Hurricane formation and GW

[bocadad]

By all accounts, this has been a very unusual year in the tropics. Despite all the "go" signals, we are not seeing the predicted number of storms.
While I see a lot of meteorologists and regular posters scratching their heads at the unpredictability of it all and the limitations of even our best models, I have
not seen even one thread discuss the obvious, the possible reduction of hurricanes due to the effects of global warming. While I am not taking a position in this
issue, I wonder how it can be left out in any serious discussion attempting to explain what is happening out there.

In an opinion piece back in 2011, Dr. Landsea wrote of the possible consequences of global warming. I quote here from his article.

" How Should Global Warming Affect Hurricanes?

Hurricanes are natural heat engines. They extract energy from the moist, warm air over the tropical and subtropical oceans, liberate this energy in the process of forming clouds and rainfall, but lose most of this energy in the cold exhaust of the cyclone in the upper part (~8 mi, or ~12 km) of the atmosphere. A very small percentage (less than 1%)5 of this released energy is used to warm the air within the hurricane, drop the air's density and pressure, and cause the swirling winds to spin faster and faster.

It's also important to point out that ocean temperatures are not the only factor that is crucial in knowing which disturbances will develop into a tropical storm and which systems will intensify to become extremely strong hurricanes. Other physical "ingredients" in the hurricane "recipe" include moist air and numerous thunderstorms, weak vertical wind shear (the difference in winds near the ocean versus the upper part of the atmosphere), and a triggering disturbance (in the Atlantic this is often from an African easterly wave in the atmosphere)6. Any manmade alterations to the air's moisture, thunderstorm activity, vertical shear, and originating disturbances may be as or even more important that changes to the ocean temperatures themselves. All climate models predict that for every degree of warming at the ocean that the air temperature aloft will warm around twice as much7. This is important because if global warming only affected the earth's surface, then there would be much more energy available for hurricanes to tap into. But, instead, warming the upper atmosphere more than the surface along with some additional moisture near the ocean means that the energy available for hurricanes to access increases by just a slight amount. Moreover, the vertical wind shear is also supposed to increase, making it more difficult (not easier) for hurricanes to form and intensify8.

The bottom line is that nearly all of the theoretical and computer modeling work suggest that hurricanes may be slightly stronger (by a few percent) by the end of the 21st Century, even presuming that a large global warming will occur9.

http://www.aoml.noaa.gov/hrd/Landsea/gw_hurricanes/

The climate models are also coming into agreement that the number of tropical storms and hurricanes will not go up and may perhaps even decrease (by around one-fourth fewer) because of the increased vertical wind shear.

Political considerations, or even whether humans are (in whole or in part) responsible for climate change, should not tamper with the scientific process. People should feel free to discuss any issues related to meteorology. Certainly, the hypothesis of global warming causing increase vertical shear thereby reducing the number of tropcial storms or hurricanes should be discussed. Some people, such as Chris's mentor Dr. Gray, are strongly associated with the anti-global warming position. Is it possible that being locked into that mindset makes it more difficult to acknowledge any connection between the two, if it does indeed exist?

Just posing the question as I am at a loss to understand how it can not be a part of this discussion.

[Ntxw]

Not enough data to pinpoint it to global warming. If GW causes less canes why was the period between 1995-2005 so active? Did global warming get less from the 80s? Too much conflicting data.

[tolakram]

Please remember that any politics entering into the discussion will elicit a suspension.

I agree with Ntxw, not enough data one way or the other.

Here is a ACE graph going back to the early 70's. Perhaps we have just flipped into the slow period earlier than forecasters expected?

[Ptarmigan]

Please remember that any politics entering into the discussion will elicit a suspension.

I agree with Ntxw, not enough data one way or the other.

Here is a ACE graph going back to the early 70's. Perhaps we have just flipped into the slow period earlier than forecasters expected?

I notice the 1990s has quite high ACE, especially 1993, 1994, and 1998. Most of the ACE are from the Pacific. I would guess a combination of El Nino and warm Pacific Decadal Oscillation (PDO). On the other hand, ACE is lower in the 1980s despite warm PDO and strong El Nino of 1982-1983. I also notice another peak from 2004 to 2007, peaking at 2005 and 2006. Again, PDO is warm that time, but La Nina occurrs in late 2005 to early 2006. Mid to late 2006 was El Nino.

It shows that not all El Ninos are the same. Strong Eastern Equatorial El Ninos occur when PDO is warm, like in 1982-1983 and 1997-1998. 1991-1992 was a strong Modoki El Nino, like 2009-2010.