Arctic Geochemical Cycle Research Group

Introduction

In recent years, temperatures exceeding 30℃ have been observed in various areas around the Arctic, raising concerns about the progression of global warming. It has also been suggested that large-scale forest fires and the melting of glaciers and permafrost may increase atmospheric concentrations of chemical substances that affect the greenhouse effect, potentially further accelerating warming.

To better understand how these changes are interconnected, the Arctic Chemical Cycle Research Group conducts research combining in situ observations, satellite observations, and numerical models for aerosols and greenhouse gases such as carbon dioxide and methane, which have significant impacts on climate in the Arctic region. Through this approach, the group evaluates the effects of local anthropogenic sources in the Arctic, boreal forest fires, and inflow from surrounding regions such as China, and conducts assessments of health impacts and estimates of allowable future emissions. In addition, by providing scientific evidence that contributes to international efforts aimed at emission reductions, including those under the Arctic Council and UNEP/CCAC, the group aims to contribute to Arctic policy both in Japan and internationally.

What is known and what remains unknown

• Short-lived climate forcers (SLCFs), which have shorter atmospheric lifetimes than carbon dioxide—particularly methane and black carbon—show large regional differences in their warming effects.
• In chemical transport models used in studies such as those contributing to the IPCC, atmospheric concentrations of black carbon near source regions are reproduced relatively well by observations. However, reproducibility remains low in remote regions such as the polar region, and inter-model differences are still extremely large, approaching one order of magnitude.
• For methane, whose mitigation effects through emission controls are more likely to appear than those of carbon dioxide, many aspects remain poorly understood, including emissions from land and ocean surfaces and atmospheric loss processes.
• Analyses using models that can accurately represent atmospheric transport and transformation processes are needed, together with precise and continuous observations within the Arctic region and in the “circum-Arctic subarctic region,” which serves as a source region for transport.

Expected outcomes

• Evaluation of the amounts and transport pathways of black carbon and methane from mid-latitude regions, particularly Asia, to the polar region, as well as their deposition and transformation along these pathways.
• Improvement of estimates of the methane budget in the Arctic region and globally, and refinement of assessments of the climate impacts of black carbon and methane.
• More accurate representation of the effects of aerosols emitted from forest fires and other sources on cloud formation, rainfall and snowfall processes, and radiation such as sunlight, thereby enabling more precise assessment of their impacts on Arctic warming.