(1)(a) The department shall commence the program by January 1, 2023, by determining an emissions baseline establishing the proportionate share that the total greenhouse gas emissions of covered entities for the first compliance period bears to the total anthropogenic greenhouse gas emissions in the state during 2015 through 2019, based on data reported to the department under RCW 70A.15.2200 or provided as required by this chapter, as well as other relevant data. By October 1, 2022, the department shall adopt annual allowance budgets for the first compliance period of the program, calendar years 2023 through 2026, to be distributed from January 1, 2023, through December 31, 2026.

(b) By October 1, 2026, the department shall add to its emissions baseline by incorporating the proportionate share that the total greenhouse gas emissions of new covered entities in the second compliance period bear to the total anthropogenic greenhouse gas emissions in the state during 2015 through 2019. In determining the addition to the baseline, the department may exclude a year from the determination if the department identifies that year to have been an outlier due to a state of emergency. The department shall adopt annual allowance budgets for the second compliance period of the program, calendar years 2027 through 2030, that will be distributed from January 1, 2027, through December 31, 2030.

(c) By October 1, 2028, the department shall adopt by rule the annual allowance budgets for calendar years 2031 through 2040.

(2) The annual allowance budgets must be set to achieve the share of reductions by covered entities necessary to achieve the 2030, 2040, and 2050 statewide emissions limits established in RCW 70A.45.020, based on data reported to the department under chapter 70A.15 RCW or provided as required by this chapter. Annual allowance budgets must be set such that the use of offsets as compliance instruments, consistent with RCW 70A.65.170, does not prevent the achievement of the emissions limits established in RCW 70A.45.020. In so setting annual allowance budgets, the department must reduce the annual allowance budget relative to the limits in an amount equivalent to offset use, or in accordance with a similar methodology adopted by the department. The department must adopt annual allowance budgets for the program on a calendar year basis that provide for progressively equivalent reductions year over year. An allowance distributed under the program, either directly by the department under RCW 70A.65.110 through 70A.65.130 or through auctions under RCW 70A.65.100, does not expire and may be held or banked consistent with RCW 70A.65.100(6) and 70A.65.150(1).

(3) The department must complete evaluations by December 31, 2027, and by December 31, 2035, of the performance of the program, including its performance in reducing greenhouse gases. If the evaluation shows that adjustments to the annual allowance budgets are necessary for covered entities to achieve their proportionate share of the 2030 and 2040 emission reduction limits identified in RCW 70A.45.020, as applicable, the department shall adjust the annual allowance budgets accordingly. The department must complete additional evaluations of the performance of the program by December 31, 2040, and by December 31, 2045, and make any necessary adjustments in the annual allowance budgets to ensure that covered entities achieve their proportionate share of the 2050 emission reduction limit identified in RCW 70A.45.020. Nothing in this subsection precludes the department from making additional adjustments to annual allowance budgets as necessary to ensure successful achievement of the proportionate emission reduction limits by covered entities. The department shall determine and make public the circumstances, metrics, and processes that would initiate the public consideration of additional allowance budget adjustments to ensure successful achievement of the proportionate emission reduction limits.

(4) Data reported to the department under RCW 70A.15.2200 or provided as required by this chapter for 2015 through 2019 is deemed sufficient for the purpose of adopting annual allowance budgets and serving as the baseline by which covered entities demonstrate compliance under the first compliance period of the program. Data reported to the department under RCW 70A.15.2200 or provided as required by this chapter for 2023 through 2025 is deemed sufficient for adopting annual allowance budgets and serving as the baseline by which covered entities demonstrate compliance under the second compliance period of the program.

(5) The legislature intends to promote a growing and sustainable economy and to avoid leakage of emissions from manufacturing to other jurisdictions. Therefore, the legislature finds that implementation of this section is contingent upon the enactment of RCW 70A.65.110.