Just as politics could thwart local progress on climate change in New Mexico, politics dominates the stage during the climate talks. But for just a few moments during the opening ceremony on Nov. 29, the chairman of Intergovernmental Panel on Climate Change (IPCC), Rajendra Pachauri makes a pitch for science. 

The UN created the IPCC in 1988 so scientists could objectively assess climate change data and help policymakers evaluate the state of the science of climate change. So far, the IPCC has produced four assessment reports—in 1990, 1995, 2001 and 2007—and has begun work on a fifth report that will be released in November 2014.

The fourth assessment report involved the work of 3,750 experts who evaluated 18,000 documents and some 19,000 comments that came in during various stages of drafting, Pachauri says. And scientists made a crucial finding: 

“The warming of the climate system is unequivocal.” It has been observed in the average air and water temperatures, he says, and the melting snow and ice that is causing rising sea levels. 

Pachauri also points out that as many as 30 percent of the plant and animal species assessed so far are at risk of extinction if the planet exceeds the 1.5- to 2.5-degrees-Celsius rise in temperatures, and adds that global carbon emissions should peak no later than 2015 and decline thereafter. Such action must occur if humanity seeks a chance at averting abrupt and irreversible climate change. Already, some impacts are inevitable, he says, such as sea level rises from the melting of sea ice that has already taken place. 

Pachauri goes on to talk about adaptation and mitigation, pointing out that the response to climate change involves an integrated risk-management process—and that changes of lifestyle and patterns can contribute to climate change mitigation. 

And for a moment, Pachauri pleads with negotiators, asking them to take significant action while in Cancún: “The available scientific knowledge justifies it,” he says, “and the global community rightly expects it.”

But throughout the next two weeks, politics’ triumph over science is evident. 

During the second week of meetings, for instance, a room packed full of reporters takes note of the daily briefing by Todd Stern—who each day reiterates the same message (“The US seeks a balanced package of decisions”) and deflects the rare, pointed question from the press. Moments later, the room is nearly empty when representatives from UN Environment Programme and the Stockholm Convention on Persistent Organic Pollutants present findings on how the warming climate, rising seas and extreme weather events are causing the re-emergence of what are called persistent organic pollutants, or POPs. 

POPs are chemicals such as DDT, mercury and PCBs. Although many have been banned in recent decades, they persist within the environment. 

As UNEP’s head of media Nick Nutall points out, climate change is intensifying POPs’ spread across the planet. As the ice melts in places such as the Arctic and from mountain glaciers, chemicals such as mercury are being re-mobilized into the food chain—krill and fish are eaten by mammals such as seals and whales, which in turn are eaten by humans. 

“We’re all in this together,” Nutall says to a dispersed group of fewer than 20 journalists. “POPs travel all over the world—they don’t have passports—and they get into the food chain. Whether you’re in Sweden or Sri Lanka, they’re going to get into your food.” 

Indeed, people across the world are already experiencing the changing climate. Seas are rising—on the Solomon Islands and Seychelles, people are already migrating inland—Arctic sea ice and mountain glaciers worldwide are melting and, in many places, droughts are lengthening. Climate change is affecting water supplies and agriculture, increasing the risk of forest fires (from the Amazon to the American West) and also causing certain species of wildlife to migrate or breed at different times. And climate change is also having an impact on the way business is done. 

Trends in warming have been statistically significant, and a global rise in average temperature matters, David Gutzler, a University of New Mexico professor in the Department of Earth and Planetary Sciences, says. 

For instance, temperature changes factor into regulatory hearings with regard to electricity. 

“Electricity demand goes up when the temperature warms up, and they figure into natural gas rates because heating needs to go down when the temperature goes up,” he says. “So these trends are big enough to affect regulatory hearings.” 

Temperature trends have also changed how the National Weather Service makes predictions.

“If you look at seasonal predictions for next spring and summer, [they] are for above-average temperatures for the Southwest,” Gutzler says. “The basis for the prediction is: The temperature trend we’ve seen over the past decades are large enough that the Weather Service always expects the temperature to be above average.” 

He pauses, then explains it again: “It’s simply a statement that the way we define average climate—by looking back at the last 30 years—is not actually very representative of actual climate today,” he says, “because it’s warming up.”