The recent Australian summer shows that climate change is well underway

Sydney residents make the most of the heat wave. Image: Getty.

Australia’s summer is officially over, and it’s certainly been a weird one. The centre and east of the continent have had severe heat with many temperature records falling, particularly in New South Wales and Queensland. The Conversation

For much of the country, the heat peaked on the weekend of 11-12 February, when many places hit the high 40s. That heatwave, which mainly affected NSW, was quickly attributed to climate change. But can we say whether the whole summer bore the fingerprint of human-induced climate change?

Overall, Australia experienced its 12th-hottest summer on record. NSW had its hottest recorded summer.

Parts of eastern Australia had their hottest summer on record, but it was a different story in the west. Image: Bureau of Meteorology/author provided.

The NSW record average summer temperatures can indeed be linked directly to climate change. We have reached this conclusion using two separate methods of analysis.

First, using coupled model simulations from a paper led by climatologist Sophie Lewis, we see that the extreme heat over the season is at least 50 times more likely in the current climate compared to a modelled world without human influences.

We also carried out an analysis based on current and past observations (similar to previous analyses used for record heat in the Arctic in 2016 and central England in 2014), comparing the likelihood of this record in today’s climate with the likelihood of it happening in the climate of 1910 (the beginning of reliable weather observations).

Again, we found at least a 50-fold increase in the likelihood of this hot summer due to the influence of human factors on the climate.

New South Wales had its hottest summer since at least 1910 when reliable national records began. Image: Bureau of Meteorology/author provided.

It is clear that human-induced climate change is greatly increasing the likelihood of record hot summers in NSW and Australia as a whole.

When we look at record summer heat, as represented by average maximum temperatures, we again find a clear human fingerprint on the NSW record.

Climate change is increasing the frequency and intensity of extreme summer heat (high average maximum temperatures) in New South Wales. Image: Climate Central/author provided.

The Sydney and Canberra heat

So what about when we dig down to the local scale and look at those severe heatwaves? Can we still see the hand of climate change in those events?

As climate varies more on local scales than it does across an entire state like NSW, it can be harder to pick out the effect of climate change from the noise of the weather. On the other hand, it is the local temperature that people feel and is perhaps most meaningful.

In Canberra, we saw extreme heat with temperatures hitting 36℃ on February 9 and then topping 40℃ for the following two days. For that heatwave, we looked at the role of climate change, again by using the Weather@home model and by comparing past and present weather observations.

Both of these methods show that climate change has increased the likelihood of this kind of bout of extreme heat. The Weather@home results point to at least a 50 per cent increase in the likelihood of this kind of heatwave.

For Sydney, which also had extreme temperatures, especially in the western suburbs, the effect of climate change on this heatwave is less clear. The observations show that it is likely that climate change increased the probability of such a heatwave occurring. The model shows the same, but the high year-to-year variability makes identifying the human influence more difficult at this location.


A sign of things to come?

We are seeing more frequent and intense heatwaves across Australia as the climate warms. While the characteristics of these weather events vary a great deal from year to year, the recent heat over eastern Australia has been exceptional. These trends are projected to continue in the coming decades, meaning that the climate change signal in these events will strengthen as conditions diverge further from historical averages.

Traditionally, Sydney’s central business district has had about three days a year above 35℃, averaged over the period 1981-2010. Over the decades from 2021 to 2040 we expect that number to average four a year instead.

To put this summer into context, we have seen a record 11 days hitting the 35℃ mark in Sydney.

It is a similar story for Canberra, where days above 35℃ tend to be more common (seven per year on average for 1981-2010) and are projected to increase to 12 per year for 2021-40. This summer, Canberra had 18 days above 35℃.

All of these results point to problems in the future as climate change causes heatwaves like this summer’s to become more common. This has many implications, not least for our health as many of us struggle to cope with the effects of excessive heat.

Some of our more unusual records

While the east battled record-breaking heat, the west battled extreme weather of a very different sort. Widespread heavy rains on 9-11 February caused flooding in parts of Western Australia. And on 9 February, Perth experienced its coldest February day on record, peaking at just 17.4℃.

Back east, and just over a week after the extreme heat in Canberra, the capital’s airport experienced its coldest February morning on record (albeit after a weather station move in 2008). Temperatures dipped below 3℃ on the morning of February 21.

The past few months have given us more than our fair share of newsworthy weather. But the standout event has been the persistent and extreme heat in parts of eastern Australia – and that’s something we’re set to see plenty more of in the years to come.

Andrew King is climate extremes research fellow, and David Karoly professor of atmospheric science, at the University of MelbourneGeert Jan van Oldenborgh is a climate researcher at the Royal Netherlands Meteorological InstituteMatthew Hale is research assistant, and Sarah Perkins-Kirkpatrick a research fellow, at UNSW.

Data were provided by the Bureau of Meteorology through its collaboration with the ARC Centre of Excellence for Climate System Science. This article was co-authored by Heidi Cullen, chief scientist with Climate Central.

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

Was the decline in Liverpool’s historic population really that unusual?

A view of Liverpool from Birkenhead. Image: Getty.

It is often reported that Liverpool’s population halved after the 1930s. But is this true? Or is it a myth?

Often, it’s simply assumed that it’s true. The end. Indeed, proud Londoner Lord Adonis – a leading proponent of the Liverpool-bypassing High Speed 2 railway, current chair of the National Infrastructure Commission, and generally a very influential person – stood on the stairs in Liverpool Town Hall in 2011 and said:

“The population of Liverpool has nearly halved in the last 50 years.”

