IPCC temps

IPCC 2013 summary report

The IPCC graphic shows a warming world with average termperature changes of about 1 degree centigrade forthe dark beige areas of the map at right to 5 degrees or more of  warming by 2100 for the areas of the earth shown in light red to darker reds.

Back to the future: Experts confident in U.N. climate forecast

by Jenny Draper
Oct 28, 2013

R. Alley (Jenny)

Jennifer Draper/MEDILL

Richard Alley talks about the risks of climate change and the need for society to address them just as everyone addresses the risks of auto accidents with insurance, car seats for kids and other protection.

Climate scientists are confirming the latest United Nations forecast of rising sea levels, shrinking glaciers and intensifying heat due to human activities that lock ever more greenhouse gases in the atmosphere.

The fifth Intergovernmental Panel on Climate Change (IPCC) recently reported that the Earth is getting increasingly warmer and humans are influencing the climate system through rising fossil fuel emissions.

“It’s clear that we can’t use the atmosphere as a garbage can for CO2,” said geochemist Wally Broecker of Columbia University who is a pioneer of climate change science.

He and other scientists reinforced the IPCC findings while gathered at the four-day Comer Abrupt Climate Change Conference held in Wisconsin this month.

Carbon dioxide is a greenhouse gas that holds heat in the atmosphere, a thermostat linked to global warming.

“The warming influence of CO2 is so clear, it's so physically unavoidable that as you look through the reports, it hasn't changed,” said Richard Alley, a geosciences professor at Pennsylvania State University and emcee for the conference. “You can see us dotting more of the i’s and crossing more of the t’s” with more research.

Alley played a small role as a reviewer in the recent assessment, but contirbuted to writing previous IPCC reports. He has frequently testified about climate change before the U.S. House Committee on Science and Technology.

Describing the IPCC as the “mother of all committees,” Alley said the most significant updates in the “fine-tuned” report include more studies feeding it and greater confidence in the results.

“This time they did dabble with the idea of a carbon pie,” Broecker said, referring to an international goal to stay below a key limit of global greenhouse emissions.

Specifically, society cannot emit more than about 1 trillion tons of carbon to remain below the global temperature target of less than 3.6 degrees Fahrenheit. But the trillion-ton limit would be exceeded in about 30 years at currently increasing levels of fossil fuel use.

Sean Birkel, a Climate Change Institute assistant professor at the University of Maine, has been localizing the IPCC simulations to see how regional climates might change in the future.

“The IPCC models show a more significant rise than what we see from the historical records," he said. So the question arises as to whether the IPCC models are correct. “I think they likely are, by and large, but is that rate of change going to play out?” Birkel said.

Birkel added that the inherent chaos in climate change causes some uncertainty in long-term projections, likening it to a weatherman’s accuracy in a seven-day forecast.

“The weather will probably turn out pretty close to the forecast one day out," he said. "Two days out, less certainty; three days out, not very good; a full week out, it becomes fictitious, almost.” 

Some parallels exist between Birkel’s research and the IPCC report, most notably a subtle rise in the average temperature and frequency of heat waves on the East Coast.

“So it’s just changing a little bit, but that little bit can be quite important for people who could die from heat stroke,” Birkel said. “I mean it really affects the young and the elderly who may have some pre-existing health condition.”

Sea levels are another factor. Sea levels could rise 3.3 feet by 2100 if emissions from fossil fuels remain high, according to the 2013 IPCC report, a threat to coastal areas and many islands.

However, Alley said the IPCC assessment gives society the opportunity to take the science and use it to end up better off.  

“There's just almost no question that using this knowledge wisely does not tell you what laws to pass, does not tell you who you have to elect,” Alley said. “But you can end up with a better economy, with more money, more jobs, with a cleaner environment if you use this knowledge.”