CMIP6 Cranks Up the Climate Sensitivity Estimate for COP26

By Eric Worrall – Re-Blogged From WUWT

Even worse than we thought ™ – global warming estimates have been raised, just in time for next year’s COP26 conference. But one of high end CMIP6 models, CESM2 (highlighted above), has already been invalidated by a paleo study.

Just how hot will it get this century? Latest climate models suggest it could be worse than we thought

Michael Grose Climate Projections Scientist, CSIRO
Julie Arblaster Associate Professor, Monash University
May 18, 2020 5.58am AEST

Climate scientists use mathematical models to project the Earth’s future under a warming world, but a group of the latest modelshave included unexpectedly high values for a measure called “climate sensitivity”.

CMIP6 Climate Sensitivities, with CESM2 highlighted (see the explanation at the bottom of this post). Source Carbon Brief

Climate sensitivity refers to the relationship between changes in carbon dioxide in the atmosphere and warming.

The high values are an unwelcome surprise. If they’re right, it means a hotter future than previously expected – warming of up to 7℃ for Australia by 2100 if emissions continue to rise unabated.

Our recent study analyses these climate models (named CMIP6), which were released at the end of last year, and what insights they give for Australia.

These models contain the latest improvements and innovations from some of the world’s leading climate modelling institutes, and will feed into the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report in 2021.

But the new climate sensitivity values raise the question of whether previous climate modelling has underestimated potential climate change and its effects, or whether the new models are overdoing things.

If the high estimate is right, this would require the world to make greater and more urgent emission cuts to meet any given warming target.

Read more: https://theconversation.com/just-how-hot-will-it-get-this-century-latest-climate-models-suggest-it-could-be-worse-than-we-thought-137281

A few weeks ago WUWT reported a study which determined CESM2 predictions are incompatible with the fossil record, because CESM2 incorrectly hindcasts temperatures which would have created lifeless tropical deserts during the Early Eocene, a period of high atmospheric CO2 and abundant tropical life.

Some of the newest models used to make future predictions may be too sensitive to increases in atmospheric carbon dioxide and thus predict too much warming,” said U-M’s Chris Poulsen, a professor in the U-M Department of Earth and Environmental Sciences and one of the study’s three authors. – source Science Daily

CESM2 is a component of high end CMIP6 projections (see the diagram at the top of the page).

CONTINUE READING –>

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