.


  • Written by Andrew King, Climate Extremes Research Fellow, University of Melbourne

The release of the Finkel report has refocused national attention on climate change, and how we know it’s happening.

On a Q&A episode following the report’s release, Climate Council CEO Amanda McKenzie said we’ve seen:

… worsening heatwaves, hot days doubling in Australia in the last 50 years.

Excerpt from Q&A, June 12, 2017. Quote begins at 2:12.

Her comment provides the perfect opportunity to revisit exactly what the research says on heatwaves and hot days as Australia’s climate warms.

Examining the evidence

When asked for sources to support McKenzie’s assertion, a Climate Council spokesperson said:

Climate change is making hot days and heatwaves more frequent and more severe. Since 1950 the annual number of record hot days across Australia has more than doubled and the mean temperature has increased by about 1°C from 1910.

Specifically, there has been an increase of 0.2 days/year since 1957 which means, on average, that there are almost 12 more days per year over 35°C.

You can read full response from the Climate Council here.

How do we define ‘heatwaves’?

Internationally, organisations use different definitions for heatwaves.

In Australia, the most commonly used definition (and the one used by the Climate Council) is from the Bureau of Meteorology (BOM). It provided the first national definition of a heatwave in January 2014, describing it as:

A period of at least three days where the combined effect of excess heat and heat stress is unusual with respect to the local climate. Both maximum and minimum temperatures are used in this assessment.

The BOM uses a metric called the “excess heat factor” to decide what heat is “unusual”. It combines the average temperature over three days with the average temperature for a given location and time of year; and how the three day average temperature compares to temperatures over the last 30 days.

We can also characterise heatwaves by looking at their their intensity, frequency and duration.

Researchers, including Australian climate scientist Dr Sarah Perkins-Kirkpatrick, are trying to standardise the definitions of “heatwaves” and “hot days” and create a framework that allows for more in-depth studies of these events.

Are heatwaves ‘worsening’?

There’s not a large body of research against which to test this claim. But the research we do have suggests there has been an observable increase in the frequency and intensity of heatwaves in Australia. Research published in 2013 found a trend towards more heat waves in Australia between 1951 and 2008.

A review paper published in 2016 assessed evidence from multiple studies and found that heatwaves are becoming more intense and more frequent for the majority of Australia.

The following chart shows heatwave days per decade from 1950 to 2013, highlighting a trend toward more heatwave days in Australia over time:

image We’ve seen a trend towards more heatwave days over Australia. Trends are shown for 1950-2013 in units of heatwave days per decade. Stippling indicates statistical significance at the 5% level. Adapted from Perkins-Kirkpatrick et al. (2017)

Have hot days ‘doubled’ in the last 50 years?

While the number of “hot days” (as defined by the BOM) has not doubled over the last 50 years, as McKenzie said, the number of “record hot days” certainly has. “Record hot days” are days when the maximum temperature sets a new record high.

Given that McKenzie made her statement on a fast paced live TV show, it’s reasonable to assume she was referring to the latter. Let’s look at both figures.

The BOM defines “hot days” as days with a maximum temperature higher than 35°C. The BOM data show there were more hot days in Australia in 2013, 2014, 2015 and 2016 than in any of the 50 years from 1966 to 2016 (the last year for which data are available).

In fact, there were more hot days in the years 2013-2016 than in any other year as far back as 1910. If we compare the decades 1966-76 and 2006-16, we see a 27% increase in the number of hot days.

The following map shows the trend in the number of days per year above 35 °C from 1957–2015: image Bureau of Meteorology

A 2010 Bureau of Meteorology/CSIRO report found record hot days had more than doubled between 1960 and 2010. That data was collected from the highest-quality weather stations across Australia.

image Number of record hot day maximums at Australian climate reference stations, 1960-2010. Bureau of Meteorology 2010 image Number of days in each year where the Australian area-averaged daily mean temperature is extreme. Extreme days are those above the 99th percentile of each month from the years 1910-2015. Bureau of Meteorology

Why are heatwaves worsening, and record hot days doubling?

The trend in rising average temperatures in Australia in the second half of the 20th century is likely to have been largely caused by human-induced climate change.

