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Carbon dioxide emissions, global average temperature, atmospheric CO 2 concentrations, and surface ocean mixed layer acidity are extrapolated using analyses calibrated against extensive time series data for nine global regions. Extrapolation of historical trends without policy-driven limitations has China responsible for about half of global CO 2 emissions by the middle of the twenty-first century. Results are presented for three possible actions taken by China to limit global average temperature increase to levels it considers to be to its advantage: (1) Help develop low-carbon energy technology broadly competitive with unbridled carbon emissions from burning fossil fuels; (2) Entice other countries to join in limiting use of what would otherwise be economically competitive fossil fuels; (3) Apply geo-engineering techniques such as stratospheric sulfur injection to limit global average temperature increase, without a major global reduction in carbon emissions. Taking into account China's expected influence and approach to limiting the impact of anthropogenic climate change allows for a narrower range of possible outcomes than for a set of scenarios that are not constrained by analysis of likely policy-driven limitations. While China could hold back on implementing geoengineering given a remarkable amount of international cooperation on limiting fossil carbon burning, an outcome where geoengineering is used to delay the perceived need to limit the atmospheric CO 2 concentration may be difficult to avoid.

Probability distributions for carbon burning, atmospheric CO2, and global average temperature are produced by time series calibration of models of utility optimization and carbon and heat balance using log-linear production functions. Population growth is used to calibrate a logistically evolving index of development that influences production efficiency. Energy production efficiency also includes a coefficient that decreases linearly with decreasing carbon intensity of energy production. This carbon intensity is a piecewise linear function of fossil carbon depletion. That function is calibrated against historical data and extrapolated by sampling a set of hypotheses about the impact on the carbon intensity of energy production of depleting fluid fossil fuel resources and increasing cumulative carbon emissions. Atmospheric carbon balance is determined by a first order differential equation with carbon use rates and cumulative carbon use as drivers. Atmospheric CO2 is a driver in a similar heat balance. Periodic corrections are included where required to make residuals between data and model results indistinguishable from independently and identically distributed normal distributions according to statistical tests on finite Fourier power spectrum amplitudes and nearest neighbor correlations. Asymptotic approach to a sustainable non-fossil energy production is followed for a global disaggregation into a tropical/developing and temperate/more-developed region. The increase in the uncertainty of global average temperature increases nearly quadratically with the increase in the temperature from the present through the next two centuries

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