The question of climate sensitivity to atmospheric carbon dioxide levels is unsettled. If we only knew the correct level of temperature sensitivity to CO2 concentration we would have a much more accurate view of what is in store for our climate future. But no. A new paper argues that the climate is far more sensitive to CO2 changes than previously thought.
The climate may be 30–50 percent more sensitive to atmospheric carbon dioxide in the long term than previously thought, according to a study published in Nature Geoscience yesterday.
Projections over the next hundreds of years of climate conditions, including global temperatures, may need to be adjusted to reflect this higher sensitivity.
Is this report correct? I think it illustrates how little we know about the potency of CO2 as a greenhouse warming gas. Here we are in 2009 and some researchers argue that the climate sensitivity to CO2 is much larger than previously thought. Will this turn out to be an underestimate or overestimate?
Sounds like a correlation study. Even assuming that it is possible to accurately measure temperatures millions of years ago the study doesn't prove the direction of causation.
A team of scientists, led by the University of Bristol and including the U.S. Geological Survey, studied global temperatures 3.3 to 3 million years ago, finding that the averages were significantly higher than expected from the atmospheric carbon dioxide levels at the time.
These underestimates occurred because the long-term sensitivity of the Earth system was not accurately taken into account. In these earlier periods, Earth had more time to adjust to some of the slower impacts of climate change. For example, as the climate warms and ice sheets melt, Earth will absorb more sunlight and continue to warm in the future since less ice is present to reflect the sun.
We could change the albedo (reflectivity) of the planet Earth by painting roofs white and cool the planet.
|Share |||Randall Parker, 2009 December 10 10:52 PM Climate Trends|