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<img src="https://counter.theconversation.edu.au/content/67223/count.gif?distributor=republish-lightbox-basic" alt="The Conversation" width="1" height="1">
GUEST OBSERVER
Do you ever feel that the weather is worse on the weekend? Well you might be right!
Our research, published in Environmental Research Letters, shows that in Australia’s biggest cites, the temperature is on average up to 0.3℃ cooler on Sundays compared to Thursdays and Fridays.
Not only are humans affecting the temperature on a global scale, we’re also doing it in our own backyards. 
There is nothing in nature that occurs on a weekly cycle. Therefore any weekly pattern seen in weather (such as temperature and rainfall) must result from human activity, such as generating electricity, powering motor vehicles and using air-conditioners. 
Most of these activities deposit waste heat and pollution into the atmosphere, and weekly cycles in temperature provide valuable insights into the consequences of such activities on the urban environment. 
Our study shows that weekly cycles in daytime temperature occur in almost all Australian major cities. Sundays are often the coolest and Thursday or Friday the hottest due to human activity. This differs according to the time of day, with early mornings showing a much stronger signal than the afternoon. 
<h2>Rush hour weekly cycle</h2>
Early mornings are often associated with cooler air temperatures, which can trap any waste heat near the surface. By contrast, in the afternoon the temperature has warmed and the local surface heat can be carried away to higher levels. So we see less of a strong relationship between human activity and temperature.
Hence the 9am temperature is higher during the week (coinciding with the morning rush hour) and much cooler on the weekend (when the traffic volume is quieter).
<a href="/images/2016/10/19/image-20161018-12447-dxp8ox.jpeg" target="_blank">Click to enlarge</a>
<img src="/images/2016/10/19/image-20161018-12447-dxp8ox.jpeg" alt="">
<h4>Melbourne 1955-2013 average midnight and morning (9am) temperature</h4>
Melbourne and other major Australian cities are cooler at the weekend during the day, because they’re less busy. But what about night life? 
In western cultures, with Saturdays and Sundays being days off work for a large proportion of the population, Friday and Saturday evenings have become popular with people going to restaurants, pubs, and theatres. This means there is more traffic and human activities in the city centres on these evenings through to the early hours of the following day. 
Melbourne’s midnight temperature is warmest on Saturday (Friday night) and Sunday (Saturday night), which is the opposite to what we see for 9am.
<h2>Islands of heat</h2>
Cities are also generally warmer than their surroundings, a phenomena known as the “urban heat island” effect. Don’t rush off to the beach though – it’s only hotter in the city. We can see this in weekly temperatures by comparing city centres to surrounding suburbs. 
When we compare Melbourne city temperature to the airport temperatures at Tullamarine, Laverton and Moorabbin, the city is a lot warmer than the airports, especially at night time. This difference is largest on Saturdays and Sundays, showing that Melbourne’s active night-life is increasing the urban heat island effect. 
<a href="/images/2016/10/19/image-20161018-12431-l50gel.jpeg" target="_blank">Click to enlarge</a>
<img src="/images/2016/10/19/image-20161018-12431-l50gel.jpeg" alt="">
<h4> </h4>
<h4>1972-2013 average difference between Melbourne city temperature airport temperatures at midnight and 9am.</h4>
The difference is less in the morning, especially on Saturdays and Sundays. There is even a small urban cool island on Sunday mornings compared to some suburbs.
Temperatures are closely linked to traffic volumes within cities. These can be used as a good indicator of the overall level of human activity.
<a href="/images/2016/10/19/image-20161018-12425-1cxmspl.jpeg" target="_blank">Click to enlarge</a>
<h4><img src="/images/2016/10/19/image-20161018-12425-1cxmspl.jpeg" alt=""></h4>
<h4>Traffic volume at a typical Melbourne CBD junction during October 2014.</h4>
Consistent with traffic volumes (at a typical busy inner-city intersection), temperatures on Sunday mornings are much less than weekday mornings. It’s this difference in morning traffic that allows us to measure the difference of the city without cars (Sunday) and with cars (Monday to Friday) at the same time of day.
Figures show that traffic congestion costs about A$4.6 billion in Melbourne each year. Reducing this is high on the agenda for Infrastructure Victoria and the state government, putting forward numerous traffic reducing strategies including peak-time penalties for motorists and a London-style congestion charge for central Melbourne. 
Beyond Victoria, the Australian government is concerned with the need to create cooler, greener and more liveable cities in the face of climate change. 
Reducing traffic has obvious benefits for travel time and sanity, but our study shows that Melbourne is significantly cooler when traffic levels (and general human activity) are low, based on the weekly cycles of urban temperatures.
