Earth still absorbing CO2 even as emissions rise
August 1, 2012
Ashley Ballantyne
A just released study by CU-Boulder researchers reveals that despite humancaused carbon dioxide emissions quadrupling in the last several decades,
Earth’s vegetation and oceans continue to soak up about half of them,
lessening the warming impacts on Earth’s climate.
The study, led by CU-Boulder postdoctoral researcher Ashley Ballantyne,
looked at global CO2 emissions reports from the past 50 years and compared
them with rising levels of CO2 in Earth’s atmosphere during that time.
CUT 1 “We just wanted to really simplify the analysis and look at the observations
and the estimates of CO2 through fossil fuel burning and land use change. (:12)
What we were surprised to learn is that the Earth continues to take up more and
more CO2 every year. How long into the future will the Earth be able to take out
these emissions remains to be scene.” (:27)
Ironically, the reason the Earth continues to absorb CO2, says Ballantyne, may be
because of melting ice cover in the Northern Hemisphere. As ice recedes on land
more CO2-absorbing vegetation appears and as sea ice disappears, more ocean is
available to take in CO2.
CUT 2 “In the Arctic there’s been this greening of the Northern Hemisphere that’s
been pretty well documented from satellites and we suspect that there’s increased
vegetation cover. (:12) Also, some evidence that there’s increased ocean
productivity as sea ice retreats, of course then you’re uncovering ocean, and that
ocean has the capacity to exchange carbon with the atmosphere.” (:28)
But how long these CO2 sinks, as they are called, can continue to absorb greenhouse
gases remains unclear, says Ballantyne. One indicator that we may be approaching
the uptake limit is that the carbon cycle is oscillating and becoming less stable.
CUT 3 “The carbon system is becoming increasingly less stable. (259) Jim White,
one of my co-authors, likened this to a race car -- when you are maxing it out and
things start to shake you have reason to be worried and we might want to back off
on the throttle a little bit. (:22) So there are these oscillations that may be
harbingers of major changes in the global carbon cycle.” (:30)
How long the Earth continues to absorb CO2 remains to be seen, says Ballantyne.
But, he says, several recent studies indicate less and less is being absorbed in the
forests and oceans of the Southern Hemisphere.
-CU-