One of the most devastating but still not widely known consequences of climate change concerns the ‘wet-bulb temperature’ (Tw), which is usually taken as maximum 35°C.
The paper points out that, if global average temperatures rise to 1.5 and 2°C above preindustrial levels – which is likely to happen over the next few decades on a business-as-usual trajectory – this “could affect hundreds of millions of people… especially when combined with urban heat island effects”.
In medium to high emission scenarios, certain regions such as south and south-west Asia would go “beyond the limit of survivability” and more extreme scenarios beyond 7°C “would render large parts of the world uninhabitable”.
These existential risks are particularly serious because, if we breach 1.5°C, we are increasingly likely to trigger climate tipping points that could lead to further abrupt and irreversible global warming.
The current rate of increase in emissions suggests we are heading toward a dangerous 2 to 3°C world.