Copenhagen, Sep 28 (IANS/EFE): Climate scientists believe it is "extremely likely" that human activity is to blame for the bulk of global warming since the 1950s, the UN Intergovernmental Panel on Climate Change (IPCC)has said.

IPCC experts are now 95 percent certain about the preponderant role of humans in climate change, compared with the 90-percent certainty the panel cited in its previous report, issued in 2007, a report released Friday said.

"Observations of changes in the climate system are based on multiple lines of independent evidence," Qin Dahe, co-chair of IPCC Working Group I, said during the presentation in Stockholm.

"Our assessment of the science finds that the atmosphere and ocean have warmed, the amount of snow and ice has diminished, the global mean sea level has risen and the concentrations of greenhouse gases have increased," he said.

Acknowledging that the pace of warming slowed during the period 1998-2012, the IPCC attributed the phenomenon to the presence of volcanic ash in the atmosphere and to a cyclical reduction in the energy from the sun.

The 2013 report stresses the unequivocal evidence of decade-to-decade warming since the mid-20th century and describes the interval from 1983-2012 as probably the warmest 30-year period in the Northern Hemisphere in the last 1,400 years.

Absent significant reduction in emissions of greenhouse gases, temperatures will climb by more than 1.5 C (2.7 F) above pre-industrial levels by the end of this century, according to the report.

Temperatures could rise by upwards of 4 C (8 F) if emissions continued to increase, while warming will cause sea-levels to rise as much as 82 centimetres (32 inches) by 2100, the IPCC said.