IPCC's worst case global warming scenario by the end of the century is extremely unlikely, according to study

A new study recently published in the journal Nature has reduced the range of possible end-of-century global temperature rise outcomes by more than half.

The report, which was led by professor Peter Cox from the University of Exeter (UK), states that the worst case warming scenario set by the United Nations IPCC (4-5 degrees Celsius warming by the year 2100) is not credible.

<em>"Our study all but rules out very low and very high climate sensitivities," said Cox.</em>

For the last 25 years, the IPCC has put the potential range of warming by the end of this century in the 1.5 to 4.5 degrees Celsius range.

IPPC emission scenarios and their projected potential warming by the end of the century. This latest study says that this range should be much narrower.
<img src="https://vortex.accuweather.com/adc2004/pub/includes/columns/climatewx/2018/590x330_01250208_screen-shot-2018-01-24-at-8.32.48-pm.png"/>

Using a new method, Cox and his team have found that a much more narrow range of 2.2 to 3.4 degrees Celsius warming by 2100 is much more realistic.

Despite these positive findings, the authors state that we still need to tackle climate change, as even a 1.5-degree increase will have consequences, according to the <a href="https://phys.org/news/2018-01-worst-case-global-scenarios-credible.html" target=n>Phys.org report</a>

<em>"We will still see significant warming and impacts this century if we don't increase our ambition to reduce CO2 emissions," said Piers Forster, director of the Priestley International Centre for Climate at the University of Leeds.</em>

The team came to their narrower temperature range by analyzing the responsiveness of short-term changes in temperature to "nudges and bumps" in the climate system, said Richard Allan, a climate scientist at the University of Reading. They were able to exclude the outcomes that would have resulted in devastating increases of 4 degrees Celsius or more by the end of the century.

However, the Earth's climate system can undergo abrupt changes or "tipping points," said Cox.

These quick changes could quickly alter this equation, and not in a good way.

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