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KLIMAFORSK-Stort program klima

Climate implications of rapid changes in Asian Anthropogenic Aerosol emissions: Temperature, Hydrological cycle and variabilitY

Alternative title: Klimakonsekvensene fra raske endringer i asiatiske utslipp av aerosoler: Temperatur, hydrologisk syklus og variabilitet

Awarded: NOK 11.9 mill.

Project Number:

324182

Application Type:

Project Period:

2021 - 2025

Funding received from:

Partner countries:

Human caused emissions of small, airborne particles - called aerosols - strongly affect our climate, and have historically counteracted some of the warming from greenhouse gas emissions. Today, aerosols are thought to cool the Earth's surface by up to half a degree Celsius, and to influence rainfall patterns, the Asian and African monsoons, and the variability of the weather. Asian countries, notably India and China, have been major sources of aerosol emissions over the last decades. Now, however, concerns over air quality are leading to rapid changes in the amounts, geographical patterns and composition of such emissions. Effects on the climate can be expected, both locally and further away from the sources, but as yet the details of this potentially quite strong influence are not known. In 2022-2023, the CATHY partners have further developed tools for studying Asian emissions of aerosols, and performed a range of analyses with these tools. Three activities can be highlighted: 1) Completion of a Green's function that links changes in aerosol emissions in Asia to climate effects locally and further afield, development of a technical article describing them, and another technical article that dives deeper into the results (both articles are close to submission). 2) Development and presentation of the first results from the model intercomparsion project RAMIP (Regional Aerosol Model Intercomparison Project), which is led by CATHY partners (Wilcox, Samset, Allen) 3) Close collaboration with the HETCLIF center at the Center for Advanced Studies in Oslo. HETCLIF has the same overall theme as CATHY, but expands the problem to also apply to African aerosols and changes in forest cover. Several new initiatives have been launched here, which will be completed in the second half of CATHY. We have held both physical and virtual meetings, and the international collaboration within the project is both active and dynamic.

Emissions of Asian Anthropogenic Aerosols (A3) are rapidly changing - most notably black carbon and sulphate aerosol precursors from India and China. The resulting range of climate impacts and societal hazards may dominate regionally over greenhouse gas induced trends for the next several decades, but the implications are as yet insufficiently explored. CATHY (Climate implications of rapid changes in Asian Anthropogenic Aerosol emissions: Temperature, Hydrological cycle and variabilitY) tackles the urgent need for quantifying climate related hazards resulting from ongoing and projected changes in A3 emissions. Why: Today, the Earth’s climate is significantly influenced by Asian aerosol emissions, with impacts affecting up to two billion people in the near-source regions alone. This regional influence is set to change, along with teleconnections affecting remote regions (Arctic, Europe, North Africa). The implications for climate and society are however highly uncertain, due to limited knowledge of physical processes, modelling capability, and future policy choices. Improved quantification of the aerosol-climate influence on physical hazards – in Asia and around the globe – is therefore critical. How: CATHY will merge observed changes, projected emission patterns, and advances in modelling and analysis techniques. Key opportunities for scientific breakthroughs include recent trends in Chinese and Indian emissions, Large Ensemble modelling and the diversity of aerosol assumptions made in the Shared Socioeconomic Pathways. Novelty: CATHY will disentangle dynamical responses to localized forcing through development of a novel reduced-complexity Green’s function, investigate remote impacts via a machine learning based circulation pattern analysis, separate the active mechanisms differentiating absorbing and scattering aerosols, and frame the resulting improved understanding as quantification of physical hazards driving climate risk.

Funding scheme:

KLIMAFORSK-Stort program klima