New study increases concerns about climate model reliability

Dec 11, 2007

A new study comparing the composite output of 22 leading global climate models with actual climate data finds that the models do an unsatisfactory job of mimicking climate change in key portions of the atmosphere.

This research, published on-line Wednesday in the Royal Meteorological Society’s International Journal of Climatology, raises new concerns about the reliability of models used to forecast global warming.

“The usual discussion is whether the climate model forecasts of Earth’s climate 100 years or so into the future are realistic,” said the lead author, Dr. David H. Douglass from the University of Rochester. “Here we have something more fundamental: Can the models accurately explain the climate from the recent past? “It seems that the answer is no.”

Scientists from Rochester, the University of Alabama in Huntsville (UAH) and the University of Virginia compared the climate change “forecasts” from the 22 most widely-cited global circulation models with tropical temperature data collected by surface, satellite and balloon sensors. The models predicted that the lower atmosphere should warm significantly more than it actually did.

“Models are very consistent in forecasting a significant difference between climate trends at the surface and in the troposphere, the layer of atmosphere between the surface and the stratosphere,” said Dr. John Christy, director of UAH's Earth System Science Center. “The models forecast that the troposphere should be warming more than the surface and that this trend should be especially pronounced in the tropics.

“When we look at actual climate data, however, we do not see accelerated warming in the tropical troposphere. Instead, the lower and middle atmosphere are warming the same or less than the surface. For those layers of the atmosphere, the warming trend we see in the tropics is typically less than half of what the models forecast.”

The 22 climate models used in this study are the same models used by the UN Intergovernmental Panel of Climate Change (IPCC), which recently shared a Nobel Peace Prize with former Vice President Al Gore.

The atmospheric temperature data were from two versions of data collected by sensors aboard NOAA satellites since late 1979, plus several sets of temperature data gathered twice a day at dozens of points in the tropics by thermometers carried into the atmosphere by helium balloons. The surface data were from three datasets.

After years of rigorous analysis and testing, the high degree of agreement between the various atmospheric data sets gives an equally high level of confidence in the basic accuracy of the climate data.

“The last 25 years constitute a period of more complete and accurate observations, and more realistic modeling efforts,” said Dr. Fred Singer from the University of Virginia. “Nonetheless, the models are seen to disagree with the observations. We suggest, therefore, that projections of future climate based on these models should be viewed with much caution.”

The findings of this study contrast strongly with those of a recent study that used 19 of the same climate models and similar climate datasets. That study concluded that any difference between model forecasts and atmospheric climate data is probably due to errors in the data.

“The question was, what would the models ‘forecast’ for upper air climate change over the past 25 years and how would that forecast compare to reality?” said Christy. “To answer that we needed climate model results that matched the actual surface temperature changes during that same time. If the models got the surface trend right but the tropospheric trend wrong, then we could pinpoint a potential problem in the models.

“As it turned out, the average of all of the climate models forecasts came out almost like the actual surface trend in the tropics. That meant we could do a very robust test of their reproduction of the lower atmosphere.

“Instead of averaging the model forecasts to get a result whose surface trends match reality, the earlier study looked at the widely scattered range of results from all of the model runs combined. Many of the models had surface trends that were quite different from the actual trend,” Christy said. “Nonetheless, that study concluded that since both the surface and upper atmosphere trends were somewhere in that broad range of model results, any disagreement between the climate data and the models was probably due to faulty data.

“We think our experiment is more robust and provides more meaningful results.”

Source: Wiley-Blackwell

Explore further: MEPs back plans to slash use of plastic shopping bags

add to favorites email to friend print save as pdf

Related Stories

Meteorites yield clues to Martian early atmosphere

15 hours ago

(Phys.org) —Geologists who analyzed 40 meteorites that fell to Earth from Mars unlocked secrets of the Martian atmosphere hidden in the chemical signatures of these ancient rocks. Their study, published ...

Agriculture's growing effects on rain

Apr 15, 2014

(Phys.org) —Increased agricultural activity is a rain taker, not a rain maker, according to researchers at Pacific Northwest National Laboratory and their collaborators at the University of California Los ...

UN weather agency warns of 'El Nino' this year

Apr 15, 2014

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

Bailing out the world's fresh water bank

Apr 14, 2014

An Australian-based water scientist is testing a new technology to help save imperilled underground water resources in Australia and around the world as climate change tightens its grip on the global food supply.

Recommended for you

More, bigger wildfires burning western US, study shows

6 hours ago

Wildfires across the western United States have been getting bigger and more frequent over the last 30 years – a trend that could continue as climate change causes temperatures to rise and drought to become ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

NotParker
1 / 5 (2) Dec 11, 2007
DUH!
mikiwud
1 / 5 (1) Dec 12, 2007
The IPCC say that it is the Data that is wrong!?
So,if I use a ruler to measure 20mm then another 20mm and look at the ruler and it shows 40mm overall but their computer model shows it should be 45mm,my ruler is wrong?GIVE ME A BREAK!!!

More news stories

There's something ancient in the icebox

Glaciers are commonly thought to work like a belt sander. As they move over the land they scrape off everything—vegetation, soil, and even the top layer of bedrock. So scientists were greatly surprised ...

Clean air: Fewer sources for self-cleaning

Up to now, HONO, also known as nitrous acid, was considered one of the most important sources of hydroxyl radicals (OH), which are regarded as the detergent of the atmosphere, allowing the air to clean itself. ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...

Hackathon team's GoogolPlex gives Siri extra powers

(Phys.org) —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...