Analysis of recent anthropogenic surface emissions from bottom-up
inventories and top-down estimates: are future emission scenarios valid
for the recent past?
Abstract
This study compares recent CO, NO, NMVOC, SO, BC and OC anthropogenic
emissions from several state-of-the-art top-down estimates to global and
regional bottom-up inventories and projections from five SSPs in several
regions. Results show that top-down emissions exhibit similar
uncertainty as bottom-up inventories in most regions, and even less in
some such as China. In general, for all species the largest
discrepancies are found outside of regions such as the U.S., Europe and
Japan where the most accurate and detailed information on emissions is
available. In some regions such as China, which has undergone dynamical
economic growth and changes in air quality regulations during the last
several years, the top-down estimates better capture recent emission
trends than global bottom-up inventories. These results show the
potential of top-down estimates to complement bottom-up inventories and
to aide in the development of emission scenarios, particularly in
regions where global inventories lack the necessary up-to-date and
accurate information regarding regional activity data and emission
factors such as Africa and India. Areas of future work aimed at
quantifying and reducing uncertainty are also highlighted. A regional
comparison of recent CO and NO trends in the five SSPs indicate that
SSP126, a strong-pollution control scenario, best represents the trends
from the from top-down and regional bottom-up inventories in the U.S.,
Europe and China, while SSP460, a low-pollution control scenario, lies
closest to actual trends in West Africa. This analysis can be a useful
guide for air quality forecasting and near-future pollution
control/mitigation policy studies.