Controversy over U.N. report on climate change as warming appears to slow

QAQORTOQ, GREENLAND - JULY 30: Calved icebergs from the nearby Twin Glaciers are seen floating on the water on July 30, 2013 in Qaqortoq, Greenland. Boats are a crucial mode of transportation in the country that has few roads. As cities like Miami, New York and other vulnerable spots around the world strategize about how to respond to climate change, many Greenlanders simply do what theyve always done: adapt. "Were used to change, said Greenlander Pilu Neilsen. "We learn to adapt to whatever comes. If all the glaciers melt, well just get more land. (Photo by Joe Raedle/Getty Images) Joe Raedle/Getty Images

Climatologists and climate-change deniers agree on at least one thing this week: everyone is awaiting the landmark U.N. report on climate change that will be presented at next week's meeting of the Intergovernmental Panel on Climate Change (IPCC).

The report will detail the scientific and technical elements of climate change, and will note that greenhouse emissions continue to rise. It will provide policymakers with actionable data and recommendations.

The report will also include data that indicates the rate of warming from 1998 to 2012 slowed to about half the average rate since 1951, citing natural variability in the climate system, as well as cooling effects from volcanic eruptions and a downward phase in solar activity.

All of this will be in the report. What won't be there is a more thorough explanation for the supposed decline in warming.

Climate skeptics have used the lull in surface warming since 1998 to cast doubt on the scientific consensus that humans are warming the planet by burning fossil fuels and cutting down CO2-absorbing forests.

Because of this, according to documents obtained by the Associated Press, government officials from the U.S., Germany, Belgium and Hungary are calling on the IPCC to include a detailed, scientific explanation.

"I think to not address it would be a problem because then you basically have the denialists saying, 'Look the IPCC is silent on this issue,'" Alden Meyer, of the Washington-based Union of Concerned Scientists, told the AP.

But some scientists, including Gavin Schmidt, Deputy Chief of NASA's Goddard Institute for Space Studies, are arguing that the explanation is arbitrary. The data looks at a 15-year time period, while the overall report is meant to cover the big picture.

"This whole thing is just a blogstorm in a teacup," the British climatologist told CBSNews.com "The IPCC is there to assess the literature and tell people what the scientists are saying." The report is meant to explain what scientists have reported, not conduct original science, he continued. "The idea that IPCC needs to be up to date on what was written last week is just ridiculous."

There are a handful of reasons why data might indicate that global warming seems to be slowing.

First of all, the data in the IPCC report starts with 1998, which was an unusually warm year. When scientists draw a trend line through climate data from 1998 to 2013, the increase is barely significant. But if, instead, the data set starts with 1970 and goes through to 2013, the global rise in temperature continues at an even rate.

"1998 was a single year that was so extreme, even more of an extreme outlier than people realized at the time," Schmidt explains. El Nino events contributed to the extreme temperatures. More recently, 2010 and 2011 were big years for La Nina events, a natural cooling cycle.

"It skews all of these diagnostics. Look at the long-term content, and ocean heat temperature is rising. We're doing things to the planet that are geological in scope. I don't use those words lightly."

The deep ocean temperatures, scientists agree, is the most important measurement.

"By keeping track of the energy in the oceans, we're keeping track of the energy in the whole system. The ocean keeps increasing, so it's still out of balance and still going to get warmer," Schmidt said.

The National Oceanographic and Atmospheric Administration announced Thursday that ocean temperatures in August 2013 tied for the warmest on record, an indication that climate change is hardly abating.

Also, a 2013 study by Kevin Trenberth at the National Center for Atmospheric Research found dramatic recent warming in the deeper oceans.

But neither of these findings will be covered by the IPCC because, as Schmidt reiterated several times, the IPCC is not an up-to-the-minute journal. It is a report on peer-reviewed science completed before a set cut-off date.

Schmidt is the climatologist behind the website RealClimate.org, a blog run by scientists in order to respond to climate stories and keep the record straight. In 2011 he was awarded recognition as the top climate change communicator by EarthSky Global Science Advisors.

He doesn't expect the IPCC to devote much time to the issue of the apparent lull. "This whole thing has an element for 'what can we find to try to undermine the IPCC' before it's even done, and there's a lot of that going around this week," he said.

One group keen on undermining the IPCC: the climate change deniers.

Their argument that the rise in global average temperatures stopped in the late 1990s has gained momentum among some media and politicians, even though the scientific evidence of climate change keeps piling up: the previous decade was the warmest on record and, so far, this decade has been even warmer. Meanwhile, Arctic sea ice melted to a record low last year and the IPCC draft said sea levels have risen by 7.5 inches (19 centimeters) since 1901.

The deniers' approach, says Schmidt is, "sling enough mud and hope something sticks. This seems to be a little sticky so this will be what they focus on."

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