To understand global warming just put a pot on the stove, fill it about one quarter full of cold water, put on the lid – a glass see-through is preferable – then turn the heating element to low and watch patiently.

For the longest time nothing seems to happen. Gradually, however, water droplets will appear on the underside of the lid indicating a rise in humidity. Then, at some undetermined time, the silent heating process suddenly begins to hiss and mists of vapour begin drifting through the confined air. Eventually, the still and quiet confines of the pot become a turbulence of churning water and steaming air.

Although this pot experiment is an extremely simplified model of global warming, it illustrates the consequences of adding heat to a climate system. The dynamics on Earth, of course, are incredibly more complicated than the space inside a pot. But the principle remains the same. Added heat causes average humidity to rise, precipitation to increase and the convection currents of ocean and atmosphere to move more vigorously.

We humans would like to perceive ourselves as an insignificant force in the great scheme of climate. But the cumulative effect of 250 years of huge carbon dioxide emissions from burning fossil fuels to energize our industrial activity is having an effect on weather. We are still in the early stages of the pot-heating experiment. But the air is beginning to move more vigorously, the humidity is rising, and more water is condensing and dripping from the lid. Scientists are now concerned about the inevitable shift from silence to hiss, the unpredictable “tipping point” that suddenly and radically re-organizes the entire system – Systems Theory calls this moment “emergence”.

So far the heating process has been relatively gradual – we add a little more carbon dioxide to the atmosphere and the planet gets a little warmer. But we may be approaching a threshold of radical change. Thawing permafrost is now releasing huge stores of methane locked in frozen northern bogs – methane is about 20 times more potent a greenhouse gas than carbon dioxide. And rock-like methane deposits held deep in the oceans by cold and pressure may become volatile in warmer water. Since warmer oceans hold less dissolved gas, less of our carbon dioxide will be transferred from the atmosphere to the oceans, thereby accelerating global warming. Meanwhile, melting polar ice is exposing more ocean water to solar heating, further accelerating the warming process. Warmer oceans also destabilize glaciers that are footed in them, thus reducing ice cover while adding to sea-level rise by melt and water expansion.

We humans build our settlements and establish our livelihoods on the basis of normal conditions. A change from normality is usually a threat to our security. On the West Coast, changes in ocean temperature are threatening fisheries by introducing foreign predators and diseases to local waters. In Arctic territory, melting permafrost is eroding shorelines, washing away villages and collapsing roads, airports and forests. The torrential Australian rains that recently brought flooding and then the 300 km/hr winds of Cyclone Yasi to Queensland are both being attributed to warmer water in the nearby Coral Sea.

Statistically, weather is changing everywhere on our planet. Generally, it is becoming more extreme and more damaging, precisely what we should expect from rising temperatures. Dry places are getting drier and wet places are getting wetter. The abnormality of heatwaves, droughts, floods and storms that disrupt our ecologies and our lives are becoming increasingly commonplace.

The rise in global ocean surface temperature of about 0.1°C (to a depth of 700 metres) compared to the 0.6°C rise in atmospheric temperature can be explained by oceans being the indirect recipient of generated greenhouse heat and water holding many times more heat than air. A 0.1°C temperature increase may seem trivial in the great scheme of things, except that climate systems are intricately balanced, extremely complex, very active and notoriously unstable. And oceans – covering about 70 percent of our planet – are a primary generator of weather.

The pot experiment is a simple way of illustrating the dynamics of climate and reminding us that the impacts of global warming are imminent and already discernible. Most scientists are clearly alarmed about the reticence of both politicians and public to respond to the innumerable warnings from their studies and predictions. Some scientists say we have but a short few years to radically reduce our carbon dioxide emissions; others say we have already gone beyond the point of no return and are now launched into dire and unstoppable consequences. Most scientists seem to agree we should have taken action three decades ago, when the warnings were first sounded and the required corrective measures would have been less extreme and shocking.

Given human behaviour, the more extreme and shocking the required corrective measures and the more disruptive their effects on our entrenched habits and enterprises, the less inclined we are to undertake them. Paradoxically, as the urgency to radically reduce greenhouse gases increases, effective corrective measures become increasingly unlikely – almost as if our human character were programmed for unavoidable appointments with catastrophe.

However, if we recognize this human failing, we can correct it. Before the water in the pot reaches a boil, we can each undertake to do something – anything – to reduce the heat.