Climate change - is it making hurricanes worse?


hurricanes and climate change sailing thea atlantic

A warmer world is bringing us a greater number of hurricanes and a greater risk of a hurricane becoming the most powerful category 5.  There's an increased risk of flood damage - whether related to climate change, rising sea levels or more people moving into flood-prone areas.


Last year was horrendous for hurricanes - and not just in the Caribbean.

In total there were 17 named storms in, 10 hurricanes and 6 major hurricanes (category 3 or higher) - an above average year.  The 10 hurricanes formed consecutively, without weaker tropical storms interrupting the sequence.  The only other time this has been recorded was in 1893.  Are these storms getting worse? And does climate change have anything to do with it?

What did this mean for the Atlantic Hurricane season?


The 2017 hurricane season was particularly bad.  There was Harvey, which battered the United States in August.  It brought the largest amount of rain on record from any tropical system - 1,539mm.  It caused the sort of flooding you'd expect to see once every 500 years, causing an estimated $200bn worth of damage to Houston,Texas.

September brought Irma, which devastated many Caribbean communities. It was the joint second strongest Atlantic hurricane ever, with sustained winds of 185mph.  Those winds were sustained for 37 hours - longer than any tropical system on record, anywhere in the world.

Next came Hurricane Maria - another category 5 hurricane, with sustained winds of 175mph - which destroyed Puerto Rico's power grid.


Finally,Hurricane Ophelia spanning Portugal and Spain - the farthest east any major Atlantic hurricane has ever gone.


hurricane chart saffir
              simpson scale sailing the atlantic

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Despite this, 2017 wasn't the worst year in some key respects.  It didn't produce the strongest storm - that was Hurricane Allen in 1980, with sustained winds of 190mph.  Nor did it have the greatest number of storms - that was 2005, which saw an incredible 28 named storms, including seven major hurricanes. One of them was the infamous Hurricane Katrina.

But 2017 was probably the costliest. Estimates for the cost of the hurricane season vary and continue to be revised, ranging up to $385bn.  By comparison, 2005 racked up $144bn in damage according to the National Hurricane Center - about $180bn today, adjusted for inflation.

So, are hurricanes getting worse?


There have been 33 of the strongest category 5 hurricanes since 1924. Eleven of these have occurred in the past 14 years.  We know that hurricanes are powered by warm seas and over the past 100 years global average sea temperatures have risen by about 1C.

But when you look at the total strength of storms in each year since records began, some years are more fearsome than others.

Meteorologists use accumulated cyclone energy (ACE) to calculate the total wind power of all the storms in any given year.

As you can see, there's no clear upward trend.


storm energy hurricanes sailing the atlantic
CREDIT:NHC/NOAA


Why not?


Even though seas are getting warmer, other factors can prevent hurricanes forming in particular years.  Saharan dust can interfere with hurricane formation as can the close proximity of African storms to the equator.  But one of the great weather ironies is that hurricanes hate strong winds.  Strong winds in the Atlantic interfere with the circulation of air through a developing storm. This stops the storm growing into a hurricane.

During a phenomenon called El Niño, the Pacific Ocean near the equator gets warmer than usual. This affects global wind patterns, leading to stronger winds in the Atlantic.
That means El Niño years tend to be quiet years for hurricanes.

But when the Pacific is cooler (known as La Niña), the reverse is true - making it easier for hurricanes to form. And 2017 was a La Niña year.  In fact, the total storm strength in La Niña years has been rising decade by decade.

Climate change is also causing seas to rise.  Melting glaciers and land-based ice sheets contribute to higher sea levels.Image capti  Also warmer water occupies a larger volume. So as seas warm up, sea levels rise.

melting glacier sailing the
              atlantic

We all have a responsibility to our world, and one way we can help is with not polluting our seas with plastic - read more here.