Shifting Summers

 

Photo taken in Orange (New South Wales, Australia), showing a farmer helping a sheep suffering from drought conditions (the sheep survived!) | Photo by Jasper Wilde (@jasperwilde Unsplash) |

 

We never know what we are getting when it comes to Summer. Sometimes they scorch the Earth: widespread drought upper-cuts Australian farmers and bushfires burn without break. Other times, it’s not nearly as hot. Summer passes without any fuss and we’re left in peace. But why does this happen? Why aren’t all Summers made equal? 

 

The main reason we have unequal summers is due to a large pool of warm water that sloshes back and forth between Australia and South America. This may seem strange that water controls our weather, but it is actually one of the largest influences of the world’s weather outside of the Sun. 

 

This is no small amount of warm water, it covers most of the Pacific Ocean and can increase the sea surface temperatures around Australia by 4˚C. 4˚C may not sound like much, but this is a massive amount of energy. Energy that works its way into the surrounding atmosphere, causing updrafts, bringing more water vapour to the upper-atmosphere. Thus, more clouds and rain.

 

When warm waters border Australia, we receive a bit more rain and bit less heat.  Any threatening bushfires get doused with rain and transforms into less of a threat. Here’s a simple way to remember this: warm water = more rain and less heat.

 

And, you guessed it, when these warm waters leave Australia, and is replaced by cold waters, we are confronted with extreme Summers. Coldwater suppresses water from rising up to the upper atmosphere. Less rain causes hotter weather, and the Summer from hell returns with a fiery fury. More simply: cold water = less rain and less heat.

 

Unsurprisingly, since it seems to be human nature, we have given a name to the wet and the dry phases. The wet phase goes by La Nina, and the dry phase El Nino. They are both different phases of the El Nino Southern Oscillation –  an oscillation of warm water back and forth in the Pacific ocean. One oscillating cycle takes anywhere between 2 to 7 years. This is the main reason why not all Summers are equal. We have our scorchers and our peaceful passers. 

 

El Nino Southern Oscillation has played a big part in Australia’s history. Such as during first European settlement in Sydney in 1788, where a massive El Nino event was in play. Drought ensued, which crippled the crops and wasted-away water supplies. Life for these new arrivals wasn’t going well. This then took a turn to even worse, when a few years later, a strong La Nina took hold. Flooding rains poured in, river levels rose and swept away livestock, crops and houses. These new people were not used to variable weather like this before. Unlike the Aboriginal people, who new and warned the early settlers that flooding rains were inbound.

 

El Nino Southern Oscillation, the principal driver of variability in Australia’s weather. The sole cause of our too hot Summers, that fuels deadly bushfires and dire droughts. And when it’s not doing that, it can bring flooding rains of comparable destruction. If there is severe weather in Australia, it’s likely El Nino Southern Oscillation was one of the culprits. 


3 Responses to “Shifting Summers”

  1. ddnguyen says:

    You gave a very clear description on how the summer shifts. Im interested to know if this is human-related, or just a natural occurrence or both.

  2. Stasis van Gott says:

    Liked that topic! I was questioning about the seasonal weather in Australia too:)

  3. Kaih Mitchell says:

    I’d never thought about a 4 degree rise in ocean temperatures in terms of energy before, but you’re right, that’s a massive amount of energy.
    Which phase of the El Nino Southern Oscillation are we in now?

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