2020-10-27_PERMIT FILE - C1981035 ‎(22)‎

• Permit No: C1981035
• IBM Index Class Name: Permit File
• Doc Date: 10/27/2020
• Section_Exhibit Name: KII Appendix 16 Dunn Ranch LBA Technical Resources Report
• Media Type: D
• Archive: No

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Figure 2.2-10 CO2e Atmospheric Concentration Projections
A growing body of analysis on coupled climate-carbon models have shown that temperature is closely
related to the total amount of CO2 emissions released over time,where the cumulative emissions(i.e.the
area under the curve), rather than the timing or shape of the emissions curve is more important for peak
warming estimates. This also means that mitigation requirements can be quantified using a budget
approach, or the amount of CO2 emissions that can still be emitted (cumulatively) relative to a target
temperature (global mean temperature increase) with varying degrees of probability that such a budget
will limit warming to not more than the target. In general, the world has come to the consensus that
limiting warming to 1.5°C or less than 2°C can avoid some of more dire consequences associated with
projected climate change. A tremendous amount of effort has been put forth by the climate science
community to estimate a bright-line budget consistent with the consensus temperature targets. The
budget has evolved overtime as scientists refine data and estimates of cumulative carbon emissions that
have already occurred. For example,scientists recently revised the budget as described in the IPCC Special
Report to account for problems associated with the Earth System Models used in the AR5 budget
estimates. These models underestimated historical cumulative CO2 emissions and were projecting
temperatures warmer than have been observed. The new estimates rely on observational constraints to
make the budget calculations, which have been widely accepted by climate scientists as being more
accurate.
The newest budget estimates are expressed as the remaining cumulative CO2 emissions from the start of
2018 until the time of net zero global emissions and suggest a value of approximately 420 GtCO2 for a
two-thirds chance of limiting warming to 1.5°C, and about 580 GtCO2 for an even chance (50/50).
However, the estimates contain uncertainties that are characteristic of scientist's current understanding
Dunn Ranch Area LBA and Mining Plan Modification 40
Technical Resources Report