beach erosion, including in Australia.

Mitigating our emissions even further, to achieve the Paris goal of keeping temperature rise to well below 2°C, would be a major step in reducing beach loss.

Why coastal erosion is hard to predict

Projecting sea-level rise and resulting beach erosion are particularly difficult, as both depend on many factors.

For sea level, the major problems are estimating the contribution of melting Antarctic ice flowing into the ocean, how sea level will change on a regional scale, and the amount of global warming.

The beach erosion calculated in this new study depends on several new databases. The databases of recent shoreline movement used to project ongoing natural factors might already be influenced by rising sea levels, possibly leading to an overestimate in the final calculations.




Read more:
Sea level rise is inevitable – but what we do today can still prevent catastrophe for coastal regions


The implications

Regardless of the exact numbers reported in this study, it’s clear we will have to adapt to the beach erosion we can no longer prevent, if we are to continue enjoying our beaches.

This means we need appropriate planning, such as beach nourishment (adding sand to beaches to combat erosion) and other soft and hard engineering solutions. In some cases, we’ll even need to retreat from the coast to allow the beach to migrate landward.

And if we are to continue to enjoy our sandy beaches into the future, we cannot allow ongoing and increasing greenhouse gas emissions. The world needs urgent, significant and sustained global mitigation of greenhouse gas emissions.The Conversation

John Church, Chair Professor, Climate Change Research Centre, UNSW

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