C’mon, docs. Give it to us straight.

That’s the message one researcher has for the planet’s physicians, the climate scientists who are diagnosing whether a new international agreement can keep us from busting the boundary of dangerous global warming.

Oliver Geden, a senior research fellow at the German Institute for International and Security Affairs in Berlin, makes the case that the accord expected to be signed in Paris in December won’t even put the world within reach of keeping global temperatures from rising more than 2 degrees Celsius above preindustrial levels. He contends that scientists and economists must level with the public and stop spreading what he calls “false optimism” that the target can ever be reached.

“Climate scientists and economists who counsel policy-makers are being pressured to extend their models and options for delivering mitigation later. This has introduced dubious concepts, such as repaying ‘carbon debt’ through ‘negative emissions’ to offset delayed mitigation—in theory,” Geden wrote in a commentary published yesterday in the journal Nature.

“Scientific advisers must resist pressures that undermine the integrity of climate science. Instead of spreading false optimism, they must stand firm and defend their intellectual independence, findings and recommendations—no matter how politically unpalatable,” he argued.

The piece is the latest salvo in the many-faceted war over the 2-degree target. The debate ranges from whether the so-called guardrail is sufficient(ClimateWire, May 4) to whether it is even an appropriate metric for measuring planetary health. Some question whether Paris will keep the world below 2 degrees (ClimateWire, Aug. 21, 2014); others contend we’ve already blown our chances.

‘Scientists should draw a line’

Geden’s piece draws heavily from University of California, San Diego, political scientist David Victor, who argued in a controversial Nature article last year that the internationally accepted goal just isn’t squaring with reality. The world’s emissions trajectories and continued reliance on fossil fuels, he argues, blow us past 2 degrees.

Victor said the target, enshrined at a 2009 climate summit in Copenhagen, Denmark, has great political and symbolic value, and will be difficult for leaders to back away from. But, he told ClimateWire, “it’s focusing people on things that can’t be done” and diverts attention from helping communities adapt to the consequences of the warming that will certainly occur.

“My own view is that it matters in ways that is making it hard to focus on serious climate policy, in part because pretending that this is realistic is getting people to focus on emissions trajectories that can’t be achieved in the real world,” Victor said. “Because we have dawdled on climate policy for 25 years, we don’t have the same options available today that we did in the early 1990s.”

Victor also said he agrees with Geden’s premise, that some scientists are contorting their models to show that the 2-degree target is still feasible.

“The moment you step back from an iconic number like 2 degrees, then the whole policy apparatus is at sea and requires new goals,” he said.

Specifically, Geden takes aim at studies like the U.N. Environment Programme’s (UNEP) “gap” report that each year looks at the space between what nations are doing to cut emissions, what they say they have plans to do, and what is actually needed in order to stay within 2 degrees.

He argued that the report originally used 2020 as the benchmark of emissions growth to measure whether achieving the goal is reachable. But in recent years, he said, it has “shifted the goal post” to 2030. He writes that economists got around the original “make or break point” by adding what he describes as negative emissions—the removal of greenhouse gases from the atmosphere during the second half of the century by things like carbon capture and storage.

In an interview, Geden argued that scientists who claim the goal is still viable do so out of political pressure not to admit otherwise. Leaders have widely recognized that the new emissions-cutting goals countries are offering up for the Paris deal won’t in themselves keep temperatures below 2 degrees. But they also argue that if the agreement forces countries to ratchet up their pledges over time—as many hope it will—that will help ensure success.

“All the policymakers want to hear is, ‘It’s OK, we can still make it,’” he said. But, he argued, “scientists should draw a line.”

A claim with no factual basis?

Bill Hare, who leads a group of top climate scientists and economists at Berlin-based Climate Analytics who helped produce the UNEP gap report, said Geden’s accusations “could not be more wrong” and lumped the researcher in with climate skeptics and other naysayers “who systematically downplay the risks of climate change and argue against action to reduce emissions on spurious and ill-founded grounds.”

Writing in response to the Nature commentary, Hare declared that there is no factual basis for Geden’s argument that scientists are extending their models to let governments claim they will deliver emissions cuts later. Changes in mitigation models, he said, are the result of better understanding about how technologies penetrate markets and are spurred by public policy, not political pressure.

“Geden fails to understand the energy system modeling literature, and seems not to have read the IPCC assessment on transformation pathways. All mitigation scenarios he refers to represent technologically and economically feasible pathways. Making statements about their plausibility for the real-world is an expression of political, not scientific, opinion,” Hare wrote.

He and other climate scientists say they stand firmly by their analyses that 2 degrees is still within reach.

“It is physically possible,” said Michael MacCracken, chief scientist for climate change programs at the Climate Institute. “It would take a major change of society around the world to do it. It may not be likely in the political sense, but engineering-wise, if we chose to do it and invest in it, we could.”

McCracken argued that keeping to the 2-degree target will take not just a concerted effort to cut carbon but a serious effort in other areas, like reducing short-lived climate pollutants.

“It’s too depressing to think we can’t find a path,” he said. “We’re trying to make clear, I think, that you’ve got to do a lot, you’ve got to do it early, and it just can’t be one approach. A great deal has to go on, and the countries aren’t yet near showing they’re committed to doing enough.”

Princeton scientist—it’s too early to admit defeat

Michael Oppenheimer, a professor of geosciences and international affairs at Princeton University, said he also believes scientists have been clear about what sticking to 2 degrees will entail and how far nations are from getting there.

“Most scientists are realistic about it. It’s going to be hard, and if we don’t move firmly on emissions reductions, it ain’t gonna happen,” he said.

But, Oppenheimer added, it’s way too early from a physical science standpoint to admit defeat on 2 degrees.

“The reality is, it depends partly on what human beings chose to do from here on out,” he said. “Part of it is out of our control, because it depends on gases already emitted into the atmosphere,” he said. Of Geden’s piece, he said, “What does he want us to say? That it can’t be done? That would be unscientific.”

Others, like Tom Burke, founding director of U.K.-based environmental group E3G, dismissed the Nature piece as “an ivory-tower view of life” that focuses on what is being said in academic literature rather than what is happening on the ground as countries slowly but surely buckle to international pressure to take on climate responsibly.

“What the people who are deeply involved in actually trying to make this work are focused on is expanding the bounds of the possible. It’s not exactly news that getting to 2 degrees is not within the bounds of the politically possible. But the real challenge of the [U.N. climate regime] is expanding the bounds of the politically possible,” Burke said.

Geden, meanwhile, said he believes that island nations and other vulnerable countries demanding that politicians raise the bar and stick to a maximum 1.5-degree rise of global mean temperatures are “morally right.” But, he said, it’s time to stop living in a “fantasy world.”

“It’s only credible to say the chances are really, really low that we can make it,” he said. “I do not think we will stay in the carbon budget associated right now with the 2-degree target.”

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500