Climatic impacts of black carbon aerosols over South-East Atlantic underestimated, research shows

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New research has revealed that the full impact of smoke from Central African seasonal fires and in particular the potential climate warming resulting from absorption by black carbon from aerosolis was underestimated by climate models for the South-East Atlantic.

Some of the CMIP6 climate model models are underestimated, which help to guide the 2018 Paris Agreement decisions to limit global warming to 1.5C.

Marc Mallet, MeteoFrance, in Toulouse, has led a pioneering study that used satellite and ground-based remote sense data, backed up by aircraft measurements, to identify shortfalls in climate modelling in capturing the true climate effect of biomass-burning airsols being transported over the South East Atlantic.

Professor Jim Haywood, University of Exeter, led UK involvement in field supporting measurement campaigns and was a key partner in the modeling study conducted by Dr. Mallet.

Science Advances published the study on Friday, 8 October 2021.

Black carbon aerosols, microscopic particulates suspended within the atmosphere, are microscopic. They can be generated by natural and man-made fires, and they absorb significant amounts of sunlight.

Because black carbon can absorb sunlight, it can play an important role in heating the atmosphere and in determining the impact of climate change on regional and continental scales.

Researchers from CNRM and the University of Lille compared how the CMIP6 models represented key variables, including smoke aerosols, low level stratocumulus clouds, and solar absorptionusing innovative, recent remote-sensing observation, backed up by aircraft observations.

It was shown that biomass-burning aerosols increase absorbed sunlight in the South East Atlantic. This would likely heat the climate system, whereas many models suggest the opposite.

This research is the result of many years of international efforts to investigate smoke aerosols in the SE Atlantic from African seasonal fires. The satellite-based, surface-based and in-situ sampling were all part of the effort.

These efforts included the operation of the UK's highly equipped FAAM research plane in August and September 2017. The aircraft was based on Ascension Island, in the middle Atlantic ocean. It also served as a base for the ORACLES and LASIC programs in the USA and the AEROCLO–Sa project in France.

Professor Jim Haywood was the leader of the Ascension Island detachment. He is also a professor of Atmospheric Science and Research Fellow at Met Office Hadley Centre. Our climate models are still not able to accurately model the climate impacts of aerosols, despite decades of research. This leads to substantial uncertainties in future climate projections.

Dr. Ben Johnson from the Hadley Centre said that heating from black carbon aerosol also causes unique effects on clouds and regional rainfall patterns. This makes it an important process for climate simulations to capture and understand. These issues are being studied closely by the Met Office and University of Exeter, as well as other academic partners from the UK and the wider international community. This will help to understand aerosols' role in climate change past and future.

Continue reading. Observations show that aerosols derived from plant-emitted substances can make clouds brighter

Further information: Marc Mallet. Climate models generally underestimate the warming caused by Central Africa's biomass-burning aerosols in the Southeast Atlantic. Science Advances (2021). Journal information: Science Advances Marc Mallet, Climate models generally underrepresent the warming by Central Africa biomass-burning aerosols over the Southeast Atlantic,(2021). DOI: 10.1126/sciadv.abg9998