The Intergovernmental Panel on Climate Change (IPCC) will release a draft summary early tomorrow morning that aims to encapsulate our current understanding of climate and our relationship with it. Greens, policymakers, and green policymakers all over the world will be paying close attention to this summary, because it represents the clearest communication from the scientific community to national and international leaders regarding global warming.At the heart of it, humanity’s relationship is, as US Department of Energy Secretary Ernest Moniz put it, simple: “greenhouse gases make the earth warmer, and we are emitting more and more of them into the atmosphere.” But those two statements aren’t enough for policymakers to bet their political futures on. We need to know more: How sensitive is our climate to greenhouse gases? How much can we expect temperatures to rise? What are the costs of doing nothing? What are the costs of cutting out emissions altogether?The IPCC’s new report won’t answer all of these questions. Some of them fall outside the purview of science, and some remain, frustratingly, beyond our understanding. But the panel has been meeting in Stockholm this week, diligently ironing out a consensus.Drafts of the report seen by Reuters say that there is a “95 percent probability [that human activities are] the main cause of warming since the 1950s.” That’s up 5 percent from the panel’s 2007 report, and a whopping 29 percent from 2001.The IPCC’s chairman is also its most controversial figure. Rajendra Pachuari has led the panel since 2002, and his work won him a Nobel Peace prize in 2007, but since then he’s made headlines for overstating his case. The IPCC’s 2007 report predicted that the Himalayan glaciers would be gone by as early as 2035, melted under a warmer climate. That prediction was way off and, in Pachuari’s own words, “poorly substantiated.” But he rebuffed calls for his resignation, and remained optimistic about this report’s veracity, informing the FT that “everything humanly possible has been brought to bear on this report to see that we don’t have any errors.”By far the most pressing issue this report will have to address is the recent slowdown in warming. Surface temperatures are well below what climate models predicted, and they’ve been that way for the past decade or so. Here’s why that’s so problematic: most policies aimed at reducing greenhouse gas emissions require curtailing growth, charging a premium, or requiring a critical mass of consumers to ratchet down their lifestyles to a more ascetic level. This is largely why green policies have failed so spectacularly, one after another, and it’s also why policymakers are wary of putting new ones in place. If we can prove that catastrophe is on our doorstep, leaders will have the motivation to pass and implement these laws. But if that proof wavers, then the politicians who pushed growth-constraining green policies through will soon find themselves out of a job.We’re working on picking the low-hanging fruit of green policy, the kinds of measures that make sense to pass even if they don’t reduce emissions, like energy efficiency measures or encouraging telework. Beyond that lie riskier ideas. And for every move a politician is willing to make toward those ideas, he or she will need a corresponding increase in scientific certainty that the dangers of inaction outweigh the political risk.So we’ve risen from 90 to 95 percent certainty that humans are the main driver behind recent warming. That’s something, but it won’t be enough to realize what most greens would like to see happen. There’s still so much we don’t know, not least where increased concentrations of methane are coming from (though at least they’ve got it narrowed down to wellheads and wetlands at this point).For now, the question on everyone’s minds remains: where did the warming go? Pachuari promised the FT that the report “will have something to say on that,” though what that means is unclear. Many scientists believe surface temperatures have stalled because much of the planet’s recent heating has been stored in deep oceans. But there are a number of other variables at play, including the possibility that our atmosphere might simply be less sensitive to concentrations of greenhouse gases.Barring some paradigm-shifting announcement, here’s what we’re expecting to learn from tomorrow’s report: humans are responsible for recent warming, though to what degree we still don’t know. To the layperson, everything else is window dressing. The panel has reportedly been making a concerted effort this week to write the report with the widest possible audience in mind. Shoring up the foundation—convincing the world of what we do know rather than bludgeoning it with what we’re worried about—sounds like the right move to us. Just don’t expect a global climate treaty to follow.
[Earth image courtesy of Wikimedia Commons]