Antarctic Ice Sheet not in Danger from Global Warming
Fears that the Western Antarctic ice sheet (WAIS) is experiencing accelerated declines due to global warming are unfounded, according to a new study in the Jan. 3 issue of Science. A team of scientists, led by John O. Stone with the Quaternary Research Center and Department of Earth and Space Sciences at the University of Washington, found that deglaciation of the WAIS began at least 10,000 years ago and that the rate of melting has remained constant until the present time.
Robert P. Ackert, Jr., of Woods Hole Oceanographic Institution, notes in a perspective on the research that only recently have scientists been able to determine conclusively that, “In large and critical areas, the ice sheet surface is lowering and ice volume is decreasing.” This has caused concern because even a 1 percent decrease in ice volume would raise sea level by 5 centimeters and could eventually raise sea level by as much as 5 meters.
“Are we witnessing the early stages of rapid ice sheet collapse, with potential near-term impacts on the worlds coastlines?” asks Ackert. “To answer this question, we must view the new short term measurements in the context of recent ice sheet history and ask whether the observed changes are unusual compared with those of the last 10,000 years. Stone et al. provide a partial answer by reconstructing the recent history of a previously largely unexamined sector of the WAIS.”
Stone et al. found that, “Surface exposure ages of glacial deposits in the Ford Ranges of western Marie Byrd Land indicate continuous thinning of the West Antarctic ice sheet by more than 700 meters near the coast throughout the past 10,000 years. Deglaciation lagged the disappearance of ice sheets in the Northern Hemisphere by thousands of years and may still be under way. These results provide further evidence that parts of the West Antarctic ice sheet are on a long term trajectory of decline. West Antarctic melting contributed water to the oceans in the late Holocene and may continue to do so in the future.”
Ackert notes that, “Recent ice sheet dynamics appear to be dominated by the ongoing response to deglacial forcing thousands of years ago, rather than by recent anthropogenic warming or sea level rise.” On the whole, the WAIS has thinned at a consistent rate of 2.5 to 9 cm/year over the last 9300 years. Ackert also points out that contrary to prior assumptions, “The results suggest that the WAIS is not in equilibrium with present environmental conditions and has been thinning for the last 10,000 years.”
This means that predicting the future behavior of the ice sheet is significantly more difficult than simply building “quasi-steady state models that reproduce the current ice sheet and then perturb them with possible climate or sea-level forcing.” Instead, scientists must use “dynamic models that reproduce the deglacial historyas a baseline.”
New Findings Lead to New Predictions
What happens when you feed real world data into the Intergovernmental Panel on Climate Changes climate models? That is the question answered in a new study in the most recent issue of Climate Research. The researchers, led by Patrick J. Michaels, a climatologist at the University of Virginia, found that if the IPCCs model is applied to scientific findings that have appeared since the release of its Third Assessment Report, the resulting predictions are significantly less frightening.
The researchers used the IPCCs six major storylines, or projections about population and economic growth, and energy use, and incorporated assumptions that agree with recent scientific developments:
- Research showing that black carbon aerosols offset the cooling affect of sulfate aerosols that scientists had assumed was masking anthropogenic warming.
- The iris effect, where high-level tropical cloudiness diminishes in response to temperature increases, allowing the surface to cool, thereby offsetting anthropogenic warming.
- Adjustments to the rate of increase of atmospheric carbon dioxide levels, from a previously assumed exponential increase, to a constant increase as has been observed for the last 25 years.
- Research showing that the carbon cycle does not intensify in response to higher temperatures.
Plugging this new empirical data into the models, the researchers found that projected warming over the next 100 years falls in the range of 1.0 to 1.6 degrees C, instead of the IPCCs projection of 1.4 to 5.8 degrees C.
The study concludes that the upper bound of the new projection is the most likely outcome. This is due to the fact that nearly all climate models show human-induced warming to be constant, and a simple linear extrapolation from those results leads to about 1.5 degrees warming over the next 100 years. This is also borne out in the observed temperature data.
