90 percent chance Earth warms by more than 2 degrees

James Marshall
August 1, 2017

Global carbon emission projections through the year 2100, per year (left) and cumulative (right).

This increase, typically thought by climate experts as a "tipping point", would lodge Earth in the mid-range warming scenarios detailed by the Intergovernmental Panel on Climate Change (IPCC) of the United Nations. It shows a mere 1 percent chance that warming could be at or below 1.5 degrees, the target set by the 2016 Paris Agreement.

"Our analysis shows that the two-stage target is achieved only in the ideal scenario and can be achieved, but only by significant and sustained efforts on all fronts over the next 80 years", adds -he.

On the basis of these data, "the increase of the temperature is probably 2°C to 4.9° C, with a median value of 3.2°C and a 5% chance that it is less than 2°C", the researchers write.

They said even if we turned off everything that creates carbon dioxide tomorrow, global temperatures will still be higher by the end of the century. The study was published Monday in the journal Nature Climate Change.

"The big problem with scenarios is that you do not know how likely they are, and whether they span the full range of possibilities or are just a few examples", Raftery said. "Scientifically, this type of storytelling approach was not fully satisfying".

The study focused on three factors shaping future greenhouse gas emissions: total world population, gross domestic product per person, and carbon intensity, or the amount of carbon emitted for every dollar of economic activity.

With each passing year, the odds get worse that climate change mitigation efforts will be able to stave off catastrophic warming of more than 2 degrees Celsius, or 3.6 degrees Fahrenheit.

Governments settled on the 2C threshold partly through political expediency but also because scientists have warned of severe consequences from sea level rise, drought, heatwaves and social unrest should the temperature rise beyond this.

"Our results show that an abrupt change of course is needed to achieve these goals", said Frierson. A study that Raftery worked on in 2014 showed that world population is unlikely to stabilize this century.

According to the united Nations, the global population will climb from approximately 7.5 billion people now to 11.2 billion by 2100, increasing the pressure on energy resources. This is because the greatest population growth is expected in Africa. Instead, he was surprised to learn that population has a fairly small impact.

NY Magazine writer David Wallace-Wells argued if nothing was done to curb fossil fuel use "parts of the Earth will likely become close to uninhabitable, and other parts horrifically inhospitable, as soon as the end of this century". So as emissions fall - and aerosols wash out of the air - we might find ourselves on track for even more warming than we realized, said Robert Pincus, a scientist with the University of Colorado, Boulder, and NOAA's Physical Sciences Division.

There is only a 1% chance of meeting the more ambitious 1.5C target set in the Paris Agreement. However, according the latest research it seems highly unlikely as there is only 1% chance that temperatures will rise by less than 1.5 degrees, even if work voraciously to keep the carbon emissions in check.

Other reports by Click Lancashire

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