Tropical Cyclones and Global Warming: A Reality Check

Recently there was widespread media reporting of Queensland Emergency Services Minister Craig Crawford’s release of “a plan designed to help first responders get ready for future weather extremes.”

In the ABC Online report, these quotes from Mr Crawford are emphasised:

“There are plenty of people out there who are climate change sceptics… but the consensus is our fire seasons are getting hotter and longer and our flood and cyclone seasons are certainly getting stronger and more frequent.”

“If we’re going to have cyclones happening in parts of Queensland that they don’t normally happen right now it means that we’re going to have to expand all the areas where we have response training, capability and everything like that,” Mr Crawford said.

Cyclone seasons getting stronger and more frequent?  Cyclones happening in parts of Queensland that they don’t normally happen right now?  Time for a reality check.

The Bureau of Meteorology has a useful resource in its Southern Hemisphere Tropical Cyclone Data Portal  which shows the tracks of all cyclones since the 1969-1970 season.  By clicking on each track you find details of each.   This is the 2017/18 season:

Fig. 1:  Cyclones of the 2017/18 season

Cyclone portal

I have used it to look at all cyclones that have crossed the coast of Australia (and I have included TC Nancy which came very close and whose impact was strongly felt without actually crossing the coast.)  I have counted the cyclones that crossed the coast in every month from October 1969 to now, allocating them to those parts of the northern coastline that they predominantly affected- the north-west, Northern Territory, Gulf of Carpentaria and northern Cape York, north-east Queensland, south-east Queensland (south of the Tropic of Capricorn), and New South Wales.

So here are some facts to annoy our Global Warming Enthusiast friends, and to demonstrate how ill-informed our Emergency Services Minister is.

Fig. 2: Total number of cyclones per season

All cyclones Aust

There has been a decrease in the number of cyclones over the past 48 years, a rate of five less in 100 years.  There has been little change in Western Australian cyclones:

Fig. 3: Total number of cyclones per season hitting North-West Australia

All cyclones NW

Whereas there has been a very noticeable decrease on the east coast (Queensland and NSW):

Fig. 4: Total number of cyclones per season hitting the east coast

All cyclones East coast

which is well illustrated by this plot of cyclones crossing the Queensland coast south of the Tropic of Capricorn:

Fig. 5: Total number of cyclones per season hitting south-east Queensland

All cyclones SEQ

And these images of cyclone tracks are instructive:

Fig. 6: Cyclones of south-east Queensland 1969-1992

SEQ cyclones to 92

Fig. 7: Cyclones of south-east Queensland 1992-2018

SEQ cyclones since 92

Oswald, Marcia and Debbie crossed the coast north of the Tropic of Capricorn and were rain depressions by the time they reached the south-east.

The difference is obvious.  No cyclone has crossed the coast south of Yeppoon since TC Fran in 1992.  26 years without a cyclone- people (and Mr Crawford) forget we had three in 1971.  If we do get another one no doubt it will be blamed on climate change.

So what connection is there between temperature and cyclones?

Fig. 8:  Australian tropical cyclones as a function of sea surface temperature

All cyclones Aust vs sst trop

As temperatures go up, cyclones go down!

Fig. 9:  Australian tropical cyclones as a function of Southern Oscillation Index

All cyclones Aust vs soi

The SOI is an indicator of El Nino, La Nina, or neutral conditions.  According to the BOM, consistently below -7 indicates El Nino, and above +7 indicates La Nina.  It is obvious that there have been very few cyclones in seasons with El Nino conditions, with the vast majority in neutral or La Nina conditions, and higher SOI indicates greater likelihood of cyclones crossing the coast.  This is not new, and the Bureau makes this clear.

Fig. 10:  Tropical cyclones in La Nina years

BOM map la Nina

Fig. 11:  Tropical cyclones in El Nino years

BOM map el nino

Future trends:

The Bureau discusses future trends at length at http://www.bom.gov.au/cyclone/climatology/trends.shtml

but seems to base its conclusions entirely on climate models:

There remains uncertainty in the future change in tropical cyclone frequency (the number of tropical cyclones in a given period) projected by climate models, with a general tendency for models to project fewer tropical cyclones in the Australia region in the future climate and a greater proportion of the high intensity storms (stronger wind speeds and heavier rainfall).

