Model simulations of short-lived climate forcers in the Arctic
Résumé
The Arctic Council’s Arctic Monitoring and Assessment Programme (AMAP) is preparing an assessment of short-lived climate
forcers (SLCFs) to report on the distribution, trends, and impacts of SLCFs on climate, health, and ecosystems in the Arctic. As
part of this effort, several atmospheric and Earth system models were run to simulate SLCFs globally and in the Arctic.
Participating models, using the ECLIPSE v6b anthropogenic emissions, simulated atmospheric concentrations and deposition of
SLCFs such as black carbon, sulfate, ozone, methane, and ozone precursors, as well as optical properties of aerosols, and cloud
properties.
To provide confidence in the modelled impacts of SLCFs and understand their uncertainties, all model simulations were
evaluated against a vast set of measurements. These include surface monitoring networks, aircraft- and ship-based campaigns,
and ground-based and satellite remote sensing. While the focus of the AMAP SLCF report is on the near surface Arctic region,
the model evaluation includes the entire Northern Hemisphere from the surface to the upper-troposphere/lower-stratosphere in
order to assess long-range transport of SLCFs in addition to the local and regional emissions.
Our results suggest that models have recently improved in their ability to simulate aerosol seasonal cycles in the Arctic.
However, the vertical distribution of black carbon still show large variability among models, sometimes varying by a couple
orders of magnitude. Generally, models show similar spatial patterns in their biases, but with greater variability in the Arctic.
Trends in Arctic surface concentrations (1990-2015) were well-modelled over that time period compared to measurements. All
showed a decrease in black carbon and sulfate over that time period, and little-to-no change in the mixing ratio of ground-level
ozone. Deposition remains a significant source of uncertainty, with large variability between models. This has implications for
the long-range transport of SLCFs in models.