Improved knowledge of glacial-to-interglacial global temperature change
implies that fast-feedback equilibrium climate sensitivity is at least
~4{\deg}C for doubled CO2 (2xCO2), with likely range 3.5-5.5{\deg}C. Greenhouse
gas (GHG) climate forcing is 4.1 W/m2 larger in 2021 than in 1750, equivalent
to 2xCO2 forcing. Global warming in the pipeline is greater than prior
estimates. Eventual global warming due to today's GHG forcing alone -- after
slow feedbacks operate -- is about 10{\deg}C. Human-made aerosols are a major
climate forcing, mainly via their effect on clouds. We infer from paleoclimate
data that aerosol cooling offset GHG warming for several millennia as
civilization developed. A hinge-point in global warming occurred in 1970 as
increased GHG warming outpaced aerosol cooling, leading to global warming of
0.18{\deg}C per decade. Aerosol cooling is larger than estimated in the current
IPCC report, but it has declined since 2010 because of aerosol reductions in
China and shipping. Without unprecedented global actions to reduce GHG growth,
2010 could be another hinge point, with global warming in following decades
50-100% greater than in the prior 40 years. The enormity of consequences of
warming in the pipeline demands a new approach addressing legacy and future
emissions. The essential requirement to "save" young people and future
generations is return to Holocene-level global temperature. Three urgently
required actions are: 1) a global increasing price on GHG emissions, 2)
purposeful intervention to rapidly phase down present massive geoengineering of
Earth's climate, and 3) renewed East-West cooperation in a way that
accommodates developing world needs.Comment: 48 pages, 27 figures. Correction of formatting error on page 21,
which messed up placement of all following figure