Frankenstorm!!

This week, the East Coast of the US has somewhat resembled a scene from 'The Day After Tomorrow', with up to a million people ordered to evacuate their homes which lie in the path of Hurricane Sandy. The storm, which has made unusually strong landfall on the East Coast (Monday 29, 20:00 local time) has already caused widespread power outages, snowfall and flooding; the NYC subway system felt the effects of a 4m storm surge when seawater seeped into the 108-year-old tunnels; and a tanker ship was even reported washed up in a street in Staten Island!!

The storm is expected to wreak havoc over 12 states for up to 36 hours, although it has now been downgraded from hurricane status to a strong storm. Even so, Sandy is expected to cost the US up to $20bn in economic losses (surely a realistic forecast seeing as though Wall Street has been forced to close its financial markets for the past 2 days).

It's not unusual for the US to experience a category 1 hurricane at this time of year, but Sandy's super strength is spurred on by incoming winter storm systems from the North West, as well as abnormally warm sea surface temperatures in the Atlantic Ocean. Both of these elements mean that Hurricane Sandy is more powerful than an average Category 1 system and with climate change increasing global sea temperatures and atmospheric moisture, could systems like Sandy be the norm of the future?

NASA satellites tracked the formation and spread of Hurricane Sandy (NASA 27/10/12)

Keep checking in for updates and an explanation of hurricane formation which is to follow shortly...

The past is no longer key to the future..

There are many definitions of 'extreme weather events', but to start simply I'm just going to take a definition from good old Wikipedia:

Extreme weather includes unusual, severe or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past.The most commonly used definition of extreme weather is based on an event's climatological distribution: Extreme weather occurs only 5% or less of the time.

The general consensus is that this term covers tropical storms, wind storms, droughts and flooding to name a few. As this blog shall explore, the frequency of extreme weather events is set to increase in view of climate change, meaning that future populations may not consider our present extremes to, well...be just that- extreme.

The world has warmed ~1°C in the past 100 years, which does little to affect the climate on its own. Amplifying feedbacks, however, increase the impacts felt by this small rise in temperature so it has a greater affect on climatic conditions. For example, increased heat in the atmosphere creates a greater disequilibrium between the temperature of the ocean and that of the atmosphere: this leads to heating of the sea surface and greater evaporation of surface waters. Hurricanes are a product of thermal heating over waters, and amplifying factors mean that a 1°C rise in ocean temperature can account for a 7% rise in hurricane occurrence.

This summary by the IPCC on feedbacks is a little long for the point I'm trying to make, but if you read the last 3 paragraphs you can get an idea of the complicated feedback system that the Earth possesses.

Similar to hurricanes, droughts can also be subject to amplifying feedbacks- long periods of drought can follow equally long periods of intense rainfall. But little rain can lead to extremely low soil moisture - this then means that no or little moisture is available for evaporation, leading to reduced cloud cover over land and increasing the likelihood of a prolonged drought. It was said of the US 2012 drought in the southern Midwest that

Drought is a “vicious,” self-reinforcing cycle. Much of the summertime rainfall in the Midwest and Great Plains is convective “recycled” rainfall that originates from evaporated soil moisture. Drier soils at the beginning of summer make precipitation less likely. The lack of water in the soil also means that the soils absorb heat and warm more quickly, helping to wring yet more moisture out of the soils.

These are just some of the extremes which are to be affected by a warming world and will be addressed in more detail later. But it is clear that past climatic records can no longer act as a direct forecast for the future- the climate is definitely changing...

(Image taken from the NASA  Earth Observatory website)