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Olives, the universe and everything

as seen from from the Hunter Valley

University of Newcastle

I am the second year of a 3 year degree course in Environmental Science and Management at the University of Newcastle, Callaghan Campus. This 3 year degree will probably take me about 5 years, but I'm not in a hurry.

I am doing this because it is the most interesting thing I can do.

How does the planet work?

How did we get where we are today?

Where to from here?

 

All Big Questions: and I'm enjoying finding out the answers.

Koalas

Koalas have been around in this country for longer than you think - about 25 million years. Think about that. Homo sapiens can claim about 150,000 years. In this time the koala has evolved to be able to eat leaves that are low in nutrient and full of dangerous chemicals that the tree uses to defend itself. They have evolved with the climate - as it dried out they have adapted. It is quite feasible given the available environment and before human intervention 40,000 years ago that there were millions of koalas in Australia. Millions of koalas eat a lot of leaves and thin out the foliage so light gets to the ground for other plants and species to thrive: a pretty important role.

So what do we do? Hunt them for food, for their skins and destroy their habitat. Introduce predators, clear land and consign koalas to Koala Parks. Nice one, humanity! The property developers and in-bound tourism operators are pretty happy with the arrangement.

Weather

Can we predict the weather, and what drives the changes? Well, to some degree yes we can. The excellent Bureau of Meteorology website www.bom.gov.au will take you to plenty of information compiled by the best in the business. As we approach the summer od 2019-20 there are bush-fires burning throughout much of the country and no signs of rain to put them out. Why is it so?

There are three major drivers of our weather - the El Nino Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD) and the Madden Julian Oscillation (MJO). ENSO operates in the Pacific Ocean, IOD does much the same thing in the Indian Ocean. To take the well-studied ENSO as a starting point: there is a cold ocean current running up the west coast of South America. Cold water holds more oxygen and more nutrient than warmer water. This tends to pool off the coast of Peru, where the up-welling of cold nutrient rich water supports a huge fishing industry, and the fish feed on the oceans nutrients. Cold ocean surface waters are fairly stable, and the tendency is for a high pressure area to form in the air above stable, cold water. If the water is warmer, heat rises and causes the air to heat and rise, leading to a low pressure area. Wind tends to blow from high pressure to low pressure areas.

On the other side of the Pacific at the same latitude, off the east coast of Indonesia, there is no cold current, so the water warms. As it warms there is evaporation, and the air, now laden with moisture, tends to rise. This creates a low pressure area at the ocean surface. Once this warmed, moist air has risen it tends to move east driven by the rotation of the Earth, until it hits the mountains of Peru, where the air mass cannot rise over the Andes without getting rid of its moisture - so it rains in Peru. The air will then sink as it loses it's moisture, pushing the colder air to the west. This col dry air flows along the surface of the ocean until it gets to Indonesia, warms and rises. This is the normal pattern.

The effect of this is a circulation of cold surface air moving across the Pacific from East to West. As the cold air reaches warmer waters it rises and rain form, bringing rain to Australia's Cape York and beyond. This generally happens in summer, so we get summer storms in Queensland, cyclones if the storms are big enough. However: in an El Nino year warmer water than usual arrives at the coast of Peru due to some interruption in the cold water flow (many reasons why this can happen). This tends to mean the focus of the up-welling isn't off the coast of Australia and Indonesia, but further west towards the mid-Pacific. This means more rain for Tonga and Kiribati, less for Australia.

A similar pattern in the Indian Ocean from the IOD can block the annual monsoon rains from Western Indonesia, Papua New Guinea and northern / western Australia. As this rain tends to drift south and provide rainfall for farming in much of Australia, the result is drought. There is so little moisture in the are air that clear skies are normal, bringing heatwaves too.