The study also notes that the lower range of its projection is also possible due to the well-known fact that the temperature response to carbon-forcing is logarithmic, or decreases as atmospheric concentrations of carbon dioxide increases. Atmospheric carbon dioxide data “indicate that any exponential rise in atmospheric CO2 concentrations is weak at best. Consequently the current linear warming may in fact be the adjustment to exponential growth in CO2 that took place prior to 1975 [emphasis in original].”
Regardless of whether warming will continue to be linear or damp off in the next 100 years, the study concludes that there is little to fear from global warming.
No Flooding Trends in the U.S.
A new study in Geophysical Research Letters (December 24, 2002) finds that fears about an increased hydrological cycle (more flooding) from global warming may be overblown. The researchers, Greg McCabe and David Wolock with the U.S. Geological Survey, analyzed the annual maximum, median and minimum streamflow values from 400 gauging stations throughout the United States from 1941 to 1999. What they found was that after 1970 there is a clear trend of higher average streamflow across the U.S., which is more pronounced in the median and low flow cases than in the high flow case.
They also note, however, that there is a definite jump in 1970 in streamflow levels. McCabe and Wolock then looked at all time periods of all possible durations with a minimum of 10 years and found that there were trends in all time periods that included 1970, but few trends in time periods that do not include that year. In other words, trends in streamflow are rare before and after 1970. The abrupt change in 1970 gives a false impression of a longterm upward trend in streamflow.
Finally, most of the trends are concentrated in the median and low flow categories. Only 60 sites saw trends in the annual high flow category, while 202 showed increases in the low flow category. What this means is that there has been an increase in rainfall during the times of year when water is in short supply, but that there has been no increase in flooding, a rather happy result.
Etc.
Many parts of the world are gripped in some of the most frigid and snowy weather experienced in a long time or ever. Beijing, China had 6 consecutive days of snowfall at Christmas time, the longest consecutive snowfall in that city in 128 years. Chinas largest desert, Taklimakan, received 14 centimeters of snow over several consecutive days.
“Taklimakan has had snow every year since the Xinjiang Regional Meteorological Bureau set up a monitoring station in the desert in the 1990s, but the recorded precipitation has been light. It is rare for the desert to have such a heavy snow,” said Lu Guoying, an expert at the regional meteorological bureau. In northern India and Bangladesh, over 250 people have died from exposure to the cold, as temperatures plummeted to well below freezing.
Even more surprising, people are dying in traditionally cooler climates where a combination of record cold and inadequate energy supplies is taking their toll. Record low temperatures in Norway have wreaked all sorts of havoc for its people. Much of the transit system has been frozen out of service, and electricity prices have skyrocketed as demand for home heating is outstripping inadequate electricity supplies.
Unfortunately, several elderly citizens had to be admitted to the hospital with dangerously low body temperatures. At least three have died from the cold after being found in unheated apartments. According to the Norwegian newspaper Aftenposten (January 6, 2003), “Many thrifty, elderly residents have grown worried by reports of record high electricity prices. Too many have opted to turn their heat down to avoid expensive utility bills.” Norway has not built a new power plant in ten years due to environmental politics, according to Still Waiting for Greenhouse (www.john-daly.com).
Many places in Finland have also reached record lows this winter, and the Baltic Seas ice cover is more extensive than it has been in decades. The ice is also 5 to 20 centimeters thicker than usual. According to Helsingin Sanomat (January 8, 2002) “Experts say that the whole Baltic Sea could freeze over all the way to the Straits of Denmark, for the first time since 1948.” Finland is also experiencing shortfalls in electricity supply and has had to import almost 2,000 MW of electricity from Russia and Sweden to keep the lights on and the heaters running.
Finally, 40 ships have been trapped in the ice in the Gulf of Finland in Russia. Moscow reached temperatures as low as -37 degrees C, and as many as 23,000 people are without heat as antiquated systems have broken down.