Man-made emissions have been pushing up Earth’s temperature through the Greenhouse Effect (see gif below), and much more warming is expected during our lifetimes if emissions aren’t reduced. But warming may not always be steady– passing a ‘tipping point’ can cause sudden or irreversible change. Scientists are now worried that we’re approaching some climate tipping points, beyond which rapid and difficult-to-reverse climate changes may occur.
The key driver of tipping points are positive feedback loops. Strong positive feedback loops can quickly amplify small changes – this happens when a change in A leads to a change in B which in turn produces more change in A and so on. This is what happens when you hear feedback from a mic and a speaker being too close to each other – the noise picked up the mic is amplified by the speaker which is picked up by the mic again.
In the climate system, an example of a positive feedback loop is the ice-albedo effect (illustrated above) – less sea ice due to warming results in a darker sea surface overall, which reflects less heat, raises local temperatures, and leads to yet more sea ice loss. If this process isn’t stopped by a negative feedback then a tipping point is hit beyond which a large shift to a new state becomes inevitable.
You can think of tipping points as being like a see-saw – before the pivot you have to keep pushing the ball yourself, but after the pivot the ball rolls away quickly without any further pushing. This is an example of a gradual change (like increasing temperature) hitting a critical threshold beyond which the change becomes self-perpetuating until a ‘new normal’ is reached. Once you’re past a tipping point it’s more difficult to get back – the system has found a new stable state.
There are many potential tipping points in the climate system that could significantly affect us – visit ‘How may Climate Tipping Points affect us?‘ to find out more.
Updates: 25/11/19 with some clarifications and links