Actually the IPCC and others in the climate community don't make forecasts, they have various scenarios.
From The Associatede Press, November 28:
A climate conference hosted by an oil-rich country. That’s just one of the contradictions at the Dubai talks
The world is heading for considerably less warming than projected a decade ago, but that good news is overwhelmed by much more pain from current climate change than scientists anticipated, experts said.
That’s just one of a set of seemingly contradictory conditions facing climate negotiators who this week gather in Dubai for marathon United Nations talks that include a first-ever assessment of how well the world is doing in its battle against global warming. It’s also a conference where one of the central topics will be whether fossil fuels should be phased out, but it will be run by the CEO of an oil company.
Key to the session is the first “global stocktake” on climate, when countries look at what’s happened since the 2015 Paris climate agreement, how off-track it is and probably say what’s needed to get back on track.
Even though emissions of heat-trapping gases are still rising every year, they’re rising more slowly than projected from 2000 to 2015. Before the Paris deal, scientists at Climate Action Tracker and the United Nations Environment Programme were projecting about 3.5 degrees Celsius (6.3 degrees Fahrenheit) of warming over pre-industrial levels based on how much carbon dioxide countries were spewing and what they planned to do about it.
That 3.5 “is totally out of the picture. It will not happen,” said NewClimate Institute scientist Niklas Hohne, who works on Climate Action Tracker. “Our number is 2.7 (4.9 degrees Fahrenheit). It could be even lower with pledges and with net zero targets.”....
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