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.
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.
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...
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