BY: Follow @lachlan
Critics of a new United Nations report on global warming say their skepticism is based on discrepancies between the UN’s climate models and actual, observable conditions.
The UN’s Intergovernmental Panel on Climate Change (IPCC) will release its full report on Monday. It expresses 95% certainty that human activity is primarily responsibly for an observed rise in global temperatures over the past century. Environmentalists have said that even mild criticism of such reports on global warming as science “denial.”
Skeptics have already pointed to what they say are flaws in the report’s methodology and resulting problems with its findings.
Past discrepancies between the IPCC’s models and either subsequent environmental conditions or contradictory scientific work at the time demonstrate why those models should not be taken at face value, the critics say.
The IPCC predicted in 1995 that global sea levels would rise by up to 55 centimeters by 2100 “for the range of emissions scenarios.”
“Sea level rise is one of the most visible effects of climate change and the report found that sea levels are increasing more rapidly than in previous decades,” wrote Andrew Freedman of Climate Central about the IPCC’s new report.
But recent peer-reviewed work has cast doubt on the linkage between global temperatures and sea level rise.
“Confidence in projections of global-mean sea-level rise (GMSLR) depends on an ability to account for GMSLR during the 20th century,” according to a July study published in the Journal of Climate.
That study found “small or no acceleration, despite the increasing anthropogenic forcing.”
The rhetoric coming from global warming alarmists is inconsistent with actual findings, said Chip Knappenberger, assistant director of the Center for the Study of Science at the Cato Institute.
“There is a growing discrepancy between what real world observations are telling us about the evolution of the climate under increasing atmospheric greenhouse gas concentrations, and climate model simulations of that evolution,” said Knappenberger.
Knappenberger noted that despite the panel’s climate models, the earth does not appear to have warmed over the past 15 years.
A peer-reviewed study by John C. Fyfe, Nathan P. Gillett, and Francis W. Zwiers of the Canadian Center for Climate Modeling and Analysis, published in the prestigious journal Nature Climate Change in August, faulted IPCC modeling for failing to account for the trend.
“The evidence … indicates that the current generation of climate models … do not reproduce the observed global warming over the past 20 years, or the slowdown in global warming over the past fifteen years,” the study found.
IPCC authors cautioned against reading too much into that data point, insisting that 15 years is too small of a window to draw conclusions about climate modeling. Natural phenomena such as solar cycles and volcanic eruptions can account for temperature fluctuations in the short term, they note.
Fyfe, et al., acknowledge that possibility, but stand by their conclusions.
“Although these three natural variations account for some differences between simulated and observed global warming, these differences do not substantively change our conclusion that observed and simulated global warming are not in agreement over the past two decades,” they wrote.
IPCC’s failure to adequately account for these facts, Knappenberger insists, represents a fatal flaw. “This is why I cave called the report both obsolete and misleading,” he wrote in an email.
“We have a situation in which the latest science on two key issues – how much the earth will warm as a result of human greenhouse gas emissions, and how well climate models perform in projecting the warming – is largely not incorporated into the new IPCC report,” Knappenberger explained.
Other recent phenomena have cast doubt on predictions by IPCC models.
Its 2007 climate change report predicted that Arctic sea ice would continue a decades-long trend of reduction as the Earth continued to warm.
“Satellite data indicate a continuation of the 2.7 ± 0.6% per decade decline in annual mean arctic sea ice extent since 1978,” the report predicted.
While Arctic sea ice remains below levels of the last decade, it has recovered about 60% of its mass this year, according to a report in the Daily Mail.
IPCC’s 2007 report also predicted that Antarctic sea ice would continue to decline. But according to a peer-reviewed study published in the Journal of Climate in March, that may also have been based on faulty modeling.
“In contrast to the satellite data, which exhibit a slight increase in SIE [sea ice extent], the mean SIE of the models over 1979–2005 shows a decrease in each month,” the report explained.
“The negative SIE trends in most of the model runs over 1979–2005 are a continuation of an earlier decline, suggesting that the processes responsible for the observed increase over the last 30 years are not being simulated correctly,” it concluded.