Projection: In 2007, IPCC reported with “high confidence” that “methane emissions from tundra… and permafrost have accelerated in the past two decades, and are likely to accelerate further.” However, the IPCC offered no projections regarding permafrost melt.
Reality: Scientists estimate that the world’s permafrost holds 1.5 trillion tons of frozen carbon. That worries scientists: The Arctic is warming faster than anywhere else on earth, and researchers are seeing soil temperatures climb rapidly, too. Some permafrost degradation is already occurring.
Large-scale tundra wildfires in 2012 added to the concern.
Why the miss? This is controversial science, with some researchers saying the Arctic tundra is stable, others saying it will defrost only over long periods of time, and still more convinced we are on the verge of a tipping point, where the tundra thaws rapidly and catastrophically. A major 2005 study, for instance, warned that the entire top 11 feet of global permafrost could disappear by century's end, with potentially cataclysmic climate impacts.
The U.N. Environmental Programme revealed this week that IPCC’s fifth assessment, due for release starting in September, 2013, will again "not include the potential effects of the permafrost carbon feedback on global climate."
The IPCC has been silent on tipping points – non-linear "light switch" moments when the climate system abruptly shifts from one paradigm to another.
Projection: IPCC has made no projections regarding tipping-point thresholds.
Reality: The scientific jury is still out as to whether we have reached any climate thresholds – a point of no return for, say, an ice-free Arctic, a Greenland meltdown, the slowing of the North Atlantic Ocean circulation, or permanent changes in large-scale weather patterns like the jet stream, El Niño or monsoons. The trouble with tipping points is they’re hard to spot until you’ve passed one.
Why the miss? Blame the computers: These non-linear events are notoriously hard to model. But with scientists recognizing the sizeable threat tipping points represent, they will be including some projections in the 2013-14 assessment.
This article originally appeared at The Daily Climate, the climate change news source published by Environmental Health Sciences, a nonprofit media company.