Global warming may be worse than predicted
Global warming may be worse than predicted
May 22, 2006
Climate change estimates for the next century may have substantially underestimated the potential magnitude of global warming says a new study from a team of European scientists. The paper, published in the May 26 issue of Geophysical Research Letters, says that warming may be 15-to-78 percent higher than estimates that do not consider the feedback mechanism involving carbon dioxide and Earth’s temperature.
Greenhouse gas/temperature feedback mechanism may raise warming beyond previous estimates
American Geophysical Union Release
A team of European scientists reports that climate change estimates for the next century may have substantially underestimated the potential magnitude of global warming. They say that actual warming due to human fossil fuel emissions may be 15-to-78 percent higher than warming estimates that do not take into account the feedback mechanism involving carbon dioxide and Earth’s temperature.
In a paper to be published on 26 May in Geophysical Research Letters, Marten Scheffer of Wageningen University in the Netherlands and colleagues at the Potsdam Institute for Climate Impact Research in Germany and the Centre for Ecology and Hydrology in the United Kingdom use newly acquired ancient climate data to quantify the two-way phenomenon by which greenhouse gases not only contribute to higher temperatures, but are themselves increased by the higher temperatures. This higher concentration leads to still higher temperatures, in what scientists call a positive feedback loop.
The researchers achieved their breakthrough by interpreting the high-resolution data from polar ice cores and temperature reconstructions based on geological proxy data in a new way. Although the effect of greenhouse gases on temperature is well known, the reverse effect is usually ignored. The latter has now been estimated through a correction of the past climate data, using a model of the greenhouse effect.
One complicating factor was that some of the processes that play a role in the feedback loop are quite fast, taking place over a period of years, while others take centuries or even millennia. This implies that the strength of the feedback effect depends on the time scale being analyzed. Another factor was that the modern world looks quite different than it did tens of thousands of year ago, when the ice in the cores was formed.
Therefore, the authors focused especially on relatively recent climatic anomaly known as the “Little Ice Age.” During this period (about 1550-1850), immortalized in many paintings of frozen landscapes in Northern Europe, Earth was substantially colder than it is now. This, scientists have concluded, was due largely to reduced solar activity, and just as during true ice ages, the atmospheric carbon level dropped during the Little Ice Age. The authors used this information to estimate how sensitive the carbon dioxide concentration is to temperature, which allowed them to calculate how much the climate-carbon dioxide feedbacks will affect future global warming.
As Marten Scheffer explains, “Although there are still significant uncertainties, our simple data-based approach is consistent with the latest climate-carbon cycle models, which suggest that global warming will be accelerated by the effects of climate change on the rate of carbon dioxide increase. In view of our findings, estimates of future warming that ignore these effects may have to be raised by about 50 percent. We have, in fact, been conservative on several points. For instance, we do not account for the greenhouse effect of methane, which is also known to increase in warm periods.”
Global warming to be more moderate than some expect April 19, 2006
A new study published in Nature says that climate change will be more moderate than some recent projections. Nevertheless, says lead author Gabriele C. Hegerl of Duke University, we can expect significant changes in the future.
“This still commits us to quite a bit of climate change, but it leaves the door open to avoiding the largest and most devastating consequences,” Dr. Hegerl told the Washington Post. The study looked to refine “climate sensitivity”, or the change in global mean surface temperature in response to a doubling of atmospheric carbon dioxide levels. In 2001, the Intergovernmental Panel on Climate Change (IPCC) estimated that this value would likely fall in the range of 1.5 to 4.5 degrees Celsius (2.7-8°F), but other groups have projected much broader ranges. Currently carbon dioxide levels stand at 381 parts-per-million (ppm) or about 36 percent higher than pre-industrial levels. The IPPC projects that projects that atmospheric carbon dioxide levels could reach 450-550 ppm by 2050.
Slowing global warming may be less costly than initially thought March 9, 2006
Preventing carbon dioxide levels from rising to potentially dangerous levels could cost less far less than originally projected—less 1 percent of gross world product as of 2050—but a major shift in the way energy is found, transformed, transported and used will be necessary to prevent a severe energy crisis within the next century, say researchers from the The Earth Institute. In a report published in the most recent issue of Brookings Papers on Economic Activity, Klaus S. Lackner and Jeffrey D. Sachs of The Earth Institute argue that significant technological developments will be required to meet future energy needs and stave off potential cataclysmic effects of climate change.
This article includes a modified news release from the American Geophysical Union.