IPCC Climate Report Might Underestimate Risks

Franz Josef Fjord and glacierFellow blogger Joshua Hill has already expressed his aggravation with the U.S.’s efforts to water down the latest climate change assessment from the Intergovernmental Panel on Climate Change, but things might be even worse than they already sound.

A new report from The Climate Institute in Australia examines the latest research on climate change and concludes the IPCC’s most recent assessment is already outdated.

“(T)he IPCC report only uses material published up to mid-2006, and many new important observations have been published since,” states the report, written by Dr Graeme Pearman in collaboration with the Climate Adaptation Science and Policy Initiative at the University of Melbourne. “These suggest that the IPCC assessment is underestimating the risks of adverse impacts due to increased warming during this century and that impacts previously considered to be at the upper end of likelihood are now more probable.”

“Evidence of Accelerated Climate Change” cites data showing that carbon dioxide emissions are rising nearly three times as fast this decade as in the last — 3-plus percent per year for 2000 to 2004, versus 1.1 percent per year for 1990 to 1999. The current growth rate, the report says, exceeds that used in the IPCC’s most emissions-intensive climate scenario.

The report adds we’ve already reached greenhouse gas atmospheric levels equivalent to 450 parts per million of carbon dioxide, the point at which the IPCC says we risk slipping into “dangerous climate change.” While the IPCC assessment acknowledges carbon dioxide-equivalent levels are around 455 parts per million, it assumes the actual climate impact is still below the danger point thanks to the cooling effects of atmospheric aerosols and pollutants. The Climate Institute report notes those aerosol levels are dropping — thanks to pollution-control efforts — while greenhouse gas emissions continue to rise.

The IPCC’s climate scenarios also fall short of what is actually being seen in the Arctic, the report adds.

“Models show declining Arctic ice cover, but very few model simulations show trends as large as are observed,” states the report. “The current summer minima are approximately 30 years ahead of a range of simulation model forecasts.” That means we might seen an ice-free Arctic Ocean well earlier than the IPCC’s predicted dates of somewhere between 2050 and 2100.

But wait, there’s more. The Australian report’s most disconcerting finding is that the IPCC, in trying to craft an assessment that represents “the full range of uncertainties” in climate science, might not be giving enough attention to low-probability events with high-impact results. Those would include things like multiple feedback loops that cause a rapid collapse of the world’s ice sheets or a catastrophic release of stored carbon — thousands of gigatons’ worth — from undersea hydrate reservoirs.

“To the extent that the impacts of climate change may be in the more severe range of those outlined in the IPCC Fourth Assessment Report, the case for a policy of risk management and more urgent intervention is strengthened,” the report concludes.

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