This is the BOM plot of severe and non-severe cyclones, which includes all tropical cyclones from 90E to 160E south of the Equator, many of which remained well offshore.

Fig. 12: Severe and non-severe tropical cyclones

BOM graph

Is there any evidence for cyclones becoming stronger, if fewer?  According to the BOM’s history of cyclones, no.  This graph plots the number of cyclones rated as severe by the Bureau (<970 hPa central pressure at peak intensity- low pressure is a good predictor of wind speed).  Interestingly, Marcia and Debbie are not listed as severe, but are described as severe in their reports, and definitely were, so I have included them in the tally.

Fig. 13: Severe land-falling tropical cyclones

Severe cyclones Aust

And showing how the proportion of severe tropical cyclones as a percentage of all land-falling cyclones has changed:

Fig. 14: Proportion of land-falling tropical cyclones rated as severe

Severe cyclones Aust %

Tropical cyclones in the past 48 years have decreased in number and intensity, and the proportion of severe tropical cyclones has also decreased, although it is entirely likely that this situation could reverse due to natural variability.

The Government’s Response

The Queensland Government is concerned cyclones may strike further south than they currently do.  They have records of cyclones going back 150 years.  Many, many of them have affected south-east Queensland and NSW.

The worst natural disaster in recorded Australian history was in March 1899 when TC Mahina (the Bathurst Bay cyclone) killed 307 people.

Here are some other significant tropical cyclones recorded by the Bureau:

February 1893 a cyclone crossed near Yeppoon.  This led to the Brisbane River floods.

January 1918. The Mackay cyclone, which caused many deaths.  There was a large storm surge and a barometric pressure reading of 932.6 hPa in a private barometer, and less than 944.8 hPa at the Post Office as the flange on the instrument prevented the needle from going lower.  Inland rainfall caused the highest recorded flood in the Fitzroy River.

March 1918. The Innisfail cyclone.  The pressure dropped to 926 hPa at Mourilyan Sugar Mill.  There was a large storm surge.  Almost all buildings in the town were destroyed or badly damaged.

March 1949.  A cyclone struck Rockhampton and Gladstone.

1967 TC Dinah affected southern Queensland and NSW.  The pressure dropped to 944.8 hPa at Sandy Cape.

In Queensland, counting only those cyclones that have actually crossed the coast, not just approached, here is a list of tropical cyclones since 1970 (see Figure 6) that have struck south of the Tropic of Capricorn (Rockhampton or Yeppoon.)

February 1971 TC Dora

February 1972 TC Daisy

March 1972 TC Emily

January 1974 TC Wanda

March 1974 TC Zoe

February 1976 TC Beth

March 1976 TC Dawn

February 1981 TC Cliff

March 1992 TC Fran

TC Nancy (January 1990) came close but did not actually cross the coast.

TC Marcia in February 2015 crossed the coast near Shoalwater Bay before moving south over Rockhampton.

There is also an impressive list of cyclones which have caused deaths and wind, wave, and flooding damage in NSW.   These include cyclones from 1892.  Included are:

March 1939, TC crossed the coast at Cape Byron.

January 1950   The Sydney cyclone of 1950, when the pressure dropped to 988 hPa in Sydney.

February 1954, TC crossed the coast at Tweed Heads, where the pressure dropped to 973 hPa.

February 1957 TC crossed the coast south of Port Macquarie.

January 1967 TC Dinah caused a large storm surge in the Tweed River.

February 1967 TC Barbara crossed the coast near Lismore.

March 1974 TC Zoe crossed the coast just north of the border and travelled through northern NSW.

January 1990  TC Nancy did not cross the coast but passed about 50km east of Cape Byron.

The Reality

Contrary to Minister Crawford’s claim, and the media’s breathless and uncritical reporting, tropical cyclones in the past 48 years have decreased in number and intensity, and the proportion of severe tropical cyclones has also decreased.  Predictions of future trends are purely speculative.  The current 26 year lull in tropical cyclones hitting the south of Queensland and northern NSW is unusual.  In the past it was normal for cyclones to strike much further south than they do now.  We should not become complacent.

