Denial about the human role in climate change has to end if the world hopes to keep major coastal cities such as New York and London above water.

That's the startlingly blunt message from a new draft report by the United Nations Intergovernmental Panel on Climate Change.

The report says "human influence on climate caused more than half of the observed increase in global average surface temperature from 1951 to 2010."

The Nobel Prize-winning group's fifth assessment on climate change declares that it is 95 percent certain that the burning of fossil fuels worldwide is making the planet warmer, melting ice caps at the poles and raising water levels throughout the world. (Its 2007 report made similar assertions with 90 percent certainty.) Avoiding that catastrophic scenario should be a top priority for all nations.

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To be fair, the report is not final. Scientists and government leaders will hold closed-door meetings about the study in Stockholm in late September before releasing an official version in sections. But The New York Times, which revealed the leaked report, said that typically these draft reports closely resemble the final report.

Some are sure to dismiss the report's findings, firm in their disbelief that humans can affect the planet so drastically or they're in denial that it matters all that much. But the panel's review of the latest scientific literature -- it conducts no original research -- shows that there is a growing scientific consensus that humans are responsible for climate change. That means that we have a duty to remedy it or at least mitigate its consequences.

With New York, London, Shanghai, Venice and other cities possibly threatened by an almost two-foot deluge by 2100 as the oceans rise and other changes occur, the world ought to err on the side of caution. That means that nations must get serious about the issue of jointly limiting carbon dioxide emissions and taking other preventative measures.

For instance, it would be wise to look closely at the possibility of restricting building in low-lying areas of coastal cities. In any case, the international finger-pointing between developed and underdeveloped nations (some of them growing rapidly, like China; others flat-out poor) that grew after the United States declined to ratify the Kyoto Protocol on climate change must stop. Either we work on this issue together or we watch some of our most beloved and vital cities be eaten away like sand castles on the beach.

That would be a worldwide disgrace.