Carbon dioxide

What is the problem with carbon dioxide?

A quick bit of high-school physics here as this is definitely not straight forward. As heat streams in from the Sun (at long wave-lengths) it warms the air slightly as it passes through, but much more warmth comes from the heating of the Earth being reflected back (at shorter wave-lengths) into the atmosphere. The ground stays warm long after the sun has gone down. Some of this reflected warmth makes it back into space, but some is trapped in the atmosphere. The chief culprits for trapping the heat are water vapour and carbon dioxide: more water vapour and CO2 in the atmosphere means more heat is trapped. Most of this trapped heat has always been absorbed by the oceans, and that is where the problems really start.

The system of sunshine – reflected heat – warming atmosphere – warming ocean has been in balance pretty much since the end of last Ice Age 11,000 years ago. If for some reason the amount of CO2 in the atmosphere drops too low the oceans cool, the air cools and an ice age is created. However, the amount of CO2 in the atmosphere is going up at the moment. As the air starts to warm the water starts to warm, more water vapour is given off by evaporation – which traps more heat – which goes into the ocean – which gets warmer – which creates more evaporation – which puts more water vapour into the atmosphere – which then gets hotter .... This is called a positive feedback loop: things just keep getting hotter. When I was at school in the 50s we were taught that the amount of CO2 in the atmosphere was 0.03%. Now children learn it is 0.04%. A significant rise in just 60 years, not 10,000!

The big thing here is the effect of all this additional heat in the ocean on storms. Yes there are plenty of other things to worry about such as droughts, warmer air and more rainfall dissolving chemicals in rocks, altering water pH and destroying corals and shellfish, the melting of icecaps, release of methane from permafrost, loss of habitat etc. but a really big concern is the effect on storms.

In tropical waters off the coast of Queensland and WA the ocean water is getting hotter as a result of this CO2 / water vapour build-up. More heat in the water means more energy to drive storms: what would have been a tropical storm becomes upgraded to a cyclone; category 1 becomes category 2 and so on. This is already happening off the coast of Central and North America with huge hurricanes, off the coast of the Philippines and Japan with huge typhoons, next it is our turn. It may not happen in 2020 as there are a few other factors at play but it will happen.

The highest category storm is 5 (Hurricane Katrina for example) and meteorologists and now talking about creating category 6, based on the energy, speed of winds and damage done. Now that is scary. Not just on the damage caused by the ferocious winds of a cyclone, but on the associated flooding and massive disruption. This additional heat in the oceans is a factor we really donít understand all that well – we only have perhaps 10 years of the effects becoming obvious. For many decades the ocean just went on absorbing heat energy and nothing much changed, but there is only so much that can be absorbed without a reaction.