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Questions real journalists ought to be asking about Yasi

Posted By Joanne Nova On February 9, 2011 @ 3:11 am In Global Warming | Comments Disabled

When “experts” say that cyclones and extreme storms will be more common in a warmer world, and are “linked”, “connected”, “expected”, or “definitely” due to man-made CO2 emissions, journalists could try asking some real questions.

1. If storms are getting worse thanks to man-made CO2 emissions, why has there been no increase globally as man-made CO2 emissions rose over the last 40 years?

Last 4-decades of Global Tropical Storm and Hurricane frequency -- 12-month running sums. The top time series is the number of TCs that reach at least tropical storm strength (maximum lifetime wind speed exceeds 34-knots). The bottom time series is the number of hurricane strength (64-knots+) TCs..

Source: Global Tropical Cyclone Activity Dr. Ryan N. Maue

2. So if you admit the global trend doesn’t change, but suggest that the local or regional trends will change, which parts of the world will get fewer cyclones?

If global averages are still “average”, things have to get better somewhere else right?

3. So if climate simulations project that Queensland will experience more cyclones, and be one of the areas that get worse, but the Crompton and McAneney (2008) paper shows that in that region the number of cyclones has been falling.

(Follow up: So the global trend is the same, and the regional trend in Queensland is falling, yet we should expect that  “it will get worse”?)

The average annual weather-related normalised damage over the 40-year period is AUD$820 million with a standard deviation of AUD$960 million. The recent past has been relatively benign in terms of loss activity, with annual damage over the most recent 5 years averaging AUD$420 million, close to half the average annual loss over the entire period of the Disaster List.

Extra information: Roger, Pielke Jnr.

4. It’s not just Queensland that isn’t showing any increase in cyclones, it’s all of Australia, according to the Bureau of Meteorology records. Does this suggest that there are less Australian cyclones in a warming world?

The trend for non-severe cyclones is decreasing, and the trend for severe cyclones is flat.

Graph showing the number of severe and non-severe tropical cyclones from 1970 - 2005.

Source: Bureau of Meteorology Tropical Cyclone Trends

5. Do you think we’d see less cyclones if we reduced CO2 in the atmosphere? How far would we have to reduce it?

In 1918 the twin cyclones,” The Mackay”, and “the Innisfail”, hit in one season. In January, in Mackay there were waves 2 -3m high breaking in the main street. Over 1 meter of rain fell in two days, and 30 people were killed. In Innisfail only 12 houses were left standing and between 37 and 100 people were killed. It was also the year of the dreaded Spanish Flu which killed more than 12,000 Australians. [Clearly, global warming was at work, right? ]

Back then CO2 levels were about 302ppm and 78% of human emissions of CO2 were yet to be released.

So we could go back to horses and carts, reduce the population by two thirds, and still get cyclones like the Mackay and the Innisfail, not to mention the most deadly epidemic of the twentieth century?

6. Is there any evidence (and simulations on computers are merely theoretical calculations, not evidence)  that extra CO2 causes more cyclones?

Can you name the evidence?

If the El Nino/ La Nina cycles correlate with the decadel variations in cyclone activity and the overall trend is falling or flat, while levels of CO2 dramatically rise, doesn’t that suggest that CO2 emissions have very little to do cyclone activity in Queensland?

In North Queensland the records suggest that increasing CO2 could help reduce cyclones. (And if that sounds preposterous, ask yourself why people keep suggesting the opposite, which, on the data, appears to be even less likely.)

7. You say the long term trend is up, but Jon Nott’s paper showed that  in the last 5,000 years there were many super cyclones in Queensland that were larger than Yasi during times when man made emissions were obviously insignificant.

If they were caused by “something else”, can we name the factor or factors that were at work then, and have changed now?

If we are not sure what caused them, how can we be sure that those same unknown factors don’t explain the current pattern?

Source: High frequency of ‘super-cyclones’ along the Great Barrier Reef over the past 5,000 years

Jonathan Nott1 & Matthew Hayne2

See also the Catalyst interview, and ABC radio interview with Nott.

8. How fast were the winds at the centre?

Ken Stewart analyzed records of wind speeds close to the eye of cyclone Yasi, and was unable to find evidence to support the claims of 290km/hr winds. The eye of the cyclone passed over the gauge at Willis Island  (though was put out of action). The top speed recorded there was 185km/hr. Ken estimates that a reasonable maximum speed inferred from this could have been 230km/hr at Mission Beach and wonders why the Yasi is still recorded as a Category 5, and listed as peaking at 290km/hr. How did the BOM estimate wind speeds of 290 km/hr, and are they still confident of those estimates?

The last word (and it’s from Ken Stewart):

Yasi was indeed an enormous system in area covered by cloud, the largest we’ve seen in the satellite era.  The zone of maximum destruction (and winds) extended from roughly Silkwood to Cardwell, a distance of about 60km.  The storm was roughly the same strength as Cyclone Larry but took longer to pass.  Remarkably, it was still classed as a cyclone at Julia Creek, the furthest inland a cyclone has been recorded.

Contrary to many alarming reports, it was not the deepest cyclone (<926hPa, Mourilyan Mill, 1918) nor the highest storm surge (Bathurst Bay >10m, 1899 or Mission Beach 3.6m 1918) nor the the most rain (907mm in 24 hours at Crohamhurst, 1893) nor the deadliest (307 known fatalities, Bathurst Bay, 1899).

Which is no consolation for the residents of Cardwell, Tully, and Mission Beach.

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