Highest CO2 and Methane in 800,000 Years
- May 19, 2008
This post is by Lisa Moore, Ph.D., a scientist in the Climate and Air
program at Environmental Defense Fund.
In IPCC's Third Assessment Report (2001), scientists reported that
carbon dioxide (CO2) and methane levels were higher than at any time
in the past 420,000 years. In their latest report (2007), IPCC
scientists raised the number to 650,000 years.
Last week, scientists again revised the number upward. New research
shows that CO2 and methane levels are higher today than they have been
in at least 800,000 years.
Here's how they know.
The research, published in Nature, analyzes the atmospheric gases
trapped in ice cores extracted from Antarctica. These ice cores are
the oldest yet studied. In 2001, the 420,000-year old Vostok ice core
from eastern Antarctica set the benchmark. In 2005, scientists
analyzed a 650,000-year record from Antarctica's Dome C. Now, drilling
even deeper, scientists at Dome C have assembled an 800,000 year
record of CO2, methane and temperature.
These are the main findings:
* CO2 and methane levels are higher today than they have been in
at least the past 800,000 years.
* The strong correlations of methane and CO2 with temperature
reconstructions are consistent back 800,000 years.
* The long-term cyclic changes in temperature, methane and CO2
that follow slow changes in Earth's orbit are consistent back 800,000