Part 2: Are Hurricanes Becoming More Frequent?

Is climate change causing an increase in the power and frequency of these brutal tropical storms? Harvey and Irma are causing untold damage in the Caribbean as we reach the halfway mark for hurricane season in the atlantic. Is this the new norm?

*Side Note* This is part two of the hurricane series. If you haven’t already, view Part 1 HERE

First and Foremost

If warm moist air is the source of a hurricane’s power (See Part 1), a warming climate is going to increase the likely hood of a tropical storm gaining the destructive power of a category five hurricane.

Are WE making hurricanes more dangerous?

Moisture in the Air

As the temperature of the air rises it is able to hold more moisture. This could be up to 7% more moisture per 1 degree Celsius increase. This may not sound like much but when you think about the scale of a hurricane and the destructive power already locked, in adding more moisture to the mix isn’t a good idea.

When we release greenhouse gasses into the atmosphere, we increase the temperature. As the temperature increases the air holds more moisture. With more moisture in the air, hurricanes become more powerful.

The effect of greenhouse gas warmed environment on the intensity of a hurricane was modelled by Knutson and Tuleya (2004). In their study which modelled over 1000 simulations found that the increased temperature created more intense storms.

Urban Jungles

This is the second man-made influence making hurricanes more dangerous to humans which I would like to talk about.

Concrete. We love it. Mile after mile of our urban areas have been smoothed over and covered with the stuff. I’m a big fan of plants so I am bias but concrete has one major flaw when large amounts are put over an area. Drainage.

Green fields, soil and forests soak up rainwater where it falls, adding it to the water table. It then flows at a controlled rate through to streams and rivers until it reaches the sea. When rain falls on concrete the easy path to the water table is blocked. Concrete does not drain like soil so the water gathers and flows through drainage systems built to cope with  normal rain levels. This works until rain that is way beyond the normal level begins to fall.

During hurricanes such as Harvey, HUGE amounts of rainfall happen in a very short space of time, overwhelming the drainage capacity of the city. As the water starts to back up, sewage systems are also overwhelmed. Now peoples homes are filling up with a mixture of rainwater, street grime, storm surge and sewage. Nasty.

Disease

Untreated sewage flowing through the streets breeds disease. People already helpless are now under threat of contracting a fatal disease, putting the overstretched emergency services under even more pressure. Contaminated drinking water is a big risk for spreading diseases, especially in developing countries where access is even more limited after a natural disaster than in developed countries.

Recap

Green house gasses and concrete are two man-made factors making hurricanes more dangerous.

Next, are hurricanes becoming more frequent?

Are hurricanes becoming more frequent?

This graph found on the National Hurricane Centre’s website shows the number of tropical storms, hurricanes and major hurricanes each year since 1850!

This graph is taken from the National Hurricane Centre website. http://www.nhc.noaa.gov/climo/

As can be seen from this graph, there is an upward trend in the frequency of named storms, hurricanes and major hurricanes. In the earlier years there may have been storms missed. This could be because recording and measuring equipment was not as developed as the ones we have today. However, adequate equipment has been available for many years now and we can see from the graph an upward trend from the 1970’s onwards. This period of increasing frequency is longer than the abnormal readings taken during periods of the El Niño phenomenon which occurs every 2 – 7 years with effects lasting up to a year in some places*.

Webster, Holland, Curry, Chang

I then read the paper by Webster, Holland, Curry and Chang who examined  the number of tropical cyclones and cyclone days as well as tropical cyclone intensity over the past 35 years… They came to this conclusion:

“We conclude that global data indicate a 30- year trend toward more frequent and intense hurricanes, corroborated by the results of the recent regional assessment (29). This trend is not inconsistent with recent climate model simulations that a doubling of CO2 may increase the frequency of the most intense cyclones…”

If you want to read the paper and make your own conclusions the link is is the sources section.

The other interesting part of this paper was the table named Table 1. I have included a screenshot of it here:

Data presented by P. J. Webster, G. J. Holland, J. A. Curry and H.-R. Chang. Original can be found here: http://science.sciencemag.org/content/309/5742/1844.full

As you can see from the table, in EVERY SINGLE basin the number of hurricanes in categories 4 and 5 have increase.

Conclusion

There you have it. Not only are we making storms worse for ourselves with our liberal application of concrete but we are also seeing an INCREASE in the number and intensity of tropical storms as a result of greenhouse gas emissions and global warming. It makes me wonder, are storms like Harvey and Irma the new norm? Finally, since we are still pumping our emissions into the atmosphere another question must now be asked: How much worse is it going to get?

Leave me a comment and tell me what you think!

Liked it?

If you enjoyed this and want to know more about how hurricanes are formed, check out Part 1 HERE.

Or if you fancy something different, check out THIS piece on Vertical Farming.

ENJOY!

Sources USed

Emanuel, K. A. The dependence of hurricane intensity on climate. Nature 326, 483–-485 (1987)

Knutson, T.R. and Tuleya, R.E., 2004. Impact of CO2-induced warming on simulated hurricane intensity and precipitation: Sensitivity to the choice of climate model and convective parameterization. Journal of climate17(18), pp.3477-3495.

National Hurricane Centre Website

Webster, P.J., Holland, G.J., Curry, J.A. and Chang, H.R., 2005. Changes in tropical cyclone number, duration, and intensity in a warming environment. Science309(5742), pp.1844-1846.