Increased Arctic cloud longwave emissivity associated with pollution from mid-latitudes.

Area of Science:

• Climate Science
• Atmospheric Science
• Arctic Research

Background:

• Arctic climate is highly sensitive to greenhouse gases, with projected warming twice the global average.
• Northern Hemisphere meteorology and local radiative processes influence Arctic temperature responses.
• Anthropogenic aerosols may alter cloud radiative properties, impacting Arctic climate.

Purpose of the Study:

• To evaluate the contribution of anthropogenic aerosols to cloud emission and surface temperatures in the Arctic.
• To quantify the warming effect of aerosols under specific cloud conditions.

Main Methods:

• Utilized four years of ground-based aerosol and radiation measurements near Barrow, Alaska.
• Analyzed coincident thin water clouds and pollution events.
• Calculated changes in cloud longwave emissivity and estimated surface warming.

Main Results:

• Elevated haze levels from anthropogenic aerosols increase cloud longwave emissivity when thin water clouds are present.
• This effect results in an estimated surface warming of 3.3 to 5.2 W m(-2) (1 to 1.6 degrees C) under cloudy skies.
• Demonstrated a direct link between anthropogenic aerosols, cloud properties, and Arctic surface temperature.

Conclusions:

• Anthropogenic aerosols contribute to Arctic surface warming through enhanced cloud longwave emissivity.
• The complex feedback mechanisms in the Arctic climate system require further evaluation of this sensitivity.
• Findings highlight the importance of aerosol-cloud interactions in understanding Arctic climate change.