As for weather extremes, for the climate average too a smaller-chance-higher-risk range exists, as indicated by the light-blue climate model members to the right.

The graph was composed by a team of 25 mostly UK-based scientists led by the University of Oxford who recently published in Nature Geoscience.

The uncertainties in the temperature prediction primarily stem from “incomplete understanding of three aspects of the climate system: equilibrium climate sensitivity, rate of ocean heat uptake and historical aerosol forcing,” the researchers write.

Their model calculations more or less confirm the IPCC 4AR climate sensitivity range but their temperature projection includes “extention towards larger warming than observed in ensembles-of-opportunity typically used for climate impact assessments.”

Afraid though it doesn’t end there.

However refined their model and climatological considerations, you should not take this graph as an actual 21^st century warming forecast. Like many other climate studies it is based on the medium-range emission scenario.

In reality however we are emitting above the high-range scenario. So colour that light-blue range dark-blue and you’ll get a better impression of what we’re currently actually aiming for – as a minimum. And the higher the warming, the larger the chance climate feedback thresholds will be crossed, so the higher the probability of runaway warming scenarios.

© Rolf Schuttenhelm | www.bitsofscience.org