Study advances understanding of anthropogenic effects on climate change

RIVERSIDE, California — Anthropogenic aerosols — aerosols originating from human activities — and greenhouse gases, or GHGs, have helped modulate heat storage and distribution in the oceans since the industrial era. Isolating and quantifying the effects of the two forcings using paired climate model simulations, a team led by the University of California, Riverside have found that anthropogenic aerosols and GHGs already play distinct roles in the world’s oceans in shaping patterns of heat absorption, redistribution, and storage. .

The researchers found aerosol-driven changes in ocean circulation and heat transport between associated basins more effective at changing ocean heat distribution than those driven by increasing GHGs globally.

“A better understanding of the effects of individual anthropogenic forcing on ocean heat redistribution and the implications for regional sea level change will help develop climate mitigation strategies,” said Wei Liu, assistant professor of climate change and sustainability in the Department of Earth and Planets. Science, which led to the study published yesterday in Natural Geosciences.

Anthropogenic aerosols and GHGs have been proposed as the main drivers of climate change. The team’s results advance understanding of the effect.

Anthropogenic GHGs have continued to increase during the “historical period”, from around 1850 to the present. Anthropogenic aerosols, in contrast, first increased during this period, but then began to decline starting in the 1980s due to air quality legislation in several parts of the world.

The researchers mainly used the following climate model simulations that were run over historical periods:

• HIST-AER — a model driven solely by human-caused aerosol changes over historical periods.
• HIST-GHG — model driven solely by human-caused changes in greenhouse gases over historical periods.
• HIST — the model is driven by all factors, including human-induced changes in aerosols and greenhouse gases, land use, and volcanic eruptions over historical periods.
• piControl – all coercion is set to preindustrial time levels.

“In the aerosol forcing scenario, inter-basin heat exchange – heat exchange between ocean basins – is proportional to the change in ocean heat absorption in modifying stored heat,” Liu said. “This is especially noticeable in the Atlantic and Indo-Pacific Oceans. Under the greenhouse gas forcing scenario, heat exchange between basins is much more important than changes in ocean heat absorption. This may be due to the fact that in this scenario, ocean circulation effects are greatly offset by changes in temperature.”

Liu explained that heat exchange between basins is important for the redistribution of heat between basins, which could influence regional climate change manifest, for example in sea level rise.

“Since the last century, rapid sea level rise has been one of the most serious threats and will continue for at least another century,” he said. “Sea level rise is not uniform globally but its distribution is regional. Regional and coastal sea level changes, as well as extreme changes along the coastline, can raise community concerns, such as the relocation of coastal communities and the potential for damage to natural resources and infrastructure along the coast.”

Shouwei Li, first author of the paper and a graduate student in Liu’s lab, explains why the study found ocean heat distribution can be altered more effectively by aerosol-driven changes in ocean circulation and heat transport between associated basins than by changes brought about by global GHG increases. .

“This may be related to differences in the distribution of aerosols and GHGs,” he said. “The increase in well-mixed GHGs is global while the change in aerosols is mostly increasing in the Northern Hemisphere due to more human and industrial activities.”

The research team also used observations for comparison with their model results.

“We find the warming of the oceans from the observational model simulations to be a very good fit,” said Liu.

Liu and Li were joined in the study by Robert J. Allen of UCR, Jia-Rui Shi of Woods Hole Oceanographic Institution, and Laifang Li of Pennsylvania State University.

This study was funded by the National Science Foundation.

Research paper entitled “Ocean heat absorption and inter-basin redistribution driven by anthropogenic aerosols and greenhouse gases.”

The University of California, Riverside is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state, and communities around the world. Reflecting California’s cultural diversity, UCR’s enrollment is over 26,000 students. The campus opened a medical school in 2013 and has reached the heart of the Coachella Valley through the UCR Palm Desert Center. The campus has an annual impact of over $2.7 billion on the US economy. To learn more, visit www.ucr.edu.