climate change 101

Everything you wanted to know about climate change but were too afraid to ask.

So, what actually is global warming? The Earth's atmosphere is a miraculous thing. A semi-permeable layer of gas that stretches almost 500 kilometres into space, the atmosphere does an excellent job of keeping harmful solar radiation out, while trapping life-giving heat and water in. It's mostly made up of oxygen, nitrogen and argon – aka the air we breathe – but also contains trace amounts of carbon dioxide, methane and ozone (a naturally occurring molecule comprised of three oxygen atoms). These latter molecules are known as ‘greenhouse gases’ for their ability to absorb and transmit heat, much like a garden greenhouse.

Despite only making up around one-tenth of one per cent of the atmosphere, these greenhouse gases have a whopping big effect on what happens to the planet below. Without them, the average temperature on the surface of the Earth would be about -18°C, as opposed to the 15°C we enjoy today. When we talk about global warming, we're referring to what happens when the concentration of greenhouse gas in the atmosphere increases. The more carbon dioxide, methane and ozone there is in the atmosphere – these gases are created when we burn fossil fuels like coal and oil – the better the atmosphere becomes at trapping in heat. The result: an Earth where the average temperature is rapidly rising. Why is that bad? Over the course of its 4.5-billion-year history, the Earth has spent most of its time in one of two distinct states: icehouse and greenhouse. Whenever the state switches, it prompts devastating climate change and mass extinction events. For the past 34 million years, the Earth has been in an icehouse state. Almost every species of plant and animal alive today has evolved within the wet, moist, cooler climate conditions of an icehouse Earth. Glaciers, rainforest, tundra – we like it that way. But we might not have our way for much longer. Geological research has shown that the transition from icehouse to greenhouse is driven by the increasing concentration of carbon dioxide in the atmosphere – a process that typically takes tens of millions of years to see through. Humans, on the other hand, have had heavy industry for a little over 200 years, and in that time have already had a geologically significant effect on the levels of carbon dioxide in our atmosphere. At a time when we should be gently sliding into another Ice Age, we are, instead, in danger of causing a full-blown greenhouse transition. Couldn't this be caused by natural processes? In a word, no. While all the Earth's previous transitions have been associated with natural events and trends – the Late Devonian extinction that took place about 360 million years ago was literally caused by an excess of trees – these have also all occurred over tens of thousands, if not millions of years. The speed of the increase in carbon dioxide we're witnessing right now is almost unprecedented, from 280 parts per million at the beginning of the Industrial Revolution in the late 1700s, to 410 parts per million in 2018, the highest level in some 20 million years. We are basically a mega-volcano and the asteroid from Armageddon rolled into one. What's the difference between global warming and climate change? You’ve probably heard the two terms being thrown about, and they’re essentially referring to the same thing, although global warming is generally understood as the phenomenon that causes

climate change. However, as a phrase, climate change offers a more expansive description of what a warming Earth will actually involve. While many parts of the Earth will, in fact, get hotter and drier, the mechanics of our climate are sufficiently complex that other places will become much colder and more prone to extreme weather events, like hurricanes, typhoons and snow storms. These effects are already being seen. Australia's fire season is starting earlier; the Eastern seaboard of America is getting snowier; the Middle East is getting drier; South-east Asia is getting wetter; and recently, the North Pole hit a balmy 6°C. You can't make glaciers with that.

What does this mean for the planet?

In 2015, 196 of the world's nations came together in Paris and hashed out a plan to try to keep the increase in global temperatures this century to 1.5°C or less (this was known as the Paris Agreement). To achieve this, greenhouse gas emissions could peak no later than 2030. It was hoped that if this goal could be met, some of the more drastic consequences of climate change might be avoided – the disappearance of the ice caps; large-scale desertification and drought; dramatic rises in sea level; permanent flooding of coastal areas; ocean acidification; mass extinctions; the wholesale disappearance of rainforests and coral reefs; and the displacement of hundreds of millions of people. More specifically, in Australia, we could face hotter and drier weather conditions resulting in more bushfires; dwindling coastlines; intense cyclones; and extreme rainfall and thunderstorm events. But even if the Paris goals are met, conditions on our planet are changing rapidly, and not for the better: a recent UN report estimated the global cost of adapting to climate change at $300 billion a year by 2030.

Why are people denying that global warming is an issue?

Basically, the world as we know it – every comfort and convenience that we enjoy on a day-to-day basis – was built on the burning of coal and oil. These two resources form the backbone of the global economy, which also means they represent powerful and deeply entrenched political interests. Countries and companies that have made trillions of dollars from the ‘carbon economy’ are leery of change, and in no particular rush to give up the system that made them rich and powerful. So, much like cigarette companies in the 1970s, they’ve staged long-running PR and lobbying campaigns designed to sow misinformation and doubt among the public as to the causes and extent of man-made global warming. This is why we now face a situation where 97 per cent of the world's climate scientists agree global warming is happening and we're responsible for it, yet our political debate is often run as if it's a 50-50 question.

Where do we find hope?

It's easy to despair when you see the ice caps melting and forests burning at the same time Donald Trump pulls out of the Paris Agreement and Australia dumps its climate change policy entirely. However, there's reason for cautious optimism. Firstly, carbon abatement technologies (which enable fossil fuels to be used with reduced carbon dioxide emissions) are increasingly popular. As the effects of climate change become more palpable, more and more people are becoming convinced we need to do something about it. This leads to electoral pressure on our politicians, as well as pressure on corporations to change their polluting behaviours. Second, the Paris Agreement is moving forward and most nations – Australia and America notwithstanding – appear to be taking their commitments seriously. Third, and perhaps most importantly, technological advances are making