Global warming may be the last thing on the mind of some Pittsburghers as the wind chill… Global warming may be the last thing on the mind of some Pittsburghers as the wind chill went below freezing earlier this week.

But it shouldn’t be, according to a report sanctioned by the United Nations.

The U.N.’s Intergovernmental Panel on Climate Change said in its 21-page report released Friday that global warming is “unequivocal” and humans are “very likely” to blame.

“I hope it raises alarm with policymakers and really forces people to begin to think about the fact that global warming is a reality,” Pitt paleoclimatologist Michael Rosenmeier said.

Rosenmeier pointed out that previous reports released by the IPCC have made the connection between global warming and human activities like fossil-fuel burning and greenhouse gas emissions.

“The linkage was made in previous IPCC publications,” he said. “But what is really important about this newest release is our understanding of how tightly coupled these phenomena are.”

While the 2001 IPCC report said human activity was “likely” the cause of global temperature increases over the past 50 years, the switch to “very likely” in this year’s report means more than an extra word.

The IPCC defines “likely” as having 66 to 90 percent sureness, with “very likely” meaning there is 90 to 99 percent certainty.

The panel, made up of scientists from the United States and 112 other countries, predicted global temperature increases of 3.2 to 7.1 degrees Fahrenheit by 2100.

However, hotter days are only the beginning.

The report predicted that sea levels will rise between seven and 23 inches in the next century, deserts will expand, deadly heat waves and droughts will increase, heavy precipitation and violent storms will become more frequent and the oceans will become more acidic.

With the grim results of this report, Pitt law student Andy Zabel said he is “cautiously optimistic” about change.

“It has been an uphill battle to make people aware of their ability to affect the world around them,” Zabel, vice president of Pitt’s Environmental Law Council, said. “This study hopefully will begin a conversation amongst politicians and regular folk to look at their effects on the world around them.”

Rosenmeier thinks that barriers blocking environmental protection policy won’t remain for long.

“Some industries are setting some of their own emission caps, sort of policing themselves even before administration acts,” he said.

Changing laws isn’t the only thing the people should be doing, Rosenmeier said.

“There are a lot of very little things we can do each day,” he said. “Pitt students and staff, we can all ride public transit for free. We should be taking advantage of public transit. If you reduce the amount of cars, you reduce the amount of emissions.”

He said simple things like turning out unneeded lights before leaving the house can make an impact on reducing energy consumption.

But Zabel said people in the United States may not take global warming seriously until they experience more life-changing effects, citing the example of how last summer’s sharp increase in gas prices finally forced people to re-evaluate what and how they drove.

“Global warming is difficult to make people take seriously when it is not seen as a current crisis,” Zabel said.

The issue is particularly important in the United States, where only 5 percent of the world’s population contributes about a quarter of the greenhouse gases in the atmosphere. That is more than any other country.

Even if we cut back emissions now, Rosenmeier said, the effects will still be present.

“We put so much carbon dioxide into the atmosphere. It’s going to hang out there for a while,” he said. “It’s going to continue to increase global temperatures, so even if we shut it off now, we’re going to see the impacts for decades to come.”

The IPCC will meet again in April to discuss the socioeconomic impact of these climate changes and further reports will be released throughout the year.

“I think it will be a wake up call,” Rosenmeier said. “Well, I certainly hope so.”