Latest California greenhouse gas emissions inventory a mixed bag. To meet 2030 target state has its work cut out

In 2016 in California, greenhouse gas (GHG) emissions reduction was big news in that the 2020 target of 431 million metric tons of carbon dioxide equivalent units (MMTCO2e) was not just reached but surpassed, the state reaching a level of 429.2 MMTCO2e, four years early.1

On the other hand, for California to reach the 2030 target of 40 percent below that 431 MMTCO2e threshold which, incidentally, equals the level of 1990, the state will need to step up its GHG-reduction work considerably. 2030’s target, meanwhile, is 258.6 MMTCO2e.

So understanding the challenge ahead, that greenhouse gas emissions in 2018 (425.3 MMTCO2e) increased with respect to those in 2017 (424.5 MMTCO2e) rose (granted a small rise but a rise nonetheless), the fact that they rose is not a good sign.

The primary area of concern had been transportation which, by the way, accounts for 41 percent of state GHG output. But, surprisingly, transportation was the one category to see improvement – 2018’s 169.5 MMTCO2e versus 2017’s 171.02 MMTCO2e and 2016’s 169.76 MMTCO2e totals. Everything else saw numbers trend oppositely. Important to note also is that 2016 is significant in that in the U.S. transportation took over energy as the leading GHG emitter, energy having held the heavyweight title since 1978 and that 2018 is the latest for which California GHG-output data is available.

So what could account for or explain the difference: The sudden reversal, in other words?

For starters, since about 2014 or 2015, the U.S. and California post-Great-Recession economies have both been doing reasonably well. This hints at consumer spending being up and points to enhanced or stimulated manufacturing, industrial, business, etc. activity. Population increase factors in too.

Where energy production and consumption is concerned, weather as well could be an influencer. Meaning, all sectors – Agriculture, Consumer and Residential, Electric Power, High GWP (Global Warming Potential), Industrial, Recycling and Waste, Transportation – could negatively affected due to such meteorological influence.

That transportation GHG in state has improved is, quite frankly, a surprise and a pleasant one at that, in fact, considering! In that all other sectors’ GHG emissions outputs went the other way, it’s time to take a closer look at the individual categories within transportation to see what is actually going on.

The main Transportation subcategories if you will are: On Road, Ships & Commercial Boats, Aviation (Intrastate), Rail, Off Road and Unspecified. On Road is sub-sub categorized further into Passenger Vehicles and Heavy Duty Vehicles.


  • On Road saw GHG drop in 2017 from 156.41 to 154.45 in 2018. Passenger Vehicles and Heavy Duty Vehicles followed suit – Passenger Vehicles went from 119.95 in 2017 to 119.45 in 2018 while Heavy Duty Vehicles fell from 36.45 in 2017 to 35.00 in 2018.
  • Improvements were also made in Ships & Commercial Boats and in the Aviation (Intrastate) areas. Ships & Commercial Boats retreated from 3.82 in 2017 to 3.74 in 2018. Aviation’s (Intrastate) improvement, meanwhile, wasn’t quite as pronounced going from 4.68 to 4.65 in 2017 and 2018, respectively.
  • Trending oppositely were Rail, Off Road and Unspecified. Rail, after seeing declines every year since 2014, experienced an increase, rising from 1.83 (2017) to 2.22 (2018).
  • Rail was joined by Off Road which also trended in the positive direction, gaining a full point going from 2.73 (2017) to 2.83 (2018) and Unspecified which also tracked upward, rising from 1.55 (2017) to 1.61 (2018).

Again, units are expressed in MMTCO2e.

Possible reasons for the On Road improvements, taken as a whole, could be substantially improved vehicle engine performance in both Passenger Vehicle and Heavy Duty Vehicle classes and/or more reliance on fleet-based hybrid and electric vehicles. Perhaps ride hailing could have played a role. What’s interesting is that in terms of the gain in the Passenger Vehicle class, this was despite an increase in the number of gallons of gasoline burned 2018 versus 2017: It rose!

As for Rail, Off Road and Unspecified, this is suggestive of greater use or activities in these areas in 2018 compared to a year earlier. Off Road, it should be noted, includes airport ground and construction, industrial, mining and oil drilling equipment.

If California is going to meet its 2030 GHG emissions-reduction target, it definitely has its work cut out.


  1. Referenced for this report was the “California Greenhouse Gas Inventory for 2000-2018” data sheet from the California Environmental Protection Agency Air Resources Board. https://ww3.arb.ca.gov/cc/inventory/data/tables/ghg_inventory_scopingplan_sum_2000-18.pdf
Gas refueling hose, nozzle and control

Image above: Copyright © 2020 Environmental Defense Fund. The original material is available at: https://www.edf.org/federal-clean-car-standards

Published by Alan Kandel

The material in this press release comes from the originating research organization. Content may be edited for style and length. Want more? Sign up for our daily email.