Cyclones and climate change

Some climate models predict two- to seven- fold increase in the frequency of Hurricane Katrina magnitude events for a 1°C rise in global temperature

By Vibha Varshney
Last Updated: Monday 17 August 2015

The severity of cyclones in Bay of Bengal, like Phailin, has triggered speculations about whether it is linked to climate change. But the impact of climate change on intensity and frequency of cyclones is not understood well and so far not been proved conclusively.

It has been observed that there is an increase in numbers and proportion of hurricanes of the category 4 and 5 globally since 1970 with a simultaneous decrease in the total number of cyclones and cyclone days. But there are very few historical records of tropical storms and this makes it difficult to understand whether the changes seen now exceed the variability expected from natural causes. Changes in observational capabilities also make it difficult to compare the cyclones then and now.

Modelling studies suggest that greenhouse warming will cause the globally averaged intensity of tropical cyclones to shift towards stronger storms, with intensity increases of 2–11 per cent along with 34 per cent decrease in the average frequency of tropical cyclones by 2100, say researchers in a study published in Nature Geoscience in 2010.

A study may prove crucial in understanding cyclone Phailin; it focuses on environmental conditions leading to cyclones in the Bay of Bengal during 13 cyclones. The researchers from National Institute of Oceanography in Visakhapatnam found that upper ocean heat content plays an important role in intensification of cyclones. These researchers had tracked 13 cyclones, which included Nargis and Sidr, using data from National Oceanic and Atmospheric Administration (NOAA) in US. The study was published in Current Science in November 2010 but the researchers point out that the sample size they took was small and further studies need to be carried out.

A modelling study published a few months ago provides a better understanding, but of cyclones in the Atlantic Ocean. The storm surges generated during the cyclones are the most harmful aspect of tropical cyclones. The researchers developed a storm surge index from six long high-frequency tide-gauge records from south-eastern United States, which provide information about Atlantic cyclone activity from 1923.

Linking this data to changes in global temperature patterns suggest that the extreme events are especially sensitive to temperature changes. Researchers from China, Denmark, Finland, Sweden, United Kingdom show that there would be a doubling of Katrina magnitude events due to increasing temperature over the 20th century. This study was published in April in journal PNAS. The researchers used warming patterns predicted by six climate models and found that in the 21st century there could be a twofold to sevenfold increase in the frequency of Katrina magnitude events for a 1°C rise in global temperature.

The impact of climate change on global tropical cyclone damage

Tropical cyclones in a warmer world

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  • The severity of the Cyclones

    The severity of the Cyclones in the recent past confirms their link to Climate change.
    Dr.A.Jagadeesh Nellore(AP),India

    Posted by: Anonymous | 7 years ago | Reply
  • Joint Typhoon Warning Centre

    Joint Typhoon Warning Centre - Bay of Bengal Region Cyclones per year during 1945-2000 [May to November] present a cyclic variation following the Northeast Monsoon precipitation pattern of Andhra Pradesh -- 56 year cycle --. Southwest Monsoon follow the opposite pattern. May & October to November present main cyclonic activity period. Also, U.S. Landfalling Hurricanes [Atlantic Basin Hurricane Counts - 1951 to 2006] presents similar to All-India Southwest Monsoon precipitation 60-year cycle.Pacific Typhoons present opposite pattern. [see my book, Climate Change: Myths & Realities, 2008; 2010 at]. Also, see historical temperature and carbon dioxide series of oceans present a long term cyclic variation -- when temperature increases carbon dioxide is released in to atmosphere; and when temperature cools carbon dioxide from the atmosphere is absorbed by oceans]. Also in the last 17 years global temperature hasn't changed and at the same time Arctic ice melt [seasonal pattern] presents below the average but within standard deviation shade. In the case of Antarctica this is above the average and within the standard deviation. Antarctica zone is far far higher than the Arctic zone. Also we know certain parts influenced by La Nina and El Nino -- cool and warm phases of a short term cyclic variation in temperature. We must not forget all these issues before making or attributing to climate change -- de facto global warming. We have seen super cyclones in the past, in the present and expect in future. Here we not forget the fact that we are in violation of environmental acts destroying coastal zones by destroying Magroves and establishing commercial activities. All these present increased effect of cyclonic activity. Instead of talking on this man's destruction we go on talking unknown global warming impacts. Let us fight on the man's destructive activities. Very recently I highlighted these issues in an article published in Telugu Velugu monthly magazine published by Eenadu group. Same we forget pollution and we talk greenhouse gases as there are plenty of funds in this!!!

    Dr. S. Jeevananda Reddy

    Posted by: Anonymous | 7 years ago | Reply
  • what is the actual reason for

    what is the actual reason for the occurrence of Phailin ? kindly explain

    Posted by: Anonymous | 7 years ago | Reply
  • ajay -- your question is like

    ajay -- your question is like why weather occurs!!! Globally different parts presents different weather patterns. Indian year is divided in to Pre-monsoon, monsoon, post-monsoon and winter. Weather follows a certain pattern in all these four periods but they are not the same pattern in each year. They contain systematic variations plus irregular variations over which man's actions modify them. Cyclones of different intensity -- divided in to low pressure, depression, deep depression, cyclone, severe cyclone, very severe cyclone, Super cyclone based on expected wind speed. They develop in bay of bengal and arabian seas wherein more occur in bay of bengal. Higher order cyclones occur in pre and post monsoons and lower order occur principally in monsoon seasons. There is no way to predict the occurrence of cyclone but we predict once it is former in terms of movement, speed, and as it intensifies its category changes.

    The question looks like human evolution???

    Dr. S. Jeevananda Reddy

    Posted by: Anonymous | 7 years ago | Reply
  • mainly cyclones occur in bay

    mainly cyclones occur in bay of bengal. phailin is also one of them.actually this is a type of tropical cyclones , which generally originate over tropical oceans . local low air pressure develops in the regions which cause air to rust into the low pressure centre at a great speed.while air whirls around the low pressure at huge rotational velocity,at the same time the centre of cyclone which is called eye remain calm. this is because of subsidence of air from above which after rushing inwards moves up.
    but the question arises why it originate over the bay of bengal, though arabian sea is also located in tropical areas.actually bay of bengal is warmer than arabian sea as warm water is generally piled up here due to effect of trade winds. further cyclone if so formed will move offshore in arabian sea rather than onshore.this is to be noted that cyclone dies out after reaching the land, however these are the storm surges which are devastating.

    Posted by: Anonymous | 6 years ago | Reply