Climate change: how big a problem?
are still trying to predict.
Theodosia Wade, senior lecturer of biology at Oxford College, wasn’t initially convinced that global climate change existed when she first heard about it in 1988.
“We had a speaker from Emory and he was trying to convince the rest of us that global climate change was a problem. And I wasn’t sure,” Wade said. “I didn’t think there was enough scientific evidence to show us. I was one of the people that thought these are natural cycles.”
But she began taking a closer look at climate change studies in order to teach an environmental science class.
What really impressed Wade was
the data from the initial report of the Intergovernmental Panel on Climate Change in 1990, which she considered a broad and rigorous source, of ice core samples showing the historical correlation of carbon dioxide levels and temperatures going back 650,000 years.
“ Well, now, when the data came out showing carbon dioxide and the correlation, I’m like, ‘ OK, I’m convinced,’” she said
Signs and anecdotes of climate shifts dot the globe, from active hurricane seasons in the past several years to rapidly melting Antarctic ice shelves, such as the Wilkins ice shelf which wasn’t estimated to begin breaking for another 15 years, to changes in migratory patterns of birds due to warmer weather.
But in its recently released Fourth Assessment Report of the IPCC, a panel of hundreds of scientists from around the world established in 1988 to examine the scientific studies, on climate change, issued the strongest statements yet on the condition of Earth’s climate and mankind’s effect.
Using words like “ unequivocal” and “ very likely” — terms scientists don’t use lightly — the report stated that the Earth is getting warmer and that greenhouse gasses generated by human activity are “ very likely” ( or more than 90 percent probable) the cause of the rising temperatures experienced in the last half of the 20th century.
The report noted the 11 hottest years on record for the last 150 years have occurred since 1995 and predicted temperatures would continue to increase anywhere from 2 to 4.5 degrees Fahrenheit in the next century.
Although an increase of a few degrees over a century may not seem like a huge difference to the lay person, the consequences can be tremendous, said Judith Curry, professor in the School of Earth and Atmospheric Sciences at Georgia Institute of Technology.
The increased energy in the atmosphere would likely bring about extremes in weather, said Curry. For Georgia, that could mean more severe heat waves, heavy rainfall events and more severe and longer droughts, such as last year’s drought and forest fire which cost Georgia more than $ 1 billion in damages.
Warmer temperatures and more humidity also could bring more diseases carried by mosquitoes, such as yellow fever and dengue.
“ In the end of the day, it’s going to hit people in Georgia in the pocketbook, if not more directly by drought or hurricane or West Nile Virus,” Curry said.
Greenhouse gasses (GHGs), which include water vapor, carbon dioxide, methane, and nitrous oxide, keep the earth at a hospitable temperature by acting as an invisible blanket or greenhouse around the earth, explained Wade, allowing in the sun’s rays but trapping some of the heat.
Normally, the GHG level is regulated by a process of exchange between land, water, air and animal and plant matter, but in the last several centuries, primarily because of burning fossil fuels for industry and transportation, along with agriculture and land use changes such as deforestation, human activities have introduced a huge amount of greenhouse gasses into the atmosphere, overloading the natural system.
From 1970 to 2004, the amount of carbon dioxide in the atmosphere increased by 80 percent, according to the IPCC report, and the concentration is now more than 380 parts per million in the atmosphere, or about 100 ppm more than the pre- industrial average.
The U. S., which has about five percent of the world’s population, produced about 20 percent of the world’s carbon emissions in 2005.
But China recently took the lead as top carbon dioxide emitter in 2007, according to a study by the Netherlands Environmental Assessment Agency, producing 6.23 billion metric tons or 7.5 percent more than the U. S.
But, per person, the U. S. still produced four times as much as China.
Although the IPCC concluded global temperatures would continue to increase at present GHG levels, there’s uncertainty in the degree and severity of the increase, said Judith Curry
Some of the unknown factors include economic and political situations, especially of developing countries like China and India.
Other sources of uncertainty are feedback processes, touched off by the warmer temperatures. One example is the melting ice caps, which reduce the amount of light reflected back into space and increases the heat absorbed by the earth, which further accelerates the melting process.
“ Feedbacks are very com- plex,” Curry said. She pointed out there were both positive and negative feedback processes that could amplify or level themselves out.
Dr. David Stooksbury, state climatologist, said while the average global climate might have warmed, Georgia and the Southeast region has cooled, in part because of the landscape change during the last century from row crops to forests.
“ What we see on the local scale and global scale may not be in step with each other,” Stooksbury said.
Last year’s drought was in line with Georgia’s climate variability, said Stooksbury, and was similar to a drought experienced in the 1950s. He said he hadn’t followed the IPCC reports, but estimates that human activity is responsible for about 30 to 70 percent of the climate change seen. Both Curry and Stooksbury agree there needs to be more planning taking into account climate predictions and better management of resources.
To that end, Curry is helping to organize a one- day “ Georgia Climate Change Summit” at Georgia Tech on May 6, to bring together scientist, industry leaders and public officials to discuss climate change and its possible impacts on health, industry, sea levels and other related topics.
“ The Southeast is behind in dealing with this issue,” said Curry. “ One of the things we want to do with the climate change summit is to start people talking about this.”
More information on the summit is available at climatesummit. gatech. edu.
To access the IPCC Fourth Assessment Report, visit www. ipcc. ch.
The above schematic drawing is a representation of the various components that affect climate and how those components interact.