This raises two questions. Firstly, did the population of the City of Liverpool really nearly halve in the 50 year period to 2011? That’s easy to check using this University of Portsmouth website – so I did just that (even though I knew he was wrong anyway). In 2011, the population of the City of Liverpool was 466,415. Fifty years earlier, in 1961, it was 737,637, which equates to a 37 per cent drop. Oops!

In fact, the City of Liverpool’s peak population was recorded in the 1931 Census as 846,302. Its lowest subsequent figure was recorded in the 2001 Census as 439,428 – which represents a 48 per cent decline from the peak population, over a 70 year period.

Compare this to the population figures for the similarly sized City of Manchester. Its peak population also recorded in the 1931 Census as 748,729, and its lowest subsequent figure was also recorded in the 2001 Census, as 392,830. This also represents a 48 per cent decline from the peak population, over the same 70 year period.

So, as can be seen here, Liverpool is not a special case at all. Which makes me wonder why it is often singled out or portrayed as exceptional in this regard, in the media and, indeed, by some badly briefed politicians. Even London has a similar story to tell, and it is told rather well in this recent article by a Londoner, for the Museum of London. (Editor’s note: It’s one of mine.)

This leads me onto the second question: where have all those people gone: London? The Moon? Mars?

Well, it turns out that the answer is bit boring and obvious actually: after World War 2, lots of people moved to the suburbs. You know: cars, commuter trains, slum clearance, the Blitz, all that stuff. In other words, Liverpool is just like many other places: after the war, this country experienced a depopulation bonanza.


So what form did this movement to the suburbs take, as far as Liverpool was concerned? Well, people moved and were moved to the suburbs of Greater Liverpool, in what are now the outer boroughs of the city region: Halton, Knowsley, St Helens, Sefton, Wirral. Others moved further, to Cheshire West & Chester, West Lancashire, Warrington, even nearby North Wales, as previously discussed here.

In common with many cities, indeed, Liverpool City Council actually built and owned large several ‘New Town’ council estates, to which they moved tens of thousands of people to from Liverpool’s inner districts: Winsford in Cheshire West (where comedian John Bishop grew up), Runcorn in Halton (where comedian John Bishop also grew up), Skelmersdale in West Lancashire, Kirkby in Knowsley. There is nothing unique or sinister here about Liverpool (apart from comedian John Bishop). This was common practice across the country – Indeed, it was central government policy – and resulted in about 160,000 people being ‘removed’ from the Liverpool local authority area.

Many other people also moved to the nearby suburbs of Greater Liverpool to private housing – another trend reflected across the country. It’s worth acknowledging, however, that cities across the world are subject to a level of ‘churn’ in population, whereby many people move out and many people move in, over time, too.

So how did those prominent images of derelict streets in the inner-city part of the City of Liverpool local authority area come about? For that, you have to blame the last Labour government’s over-zealous ‘Housing Market Renewal Initiative’ (HMRI) disaster – and the over enthusiastic participation of the then-Lib Dem controlled city council. On the promise of ‘free’ money from central government, the latter removed hundreds of people from their homes with a view to demolishing the Victorian terraces, and building new replacements. Many of these houses, in truth, were already fully modernised, owner-occupied houses within viable and longstanding communities, as can be seen here in Voelas Street, one of the famous Welsh Streets of Liverpool:

Voelas Street before HMRI implementation. Image: WelshStreets.co.uk.

The same picture after HMRI implementation Image: WelshStreets.co.uk. 

Nonetheless: the council bought the houses and ‘tinned them up’ ready for demolition. Then the coalition Conservative/Lib Dem government, elected in 2010, pulled the plug on the scheme. 

Fast forward to 2017 and many of the condemned houses have been renovated, in a process which is still ongoing. These are over-subscribed when they come to market, suggesting that the idea was never appropriate for Liverpool on that scale. 

At any rate, it turns out that the Liverpool metropolitan population is pretty much the same as it was at its peak in 1931 (depending where the local borough boundaries are arbitrarily drawn). It just begs the question: why are well educated and supposedly clever people misrepresenting the Liverpool metropolis, in particular, in this way so often? Surely they aren’t stupid are they?


And why are some people so determined to always isolate the City of Liverpool from its hinterland, while London is always described in terms of its whole urban area? It just confuses and undermines what would otherwise often be worthwhile comparisons and discussions. Or, to put it another way: “never, ever, compare apples with larger urban zones”.

In a recent Channel 4 documentary, for example, the well-known and respected journalist Michael Burke directly compared the forecast population growths, by 2039, of the City of Liverpool single local authority area against that of the combined 33 local authority areas of Greater London: 42,722 versus 2.187,708. I mean, what bizarre point is such an inappropriate comparison even trying to make? It is like comparing the projected growth of a normal sized-person’s head with the projected growth of the whole of an obese person, over a protracted period.

Having said all that, there is an important sensible conversation to be had as to why the populations of the Greater Liverpool metropolis and others haven’t grown as fast as maybe should have been the case, whilst, in recent times, the Greater London population has been burgeoning. But constantly pitching it as some sort of rare local apocalypse helps no one.

Dave Mail has declared himself CityMetric’s Liverpool City Region correspondent. He will be updating us on the brave new world of Liverpool City Region, mostly monthly, in ‘E-mail from Liverpool City Region’ and he is on twitter @davemail2017.