If all countries - including the United States - honour carbon-cutting pledges under the 196-nation treaty, the world would see 2.8 C of global warming above pre-industrial levels, the Climate Action Tracker (CAT) research group had previously calculated.
That is not nearly good enough to avoid climate catastrophe, scientists say.
The Paris pact, adopted in 2015, calls for capping the rise at "well below" 2 C, and even 1.5 C if possible, to avoid climate-addled future of extreme drought, deadly heatwaves and superstorms made more destructive by rising seas.
"This is largely due to the fact that the United States is walking away from its 2030 target, and long-term 2050 goals," CAT said in a statement.
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In 2015, the United States made a voluntary commitment to cut the country's emissions 26-28 per cent below 2005 levels by 2025. Last year, it also laid out a "mid-century strategy" that would see it's emissions slashed 80 per cent compared to a 2005 benchmark.
"China's emissions growth has slowed dramatically: in the first decade of this century, its emissions grew by 110 per cent, but between 2010 and 2015 growth slowed to only 16 per cent," the report said.
Beijing is on track to fulfil it Paris pledge - a peak in CO2 emissions by 2030 - a full decade ahead of schedule.
At the same time, CAT rates China's efforts as "highly insufficient," saying its targets are "ripe for an update."
A surge of coal, oil and natural gas consumption in China was the single largest cause of the increase, they said.
India has also stepped up its climate action, the CAT researchers said. Projected emissions in 2030 are about 20 per cent less now than they were only a year ago, they reported.
"It is clear who the leaders are here: in the face of US inaction, China and India are stepping up," said Bill Hare, a scientist at Climate Analytics, a non-profit research organisation in Berlin.