Aerosol forcing depends strongly on very uncertain estimates of the level of preindustrial aerosols.Nicholas Lewis writes, “In this context, what is IMO a compelling new paper by Bjorn Stevens estimating aerosol forcing using multiple physically-based, observationally-constrained approaches is a game changer.” Stevens is an expert on cloud-aerosol processes.Recent research indicates that the aerosol effect is much less than previously thought.The transient climate response (TCR) to greenhouse gas emissions, the warming when carbon dioxide (CO) doubles in about 125 years, was estimated by climatologist Nicholas Lewis at 1.2 °C using an energy balance approach and the new aerosol estimates but assuming that there was no natural long-term warming nor any urban heat contamination of the temperature record.Equilibrium climate sensitivity is estimated at 1.02 °C.
It is estimated to be practiced over 1 billion hectares in developing countries, and to a lesser extent in the industrialized countries.
For relatively well-preserved bones, the ‘chunk’ method of collagen preparation continues to be an acceptable alternative to more sophisticated collagen extraction protocols for C and N isotope analysis.
Summary High estimates of climate sensitivity to greenhouse gases assume aerosols caused a large cooling effect, which canceled some of the previous warming effect, and little or no natural climate change.
However, proxy records demonstrate that there are millennium scale natural climate cycles and numerous studies indicate that the major temperature indexes are contaminated by the urban heat island effect (UHIE) of urban development.
Adjusting the energy balance calculations to account for the natural recovery from the Little Ice Age and the UHIE reduces the TCR to 0.85 °C.