Energy and Changes in the Environment - Hydrogen and Fuel Cells: Advances in Transportation and Power - page 69

But, two global climate models show that even if the concentrations
of greenhouse gases in the atmosphere had been stabilized by the year
2000, we were already committed to further global warming.
There is an effort to tighten estimates of how the Earth will respond
to climate warming. The sensitivity of new climate models has improved,
but to fully understand the Earth's response to climate warming, a better
knowledge of clouds and aerosols is needed, as well as improved and
more and better records of past climate changes and their drivers.
In 2004, some studies indicated that between 1900 and 2100,
temperatures will increase between 1.4 and 5.8°C. Many scientific questions
remain regarding climate change for both policy makers and the public.
ICE CORES
The climate has the ability to shift into radically different states
according to ice cores extracted from Greenland's massive ice sheet in
the early 1990s. These rods of ice are up to three kilometers long and
provide a set of climate records for the past 110,000 years. They allow the
investigation of annual layers in the ice cores which are dated using a
variety of methods. The composition of the ice provides the temperature
at which it formed.
This work reveals a history of wild fluctuations in climate, long
deep freezes alternating with brief warm spells. Central Greenland has
experienced cold drops as great as six degrees Celsius in just a few years.
Central Greenland also experienced almost half of the heating sustained
since the peak of the last ice age (more than 10 degrees C) in just one
decade. This jump occurred about 11,500 years ago and is the equivalent of
Moscow or Minneapolis having the same climate as Madrid or Atlanta.
The 10-degree warming in the northern waters is thought to be part
of a warming trend across a broad part of the Northern Hemisphere. This
caused increased precipitation that was far reaching. In Greenland, the
thickness of the annual ice layers showed that snowfall doubled in a single
year.
Air bubbles in the ice corroborated the increased wetness in other
areas. The amount of methane in the bubbles indicates that this gas was
entering the atmosphere 50 percent faster during the warming than it
had earlier. The methane probably entered the atmosphere as wetlands
flooded in the tropics and ice and snow thawed in the north.