The Intergovernmental Panel on Climate Change's last assessment of scientific research related to climate change was issued in 2007. Almost three years later, recognizing the need for an update ahead of next month's climate talks in Copenhagen, a group of IPCC authors and other scientists released a report today that tries to fill that data gap.
What they found is a climate changing at a rate that outstrips what the IPCC projected just three years ago.
"There's a common misconception that global warming has somehow paused or declined or reversed," said Eric Steig, Professor of Earth and Space Sciences at the University of Washington and one of the report's 26 authors. "This report shows that is clearly not the case."
"The Copenhagen Diagnosis: Updating the World on the Latest Climate Science" was not produced in connection with the Nobel-winning, U.N.-founded IPCC, though it did rely on much the same methodology – combing academic journals for the hundreds of papers on climate science that may be of assistance to those trying to craft policy responses.
"There's new science and there's also three more years of data" since 2007, said co-author Richard Somerville, previously a coordinating lead author of the 2007 IPCC Fourth Assessment Report. "We felt that the Copenhagen conference needed an authoritative and comprehensive assessment since the last papers were accepted for the last IPCC report, in 2006."
The findings of the "Copenhagen Diagnosis" largely concur with those released Monday by the UN's World Meteorological Organization. The WMO said that while the average world temperature for 2008 — 14.3 degrees Celsius — was the lowest so far this decade, the planet is still headed toward an increasingly warm climate.
The most significant findings of the "Copenhagen Diagnosis" report include the fact that global carbon dioxide emissions from fossil fuels were nearly 40 percent higher in 2008 than in 1990. This means if present emissions levels remain the same for just the next 20 years, the planet may warm beyond the 2 degrees Celsius threshold set as a maximum by world leaders, said co-author Michael Mann, a former lead author for 2001's IPCC Third Assessment Report.
It also means that the status quo for Copenhagen is considerably different from that of the Kyoto Protocol negotiations in 1997, where countries discussed reducing emissions below now-distant 1990 levels.
"If we continue to burn at our current rate ... we've only got 20 years and then we need to stop right then. That's obviously unrealistic," said Steig, The only solution, he said, is to reduce emissions now.
Some findings agreed with past reports, like the steady increase of temperatures at a rate of 0.19 degrees Celsius per decade over the past 25 years — a fact, the authors say, that, looked at in the light of increases in greenhouse gas emissions over that same time span, illustrates the man-made origins of warming.
Ice Loss Accelerating
More striking, though, are recent findings that far outstrip what was foreseen by the 2007 IPCC assessment. The summer melting of Arctic ice over the three years since then, for instance, has been about 40 percent greater than the average prediction of the models in that earlier report.
Due to melting like this, satellites have shown sea levels rising about 3.4 millimeters a year over the past 15 years, about 80 percent more than IPCC predictions, the report finds. This rate means seas would rise three feet or more by the end of the century, according to Mann.
Based on the science they surveyed, the authors conclude that "average annual per-capita emissions will have to shrink to well under one metric ton CO2 by 2050. This is 80-95 percent below the per-capita emissions in developed nations in 2000." A bill in the U.S. Senate hopes to mandate an 83 percent cut in domestic emissions by 2050, based on 2005 levels. The EU has committed to a 60 to 80 percent cut over that time, based on 1990 levels.
The WMO report said the slight easing of warming temperatures is attributable to a La Niña, a cyclical weather pattern in which oceans cool, in the Pacific in late 2007.
"Natural, short- term fluctuations are occurring as usual but there have been no significant changes in the underlying warming trend," the new report said, explaining why such fluctuations do not mean climate change is no longer a threat, as some have suggested.
The WMO report also pointed to an increase in extreme climatic events. For instance, six consecutive tropical storms made landfall in the U.S. in 2008 — the first recorded time that has happened.
It also noted that the 10 hottest years since 1850, when such statistics were first recorded, have been since 1997.
Mann also pointed out Tuesday that the "interaction between the climate and the carbon cycle" has changed and will increasingly change.
"There is a decreasing ability of the ocean and the biosphere to absorb CO2 at the rate that it has historically been able to absorb that CO2" so the rate at which carbon effects are felt will increase, he said.
A report in Thursday's issue of the journal Nature backs this is up, saying that the world's oceans have become less able to absorb the increasing amounts of carbon dioxide in the atmosphere. As emissions took off in the 1950s, oceans kept up, but their absorption rate has slowed since the 1980s, and especially since 2000.
All this comes in the face of a controversy in which emails and documents from the Climate Research Unit of the University of East Anglia were stolen by hackers and posted online. The content of these documents have caused climate change skeptics to levy accusations that climate researchers manipulated the data to strengthen evidence that climate change is man-made.
The authors of the "Copenhagen Diagnosis" emphasized the objectivity of their methodology. "Many of the authors had experience with the IPCC report; they know what it means to write an objective report that is helpful, though not necessarily prescriptive, to policymakers," Somerville said.