|
Human carbon dioxide emissions will delay the
onset of the next Ice Age.
According to research published in the journal Nature
Geoscience, the next Ice Age should begin within the next
1,500 years, but will be put off because of high human-caused
emissions.
"At current levels of CO2, even if
emissions stopped now, we’d probably have a long interglacial
duration determined by whatever long-term processes could
kick in and bring [atmospheric] CO2
down," said Luke Skinner of Cambridge University.
The research scientists found the atmospheric concentration
of CO2 would have to drop below about
240 parts per million (ppm) before glaciation could begin.
The current level is about 390ppm.
Other studies have shown that even
if emissions were stopped completely, concentrations of carbon
dioxide would remain elevated for at least 1,000 years. This
would still lead to enough heat being stored in the oceans
to cause significant melting of polar ice and the rising of
sea levels. The transition from Ice Age to an interglacial
period and back again are caused by variations in the Earth’s
orbit known as Milankovitch cycles. They include the eccentricity
of the Earth’s orbit around the Sun, the degree to which its
axis is inclined and its slow rotation. This takes place over
tens of thousands of years. Although the root causes
of the transition are known, the exact way in which they change
Earth’s climate remains a mystery. Using analysis
of orbital data and samples from rock cores in the ocean floor,
Dr Skinner’s team identified an episode called Marine Isotope
Stage 19c (or MIS19c), dating from about 780,000 years ago,
as the one most closely resembling the present.
If the analogy to MIS19c remains true, this transition should
begin within the next 1,500 years. However, the researchers
claim that this would only be if CO2
concentrations were at "natural" levels, which they were not.
|
