Warmist Raymond Pierrehumbert: "CO2 accumulates in the atmosphere, ratcheting up the temperature irreversibly, at least out to several millennia"

Two Climate Analysts Fault Gas Leaks, but Not as a Big Warming Threat - NYTimes.com

[Raymond Pierrehumbert] The important thing to understand is that essentially all of the climate effects of methane emissions disappear within 20 years of cessation of emissions; in this sense, the climate harm caused by methane leakage is reversible. In contrast, CO2 accumulates in the atmosphere, ratcheting up the temperature irreversibly, at least out to several millennia.
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[Richard Muller on natural gas leaks] In fact, it would be acceptable (although not good) to have 10 percent leak.

CO2 Science

In a paper recently published in the international peer-reviewed journal Energy & Fuels, Dr. Robert H. Essenhigh (2009), Professor of Energy Conversion at The Ohio State University, addresses the residence time (RT) of anthropogenic CO2 in the air. He finds that the RT for bulk atmospheric CO2, the molecule 12CO2, is ~5 years, in good agreement with other cited sources (Segalstad, 1998), while the RT for the trace molecule 14CO2 is ~16 years. Both of these residence times are much shorter than what is claimed by the IPCC.