January 25, 2013
Global Warming May Be Curable, And Not Quite As Bad As We Thought
Lee Rannals for redOrbit.com - Your Universe Online
New estimates from a Norwegian research project show that policymakers attempting to contain global warming at less than 3.6 degrees Fahrenheit have an attainable target. While most news that comes out about global warming is typically negative and ominous, this study has put a slightly more positive twist on the unfolding story of climate change.
After the Earth's average surface temperature climbed through the 1990s, it began to level off nearly completely at its 2000 level. Ocean warming also appears to have stabilized somewhat, despite the fact that CO2 emissions and other anthropogenic factors that help contribute to global warming still being on the rise.
“In our project we have worked on finding out the overall effect of all known feedback mechanisms,” explained the project´s manager Terje Berntsen, a professor at the University of Oslo´s Department of Geosciences and a senior research fellow at the Center for International Climate and Environmental Research Oslo (CICERO).
Berntsen said the team used a method that enabled them to view the entire earth as one giant "laboratory" where humankind has been conducting collective experiments through emissions of greenhouse gases and particulates, deforestation and other activities.
They entered all the factors contributing to human-induced climate change since 1750 into their model. They also entered fluctuations in climate change that were caused by natural factors like volcanic eruptions and solar activity. The team also accounted for changes in temperatures taken from the air, on the ground and in the oceans into their model as well.
They used a single climate model that repeated calculations millions of times in order to form a basis for statistical analysis. Highly advanced calculations based on Bayesian statistics were carried out by statisticians at the Norwegian Computing Center.
Once they applied their model and statistics to analyze temperature readings from the air and ocean, they found that climate sensitivity to a doubling of atmospheric CO2 concentration will probably be 3.7°C — somewhat higher than the original IPCC predictions.
The scientists said they were surprised when they entered temperatures and other data from the decade 2000 to 2010 into the model, and found that climate sensitivity was greatly reduced to under 3.6 degrees Fahrenheit.
Berntsen said this temperature increase will take place only after we reach the doubled level of CO2 concentration, and maintain that level for an extended time because the oceans delay the effect by several decades.
When the team calculated the probability interval of what will occur, including observations and data up to 2010, they determine with 90 percent probability that global warming from a doubling of CO2 concentration would lie between 2.1 and 5.2 degrees Fahrenheit. This maximum of 5.2 degrees Fahrenheit global warming is substantially lower than many previous calculations.
Once the team factors in the observations of temperature trends of 2000 to 2010, they significantly reduce the probability of our experiencing the dramatic climate chance forecast.
“The Earth´s mean temperature rose sharply during the 1990s. This may have caused us to overestimate climate sensitivity," Berntsen explained. “We are most likely witnessing natural fluctuations in the climate system — changes that can occur over several decades — and which are coming on top of a long-term warming."
He pointed out that natural changes resulted in a rapid global temperature rise in the 1990s, but the natural variations between 2000 and 2010 may have resulted in the leveling off now being observed.
In conclusion, the authors say that if nations cut back particularly on emissions of sulphate particles in the coming years, then the impact of global warming will be much less than feared.