By Graham Pinn
The Intergovernmental Panel for Climate Change (IPCC) describes a tipping point as a “critical threshold beyond which a system reorganises, often abruptly, and/or irreversibly”. Their examples include melting polar ice with sea-level rise, increasing extreme weather events, and release of methane from thawing permafrost; currently nine potential such events have been identified, none currently occurring.
When initially discussing such events, the IPCC believed a temperature rise of 4C would be necessary for these events to occur, this figure was progressively revised down, to a 1.5C rise making them more probable, the latest figure is 1.5 – 2.5C. When looking back, to what we know has occurred historically, even the concept of temperature increase depends on the starting point.
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