Answer: Very hard. No major economy has yet made such deep cuts.
California seeks to cut greenhouse gas emissions to 40 percent below 1990 levels by 2030, and to 80 percent below 1990 levels by 2050. Both of those goals have been established by executive orders, not laws, although Senate Bill 32, which has passed the Senate and is now being considered in the Assembly, would codify the 2050 goal into law and also establish targets for 2030 and 2040.
Scientists believe such steep cuts are necessary to limit global warming. The European Union also shares the goal of cutting emissions to 80 percent below 1990 levels by 2050, as does Massachusetts. The Obama Administration has largely focused on goals not quite so far in the future.
Getting to the 2030 and 2050 cuts that California seeks will require steeper cuts than the state has yet experienced over an extended period. Reducing greenhouse gases to the 2020 levels ordered by AB 32 requires a cut of 5.5 percent between 2010 and 2020. Brown’s executive order requires a 40 percent cut below the 2020 target by 2030. That means, in theory, that California would need to reduce emissions about 7 times as quickly between 2020 and 2030 as between 2010 and 2020.
In practice, however, the acceleration may not be quite so dramatic. That’s because most experts expect California to come in below its 2020 targets. If, for example, California’s emissions come in at around 400 million metric tons of carbon dioxide equivalent in 2020, rather than at 431 (the figure needed to exactly meet its 2020 goal), California would need to cut emissions roughly three times faster between 2020 and 2030 than during the preceding decade.
Between 2030 and 2050, emissions will also need to decline much more quickly than has been the case in recent years.
These calculations come with one slight caveat: the state has specified its long-term goals only in terms of percentage reductions, rather than in terms of exact emissions figures. But the exact numbers, when they are formulated, are expected to be roughly what the percentages suggest (eg, around 260 million metric tons of carbon dioxide equivalent for 2030, and 85 metric tons in 2050).