SOURCE: The Guardian

DATE: October 9, 2018

SNIP: Key dangers largely left out of the IPCC special report on 1.5C of warming are raising alarm among some scientists who fear we may have underestimated the impacts of humans on the Earth’s climate.

The IPCC report sets out the world’s current knowledge of the impacts of 1.5C of warming and clearly shows the dangers of breaching such a limit. However, many scientists are increasingly worried about factors about which we know much less.

These “known unknowns” of climate change are tipping points, or feedback mechanisms within the climate system – thresholds that, if passed, could send the Earth into a spiral of runaway climate change.

Durwood Zaelke, founder of the Institute for Governance and Sustainable Development, said: “The IPCC report fails to focus on the weakest link in the climate chain: the self-reinforcing feedbacks which, if allowed to continue, will accelerate warming and risk cascading climate tipping points and runaway warming.”

He pointed to water vapour in the air, which traps heat in the atmosphere, as well as the loss of polar ice, the collapse of permafrost, and the migration of tropical clouds towards the poles.

Further unknowns include the effects of climate change on carbon sinks, such as soils and forests: higher temperatures could dry out some soils, causing them to release stored carbon into the air. But increased rainfall – a symptom of climate change in some regions – could in other areas be making it harder for forest soils to trap greenhouse gases such as methane.