Recent record hot summers and significant heatwaves were also made much more likely by humans’ effect on the climate.

The human influence on Australian summer temperatures has increased and we can expect more frequent hot summers and heatwaves as the Earth continues to warm.

Authors: Andrew King, Climate Extremes Research Fellow, University of Melbourne

Read more http://theconversation.com/are-heatwaves-worsening-and-have-hot-days-doubled-in-australia-in-the-last-50-years-79337

Australian jobs aren't becoming less secure

Gig platforms don't have a large share of the labour market yet.Mavis Wong, CC BY-SAA common narrative nowadays is that standard, secure full-time work is a thing of the past thanks to increasing casu...

How an alien seaweed invasion spawned an Antarctic mystery

Southern bull kelp can drift huge distances before washing ashore.Ceridwen Fraser, Author providedTwo small pieces of seaweed found by a Chilean scientist on an Antarctic beach set in train research t...

CRISPR/Cas9 gene editing scissors are less accurate than we thought, but there are fixes

We need to know gene editing technology is precise before we try to use it to cure diseases.from www.shutterstock.comCRISPR gene editing technology is revolutionising medicine and biology. This techni...

A brief history of briefs – and how technology is transforming underpants

Underpants have a long history and, it seems, a bold future.shutterstockUnderpants. We tend not to talk about them but they are a fact of life (unless you go commando). Briefs have a fascinating hist...

Russia's World Cup widely hailed as success, but will the good vibes last for Putin?

Even before the final whistle had been blown at the 2018 World Cup, the world media were already proclaiming it a huge success. The New York Times asked whether Russia 2018 was the “greatest of ...

The new national housing agreement won't achieve its goals without enough funding

There's never been enough funding to ensure affordable housing for those who need it.from shutterstock.comThis month, yet another policy agreement on housing between the Commonwealth and state and ter...

who really deserves the rewards from success?

How much is success down to skill or just a lucky break?Shutterstock/Sergey Nivens Which is more important when it comes to rewarding success: that the achievement was earned through skill, or that it...

Politics

Union demands paint a bleak future under Shorten

It’s time for Bill Shorten to come clean and rule out extreme changes to Australia’s industrial relations laws that would wind the clock back to the strike-torn Whitlam era.   As the ACTU prepares...

Doorstop at AKD Sawmill with Trevor Ruthenberg, LNP Candidate for Longman

MR TREVOR RUTHENBERG, LNP CANDIDATE FOR LONGMAN: Well morning folks. Welcome to Caboolture, welcome to Longman. This is a fantastic day for local jobs. This is a fantastic day for our community. ...

Australia’s resource and energy export figures are on track to set a new record

Resources and energy exports setting NEW records   Australia’s resource and energy export figures are on track to set a new record of $226 billion in 2017–18 – and go even higher this year – accor...

Business News

What is the best structure to use when starting up a business

Coco Hou, tax specialist and accountant, has shared her advice for people who are starting up their own businesses, setting up side gigs, or moving into consultancy work. The start of the new financ...

Leading Employment Firm in WA 2018

Only a certain few start their careers as the boss. For most of us, we get employed by companies and in most cases, we never really find the need to hire employment lawyers. But if we do, hiring an ...

Hertz collaborates with UbiPark to develop simpler mobility solution

Today, smart parking solutions provider UbiPark and leading vehicle rental brand Hertz Australia have announced a strategic collaboration to develop smarter mobility solutions. The collaboration ...

Travel

Winter In Rotorua: Things To Do

While many travelers consider the summer months to be the prime traveling season, there are thousands and thousands of travelers who love to take to their campervan hire australia journeys when the ...

Discover Hong Kong Your Way With Ecruising

From July – November 2018, Ecruising in partnership with Hong Kong Tourism and Royal Caribbean, including Azamara and Celebrity Cruises are offering travellers new and exclusive cruising itinerari...

Save on the ultimate family escape at AYANA Resort and Spa, BALI

Re-connect, relax and refresh with a school holiday break that’ll win over the whole family   SYDNEY, Australia – July 2018:  The luxury integrated AYANA Resort and Spa, BALI, overlooking beautifu...

You might also like