"I am deeply concerned that the scale of our action is still insufficient to limit the global temperature rise to below two degrees Celsius (3.6 deg Fahrenheit) from pre-industrial levels," he told climate negotiators gathered in Warsaw.
"Climate change threatens current and future generations -- we need to look no further than last week's catastrophe in the Philippines," said the UN secretary general, referring to killer Typhoon Haiyan.
Environment ministers arrived in Warsaw today, hoping to add momentum to the troubled UN talks targeting a new, global pact on climate change by 2015.
Ban urged countries to "step up finance" and boost their commitments to reducing Earth-warming greenhouse gas emissions, mainly from fossil fuel combustion.
"I urge you to construct an urgent agenda... Current pledges are simply inadequate. We must set the bar higher," he said.