Nick Earl is postdoctoral associate, School of Earth Sciences, University of Melbourne and author for The Conversation. He can be contacted <a href="https://theconversation.com/profiles/nick-earl-309773" target="_blank">here</a>.
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jchancellor-FAypfDUnLy

No it’s not your imagination, it actually is colder on the weekend (if you live in a city)

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<img src="https://counter.theconversation.edu.au/content/57114/count.gif" alt="The Conversation" width="1" height="1">
GUEST OBSERVER
Eastern Australia’s wild weather has left coastal homes teetering on the brink of collapse, and has eroded beaches by up to 50m in parts of Sydney.
Now the attention turns to the clean-up. There are several legal issues for owners of damaged properties, particularly the question of if and how they can be compensated.
While the recent events cannot be attributed directly to climate change, they are certainly consistent with a warming world. Our institutions are ill-prepared for a potential increase in the frequency and severity of such events.
<h2>Insurance</h2>
Unfortunately, the success of insurance claims for damaged homes in Sydney will depend entirely on the terms of their policies. Some policies don’t cover erosion at all. Some policies only cover it if it occurs within a certain proximity of another insured event (for example, within 48 hours of a named storm event). Some policies also comprehensively exclude coverage for damage caused by actions of the sea.
What’s more, while insurance will cover damage to buildings, policies do not extend to cover damage to or loss of land. This is especially problematic in the case of damage caused by waves and storms, because erosion will often result in loss of land.
Under the traditional law doctrine, where land is lost to erosion, the Crown automatically gains title to the inundated land, without any obligation to pay compensation. So even if a home-owner is insured, they may find themselves with no land to rebuild on.
<h2>Legal proceedings</h2>
Another potential avenue for home-owners to pursue is proceedings against the relevant local government for negligent approval of development. The success of this type of proceeding is highly speculative – much will hinge upon when the development was approved and how much information on the coastal hazards was available at that time.
Where development was approved decades ago, it may be difficult to prove that a local government was negligent, because of the limited state of knowledge at the time. In the case of more recent development approvals, there may be an argument that a local government had a high level of knowledge of the risk and control of risk information. These are the type of factors a court will look at in assessing negligence.
On the flip side, a court may also find that a landholder knew of and accepted the risk. Negligence proceedings are by no means a guaranteed avenue for landholders to recoup their loss, but are an avenue that Collaroy landholders may be able to explore.
<h2>Disaster assistance</h2>
Where insurance is not available, and there are no strict legal rights against government, landholders may request disaster relief or assistance from government.
Despite the lack of any legal compulsion to do so, Australian governments have a long history of providing disaster relief to citizens when an extreme weather event causes property damage.
A recent Productivity Commission report estimated that, over the past decade, the federal government spent A$8 billion on post-disaster relief and recovery. State governments spent a further A$5.6 billion.
However, the availability and amount of a payment are not guaranteed. This may depend upon the number of other claims for assistance, and any other demands on government resources. A claim for disaster relief from government may be an option for Collaroy landholders, but many other home-owners are also affected by flooding due to the recent extreme weather – and so potentially there are many other requests for relief.
<h2>What should we learn from this event for the future?</h2>
While the pictures of houses being lost to the sea in Collaroy are confronting, these images may become more commonplace. The most recent scientific report from the Intergovernmental Panel on Climate Change suggests that, under a business-as-usual scenario, a global sea-level rise in the range of 0.53-0.97m by 2100 is likely.
Even if emissions are immediately reduced, a global sea-level rise of 0.28-0.60m by 2100 is still possible. This will be especially problematic in Australia, with an estimated 711,000 residential addresses located within 3km of the shore and less than 6m above sea level – not to mention the billions of dollars' worth of government infrastructure also located in these regions.
As sea levels rise, some properties may be permanently inundated. Others may be hit by storm surge impacts or erosion, which may be exacerbated by sea-level rise.
If these events continue to attract disaster relief, the financial burden will become too great for governments to bear. Furthermore, government disaster assistance does not solve the more intractable problem of land being lost to the sea.
The pictures from Collaroy should therefore prompt a discussion about how we, as a society, can deal with the potential impacts of coastal hazards on existing developments.
This is a challenging question to answer, but there is an opportunity to address it in a planned and co-ordinated fashion.
Justine Bell-James is lecturer in law, The University of Queensland and author for The Conversation. She can be contacted <a href="https://theconversation.com/profiles/justine-bell-james-39245" target="_blank">here</a>.
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