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5 Responses to “Tropical Cyclones and Global Warming: A Reality Check”

  1. John in Oz Says:

    A quick search for the report the Minister is using to frighten us with led to https://www.disaster.qld.gov.au/cdmp/Documents/Adaptation-Plan/Climate-Change-Factsheet.pdf.

    For ‘Mean Climate, Heatwaves, Extreme Indices, Droughts and Floods’ they are using RCP8.5 which creates is the most unlikely scenarios from climate models.

    RCP 8.5 for year 2030, 2050, 2070 and 2090 across seasons with 10 km of spatial resolution

    From my (non-scientist) reading on these issues, I understand that climate models do not have 10Km spatial resolution due to the computing power required for such fine granularity.

    They are also using 0.8m of sea level rise by 2100, approx. 10mm/year when many global averages are quoted as 2-3mm/year.

    • kenskingdom Says:

      You are correct. Sea level rise in NQ at Mackay over the past 51 years averages 2.4mm per year, so we can expect about 20cm, about 8 inches, by 2100. And floods, rainfall, droughts, and fires were all more extreme in the past.

  2. Jamie Spry Says:

    Reblogged this on Climatism and commented:
    MASTERFUL Australian tropical cyclone report by Kenskingdom exposing more of the endless lies and falsehoods disseminated by global-warming-theory-obsessed politicians, and so eagerly published without any basic fact-checking by the global-warming-theory-obsessed, taxpayer funded national broadcaster – the ABC!

    ASTONISHING and reckless “denial” of the actual truth.

    WHAT other climate falsehoods do politicians and the ABC tell you about climate change in order to drive their pet-agenda and push fake fixes to a fake scare?

    https://climatism.blog/2017/08/16/open-letter-to-the-bureau-of-meteorology-tropical-cyclone-trends/

  3. nickreality65 Says:

    It is my contention demonstrated through experiment that since BB radiation from the surface is not possible the 396 W/m^2 upwelling LWIR is a theoretical “what if” calculation and does not in fact exist.
    (TFK_bams09):
    With no source of energy the 333 W/m^2 up/down/”back” GHG energy loop also cannot and does not exist.
    There is no energy for the GHG molecules to absorb/trap and re-emit nor “warm” the atmosphere, earth or water molecules.
    There is no man-caused global warming or climate change.

  4. ngard2016 Says:

    Ken, have you looked at HAD Crut 4 data since Dr Jones’s BBC Q&A in 2010?

    I’ve checked the HAD Crut 4 temp trends before, but it seems to have changed a lot since Phil Jones’s Q&A with the BBC in 2010, after the Climategate scandal.

    In 2010 he listed 4 warming trends since 1850 and there wasn’t much difference in the trends. The 4 trends were—-

    1860 to 1880- 0.163c dec

    1910 to 1940- 0.150 dec

    1975 to 1998- 0.166 dec

    1975 to 2009- 0.161 dec.

    Today the York Uni tool has the SAME 4 trends for Had 4 Crut at—–

    1860 to 1880- 0.156c dec lower

    1910 to 1940- 0.137 dec lower

    1975 to 1998- 0.191 dec much higher

    1975 to 2009- 0.193 dec. much higher

    So just 8 years after Jones’s BBC Q&A we see both earlier warming trends have been adjusted down and the two later trends have been adjusted up. And people wonder why we don’t trust these temp data-sets?

    And this is the temp data-set that the IPCC uses to try and convince us to waste endless billions $ for zero gain. Who are they trying to fool? And why hasn’t one of their top scientists noticed this and blown the whistle?

    Here’s Dr Jones’s 2010 BBC Q&A. See question A.

    http://news.bbc.co.uk/2/hi/science/nature/8511670.stm

    Here’s the YORK UNI tool using HAD 4 Crut krig global.

    http://www.ysbl.york.ac.uk/~cowtan/applets/trend/trend.html

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