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Do Tropical Storms correlate with CO2? In a word — No

Posted By Joanne Nova On September 6, 2011 @ 9:41 am In Global Warming | Comments Disabled

Catastrophic killer storms are coming!

‘The Australian Greens say Tropical Cyclone Yasi is a “tragedy of climate change”.’

“DESTRUCTIVE hurricanes such as Katrina and Rita are likely to be more common … Tim Flannery warns.” “These hurricanes have been a catastrophe just waiting to happen.”

The IPCC concludes:

“Studies showed … future tropical cyclones would likely become more severe with greater wind speeds and more intense precipitation.” AR4 Tropical Cyclones (Hurricanes) pp786

Wow, that’s scary! Let’s look at the studies:

“These studies fall into two categories: those with model grid resolutions that only roughly represent some aspects of individual tropical cyclones, and those with model grids of sufficient resolution to reasonably simulate individual tropical cyclones.”

Oh? That’s models, or er… other models?

But where are the observations?

CO2 levels have risen to the highest level in a million years, presumably Hurricanes, Tornadoes and Cyclones are at all time highs, stronger and nastier than we’ve ever seen.

Records of actual tropical storms or proxies for storms show:

  1. Global energy levels haven’t changed since records of that sort of thing began.
  2. Global frequencies haven’t changed either.
  3. Neither Australian or US extreme storms are becoming more common
  4. US Tornadoes are not getting worse either.
  5. Long term studies show it’s not about CO2, and not much about temperature, but more about La Ninas and El Ninos.

Globally tropical storms show no correlation with our CO2 emissions. Their global energy levels are no different to what they were 40 years ago.

Global tropical cyclones accumulated energy

Last 4-decades of Global and Northern Hemisphere Accumulated Cyclone Energy: 24 month running sums through August 31, 2011. Note that the year indicated represents the value of ACE through the previous 24-months for the Northern Hemisphere (bottom line/gray boxes) and the entire global (top line/blue boxes). The area in between represents the Southern Hemisphere total ACE. Ryan Maue

The Frequency of storms isn’t changing either.

Tropical Storms since 1970

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. Updated through August 31, 2011. Ryan Maue

See POLICLIMATE for updates and more information.
Global Tropical Cyclone Activity 2011 Activity Updates Ryan N. Maue, PhD

For background information see NOAA: “The deadliest, costliest and most intense United States Hurricanes From 1900 – 2000.” Jarrell, Mayfield, Rappaport and Landsea.

Australian cyclones

According to the BOM, the intensity of tropical cyclones has increased (but it’s not statistically significant) and the total number has decreased. Cyclones in Australia are linked to La Nina’s rather than man-made emissions of CO2.

Australian cyclones total number and intensity BOM

Total number of tropical cyclones (teal bars), and the number of intense tropical cyclones (yellow bars) in the Australian region (105-160E). An intense tropical cyclone is defined by a minimum central pressure of <970 hPa.

US Tornadoes are not getting worse either

Source: NOAA

Tornado number in the US F3 to F5 intensity

The number of strong to violent Tornadoes since 1950 shows little trend.

US Hurricanes 1850 -2006

There is no sign that human emissions make a difference to longer term trends in the US either.

US Hurricane frequency since 1850

Hurricanes USA major per decade 1850 -2006

Major Hurricanes have been striking the US at roughly the same rate for 150 years

The two graphs above come from data from NOAA, and were graphed by Buzzards Bay Natural Estuary Program.

US Hurricanes making landfall since 1850

Number of U.S. landfalling hurricanes from 1851 to 2006 (red bars), the black straight line is the long-term trend, the blue line is the seven-year running mean (from Wang & Lee 2008).

For more information see Marlo Lewis’s excellent article about US hurricanes in 2009.

In the very long term, like 5000 years, storms are not connected to the temperature, except if anything, it was worse in cold times

Fan DaiDu et al looked at proxies (microfossils, sedimentary organic layers, storm deposits, tree rings, stalagmites and corals) and found there was no simple linear relationship between typhoons and temperature over the Holocene period. Basically, it’s about La Nina’s rather than degrees C. More hurricanes and typhoons occur in China, and Central and North America during La Nina years. Even though it was warmer 8000 years ago, the storms weren’t worse.

A few case studies based on geological proxy records show that a warmer climate alone during the Holocene Optimum may not have increased the frequency of intense typhoons. In the last millennium, the frequency of typhoon activity was not found to fluctuate linearly with climatic change over the centennial timescale. On the contrary, typhoon frequency seemed to have increased at least regionally during the coldest phases of the LIA,

Johnathon Nott studied storm surges in North Queensland over the last 5,000 years and found that things have been fairly quiet for the last 200 years compared to the past.

What the longer term records show, however, is that the frequency of extreme cyclones follow a predictable long-scale pattern.

“What the record shows is we go through extended periods, hundreds of years, of high activity and extended periods of little activity,” Nott says.

“The past 100 to 150 years has been very quiet in Queensland in terms of what happened in the past. The couple of hundred years prior to that were very active.”

The Woodruff Thesis also studied a 5,000 year timescale, includes published papers and basically reaches the same conclusion: That big storms depend on the ENSO cycle — La Ninas and El Ninos. They appear to be worse during La Ninas when the sea surface temperature is lower.

Please let me know if anyone finds longer term graphs. I’d like to add them.




Fan DaiDu et al, Perspectives on the linkage between typhoon activity and global warming from recent research advances in paleotempestology Chinese Science Bulletin Volume 53, Number 19, 2907-2922, DOI: 10.1007/s11434-008-0341-2

Klotzbach, P.J. 2006. Trends in global tropical cyclone activity over the past twenty years (1986-2005). Geophysical Research Letters 33 doi: 10.1029/2006GL025881. From 1986 to 2005, there was an increase in hurricane strength (“accumulated cyclone energy”) in the North Atlantic, a decrease in the Northeast Pacific, and not much change in the other four hurricane basins. [For Pat Michaels's review, click here.]

Landsea, C.W. et al. 2005. Hurricanes and global warming. Nature 438: E11-13. Emanuel mishandled data and his methodology is flawed.

Landsea, C.W. et al. 2006. Can we detect trends in extreme tropical cyclones. Science 313: 452-454. The apparent trend towards more powerful hurricanes is a consequence of improved monitoring in recent years of non-landfalling hurricanes. [For Pat Michaels's review, click here.]

Nott1 J. & Hayne2 M. High frequency of ‘super-cyclones’ along the Great Barrier Reef over the past 5,000 years. | Nature 413, 508-512 (4 October 2001) doi:10.1038/35097055;

Swanson, K.L. 2007. Impact of scaling behavior on tropical cyclone intensities. Geophysical Research Letters 34 doi: 10.1029/2007GL030851. There is no statistically significant correlation between sea surface temperatures and average tropical cyclone intensity in either the Atlantic or western Pacific Ocean from 1950 to 2005. [For Pat Michaels's review, click here.]

Wang, C. & Lee, S.K. 2008. Global warming and United States landfalling hurricanes. Geophysical Research Letters 35(1): L02708. Warming of the Atlantic Ocean is associated with an increase in vertical wind shear, which in turn coincides with a “weak but robust” downward trend in U.S. landfalling hurricanes. See the figure below. [For Pat Michael's review, click here.]

Thanks to Baa Humbug for help with this post

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