Recent research and updates to climate models are indicating that the global climate is more sensitive to increases in carbon dioxide than previously thought. A doubling of carbon dioxide from current levels could result in a 5.6C (10F) increase in temperatures. Part of the reason for that change in predictions is that scientists are getting a better handle on the role that clouds play in moderating global temperatures.
Even more troubling, some research indicates that there is a tipping point in carbon dioxide levels, around 1,200 ppm. or roughly triple what it is now. This could be reached in a century or so if emissions remain at current levels. That would result in a sudden decrease in could levels and an extra 8C rise in temperatures.
Climate physicists at the California Institute of Technology performed a state-of-the-art simulation of stratocumulus clouds, the low-lying, blankety kind that have by far the largest cooling effect on the planet. The simulation revealed a tipping point: a level of warming at which stratocumulus clouds break up altogether. The disappearance occurs when the concentration of CO2 in the simulated atmosphere reaches 1,200 parts per million — a level that fossil fuel burning could push us past in about a century, under “business-as-usual” emissions scenarios. In the simulation, when the tipping point is breached, Earth’s temperature soars 8 degrees Celsius, in addition to the 4 degrees of warming or more caused by the CO2 directly.
Once clouds go away, the simulated climate “goes over a cliff,” said Kerry Emanuel, a climate scientist at the Massachusetts Institute of Technology. A leading authority on atmospheric physics, Emanuel called the new findings “very plausible,” though, as he noted, scientists must now make an effort to independently replicate the work.
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